Updated: 9 October 2017
Welcome to the night skies of Spring, featuring Saturn, Scorpius, Sagittarius, Aquila, Lyra and Cygnus
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The Alluna RC-20 Ritchey Chrétien telescope was installed in March, 2016.
The 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 developed for our site with our equipment over the past year.
Times for transient sky phenomena are given using a 24 hour clock, i.e. 20:30 hrs = 8.30 pm. Times are in Australian Eastern Standard Time (AEST),
which equals Universal Time (UT) + 10 hours. Daylight saving is not observed in
Queensland. Observers in other time zones will need to make their own
corrections where appropriate. With conjunctions of the Moon, planets and stars, timings indicate the closest approach. Directions (north or south) are
approximate. The Moon’s diameter is given in arcminutes ( ’ ). The Moon is usually about 30’ or half a degree across. The 'limb' of the Moon is its edge as
projected against the sky background.
Times for transient sky phenomena are given using a 24 hour clock, i.e. 20:30 hrs = 8.30 pm. Times are in Australian Eastern Standard Time (AEST), which equals Universal Time (UT) + 10 hours. Daylight saving is not observed in Queensland. Observers in other time zones will need to make their own corrections where appropriate. With conjunctions of the Moon, planets and stars, timings indicate the closest approach. Directions (north or south) are approximate. The Moon’s diameter is given in arcminutes ( ’ ). The Moon is usually about 30’ or half a degree across. The 'limb' of the Moon is its edge as projected against the sky background.
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
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.
A handspan at arm's length covers an angle of approximately
18 - 20 degrees.
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 exactly 100 times brighter than magnitude 6.0 (5 steps each of 2.51 times, 2.51x2.51x2.51x2.51x2.51 = 2.515 = 100).
The Four Minute Rule:
Aphelion and perihelion: Maximum and minimum distances of a planet, asteroid or comet from the Sun.
A handspan at arm's length covers an angle of approximately 18 - 20 degrees.
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 exactly 100 times brighter than magnitude 6.0 (5 steps each of 2.51 times, 2.51x2.51x2.51x2.51x2.51 = 2.515 = 100).
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. (The meridian is an imaginary semicircular line running from the due south point on the horizon and arching overhead through the zenith, and coming down to the horizon again at its due north point.) 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.
Sun:The Sun begins the month in the constellation of Virgo, the Virgin. It leaves Virgo and passes into Libra, the Scales on October 31.
Moon Phases: Lunations (Brown series): #1173, 1174
04:40 hrs diameter
Last Quarter: October 12 22:26 hrs diameter = 32.2'
New Moon: October 20 05:12 hrs diameter = 30.4'
First Quarter: October 28 08:22 hrs diameter = 29.9'
04 15:23 hrs
diameter = 32.8'
Last Quarter: November 11 06:37 hrs diameter = 31.9'
New Moon: November 18 21:42 hrs diameter = 29.7'
First Quarter: November 27 03:03 hrs diameter = 30.4'
Lunar Orbital Elements:
October 02: Moon at descending node at 12:03 hrs, diameter = 30.6'
October 09: Moon at perigee (366 855 km) at 15:37 hrs, diameter = 32.6'
October 15: Moon at ascending node at 08:13 hrs, diameter = 31.7'
October 25: Moon at apogee (405 164 km) at 12:38 hrs, diameter = 29.5'
October 29: Moon at descending node at 16:38 hrs, diameter = 30.3'
November 06: Moon at perigee (361
km) at 10:03 hrs, diameter = 33.1'
November 11: Moon at ascending node at 08:44 hrs, diameter = 31.8'
November 22: Moon at apogee (406 112 km) at 04:28 hrs, diameter = 29.4'
November 25: Moon at descending node at 18:22 hrs, diameter = 29.9'
Moon at 8 days after New, as on October 29.
The photograph above shows the
Moon when approximately eight days after New, just after First Quarter. A detailed map of the Moon's near side is available here. 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.
