Updated: 19 November 2024
Welcome to the night skies of
Spring,
featuring
Aquila, Cygnus, Pegasus,
Andromeda, Capricornus, Aquarius, Pisces, Aries,
Taurus, Cetus, Piscis Austrinus, Pavo, Venus, Jupiter and Saturn
Note: To read this webpage with mobile phones or tablets, please use them
in landscape format, i.e. the long screen axis should be horizontal.
The Alluna RC-20 Ritchey Chrétien telescope was installed in March, 2016.
The 20-inch telescope is able to locate and track any sky object (including Earth satellites and the International Space Station) with software called TheSkyX Professional, into which is embedded a unique T-Point model created for our site with the telescope itself.
Explanatory Notes:
Rise and
set times are given for the theoretical horizon, which is a flat horizon all the
way round the compass, with no mountains, hills, trees or buildings to obscure
the view. Observers will have to make allowance for their own actual horizon.
Transient phenomena are provided for the current month
and the next. Geocentric phenomena are calculated as if the Earth were fixed in
space as the ancient Greeks believed. This viewpoint is useful, as otherwise
rising and setting times would be meaningless. In the list of geocentric events,
the nearer object is given first.
When a planet is referred to as ‘stationary’, it means
that its movement across the stellar background appears to have ceased, not that
the planet itself has stopped. With inferior planets (those inside the Earth’s
orbit, Mercury and Venus), this is caused by the planet heading either directly
towards or directly away from the Earth. With superior planets (Mars out to
Pluto), this phenomenon is caused by the planet either beginning or ending its
retrograde loop due to the Earth’s overtaking it.
Apogee and perigee: Maximum and minimum distances of the
Moon or artificial satellite from the Earth.
Aphelion and perihelion: Maximum and minimum distances of a
planet, asteroid or comet from the Sun.
Eclipses always occur in pairs, a lunar and a solar but not necessarily in that
order, two weeks apart.
The meridian is a semicircle starting from a point on the horizon that is
exactly due north from the observer, and arching up into the sky to the zenith
and continuing down to a point on the horizon that is exactly due south. On the
way down it passes through the South Celestial Pole which is 26.6 degrees above
the horizon at Nambour. The elevation of the South Celestial Pole is exactly the
same as the observer's latitude, e.g. from Cairns it is 16.9 degrees above the
horizon, and from Melbourne it is 37.8 degrees. The Earth's axis points to this
point in the sky in the southern hemisphere, and to an equivalent point in the
northern hemisphere, near the star Polaris, which from Australia is always below
the northern horizon.
All astronomical objects rise until they reach the meridian, then they begin to
set. The act of crossing or 'transitting' the meridian is called 'culmination'.
Objects closer to the South Celestial Pole than its altitude above the southern
horizon do not rise or set, but are always above the horizon, constantly
circling once each sidereal day. They are called 'circumpolar'. A
handspan at arm's length with fingers spread covers an angle of approximately 18
- 20 degrees. Your closed fist at arm's length is 10 degrees across. The tip of
your index finger at arm's length is 1 degree across. These figures are constant
for most people, whatever their age. The Southern Cross is 6 degrees high and 4
degrees wide, and Orion's Belt is 2.7 degrees long. The Sun and Moon average
half-a-degree (30 arcminutes) across.
mv = visual magnitude or brightness. Magnitude 1 stars are very
bright, magnitude 2 less so, and magnitude 6 stars are so faint that the unaided
eye can only just detect them under good, dark conditions. Binoculars will allow
us to see down to magnitude 8, and the Observatory telescope can reach visual
magnitude 17 or 22 photographically. The world's biggest telescopes have
detected stars and galaxies as faint as magnitude 30. The sixteen very brightest
stars are assigned magnitudes of 0 or even -1. The brightest star, Sirius, has a
magnitude of -1.44. Jupiter can reach -2.4, and Venus can be more than 6 times
brighter at magnitude -4.7, bright enough to cast shadows. The Full Moon can
reach magnitude -12 and the overhead Sun is magnitude -26.5. Each magnitude step
is 2.51 times brighter or fainter than the next one, i.e. a magnitude 3.0 star
is 2.51 times brighter than a magnitude 4.0. Magnitude 1.0 stars are 100 times
brighter than magnitude 6.0 (5 steps each of 2.51 times,
2.51x2.51x2.51x2.51x2.51 = 2.515 =
The Four Minute Rule
How long does it take the Earth to complete
one rotation? No, it's not 24 hours - that is the time taken for the Sun to
cross the meridian on successive days. This 24 hours is a little longer than one
complete rotation, as the curve in the Earth's orbit means that it needs to turn
a fraction more (~1 degree of angle) in order for the Sun to cross the meridian
again. It is called a 'solar day'. The stars, clusters, nebulae and galaxies are
so distant that most appear to have fixed positions in the night sky on a human
time-scale, and for a star to return to the same point in the sky relative to a
fixed observer takes 23 hours 56 minutes 4.0916 seconds. This is the time taken
for the Earth to complete exactly one rotation, and is called a 'sidereal day'.
As our clocks and lives are organised to run on solar days of 24 hours, and the
stars circulate in 23 hours 56 minutes approximately, there is a four minute
difference between the movement of the Sun and the movement of the stars. This
causes the following phenomena:
1. The Sun slowly moves in the sky relative
to the stars by four minutes of time or one degree of angle per day. Over the
course of a year it moves ~4 minutes X 365 days = 24 hours, and ~1 degree X 365
= 360 degrees or a complete circle. Together, both these facts mean that after
the course of a year the Sun returns to exactly the same position relative to
the stars, ready for the whole process to begin again.
2.
For a given clock time, say 8:00 pm, the stars on consecutive evenings are ~4
minutes or ~1 degree further on than they were the previous night. This means
that the stars, as well as their nightly movement caused by the Earth's
rotation, also drift further west for a given time as the weeks pass. The stars
of autumn, such as Orion, are lost below the western horizon by mid-June, and
new constellations, such as Sagittarius, have appeared in the east. The
stars change with the seasons, and after a year, they are all back where they
started, thanks to the Earth's having completed a revolution of the Sun and
returned to its theoretical starting point.
We can therefore say
that the star patterns we see in the sky at 11:00 pm tonight will be identical
to those we see at 10:32 pm this day next week (4 minutes X 7 = 28 minutes
earlier), and will be identical to those of 9:00 pm this date next month or 7:00
pm the month after. All the above also includes the Moon and planets, but their
movements are made more complicated, for as well as the Four Minute Drift
with the stars, they also drift at different rates against the starry
background, the closest ones drifting the fastest (such as the Moon or Venus),
and the most distant ones (such as Saturn or Neptune) moving the slowest.
Observing astronomical objects depends on
whether the sky is free of clouds. Not only that, but there are other factors
such as wind, presence of high-altitude jet streams, air temperature, humidity
(affecting dew formation on equipment), transparency (clarity of the air),
"seeing" (the amount of air turbulence present), and air pressure. Even the
finest optical telescope has its performance constrained by these factors.
Fortunately, there is an Australian website that predicts the presence and
effects of these phenomena for a period up to five days ahead of the current
date, which enables amateur and professional astronomers to plan their observing
sessions for the week ahead. It is called "SkippySky". The writer has
found its predictions to be quite reliable, and recommends the website as a
practical resource. The website is at
http://skippysky.com.au and the
detailed Australian data are at
http://skippysky.com.au/Australia/ .
Solar System
Sun:
The Sun begins the month in the zodiacal constellation of Libra, the Scales. It leaves Libra and crosses into a claw of Scorpius, the Scorpion on November 23. It passes out of the claw and into the non-zodiacal constellation of Ophiuchus, the Serpent-bearer, on November 30. It transits Ophiuchus and crosses into Sagittarius, the Archer on December 18. Note: the Zodiacal constellations used in astrology have significant differences with the familiar astronomical constellations both in size and the timing of the passage through them of the Sun, Moon and planets.
The Moon is tidally locked to the Earth, i.e. it keeps its near hemisphere facing us at all times, while its far hemisphere is never seen from Earth. This tidal locking is caused by the Earth's gravity. The far side remained unknown until the Russian probe Luna 3 went around the Moon and photographed it on October 7, 1959. Now the whole Moon has been photographed in very fine detail by orbiting satellites. The Moon circles the Earth once in a month (originally 'moonth'), the exact period being 27 days 7 hours 43 minutes 11.5 seconds. Its speed is about 1 kilometre per second or 3679 kilometres per hour. The Moon's average distance from the Earth is 384 400 kilometres, but the orbit is not perfectly circular. It is slightly elliptical, with an eccentricity of 5.5%. This means that each month, the Moon's distance from Earth varies between an apogee (furthest distance) of 406 600 kilometres, and a perigee (closest distance) of 356 400 kilometres. These apogee and perigee distances vary slightly from month to month. In the early 17th century, the first lunar observers to use telescopes found that the Moon had a monthly side-to-side 'wobble', which enabled them to observe features which were brought into view by the wobble and then taken out of sight again. The wobble, called 'libration', amounted to 7º 54' in longitude and 6º 50' in latitude. The 'libration zone' on the Moon is the area around the edge of the Moon that comes into and out of view each month, due to libration. This effect means that, instead of only seeing 50% of the Moon from Earth, we can see up to 59%.