The photograph above shows the Moon when approximately eight days after New, just after First Quarter. A detailed map of the Moon's near side is available here. 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.
Clickhere for a photographic animation showing the lunar phases. It also shows the Moon's wobble or libration, and how its apparent size changes as it moves from perigee to apogee each month. It takes a little while to load, but once running is very cool ! All these downloads are freeware, although the authors do accept donations if the user feels inclined to support their work.
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. Recent photographs from our Alluna RC20 telescope will illustrate the objects. 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 a pair of craters in the Moon's southern hemisphere, Pitatus and Hesiodus.
The largest crater in this image is Pitatus which is 100 km in diameter. To its west (left) is its 44 km diameter neighbour Hesiodus.
Both of these craters have flat floors with multiple rilles around their circumferences. Pitatus has an off-centre mountain massif on its floor, while that of Hesiodus has two newer impact craters, both bowl-shaped. There is an unusual valley joining the floors of Pitatus and Hesiodus. A 12 km 'ghost crater', partially submerged by the lava flows from the north, is about 30 km north of Pitatus, with another to the west. From the western ramparts of Hesiodus, the 309 km long rille called Rima Hesiodus runs to the south-west and off the image. There are three craterlets visible on this narrow and shallow valley. They are so well-aligned on the rille that they are probably volcanic vents associated with the creation of the rille. It is unlikely that random impacts from space could have landed together exactly on the rille.
shows the crater Hesiodus (above centre) when the Sun was higher, reducing the
shadows and flattening the contrast. Adjoining Hesiodus to the south-south-west
is the 15 km crater Hesiodus A. This crater is remarkable in that it
contains two concentric rings like a bulls-eye. The rings only become visible
when the Sun is high enough to shine over the steep walls and illuminate them.
The picture was taken on September 2, 2017. The rings are only partially visible
in the larger picture above, which was taken on August 2, 2017.
Pitatus is named after Pietro Pitati, a 16th century Italian mathematician and astronomer. As the Julian calendar of his time had become out of phase with the seasons and was then running 10 days late, some form of calendar reform was required. Pitati suggested that three out of every four even-century years be made non-leap-years to keep the calendar true. The man who corrected the calendar in one bold step four decades later in 1582, Christoph Clavius, accepted this suggestion, declaring that the even century years 1600, 2000, 2400 etc should remain as leap-years, but the intervening even centuries (1700, 1800, 1900, 2100 etc) should not. This avoided any more accumulating errors. To remedy the existing 10-day lag, Clavius dropped 10 days from the Julian Calendar. Pope Gregory XIII ratified this, and the day after Thursday, October 4, 1582 was decreed to be Friday, October 15, 1582. This was the beginning of the Gregorian Calendar which we use today. Catholic countries complied immediately, but others were slower to act. Great Britain and her colonies did not adopt it until 1752, and Turkey was the last in 1926.
Hesiodus is named after Hesiod, an ancient Greek poet who was active in the 8th century BCE and was a contemporary of Homer. Hesiod is a major source for our knowledge of Greek mythology, religious customs, agriculture, early astronomy and time-keeping. Some call him the world's first economist.
It should be remembered that close approaches of Moon, planets and stars are only perspective effects as seen from the Earth - that is why they are called 'geocentric or Earth-centred phenomena'. The Moon, planets and stars do not really approach and dance around each other as it appears to us from the vantage point of our speeding planet.