The animation loop below shows the appearance of the Moon over one month. The
changing phases are obvious, as is the changing size as the Moon comes closer to
Earth at perigee, and moves away from the Earth at apogee. The wobble due to
libration is the other feature to note, making the Moon appear to sway from side
to side and nod up and down.
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New Moon:
November 1 22:48 hrs
diameter = 29.6' Lunation #1260 begins
Last Quarter:
November 23 11:29 hrs
diameter = 30.0'
December
Moon at 8 days after
New, as on November 10.
Dec
Dec
Dec
The photograph above shows the Moon when approximately eight days after New, just after First Quarter. A rotatable view of the Moon, with ability to zoom in close to the surface (including the far side), and giving detailed information on each feature, may be downloaded
here. A professional version of this freeware with excellent pictures from the Lunar Reconnaissance Orbiter and the Chang orbiter (giving a resolution of 50 metres on the Moon's surface) and many other useful features is available on a DVD from the same website for 20 Euros (about AU $ 33) plus postage
Lunar Feature for this Month
Each month we describe a lunar crater, cluster of craters,
valley, mountain range or other object, chosen at random, but one with
interesting attributes. A recent photograph from our Alluna RC20 telescope will
illustrate the object. As all large lunar objects are named, the origin of the
name will be given if it is important. This month we will look at an area near the Moon's North Pole that is completely crowded with walled plains and craters from large to tiny.
Six of the largest craters, beginning with those closest to the Pole, are Peary, Byrd, Nansen, De Sitter, Scoresby and Baillaud.
The North Pole itself is indicated by a blue asterisk. It lies just outside the wall of the 75 kilometre crater plain Peary, between the 14.5 kilometre cone crater Whipple and the 13.4 kilometre irregular crater Hinshelwood. The two images above
are contiguous, the left side of the second one matching the right side of the first one, with a slight amount of overlap involving the craters Nansen F, De Sitter M and the ghost crater Meton E. The first image was taken at 7:25 pm
on 4 October 2022, the second one at 8:47 pm the same night.
Like the south polar area on the Moon, the north polar area is covered with impact craters of various sizes. Close to the actual pole are the walled plains Peary
(75 kilometres diameter) and Byrd (94 kilometres diameter). Impacting Byrd's southern rim is a smaller crater-plain called Gioja, 41 kilometres in diameter. Further south are the conjoined crater-plains Main (46 kilometres) and Challis
(56 kilometres). South-east of Challis is a much more recent impact crater of identical size called Scoresby. When comparing the two, Challis has a flat, lava-filled floor and battered, worn-down walls, while Scoresby has a bowl-shaped floor and sharply-defined
walls showing little damage except for a later impact that has struck the interior of Scoresby's northern ramparts. Therefore we can assume that Scoresby is a much younger feature than Challis.
Another interesting walled plain in this image is 91 kilometre Baillaud. Its walls are reasonably high, and the original bowl-shaped floor has been filled with lava welling up from fractures in the floor when Baillaud was created. The lava forced a
way through Baillaud's south-east wall and spread over the plains to the south. Euctemon (63 kilometres) was formed in a similar way, but the lava failed to rise as high as that in Baillaud. For this reason, the floor level in
Euctemon is much lower than in Baillaud, making the walls of Euctemon appear much higher than those of Baullaud. The floors of both craters are covered in craterlets, and it is interesting that each has one larger crater on its
floor. What makes Baillaud special is the presence of a 14 kilometre perfectly-formed crater called Baillaud E in an off-centre position on its floor.
Peary, Byrd and Nansen:
The International Astronomical Union (IAU) named these walled plains in 1964 after three explorers of the Earth's north polar regions: Robert Peary (1856-1920), who claimed to have led an expedition that reached the North Pole in 1909; Richard Byrd
(1888-1957), who announced in 1926 that he had been the first to fly over the North Pole (disputed) and in 1929 flew over the South Pole (confirmed); and Fridtjof Nansen (1861-1930) who, with dog sledges and one companion, got within
420 kilometres of the North Pole, and proved that there was no open water or land there, but just ice-covered sea.
The largest walled plain in this image is Nansen, which is 123 kilometres across. It lies in the zone of libration, which means that it is only able to be viewed if the libration and lunar phase co-operate. Its floor is flat, with a line of low hills, and
is covered with craterlets. There is one 10 kilometre crater inside Nansen, but it is as yet without a name.
There is an interesting triple crater in the left-hand (western) side of this image. It is composed of two ancient conjoined crater-plains, the northern
one De Sitter M being 72 kilometres across, and to its south-west De Sitter L, being 69 kilometres across. Both of these craters shsred a common wall between them, and both have been degraded and worn down by the impacts of meteors over the 2 to
3 billion years since they were formed. Later, a third impactor heading to the Moon struck the wall between De Sitter L and De Sitter M, the blast of the impact melting all the material in the wall and throwing it to the north, half-covering
the floor of De Sitter M, and also to the south-south-west, covering three-quarters of the floor of De Sitter L. This third strike has resulted in the 65 kilometre impact crater of De Sitter which has high walls and many fractures in its
floor. The piled-up debris from the shared wall is seen clearly covering most of the floors of De Sitter L and De Sitter M.
See item #81 in the Lunar Feature of the Month Archive .
Willem de Sitter (1872-1934) made major contributions to the field of cosmology, especially with regard to Albert Einstein’s new Theory of General Relativity of 1915. Einstein knew that Vesto Slipher had announced that the study of spectra of a
number of galaxies indicated that the universe was expanding as predicted by Einstein’s own theory, but Einstein was sure that the universe was static, not moving or changing. He therefore modified his theory by introducing a force which acted to keep the
universe stopped. He called this invented force the “cosmological constant” and showed it in his revised equations as the Greek letter lambda (λ). Most astronomers thought it odd that Einstein should alter his equations in this way, but Willem de Sitter came
upon a solution with the concept of ‘de Sitter space’ in which he invented for Einstein a universe in which there is no matter at all, but a positive cosmological constant. This became known as the ‘de Sitter universe’, and results in an exponentially expanding,
empty universe controlled by a positive λ. Most astronomers at the time accepted that they had to choose between two possible models of the universe: Einstein’s static spherical universe, a finite unmoving and unchanging sphere of limited matter; De Sitter’s expanse of empty space, devoid of matter and energy but controlled by λ. The British astronomer Arthur Eddington joked that the choice was between ‘motionless matter’ and ‘matterless motion’. The work of Edwin Hubble in 1924 finally confirmed that the universe was definitely expanding. Einstein immediately abandoned his cosmological
constant, saying that it was “the greatest blunder of my life”. He co-authored a paper with Willem de Sitter in 1932 in which they discussed the implications of cosmological data for the curvature of the universe. De Sitter was also famous for his research on the
motions of the moons of Jupiter.
Astrophysicists now tell us that the universe was momentarily a ‘de Sitter universe’ 10 -33 seconds after the Big Bang, and now, as our universe continues to expand and the average density of galaxies per unit volume diminishes over trillions of years, the universe will
gradually evolve back towards a ‘de Sitter universe’.
November 3: Moon 1.9º south of Mercury at 18:28 hrs
November 3: Moon 1.6º north of the star Pi Scorpii (mv= 2.82) at 22:48 hrs
November 4: Moon occults the star Alniyat (Sigma Scorpii, mv= 2.9) between 5:36 and 6:22 hrs
November 4: Moon occults the star Antares (Alpha Scorpii, mv= 0.88) between 9:34 and 10:27 hrs
November 4: Moon 1.3º north of the star 23 Tau Scorpii (mv= 2.82) at 15:04 hrs
November 5: Moon 2.6º south of Venus at 7:54 hrs
November 6: Moon 2.5º north of the star Alnasl (Gamma Sagittarii, mv= 2.98) at 3:55 hrs
November 6: Moon 1.6º north of the star Kaus Media (Delta Sagittarii, mv= 2.72) at 9:06 hrs
November 7: Limb of Moon 41 arcminutes south of the star Nunki (Sigma Sagittarii, mv= 2.02) at 1:49 hrs
November 8: Limb of Moon 44 arcminutes south of Pluto at 7:31 hrs
November 9: Mercury 1.5º north of the star Alniyat (Sigma Scorpii, mv= 2.9) at 6:15 hrs
November 10: Moon occults the star Deneb Algedi (Delta Capricorni, mv= 2.85) between 3:35 and 4:14 hrs
November 10: Mercury 2º north of the star Antares (Alpha Scorpii, mv= 0.88) at 20:15 hrs
November 11: Moon has a grazing occultation with Saturn at 10:23 hrs
November 12: Limb of Moon 26 arcminutes north of Neptune at 11:02 hrs
November 13: Venus 1.2º south of the Lagoon Nebula (M8) at 4:15 hrs
November 13: Venus 4.8º north of the star Alnasl (Gamma Sagittarii, mv= 2.98) at 13:15 hrs
November 15: Venus 1.2º north of the star Kaus Media (Delta Sagittarii, mv= 2.72) at 9:06 hrs
November 15: Saturn at eastern stationary point at 23:27 hrs
November 15: Venus 4.8º north of the star Alnasl (Gamma Sagittarii, mv= 2.98) at 13:15 hrs
November 16: Moon 4.3º north of Uranus at 10:12 hrs
November 16: Full Moon occults five stars in the Pleiades cluster (Electra, Celaeno, Merope, Maia and Alcyone) between 15:11 and 16:35 hrs
November 16: Mercury at Greatest Elongation East (22 24') at 19:08 hrs ( diameter = 6.6" )
November 17: Uranus at opposition at 12:16 hrs ( diameter = 3.8" )
November 17: Venus 9 arcminutes south of the star Kaus Borealis (22 Lambda Sagittarii, mv= 2.82) at 18:45 hrs
November 17: Venus 9 arcminutes south of the star Kaus Borealis (22 Lambda Sagittarii, mv= 2.82) at 18:45 hrs
November 17: Moon 6.3º north of Jupiter ar 23:20 hrs
November 18: Moon occults the star Elnath (Beta Tauri, mv= 1.65) between 7:52 and 8:42 hrs
November 20: Moon 1.8º south of the star Pollux (Beta Geminorum, mv= 1.1) at 13:09 hrs
November 21: Moon 2.4º north of Mars at 10:04 hrs
November 22: Venus 1.1º north of the star Nunki ((Sigma Sagittarii, mv= 2.02) at 22:12 hrs
November 26: Mercury at eastern stationary point at 12:32 hrs ( diameter - 8.4" )
November 27: Limb of Moon 45 arcminutes north of the star Spica (Alpha Virginis, mv= 0.98) at 22:24 hrs
December 1: Moon 1.8º north of the star Pi Scorpii (mv= 2.82) at 3:03 hrs
December 1: Limb of Moon 14 arcminutes south of the star Alniyat (Sigma Scorpii, mv= 2.9) at 14:53 hrs
December 1: Jupiter 1.1º north of the star 102 Iota Tauri (mv= 4.62) at 21:02 hrs
December 1: Limb of Moon 14 arcminutes north of the star Antares (Alpha Scorpii, mv= 0.88) at 19:03 hrs
December 1: Moon 2º north of the star 23 Tau Scorpii (mv= 2.82) at 21:45 hrs
December 2: Moon 4.9º south of Mercury at 11:03 hrs
December 3: Moon 1.7º north of the star Kaus Media (Delta Sagittarii, mv= 2.72) at 17:48 hrs
December 4: Limb of Moon 45 arcminutes south of the star Nunki (Sigma Sagittarii, mv= 2.02) at 5:28 hrs
December 5: Saturn at eastern quadrature at 2:08 hrs
December 5: Moon 1.9º south of Venus at 7:36 hrs
December 5: Moon 1.2º south of Pluto at 14:53 hrs
December 6: Mercury at inferior conjunction at 12:10 hrs ( diameter = 9.9" )
December 7: Mercury at perihelion 00:23 hrs ( diameter = 9.9" )
December 7: Mars at western stationary point at 10:18 hrs ( diameter = 12.2" )
December 7: Limb of Moon 6 arcminutes south of the star Deneb Algedi (Delta Capricorni, mv= 2.85) at 7:41 hrs
December 8: Venus 52 arcminutes north of Pluto at 00:42 hrs
December 8: Neptune at eastern stationary point at 5:49 hrs ( diameter = 3.3" )
December 8: Jupiter at opposition at 6:43 hrs ( diameter = 48.1" )
December 8: Limb of Moon 25 arcminutes north of Saturn at 18:46 hrs
December 9: Moon 1.1º north of Neptune at 18:39 hrs
December 13: Moon 4.4º north of Uranus at 16:45 hrs
December 14: Limb of Moon 25 arcminutes north of the star Alcyone ((Eta Tauri, mv= 2.85) at 5:22 hrs
December 15: Moon 5.8º north of Jupiter at 5:59 hrs
December 15: Limb of Moon <2 arcminutes south of the star Elnath (Beta Tauri, mv= 1.65) at 16:06 hrs
December 16: Mercury at western stationary point at 6:49 hrs ( diameter = 8.3" )
December 18: Moon 1.2º north of Mars at 18:09 hrs
December 19: Neptune at eastern quadrature at 00:23 hrs ( diameter = 2.2" )
December 22: Uranus 2.4º south of the star 63 Arietis (mv= 5.28) at 7:02 hrs
December 25: Limb of Moon 10 arcminutes north-east of the star Spica (Alpha Virginis, mv= 0.98) at 6:35 hrs
December 25: Mercury at Greatest Elongation West (21º 58') at 16:57 hrs ( diameter = 6.6" )
December 28: Moon 1.1º north of the star Pi Scorpii (mv= 2.82) at 13:34 hrs
December 28: Venus 58 arcminutes north of the star Deneb Algedi (Delta Capricorni, mv= 2.85) at 22:02 hrs
December 28: Moon occults the star Alniyat (Sigma Scorpii, mv= 2.9) between 21:28 and 21:59 hrs
December 29: Limb of Moon 23 arcminutes north of the star Antares (Alpha Scorpii, mv= 0.88) at 12:28 hrs
December 29: Moon 2º north of the star 23 Tau Scorpii (mv= 2.82) at 3:08 hrs
December 29: Moon 6.2º south of Mercury at 14:57 hrs
December 30: Moon 2.2º north of the star Kaus Media (Delta Sagittarii, mv= 2.72) at 23:42 hrs
December 31: Moon 1.3º south of the star Nunki (Sigma Sagittarii, mv= 2.02) at 15:02 hrs
Mercury:
Venus:
(The coloured fringes to the second, fourth and fifth images below are due to refractive effects in our own atmosphere, and are not intrinsic to Venus itself. The planet was closer to the horizon when these images were taken than it was for the first and third photographs, which were taken when Venus was at its greatest elongation from the Sun.)
October 2023 May-July 2024 January 2025 March 2025 April 2025
C
Because Venus is visible as the 'Evening Star' and as the 'Morning Star', astronomers of ancient times believed that it was two different objects. They called it Hesperus when it appeared in the evening sky and Phosphorus when it was seen before dawn. They also realised that these objects moved with respect to the so-called 'fixed stars' and so were not really stars themselves, but planets (from the Greek word for 'wanderers'). When it was finally realised that the two objects were one and the same, the two names were dropped and the Greeks applied a new name Aphrodite (Goddess of Love) to the planet, to counter Ares (God of War). We use the Roman versions of these names, Venus and Mars, for these two planets.
Venus at 6.55 pm on September 7, 2018. The phase is 36 % and the angular
diameter is 32 arcseconds.
Mars:
At the beginning of November, the red planet is cruising in an easterly direction in the western part of the constellation Cancer. It rises in the north-east just before midnight. The Earth is rapidly catching up to Mars, and it is becoming bigger and brighter with each passing week. On November 1 its angular diameter will be 9 arcseconds and its brightness will be magnitude 0.1. By the end of November its magnitude will have increased to -0.5 and its angular diameter to 11 arcseconds. On that date, it will be rising earlier, at 10:25 pm. On December 7, the fact that the Earth is catching up to Mars will cause the red planet to stop and reverse its motion against the background stars. It will begin what is called a "retrograde loop". It will complete this loop on February 24, 2025. Mars will reach opposition exactly midway between these two dates, on January 16, when its diameter will be 14.5 arcseconds and its brightness will be magnitude -1.38. By then its retrograde motion will have returned it to the constellation Gemini. The waning gibbous Moon will be in the vicinity of Mars on November 20 and 21.
In this image, the south polar cap of Mars is easily seen. Above it is a dark triangular area known as Syrtis Major. Dark Sinus Sabaeus runs off to the left, just south of the equator. Between the south polar cap and the equator is a large desert called Hellas. The desert to upper left is known as Aeria, and that to the north-east of Syrtis Major is called Isidis Regio. Photograph taken in 1971.
Mars photographed from Starfield Observatory, Nambour on June 29 and July 9,
2016, showing two different sides of the planet. The north polar cap is
prominent.
Brilliant Mars at left, shining at magnitude 0.9, passes in front of the dark molecular clouds in Sagittarius on October 15, 2014. At the top margin is the white fourth magnitude star 44 Ophiuchi. Its type is A3 IV:m. Below it and to the left is another star, less bright and orange in colour. This is the sixth magnitude star SAO 185374, and its type is K0 III. To the right (north) of this star is a dark molecular cloud named B74. A line of more dark clouds wends its way down through the image to a small, extremely dense cloud, B68, just right of centre at the bottom margin. In the lower right-hand corner is a long dark cloud shaped like a figure 5. This is the Snake Nebula, B72. Above the Snake is a larger cloud, B77. These dark clouds were discovered by Edward Emerson Barnard at Mount Wilson in 1905. He catalogued 370 of them, hence the initial 'B'. The bright centre of our Galaxy is behind these dark clouds, and is hidden from view. If the clouds were not there, the galactic centre would be so bright that it would turn night into day.