October 3: Venus at perihelion at 08:28 hrs (diameter = 11.1")
November 1: Jupiter 1.9º south of the star Kappa Virginis (mv= 4.18) at 14:26 hrs
October 3: Limb of Moon 6 arcminutes south of Neptune at 22:55 hrs
October 6: Venus is 12 arcminutes north of Mars at 02:36hrs
October 7: Moon 3.2º south of Uranus at 05:28 hrs
October 8: Mars at aphelion at 09:46 hrs (diameter = 3.7")
October 9: Mercury in superior conjunction at 06:37 hrs (diameter = 4.8")
October 10: Moon 1.3º north of the star Aldebaran (Alpha Tauri, mv= 0.87) at 04:45 hrs
October 10: Pluto at eastern quadrature at 09:58 hrs (diameter = 0.1")
October 14: Mercury 2.6º north of the star Spica (Alpha Leonis, (mv= 0.98) at 03:55 hrs
October 15: Limb of Moon 14 arcminutes north of the star Regulus (Alpha Leonis, mv= 1.36) at 21:11 hrs October 17: Moon 2º north of Mars at 21:33 hrs
October 18: Moon 2.1º north of Venus at 12:54 hrs
October 18: Mercury 57 arcminutes south of Jupiter at 20:20 hrs
October 20: Uranus at opposition at 03:19 hrs (diameter = 3.7")
October 20: Moon 3.8º north of Jupiter at 16:46 hrs
October 20: Neptune 33 arcminutes south of the star Hydor (Lambda Aquarii, mv= 3.73) at 19:40 hrs
October 20: Moon 5.3º north of Mercury at 21:46 hrs
October 21: Saturn 1.7º north of the star Pi Sagittarii (mv= 3.00) at 21:16 hrs October 26: Moon 2.6º north of Pluto at 22:32 hrs
October 27: Jupiter in conjunction at 04:14 hrs (diameter = 30.6")
October 27: Mercury 1.2º south of the star Zuben Elgenubi (Alpha Librae, mv= 2.75) at 11:32 hrs
October 29: Mercury at aphelion at 22:04 hrs (diameter = 4.9")
October 31: Limb of Moon 2 arcminutes south of Neptune at 07:23 hrs
November 3: Moon 3.7º south of Uranus at 12:14 hrs
November 6: Limb of Moon 41 arcminutes north of the star Aldebaran (Alpha Tauri, mv= 0.87) at 12:43 hrs
November 7: Moon 1.6º south of the star Zeta Tauri (mv= 2.97) at 13:05 hrs
November 8: Mercury 1.8 arcminutes south of the star Delta Scorpii (mv= 2.29) at 03:56 hrs
November 11: Mercury 1.8º north of the star Sigma Scorpii (mv= 2.90) at 21:47 hrs
November 12: Moon 1.1º north of the star Regulus (Alpha Leonis, mv= 1.36) at 01:48 hrs
November 13: Jupiter 31 arcminutes north of the star Lambda Virginis (mv= 4.51) at 02:17 hrs
November 13: Mercury 2.2º north of the star Antares (Alpha Scorpii, mv= 1.06) at 05:47 hrs
November 13: Venus 15.7 arcminutes north of Jupiter at 18:12 hrs
November 15: Moon 3.1º north of Mars at 14:49 hrs
November 17: Moon 4.2º north of Jupiter at 10:09 hrs
November 17: Moon 4.1º north of Venus at 19:46 hrs
November 18: Saturn 44.7 arcminutes south of the star 58 Ophiuchi (mv= 4.86) at 23:58 hrs
November 20: Venus 46.6 arcminutes north of the star Zuben Elgenubi (Alpha Librae, mv= 2.75) at 03:17 hrs
November 20: Moon 7.3º north of Mercury at 22:04 hrs
November 21: Moon 3.3º north of Saturn at 08:57 hrs
November 22: Neptune at eastern stationary point at 21:27 hrs (diameter = 2.3")
November 23: Moon 1.8º north of the star Pi Sagittarii (mv= 2.88) at 02:43 hrs
November 23: Moon 2.6º north of Pluto at 04:21 hrs
November 24: Mercury at greatest elongation east (21º 52') at 12"23 hrs (diameter = 6.6")
November 27: Limb of Moon 44 arcminutes south of Neptune at 14:38 hrs
November 28: Mercury 3.1º south of Saturn at 19:38 hrs
November 30: Moon 3.4º south of Uranus at 22:33 hrs
November 1: Jupiter 1.9º south of the star Kappa Virginis (mv= 4.18) at 14:26 hrs
for this month:
Mercury: On October 1, Mercury will be in the eastern pre-dawn sky, too close to the Sun to be easily observed. Each day it will be closer in angular distance to the Sun, until it passes on the far side of the Sun on October 9. It will then enter the evening sky, being just above the Sun at sunset, but still too overwhelmed by the solar glare to be seen. On October 18 Mercury will be just to the left of Jupiter, and on October 20 the thin crescent Moon will join them. The three objects will still be less than eight degrees or half a handspan from the Sun on that day. By the beginning of November Mercury will be increasing its angular separation from the Sun, but it will not become an easy object until the second half of that month.