Mars near opposition, July 24, 2018
Mars, called the red planet but usually coloured orange, in mid-2018 took on a yellowish tint and brightened by 0.4 magnitude, making it twice as bright as previous predictions for the July 27 opposition. These phenomena were caused by a great dust storm which completely encircled the planet, obscuring the surface features so that they were only seen faintly through the thick curtain of dust. Although planetary photographers were mostly disappointed, many observers were interested to see that the yellow colour and increased brightness meant that a weather event on a distant planet could actually be detected with the unaided eye - a very unusual thing in itself.
The three pictures above were taken on the evening of July
24, at 9:05, 9:51 and 11:34 pm. Although the fine details that are usually
seen on Mars were hidden by the dust storm, some of the larger features can
be discerned, revealing how much Mars rotates in two and a half hours. Mars'
sidereal rotation period (the time taken for one complete rotation or
'Martian day') is 24 hours 37 minutes 22 seconds - a little longer than an
Earth day. The dust storm began in the Hellas Desert on May 31, and after
two months it still enshrouded the planet. In September it began to clear,
but by then the close approach had passed.
Central meridian: 295º.
The two pictures immediately above were taken on the evening of September 7, at 6:25 and 8:06 pm. The dust storm was finally abating, and some of the surface features were becoming visible once again. This pair of images also demonstrates the rotation of Mars in 1 hour 41 minutes (equal to 24.6 degrees of longitude), but this time the view is of the opposite side of the planet to the set of three above. As we were now leaving Mars behind, the images are appreciably smaller (the angular diameter of the red planet had fallen to 20 arcseconds). Well past opposition, Mars on September 7 exhibited a phase effect of 92.65 %.
Central meridian: 180º.
Jupiter: Jupiter passed though western quadrature (rising at midnight) on September 12. The almost Full Moon will be to the left of Jupiter, close to the north-eastern horizon soon after 9 pm on November 17. Jupiter will reach opposition on December 8.
Jupiter as
photographed from Nambour on the evening of April 25, 2017. The images were
taken, from left to right, at 9:10, 9:23, 9:49, 10:06 and 10:37 pm. The rapid
rotation of this giant planet in a little under 10 hours is clearly seen. In the
southern hemisphere, the Great Red Spot (bigger than the Earth) is prominent,
sitting within a 'bay' in the South Tropical Belt. South of it is one of the
numerous White Spots. All of these are features in the cloud tops of Jupiter's
atmosphere.
Jupiter at opposition, May 9, 2018
Jupiter as it appeared at 7:29 pm onNew Moon: December 1 16:22 hrs diameter = 30.2' Lunation #1261 begins New Moon: December 1 16:22 hrs diameter = 30.2' Lunation #1261 begins
July 2, 2017. The Great Red Spot was in a
similar position near Jupiter's eastern limb (edge) as in the fourth picture in
the series above. It will be seen that in the past two months the position of
the Spot had drifted when compared with the festoons in the Equatorial Belt, so
must rotate around the planet at a slower rate. In fact, the Belt enclosing the
Great Red Spot rotates around the planet in 9 hours 55 minutes, and the
Equatorial Belt takes five minutes less. This high rate of rotation has made the
planet quite oblate. The prominent 'bay' around the Red Spot in the five earlier
images appeared to be disappearing, and a darker streak along the northern edge
of the South Tropical Belt was moving south. In June this year the Spot began to
shrink in size, losing about 20% of its diameter. Two new white spots have
developed in the South Temperate Belt, west of the Red Spot. The five upper
images were taken near opposition, when the Sun was directly behind the Earth
and illuminating all of Jupiter's disc evenly. The July 2 image was taken just
four days before Eastern Quadrature, when the angle from the Sun to Jupiter and
back to the Earth was at its maximum size. This angle means that we see a tiny
amount of Jupiter's dark side, the shadow being visible around the limb of the
planet on the left-hand side, whereas the right-hand limb is clear and sharp.
Three of Jupiter's Galilean satellites are visible, Ganymede to the left and
Europa to the right. The satellite Io can be detected in a transit of Jupiter,
sitting in front of the North Tropical Belt, just to the left of its centre.
Jupiter reached opposition on May 9, 2018 at 10:21 hrs, and the above photographs were taken that evening, some ten to twelve hours later. The first image above was taken at 9:03 pm, when the Great Red Spot was approaching Jupiter's central meridian and the satellite Europa was preparing to transit Jupiter's disc. Europa's transit began at 9:22 pm, one minute after its shadow had touched Jupiter's cloud tops. The second photograph was taken three minutes later at 9:25 pm, with the Great Red Spot very close to Jupiter's central meridian.
The third photograph was taken at 10:20 pm, when Europa was approaching Jupiter's central meridian. Its dark shadow is behind it, slightly below, on the clouds of the North Temperate Belt. The shadow is partially eclipsed by Europa itself. The fourth photograph at 10:34 pm shows Europa and its shadow well past the central meridian. Europa is the smallest of the Galilean satellites, and has a diameter of 3120 kilometres. It is ice-covered, which accounts for its brightness and whitish colour. Jupiter's elevation above the horizon for the four photographs in order was 50º, 55º, 66º and 71º. As the evening progressed, the air temperature dropped a little and the planet gained altitude. The 'seeing' improved slightly, from Antoniadi IV to Antoniadi III. At the time of the photographs, Europa's angular diameter was 1.57 arcseconds. Part of the final photograph is enlarged below.
Jupiter at 11:34 pm on May 18, nine days later. Changes in the rotating cloud
patterns are apparent, as some cloud bands rotate faster than others and
interact. Compare with the first photograph in the line of four taken on May 9.
The Great Red Spot is ploughing a furrow through the clouds of the South
Tropical Belt, and is pushing up a turbulent bow wave.
Jupiter at opposition, June 11, 2019
Jupiter reached opposition on June 11, 2019 at 01:20 hrs, and the above
photographs were taken that evening, some twenty to twenty-two hours later. The
first image above was taken at 10:01 pm, when the Great Red Spot was leaving
Jupiter's central meridian and the satellite Europa was preparing to transit
Jupiter's disc.
The third photograph was taken at 10:41 pm, when Europa was about a third of its way across Jupiter. Its dark shadow is trailing it, slightly below, on the clouds of the North Temperate Belt. The shadow is partially eclipsed by Europa itself. The fourth photograph at 10:54 pm shows Europa and its shadow about a quarter of the way across. This image is enlarged below. The fifth photograph shows Europa on Jupiter's central meridian at 11:24 pm, with the Great Red Spot on Jupiter's limb. The sixth photograph taken at 11:45 pm shows Europa about two-thirds of the way through its transit, and the Great Red Spot almost out of sight. In this image, the satellite Callisto may be seen to the lower right of its parent planet. Jupiter's elevation above the horizon for the six photographs in order was 66º, 70º, 75º, 78º, 84º and 86º. As the evening progressed, the 'seeing' proved quite variable.
There have been numerous alterations to Jupiter's belts and spots over the thirteen months since the 2018 opposition. In particular, there have been major disturbances affecting the Great Red Spot, which appears to be slowly changing in size or "unravelling". It was very fortuitous that, during the evenings of the days when the 2018 and 2019 oppositions occurred, there was a transit of one of the satellites as well as the appearance of the Great Red Spot. It was also interesting in that the same satellite, Europa, was involved both times.
Jupiter's moon Europa has an icy crust with very high reflectivity, which
accounts for its brightness in the images above. On the other hand, the largest
moon Ganymede (seen below) has a surface which is composed of two types of
terrain: very old, highly cratered dark regions, and somewhat younger (but still
ancient) lighter regions marked with an extensive array of grooves and ridges.
Although there is much ice covering the surface, the dark areas contain clays
and organic materials and cover about one third of the moon. Beneath the surface
of Ganymede is believed to be a saltwater ocean with two separate layers.
Jupiter is seen here on 17 November
2022 at 8:39 pm. To its far right is its largest satellite, Ganymede. This
"moon" is smaller than the Earth but is bigger than Earth's Moon. Its diameter
is 5268 kilometres, but at Jupiter's distance its angular diameter is only 1.67
arcseconds. Despite its small size, Ganymede is the biggest moon in the Solar
System. Jupiter is approaching eastern quadrature, which means that Ganymede's
shadow is not behind it as in the shadows of Europa in the two sequences taken
at opposition. In the instance above as seen from Earth (which is presently at a
large angle from a line joining the Sun to Ganymede), the circular shadow of
Ganymede is striking the southern hemisphere cloud tops of Jupiter itself. The
shadow is slightly distorted as it strikes the spherical globe of Jupiter. If
there were any inhabitants of Jupiter flying across the cloud bands above, and
passing through the black shadow, they would experience an eclipse of the
distant Sun by the moon Ganymede.
Above is a 7X enlargement of Ganymede, showing markings on its rugged, icy
surface. The dark area in its northern hemisphere is called Galileo Regio.
Saturn:
The ringed planet is located in the constellation of Aquarius, and will remain there until it crosses into Pisces on April 19, 2025. Saturn reached opposition with the Sun on September 8 and on November 15 may be found a handspan north of the zenith
Left: Saturn showing the Rings when edge-on. Right: Over-exposed Saturn surrounded by its satellites Rhea, Enceladus, Dione, Tethys and Titan - February 23/24, 2009.
The photograph above was taken at 8:33 pm on October 29, 2024, 51 days after opposition. The shadow of the planet once more falls across the far side of the rings, but in the intervening 11 months the angle of the rings as seen from
Earth has lessened considerably. The ring system will be difficult to observe during 2025. The light-coloured equatorial zone on Saturn is prominent, and is crossed by the black shadow of the rings on the planet. 
The photograph above was taken at 7:41 pm on December 07, 2023, 14 days after
eastern quadrature. The shadow of the planet once more falls across the far side
of the rings, but in the intervening 13 months the angle of the rings as seen
from Earth has lessened considerably. The light-coloured equatorial zone on
Saturn shows through the gap known as the Cassini Division.
The change in aspect of Saturn's rings is caused by the plane of the ring system being aligned with Saturn's equator, which is itself tilted at an angle of 26.7 degrees to Saturn's orbit. As the Earth's orbit around the Sun is in much the
same plane as Saturn's, and the rings are always tilted in the same direction in space, as we both orbit the Sun, observers on Earth see the configuration of the rings change from wide open (top large picture) to half-open (bottom large
picture) and finally to edge on (small picture above). This cycle is due to Saturn taking 29.457 years to complete an orbit of the Sun, so the complete cycle from
"edge-on (2009) → view of Northern hemisphere, rings half-open (2013) →
wide-open (2017) → half-open (2022) → edge-on (2025) → view of Southern
hemisphere, rings half-open (2029) → wide-open (2032) → half-open (2036) →
edge-on (2039)"
takes 29.457 years. The angle of the rings will continue to reduce until they
are edge-on again in 2025. They will appear so thin that it will seem that
Saturn has no rings at all.
Uranus:
Neptune:
T
Neptune, photographed from Nambour on October 31, 2008
Pluto: The
erstwhile ninth and most distant planet passed through
The movement of the dwarf planet Pluto in two days, between 13 and 15 September,
2008. Pluto is the one object that has moved.
Width of field:
200 arcseconds
This is a stack of four images, showing the movement of Pluto over the period October 22 to 25, 2014. Pluto's image for each date appears as a star-like point at the upper right corner of the numerals. The four are equidistant points on an almost-straight line. Four eleventh magnitude field stars are identified. A is GSC 6292:20, mv = 11.6. B is GSC 6288:1587, mv = 11.9. C is GSC 6292:171, mv = 11.2.
D is GSC 6292:36, mv = 11.5. (GSC = Guide Star Catalogue). The position of Pluto on October 24 (centre of image) was at Right Ascension = 18 hours 48 minutes 13 seconds, Declination = -20º 39' 11". The planet moved 2' 51" with respect to the stellar background during the three days between the first and last images, or 57 arcseconds per day, or 1 arcsecond every 25¼ minutes.
Here are the positions of the planets above the horizon in mid-November, at
midnight: Saturn is at an altitude of 19º (about a handspan) above the western horizon. 14.3º (about three-quarters of a handspan) east of Saturn is Neptune, which will require the use of a small telescope to find. Uranus
has passed through culmination (crossing the
meridian or north-south line), and is about 43º above the northern horizon. Jupiter has an altitude of two handspans above the north-north-eastern horizon, and Mars is
half-a-handspan above the north-eastern horizon (Jupiter is much brighter than Mars).
The movements of planets including their alignments and close-up images can be watched using the freeware
Meteor
Showers:
N Taurids
November 13 and 14
Waxing gibbous Moon, 88% sunlit ZHR = 15
On November 1 there will be a fine grouping of Mars, Jupiter and Uranus in the north-eastern sky
after midnight. It will be quite spectacular, as the star clusters the Pleiades (Seven Sisters) and the Hyades will be nearby, as well as the bright stars Alderbaran, Betelgeuse and Capella. Not far away will be the stars Sirius, Rigel and Procyon,
and the Twins Pollux and Castor.. Mars is moving slowly eastwards during
November, cruising through Cancer. This movement will stop on December 7, and
Mars will head westwards, back towards Gemini. It will be performing what is
called a "retrograde loop". This movement is actually caused by the fact that
the Earth is catching up and overtaking the red planet. When Mars reaches the
centre of this loop it is sais to be at "opposition", when it is at its largest
and brightest. Jupiter will move away from the clusters in Taurus, also heading towards Gemini,
but it won't reach that constellation until June 12 next year. The waning crescent
Moon will pass through this grouping from November 16 to 21.
S Taurids
November 3 and 4
Waxing crescent Moon, 2% sunlit ZHR = 15
Radiant: Near the Pleiades star cluster. Associated with Comet
Encke
Radiant: Near the Pleiades star cluster. Associated with
Comet Encke
Leonids
November 17 and 18
Waning gibbous Moon, 96% sunlit ZHR =
12
Radiant: Near the third magnitude star Adhafera, in the Lion's mane.
Associated with Comet Tempel-Tuttle
Us
ZHR
Although most meteors are found in swarms associated with debris from comets, there are numerous 'loners', meteors travelling on solitary
paths through space. When these enter our atmosphere, unannounced and at any time, they are known as 'sporadics'. On an average clear and dark evening, an
observer can expect to see about ten meteors per hour. They burn up to ash in their passage through our atmosphere. The ash slowly settles to the ground as
meteoric dust. The Earth gains about 80 tonnes of such dust every day, so a percentage of the soil we walk on is actually interplanetary in origin. If a
meteor survives its passage through the air and reaches the ground, it is called a 'meteorite'. In the past, large meteorites (possibly comet nuclei or small asteroids) collided with the Earth and produced huge craters which still exist
today. These craters are called 'astroblemes'. Two famous ones in Australia are Wolfe Creek Crater and Gosse's Bluff. The Moon and Mercury are covered with such
astroblemes, and craters are also found on Venus, Mars, planetary satellites, minor planets, asteroids and even comets.
Comets:
This periodic comet returns every 71 years, and is in our western twilight sky at present. Look due west, close to the horizon as soon as the sky darkens. On 16 July, the comet was near the magnitude 2.2 star Suhail (Lambda Velorum).
This comet was discovered on 2 March 2022 at the Zwicky Transient Facility (ZTF)
at the Hale Observatory on Mount Palomar. It was found on CCD images taken by
the famous 48-inch Schmidt Telescope. It
Both of these comets appeared recently in orbits that caused them to dive
towards the Sun's surface before swinging around the Sun and heading back
towards the far reaches of the Solar System. Such comets are called 'Sun
grazers', and their close approach to the Sun takes them through its immensely
powerful gravitational field and the hot outer atmosphere called the 'corona'.
They brighten considerably during their approach, but most do not survive and
disintegrate as the ice which holds them together melts. While expectations were
high that these two would emerge from their encounter and put on a display as
bright comets with long tails when they left the Sun, as they came close to the
Sun they both broke up into small fragments of rock and ice and ceased to exist.
Comet 46P/Wirtanen In December 2018, Comet 46P/Wirtanen swept
past Earth, making one of the ten closest approaches of a comet to our planet
since 1960. It was faintly visible to the naked eye for two weeks. Although
Wirtanen's nucleus is only 1.2 kilometres across, its green atmosphere
became larger than the Full Moon, and was an easy target for binoculars and
small telescopes. It reached its closest to the Sun (perihelion) on December 12,
and then headed in our direction. It passed the Earth at a distance of 11.5
million kilometres (30 times as far away as the Moon) on December 16, 2018.
Green Comet ZTF (C/2022 E3)
Comet SWAN (C/2020 F8) and Comet ATLAS (2019 Y4)
Comet Lulin
This comet, (C/2007 N3), discovered
Comet Lulin at 11:25 pm on February 28, 2009, in Leo. The brightest star is Nu Leonis, magnitude 5.26.
The
LINEARNearly all of these programs are based in the northern hemisphere, leaving gaps in the coverage of the southern sky. These gaps are the areas of sky where amateur astronomers look for comets from their backyard observatories.
To find out more about current comets, including finder charts showing exact positions and magnitudes, click
here. To see pictures of these comets, click here.
The 3.9 metre Anglo-Australian Telescope (AAT) at the Australian Astronomical Observatory near Coonabarabran, NSW.
Deep Space
Sky Charts and Maps available on-line:
There are some useful
representations of the sky available here. The sky charts linked below show the
sky as it appears to the unaided eye. Stars rise four minutes earlier each
night, so at the end of a week the stars have gained about half an hour. After a
month they have gained two hours. In other words, the stars that were positioned
in the sky at 8 pm at the beginning of a month will have the same positions at 6
pm by the end of that month. After 12 months the stars have gained 12 x 2 hours
= 24 hours = 1 day, so after a year the stars have returned to their original
positions for the chosen time. This accounts for the slow changing of the starry
sky as the seasons progress.
The following interactive sky charts are courtesy of Sky and Telescope magazine. They can simulate a view of the sky from any location on Earth at any time of day or night between the years 1600 and 2400. You can also print an all-sky map. A Java-enabled web browser is required. You will need to specify the location, date and time before the charts are generated. The accuracy of the charts will depend on your computer’s clock being set to the correct time and date.