Venus: This, the brightest planet, is still to be found in the pre-dawn sky as a 'morning star', although its angular distance from the Sun continues to diminish day by day. For example, on October 1 Venus will be 25 degrees from the Sun, and by October 31 its elongation will have fallen to 17 degrees, taking it into the solar glare. This process will continue as speeding Venus curves around towards the far side of the Sun. Venus will pass behind the Sun (superior conjunction) on January 9 next year. After that, Venus will return to the western sky as an 'evening star'. In mid-October, Venus will appear in a small telescope as a tiny 'Full Moon' with a magnitude of -3.9 and an angular size of 11 arcseconds. Its phase will be 93%.
On the morning of October 6, the planet Mars will be only 13 arcminutes above Venus. On October 18, the waning crescent Moon will be just to the left of Venus in the sky.
(The coloured fringes to the first and third images below are due to refractive effects in our own atmosphere, and are not intrinsic to Venus. The planet was closer to the horizon when these images were taken than it was for the second photograph, which was taken when Venus was at its greatest elongation from the Sun).
April 2017 June 2017 December 2017
Click here for a photographic animation showing the Venusian phases. Venus is always far brighter than anything else in the sky except for the Sun and Moon. For the first two months of 2017, Venus appeared as an 'Evening Star', but on March 25 it moved to the pre-dawn sky and became a 'Morning Star'. Each of these appearances lasts about eight to nine months. Venus will pass on the far side of the Sun (superior conjunction) on January 9, 2018, when it will return to the evening sky and become an 'Evening Star' once again.
Because Venus was 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.
Mars:Having passed through conjunction with the Sun on July 27, the red planet is becoming easier to observe this month. On October 1 it will be a little more than a handspan from the Sun, and a little less than three degrees below and to the right of Venus. As the weeks pass it will increase its angular separation from the Sun and will grow in size each day, as our Earth, travelling faster, begins to catch it up. We will overtake Mars on July 27 next year. This will be a very favourable opposition, as Mars will appear bigger (24.2 arcseconds in diameter) and brighter (magnitude -2.8) than it has for many years. It will be particularly favourable for us in the southern hemisphere, as during the month of opposition it will be in the constellation of Capricornus, almost directly overhead each night from the Sunshine Coast.
Mars will approach brighter Venus in the first week of October, passing within 13 arcminutes of that planet on the morning of October 6. Then Mars will move away from Venus, and by the end of the month they wioll be about a handspan apart. When they are together on October 6, both Venus and Mars will be in the constellation of Leo, but after their apparent close encounter the faster moving Venus will head east towards the Sun, passing into Virgo (where the Sun will be) on October 10. Slower Mars will cross into Virgo on October 13. The waning crescent Moon will appear between Venus and Mars in the hour before dawn on October 18.
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.
Jupiter:We will be losing this gas giant planet as a spectacular evening object soon, as it passed through eastern quadrature (due north and crossing the meridian at sunset) on July 6. On the first day of October Jupiter will be only a handspan from the Sun, so by the time darkness falls it will be quite close to the western horizon. It is in the constellation Virgo, to the right of the first magnitude star Spica. The crescent Moon will be close to Jupiter as night falls on October 20. Jupiter will be involved in the twilight glow all through the month, and will reach conjunction with the Sun on October 27. It will move to the morning sky, rising before the Sun, and becoming visible in the second-half of November as a pre-dawn object.