To produce a real-time sky chart (i.e. a chart showing the sky at the instant the chart is generated), enter the name of your nearest city and the country. You will also need to enter the approximate latitude and longitude of your observing site. For the Sunshine Coast, these are:
latitude: 26.6o South longitude: 153o East
Then enter your time, by scrolling down through the list of cities to "Brisbane: UT + 10 hours". Enter this one if you are located near this city, as Nambour is. The code means that Brisbane is ten hours ahead of Universal Time (UT), which is related to Greenwich Mean Time (GMT), the time observed at longitude 0o, which passes through London, England. Click here to generate these charts.
_____________________________________
Similar real-time charts can also be generated from another source, by following
this second link:
The first, circular chart will show the full hemisphere of sky overhead. The zenith is at the centre of the circle, and the cardinal points are shown around the circumference, which marks the horizon. The chart also shows the positions of the Moon and planets at that time. As the chart is rather cluttered, click on a part of it to show that section of the sky in greater detail. Also, click on Update to make the screen concurrent with the ever-moving sky.
The stars and constellations around the horizon to an elevation of about 40o can be examined by clicking on
The view can be panned around the horizon, 45 degrees at a time. Scrolling down the screen will reveal tables showing setup and customising options, and an Ephemeris showing the positions of the Sun, Moon and planets, and whether they are visible at the time or not. These charts and data are from YourSky, produced by John Walker.
The charts above and the descriptions below assume that the observer has a good observing site with a low, flat horizon that is not too much obscured by buildings or trees. Detection of fainter sky objects is greatly assisted if the observer can avoid bright lights, or, ideally, travel to a dark sky site. On the Sunshine Coast, one merely has to travel a few kilometres west of the coastal strip to enjoy magnificent sky views. On the Blackall Range, simply avoid streetlights. Allow your eyes about 15 minutes to become dark-adapted, a little longer if you have been watching television. Small binoculars can provide some amazing views, and with a small telescope, the sky’s the limit.
This month,
The stars of Sagittarius and Ophiuchus are setting low in the west-south-west, but earlier in the evening the planets
Mercury and Venus would have been visible in the latter
constellation, but very close to the horizon. Just above Sagittarius, the faint stars of Capricornus,
the Sea-goat, will be gone before midnight, followed by the next faint
constellation, Aquarius, the Water Bearer. This month, Aquarius is host to the
gas giant planet Saturn., whose rings are at present very thin as seen
from Earth. There are no
stars brighter than third magnitude in Aquarius, but it does contain many interesting objects, including a group of four stars known as the 'Water Jar'. The
constellation of Pisces, the Fishes crosses the meridian at 9 pm in mid-November, and it hosts the
faint planet, Neptune . A well-known asterism in Pisces is the
Circlet, a faint circle of seven fourth and fifth magnitude stars. Pisces is followed by Aries,
the Ram, and closer to the north-eastern horizon is the constellation Taurus,
the Bull, where the planets Uranus and Jupiter are currently located.
The
centre of the Lagoon Nebula The first magnitude star Altair (Alpha Aquilae) can be seen approaching
the horizon a little north of west. Altair is the brightest star in the constellation Aquila, the Eagle. It has a fainter star above and another below, making a
vertical line of three, quite close together. These stars, from top to bottom, are Alshain, Altair and Tarazed, and they indicate the Eagle's body.
A handspan east of the bright, first magnitude Altair is a faint but easily recognised diamond-shaped group of stars, Delphinus the Dolphin. The Great Square of
Pegasus is beginning to tilt over towards the north-west, and Andromeda and Triangulum are above the northern horizon.
The names of the four stars marking the corners of the Square (starting at the top-left one and moving in a
clockwise direction around the Square) are Markab, Algenib, Alpheratz and Scheat. Although these four stars are known as the Great Square of
Pegasus, only three are actually in the constellation of Pegasus, the Winged Horse. In point of fact, Alpheratz is the brightest star of the constellation
Andromeda, the Chained Maiden. This is the best time of year to observe two close spiral galaxies, for they are due north and
at their highest elevation. M31 (in Andromeda) and M33 (in Triangulum) are members of the Local Group of galaxies (our Milky Way is a third member),
and can be easily seen with good binoculars. They are the nearest galaxies that can be observed from the large observatories in the Northern Hemisphere. Andromeda trails down from Alpheratz to below the north-eastern horizon. To its right is the zodiacal constellation of Aries, now well up in the
north-east. The brightest star in Aries is a second magnitude orange star called Hamal.
Taurus, with its two star clusters the Pleiades and the Hyades, is well above the north-eastern horizon, below Aries. The
Pleiades is a small group like a question mark, and is often called the Seven Sisters, although excellent eyes are needed to detect the seventh star without optical
aid. The group is also known as ‘Santa’s Sleigh’, as it appears around Christmas time. All the stars in this cluster are hot and blue. They are also the same age, as they
formed as a group out of a gas cloud or nebula. There are actually more than 250 stars in the Pleiades. The Japanese name for this cluster is 'Subaru', and
the cars of that make have a representation of the cluster as their badge. The Hyades cluster appears larger, with the appearance of a capital A or inverted V. At the foot of its right leg is a bright orange star called
Aldebaran (Alpha Tauri). The V shape looked to the ancients like the face of a bull, with Aldebaran as his angry orange eye. Being in the southern hemisphere,
we see it upside down. The Pleiades form the bull’s shoulder. Jupiter is
so bright that it dominates this part of the sky. It is currently between the Bull's long horns, and will cross into Gemini on
June 12 next year. Uranus is also in Taurus at present. The red planet Mars crossed from Gemini into Cancer on
October 30 last, and will continue its easterly movement through that
constellation until December 7, when it will be near the Praesepe Star Cluster
(M44). On that date it will begin its retrograde loop, heading back towards
Gemini, which it will re-enter on January 13. Mars will reach opposition on
January 16, when its brightness will have reached magnitude -1.38 and its
diameter will be 14.5 arcseconds. On that date, the Earth will overtake Mars,
and the distance between us will be 60 million kilometres, close to its minimum
distance.
The Pleiades is the small cluster at centre left, while the Hyades is the much larger grouping at centre right.
Wisps of gas can be seen around the brighter stars in the Pleiades cluster.
Orion the Hunter is rising in the east, and to its right is his Great Dog (Canis Major), marked by the brilliant white star Sirius
(the Dog Star), quite close to the horizon. Sirius is the brightest star in the night sky, because it is one of our closest neighbours, only 8.6 light-years
away. The second-brightest star in the night sky is Canopus, which is two handspans to the right of Sirius, high in the south-east.
It is bright, not because it is close, (as it is at a distance of 312 light-years, 36 times further away than Sirius), but because it is in fact a
supergiant star. About one handspan south-east of the zenith is a bright first-magnitude white star, Achernar (Alpha
Eridani). Achernar, the ninth brightest star, is at one end of a very long, faint constellation, Eridanus, the River. It winds all the way from Achernar to
Cursa (Beta Eridani), a 2.9 magnitude star just above Rigel, the brightest star in Orion (see below).
The Stars and Constellations for this month:
These descriptions of the night sky are for 10 pm on November 1 and 8 pm on November 30. Broadly speaking, the following description starts low in the
south-west and follows the zodiac, and then follows the western horizon to the right, heading round to the east, then south, then overhead.
Achernar is midway between two other bright stars, Canopus and Fomalhaut. The latter is a handspan south-west of the zenith. Slightly north of the zenith is a
mv 2.2 star. This is Beta Ceti, the brightest ordinary star in the constellation Cetus, the Whale. Its common name is Diphda,
and it has a yellowish-orange colour. By rights, the star Menkar or Alpha Ceti should be brighter, but Menkar is
actually more than half a magnitude fainter than Diphda. Menkar may be seen high in the north-east, halfway between
Diphda and Aldebaran.
Above Diphda is Fomalhaut, a bright, white first magnitude star in the faint constellation Piscis Austrinus, the Southern Fish. Fomalhaut is almost directly overhead at 8 pm on November 1. South-west of Fomalhaut is a large, upside-down flattened triangle of stars, Grus, the Crane. North of Achernar, the faint constellation of Phoenix may be seen. Its brightest star is Ankaa, a mv 2.39 star which is halfway between Fomalhaut and Achernar.
Cetus is a large constellation, and to the unaided eye it appears unremarkable. But it does contain a most interesting star, which was discovered before the telescope was invented. It is named Mira, the Wonderful (see below). Between Cetus and Pegasus is the zodiacal constellation of Pisces, the Fishes. Pisces is found just above Aries. Moving westwards from Cetus we see the zodiacal constellations of Aquarius, then Capricornus.
Rising in the south-east are the stars of the constellation Carina, and the False Cross. The true Southern Cross (Crux) is below the southern horizon, but will rise soon after midnight. Above the horizon due south, is the small constellation of Musca, the Fly. Musca is a circumpolar constellation, i.e. it is always in our sky, being too close to the South Celestial Pole to set. Alpha Centauri is close to the horizon nearby.
The zodiacal constellations visible tonight, starting from the south-western horizon and heading overhead to the north-east horizon, are Sagittarius, Capricornus, Aquarius, Pisces, Aries and Taurus.
If you would like to become familiar with the constellations, we suggest that you access one of the world's best collections of constellation pictures by clicking
here . To see some of the best astrophotographs taken with the giant Anglo-Australian Telescope, click
The amazing thing about the star Mira or Omicron Ceti is that it varies dramatically in brightness, rising to magnitude 2 (brighter than any other star in Cetus), and then dropping to magnitude 10 (requiring a telescope to detect it), over a period of 332 days.
This drop of eight magnitudes means that its brightness diminishes over a period of five and a half months to one six-hundredth of what it had been, and then over the next five and a half months it regains its original brightness. The seventeenth century Polish astronomer Johannes Hevelius named it Mira, meaning 'The Wonderful' or 'The Miraculous One'.
We now know that many stars vary in brightness, even our Sun doing so to a small degree, with a period of 11 years. One type of star varies, not because it is actually becoming less bright in itself, but because another, fainter star moves around it in an orbit roughly in line with the Earth, and obscures it on each pass. This type of star is called an eclipsing variable and they are very common.
The star Mira though, varies its light output because of processes in its interior. It is what is known as a pulsating variable. Stars of the Mira type are giant pulsating red stars that vary between 2.5 and 11 magnitudes in brightness. They have long, regular periods of pulsation which lie in the range from 80 to 1000 days.
In 2022, Mira reached a maximum brightness of magnitude 3.4 on July 16 and then
faded slowly, dropping well below naked-eye visibility (magnitude 9) by February
of 2023. It then brightened rapidly, and reached that year's maximum on June 13.
Now it has faded again, and reached its minimum brightness early in 2024. A
small telescope was needed in order to find it. By Easter it brightened again
and reached maximum brightness on May 10, 2024. It was then a morning sky
object, rising on that day at 4:48 am. Each
of these cycles lasts 332 days. Mira is now fading and will reach a minimum
around this coming Christmas. It will then brighten again and will reach its
next maximum on April 6, 2025. On that date it will rise at 7:03 am and set at
7:17 pm.
Mira near minimum, 26 September 2008 Mira near maximum, 22 December 2008
Double and multiple stars
Estimates vary that between 15% and 50% of stars are single bodies like our Sun, although the latest view is that less than 25% of stars are solitary. At least 30% of stars and possibly as much as 60% of stars are in double systems, where the two stars are gravitationally linked and orbit their mutual centre of gravity. Such double stars are called binaries. The remaining 20%+ of stars are in multiple systems of three stars or more. Binaries and multiple stars are formed when a condensing Bok globule or protostar splits into two or more parts.
Binary stars may have similar components (Alpha Centauri A and B are both stars like our Sun), or they may be completely dissimilar, as with Albireo (Beta Cygni, where a bright golden giant star is paired with a smaller bluish main sequence star).
The binary stars Rigil Kentaurus (Foot of the Centaur, or Alpha Centauri) at left, and Beta Cygni (Albireo), at right.
Rigel (Beta Orionis, left) is a binary star which is the seventh brightest star in the night sky. Rigel A is a large white supergiant which is 500 times brighter than its small companion, Rigel B, Yet Rigel B is itself composed or a very close pair of Sun-type stars that orbit each other in less than 10 days. Each of the two stars comprising Rigel B is brighter in absolute terms than Sirius (see above). The Rigel B pair orbit Rigel A at the immense distance of 2200 Astronomical Units, equal to 12 light-days. (An Astronomical Unit or AU is the distance from the Earth to the Sun.) In the centre of the Great Nebula in Orion (M42) is a multiple star known as the Trapezium (right). This star system has four bright white stars, two of which are binary stars with fainter red companions, giving a total of six. The hazy background is caused by the cloud of fluorescing hydrogen comprising the nebula.
Acrux, the brightest star in the Southern Cross, is also known as Alpha Crucis. It is a close binary, circled by a third dwarf companion.
Alpha Centauri (also known as Rigil Kentaurus, Rigil Kent or Toliman) is a binary easily seen with the smallest telescope. The components are both solar-type main sequence stars, one of type G and the other, slightly cooler and fainter, of type K. Through a small telescope this star system looks like a pair of distant but bright car headlights. Alpha Centauri A and B take 80 years to complete an orbit, but a tiny third component, the 11th magnitude red dwarf Proxima takes about 1 million years to orbit the other two. It is about one tenth of a light year from the bright pair and a little closer to us, hence its name. This makes it our nearest interstellar neighbour, with a distance of 4.3 light years. Red dwarfs are by far the most common type of star, but, being so small and faint, none is visible to the unaided eye. Because they use up so little of their energy, they are also the longest-lived of stars. The bigger a star is, the shorter its life.
Close-up of the star field around Proxima Centauri
Knowing the orbital period of the two brightest stars A and B, we can apply Kepler’s Third Law to find the distance they are apart. This tells us that Alpha Centauri A and B are about 2700 million kilometres apart or about 2.5 light hours. This makes them a little less than the distance apart of the Sun and Uranus (the orbital period of Uranus is 84 years, that of Alpha Centauri A and B is 80 years.)
Albireo (Beta Cygni) is sometimes described poetically as a large topaz with a small blue sapphire. It is one of the sky’s most beautiful objects. The stars are of classes G and B, making a wonderful colour contrast. It lies at a distance of 410 light years, 95 times further away than Alpha Centauri.
Binary stars may be widely spaced, as the two examples just mentioned, or so close that a small telescope is struggling to separate them (Acrux, Castor, Antares, Sirius). Even closer double stars cannot be split by even large telescope, buts the spectroscope can disclose their true nature by revealing clues in the absorption lines in their spectra. These examples are called spectroscopic binaries. In a binary system, closer stars will have shorter periods for the stars to complete an orbit. Eta Cassiopeiae takes 480 years for the stars to circle each other. The binary with the shortest period is AM Canum Venaticorum, which takes only 17½ minutes.
Sometimes one star in a binary system will pass in front of the other one, partially blocking off its light. The total light output of the pair will be seen to vary, as regular as clockwork. These are called eclipsing binaries, and are a type of variable star, although the stars themselves usually do not vary.
Why are some constellations bright, while others are faint ?
The Milky Way is a barred spiral galaxy some 100000 – 120000 light-years in diameter which contains 100 – 400 billion stars. It may contain at least as many planets as well. Our galaxy is shaped like a flattened disc with a central bulge. The Solar System is located within the disc, about 27000 light-years from the Galactic Centre, on the inner edge of one of the spiral-shaped concentrations of gas and dust called the Orion Arm. When we look along the plane of the galaxy, either in towards the centre or out towards the edge, we are looking along the disc through the teeming hordes of stars, clusters, dust clouds and nebulae. In the sky, the galactic plane gives the appearance which we call the Milky Way, a brighter band of light crossing the sky. This part of the sky is very interesting to observe with binoculars or telescope. The brightest and most spectacular constellations, such as Crux, Canis Major, Orion and Scorpius are located close to the Milky Way.
If we look at ninety degrees to the plane, either straight up and out of the galaxy or straight down, we are looking through comparatively few stars and gas clouds and so can see out into deep space. These are the directions of the north and south galactic poles, and because we have a clear view in these directions to distant galaxies, these parts of the sky are called the intergalactic windows. The southern window is in the constellation Sculptor, not far from the star Fomalhaut. This window is well-placed for viewing this month, and many distant galaxies can be observed in this area of the sky. The northern window is between the constellations Virgo and Coma Berenices, roughly between the stars Denebola and Arcturus. It is below the horizon in the evenings this month.
Some of the fainter and apparently insignificant constellations are found around these windows, and their lack of bright stars, clusters and gas clouds presents us with the opportunity to look across the millions of light years of space to thousands of distant galaxies.
The Milky Way
A glowing band of light crossing the sky is especially noticeable during the winter months, but it
is far less noticeable this month, virtually skirting the horizon at 9 pm. This glow is the light of millions of faint stars combined with that coming from glowing gas
clouds called nebulae. It is concentrated along the plane of our galaxy, and at the beginning of November it can be seen at 7:30 pm running from
south-south-west to north-north-west, reaching a maximum elevation above the horizon of about two handspans, due west. Constellations in the Milky Way
at this time tonight will run from Centaurus through Scorpius, Sagittarius and Aquila to Cygnus.
The plane of our galaxy from
Scutum (at left) through Sagittarius and Scorpius (centre) to Centaurus and Crux
(right). The Eta Carinae nebula is at the right margin, below centre.
The Coalsack is clearly visible, and the dark dust lanes can be seen. Taken with an
ultra-wide-angle lens.
It is rewarding to scan along this band with a pair of binoculars, looking for star clusters and emission nebulae. Dust lanes along the plane of the Milky Way appear to split it in two in some parts of the sky. One of these lanes can be easily seen, starting near Alpha Centauri and heading towards Antares.
The centre of our galaxy. The constellations partly visible here are Sagittarius (left), Ophiuchus (above centre) and Scorpius (at right). The planet Jupiter is the bright object below centre left. This is a normal unaided-eye view.