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
Jupiter as it appeared at 7:29 pm on July 2, 2017. The Great Red Spot is in a similar position near Jupiter's eastern limb (edge) as in the fifth picture in the series above. It will be seen that in the past two months the position of the Spot has 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 appears to be disappearing, and a darker streak along the northern edge of the South Tropical Belt is moving south. 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 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.
Saturn: The ringed planet is visible in the evenings this month, as it reached opposition on June 15. On October 1 it will be three handspans above the western horizon as darkness falls, 7 pm. The waxing crescent Moon will be close by Saturn on October 24. Saturn will be in conjunction with the Sun on December 22.
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, 200
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.
innermost parts of Ring B are not as bright as its outermost parts. Inside Ring
B is the faint Ring C, almost invisible but noticeable where it passes in front
of the bright planet as a dusky band. Spacecraft visiting Saturn have shown that
there are at least four more Rings, too faint and tenuous to be observable from
Earth, and some Ringlets. Some of these extend from the inner edge of Ring C to
Saturn's cloudtops. The Rings are not solid, but are made up of countless small
particles, 99.9% water ice with some rocky material, all orbiting Saturn at
different distances and speeds. The bulk of the particles range in size from
dust grains to car-sized chunks.
Saturn with its Rings wide open on July 2, 2017. The shadow of its globe can just be seen on the far side of the Ring system. There are three main concentric rings: Ring A is the outermost, and is separated from the brighter Ring B by a dark gap known as the Cassini Division, which is 4800 kilometres wide, enough to drop Australia through.
The photograph above was taken when Saturn was close to opposition, with the Earth between Saturn and the Sun. At that time, the shadow of Saturn's globe upon the Ring system was directly behind the planet and hardly visible. The photograph below was taken on September 18, 2017, when Saturn was near eastern quadrature. At such a time, the angle from the Sun to Saturn and back to the Earth is near its maximum, making the shadow fall at an angle across the Rings as seen from Earth. It may be seen falling across the far side of the Ring to the left side of the globe.
The innermost parts of Ring B are not as bright as its outermost parts. Inside Ring B is the faint Ring C, almost invisible but noticeable where it passes in front of the bright planet as a dusky band. Spacecraft visiting Saturn have shown that there are at least four more Rings, too faint and tenuous to be observable from Earth, and some Ringlets. Some of these extend from the inner edge of Ring C to Saturn's cloudtops. The Rings are not solid, but are made up of countless small particles, 99.9% water ice with some rocky material, all orbiting Saturn at different distances and speeds. The bulk of the particles range in size from dust grains to car-sized chunks.At bottom centre, the southern hemisphere of the planet can be seen showing through the gap of the Cassini Division. The ring system extends from 7000 to 80 000 kilometres above Saturn's equator, but its thickness varies from only 10 metres to 1 kilometre. The globe of Saturn has a diameter at its equator of 120 536 kilometres. Being made up of 96% hydrogen and 3% helium, it is a gas giant, although it has a small, rocky core. There are numerous cloud bands visible.
Uranus:This ice giant planet is a late night object in October, as it reached western quadrature (rising at midnight) on July 21. This month Uranus rises above the theoretical horizon at 7:07 pm on October 1 and 5:03 pm on October 31. It reaches opposition (being in the opposite direction to the Sun, rising in the east as the Sun sets in the west) on October 20. In the weeks around opposition, a planet is visible all night long. Uranus shines at about magnitude 5.8, so a pair of binoculars or a small telescope is required to observe it. It is currently in the constellation Pisces, near the south-west corner of Aries. The Full Moon will be in the vicinity of Uranus on October 6 and 7. i
Neptune:The icy blue planet is an evening object this month. It reached opposition on September 5, and in mid-October it is nearly overhead at 9 pm. Neptune is located in the constellation of Aquarius, between the magnitude 3 star Skat (Delta Aquarii) and the four-star asterism known as the Water-Jar. As it shines at about magnitude 8, a small telescope is required to observe Neptune. The waxing gibbous Moon will be extremely close to Neptune on the evening of October 3. i
Neptune, photographed from Nambour on October 31, 2008
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.