Finding the South Celestial Pole
The South Celestial Pole is that point in the southern sky around which the stars rotate in a clockwise direction. The Earth's axis is aimed exactly at this point. For an equatorially-mounted telescope, the polar axis of the mounting also needs to be aligned exactly to this point in the sky for accurate tracking to take place.
To find this point, first locate the Southern Cross. Project a line from the orange star at the top of the Cross (Gacrux) to the star at its base (Acrux) and continue straight on towards the south (to the left) for another four Cross lengths. This will locate the approximate spot. There is no bright star to mark the Pole, whereas in the northern hemisphere they have Polaris (the Pole Star) to mark fairly closely the North Celestial Pole.
Another way to locate the South Celestial Pole is to draw an imaginary straight line joining Beta Centauri low in the south-south-west to Achernar high in the south-east. Bisect this imaginary line to locate the pole. Neither method is much use on November evenings in Queensland as the Cross is below our southern horizon until after midnight and Beta Centauri is close to the horizon.
Interesting photographs of this area can be taken by using a camera on time exposure. Set the camera on a tripod pointing due south, and open the shutter for thirty minutes or more. The stars will seem to move during the exposure, being recorded on the film as short arcs of a circle. The arcs will be different colours, as the stars are. All the arcs will have a common centre of curvature, which is the south celestial pole.
A wide-angle view of trails around the South Celestial Pole, with Scorpius and Sagittarius at left, Crux and Centaurus at top, and Carina and False Cross at right.
Star trails between the South Celestial Pole and the southern horizon. All stars that do not pass below the horizon are circumpolar.
Star clusters
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The two clusters in Taurus, the Pleiades and the Hyades, are known as Open Clusters or Galactic Clusters. The name 'open cluster' refers to the fact that the stars in the cluster are grouped together, but not as tightly as in globular clusters (see below). The stars appear to be loosely arranged, and this is partly due to the fact that the cluster is relatively close to us, i.e. within our galaxy, hence the alternate name, 'galactic cluster'. These clusters are generally formed from the condensation of gas in a nebula into stars, and some are relatively young.
The photograph below shows a typical open cluster,
M7*. It lies in the constellation Scorpius, just above the scorpion's sting. It lies in the direction of our galaxy's centre. The cluster itself is the group of white stars in the centre of the field. Its distance is about 380 parsecs or 1240 light years.
Galactic Cluster M7 in Scorpius, known as Ptolemy's cluster
Outside the plane of our galaxy, there is a halo of Globular Clusters. These are very old, dense clusters, containing perhaps several hundred thousand stars, in some cases . These stars are closer to each other than is usual, and because of its great distance from us, a globular cluster gives the impression of a solid mass of faint stars. Many other galaxies also have a halo of globular clusters circling around them.
The largest and brightest globular cluster in the sky is NGC 5139** , also known as Omega Centauri. It has a slightly oval shape. It is an outstanding winter object, but this month it is below the horizon for most of the night. Shining at fourth magnitude, it is faintly visible to the unaided eye, but is easily seen with binoculars, like a light in a fog. A telescope of 20 cm aperture or better will reveal its true nature, with hundreds of faint stars giving the impression of diamond dust on a black satin background. It lies at a distance of 5 kiloparsecs, or 16 300 light years.
Although Omega Centauri is poorly placed for viewing this month, there is another remarkable globular, second only to Omega, which is in a good position. Close to the SMC (see below), binoculars can detect a fuzzy star. A telescope will reveal this faint glow as a magnificent globular cluster, lying at a distance of 5.8 kiloparsecs. Its light has taken almost 19 000 years to reach us. This is
NGC 104, commonly known as 47 Tucanae. Some regard this cluster as being more spectacular than Omega Centauri, as it is more compact, and the faint stars twinkling in its core are very beautiful. This month, Omega Centauri is not at a good position for viewing, but 47 Tucanae is well placed before midnight.
The globular cluster 47 Tucanae
Observers aiming their telescopes towards the SMC generally also look at the nearby 47 Tucanae, but there is another globular cluster nearby which is also worth a visit. This is NGC 362, which is less than half as bright as the other globular, but this is because it is more than twice as far away. Its distance is 12.6 kiloparsecs or 41 000 light years, so it is about one-fifth of the way from our galaxy to the SMC. Both NGC 104 and NGC 362 are always above the horizon for all parts of Australia south of the Tropic of Capricorn.
* M7:
This number means that
Ptolemy's Cluster in Scorpius is No. 7 in a list of 103
astronomical objects compiled and published in 1784 by Charles Messier.
Charles was interested in the discovery of new comets, and his aim was to
provide a list for observers of fuzzy nebulae and clusters which could easily be
reported as comets by mistake. Messier's search for comets is now just a
footnote to history, but his list of 103 objects is well known to all
astronomers today, and has even been extended to 110 objects. ** NGC 5139: This
number means that Omega Centauri is No. 5139 in the New General Catalogue of
Non-stellar Astronomical Objects. This catalogue was first published in 1888
by J. L. E. Dreyer under the auspices of the Royal Astronomical Society, as his New
General Catalogue of Nebulae and Clusters of Stars. As larger telescopes
built early in the 20th century discovered fainter objects in space, and also
dark, obscuring nebulae and dust clouds, the NGC was supplemented with the
addition of the Index Catalogue (IC). Many non-stellar objects in the sky
have therefore NGC numbers or IC numbers. For example, the famous Horsehead
Nebula in Orion is catalogued as IC 434. The NGC was revised in 1973, and lists
7840 objects. The recent explosion of discovery in
astronomy has meant that more and more catalogues are being produced, but they
tend to specialise in particular types of objects, rather than being
all-encompassing, as the NGC / IC try to be. Some examples are the Planetary
Nebulae Catalogue (PK) which lists 1455 nebulae, the Washington Catalogue
of Double Stars (WDS) which lists 12 000 binaries, the General Catalogue
of Variable Stars (GCVS) which lists 28 000 variables, and the Principal
Galaxy Catalogue (PGC) which lists 73 000 galaxies. The largest modern
catalogue is the Hubble Guide Star Catalogue (GSC) which was assembled to
support the Hubble Space Telescope's need for guide stars when photographing sky
objects. The GSC contains nearly 19 million stars brighter than magnitude 15.
Two close galaxies
Above the south-south-eastern horizon, two faint smudges of light may be seen. These are the two
Clouds of
Magellan, known to astronomers as the LMC (Large Magellanic Cloud)
and the SMC (Small Magellanic Cloud). The LMC is below the SMC,
and is noticeably larger. They lie at distances of 190 000 light years for the
LMC, and 200 000 light years for the SMC. They are about 60 000 light years
apart. These dwarf galaxies circle our own much larger galaxy, the Milky Way.
The LMC is slightly closer, but this does not account for its larger appearance.
It really is larger than the SMC, and has developed as an under-sized barred
spiral galaxy.
The Large
Magellanic Cloud - the bright knot of gas to left of centre is the famous
Tarantula Nebula
These two Clouds are the closest galaxies to our own, but lie too far south to be seen by the large telescopes in Hawaii, California and Arizona. They are 15 times closer than the famous Andromeda and Triangulum galaxies in the northern half of the sky, and so can be observed in much clearer detail. Our great observatories in Australia, both radio and optical, have for many years been engaged in important research involving these, our nearest inter-galactic neighbours.
The LMC is less than a handspan above the horizon, and the SMC is a little more than a handspan above and slightly to the right of the LMC.
The Andromeda Galaxy and the President of the United States
In 1901, U.S.A. President William McKinley was assassinated and his Vice-President,
Theodore Roosevelt, took his place. Theodore became a popular President, and was elected in his own right in 1904 for a second term. He was known as Teddy Roosevelt, and the Teddy Bear is named after him. As President he was a dynamic, vigorous and energetic man, very keen on preserving the wonders of nature through the creation of national parks, forests, and natural monuments such as Rainbow Bridge.Teddy made the acquaintance of noted American naturalist, scientist, explorer and author
William Beebe who shared his love of nature. They became friends and would meet regularly for dinner and an evening's conversation, sometimes with friends of similar interests. Both men had strong egos, but recognised the dangers of pride in themselves and in their accomplishments.It is said that after dinner, Roosevelt, Beebe and their friends would step outside for cigars and lengthy discussions about world affairs. At the conclusion, they would look up at the starry sky. Roosevelt or Beebe would point out a small, faint smudge of light close to the Great Square of Pegasus and they would both recite, almost as a litany, something similar to the following:
"That is the Spiral Nebula in Andromeda. It is as large as our Milky Way. It is one of a hundred million nebulae. It consists of one hundred million suns, many larger than our sun." The President would then turn to the others. "Now I think we are small enough," he would say. "Let's go to bed."
Whereas from the latitude of Washington D.C. the Andromeda Galaxy is visible for most of the year, from Australia it is so far north (41 degrees north Declination) that it is only visible in the evenings during spring and early summer. For us, this magnificent galaxy is due north at 8:50 pm in mid-November, about one handspan above the horizon.
The Great Galaxy in Andromeda, M31, photographed at Starfield Observatory with an off-the-shelf digital camera on 16 November 2007.
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