Solar System notes for September, 2015
The solar system in September 2015
Dates and times are NZST (UT + 12 hours) unless otherwise specified up to September 26. From September 27 they are NZDT (UT + 13 Hours). NZDT commences on Sunday September 27 at 2am when clocks should be put forward one hour.
Rise and set times are for Wellington. They will vary by a few minutes elsewhere in NZ.
The southern spring equinox is on September 23, with the Sun on the celestial equator at 8:21 pm
Sunrise, sunset and twilight times in September
September 1 NZST September 30 NZDT morning evening morning evening SUN: rise: 6.44am, set: 5.58pm rise: 6.55am, set: 7.27pm Twilights Civil: starts: 6.19am, ends: 6.24pm starts: 6.30am, ends: 7.53pm Nautical: starts: 5.47am, ends: 6.56pm starts: 5.58am, ends: 8.25pm Astro: starts: 5.15am, ends: 7.28pm starts: 5.24am, ends: 8.59pm
September PHASES OF THE MOON (times as shown by GUIDE)
Last quarter: September 5 at 9.54 pm (09:54 UT) New moon: September 13 at 6.41 pm (06:41 UT) First quarter: September 21 at 8.59 pm (08:59 UT) Full moon: September 28 at 3.51 pm (02:51 UT)
A partial eclipse of the Sun on September 13 will be visible from southern parts of Africa, the southern half of the Malagasy Republic, the South Indian Ocean and Antarctica. No part of the eclipse is visible from Australia of New Zealand. This is an annular eclipse but the path of annularity misses the Earth.
A total eclipse of the moon on September 28 is also not visible from Australasia. The total phase of the eclipse, lasing some 82 minutes, is best seen from countries either side of the Atlantic Ocean.
The planets in September
Mercury will be well placed for evening viewing during the earlier part of the month. Venus, Mars and Jupiter are all morning objects rising a little before the Sun. Saturn, in the evening sky, will set before midnight. An occultation of Uranus by the moon on the morning of September 2 will be visible from most of NZ.
Mercury is an easy early evening object during the first half of September, setting 2 hours or more after the Sun. On the 1st, 50 minutes after sunset the planet, magnitude 0.2, will be some 15° above the horizon to the west. On the 4th Mercury is at its greatest elongation 27° east of the Sun. For nearly two weeks after that its evening altitude slowly declines as its easterly motion through the stars slow. Then on the 17th the planet is stationary before starting to move back to the west, following a path through the stars close to the one it took in the first part of September.
The return means the distance of Mercury from the Sun rapidly declines in the latter part of September as does its evening altitude so that it slips out of view. Mercury is at inferior conjunction between the Earth and Sun at the very end of the month. The actual conjunction is at about 4 am on the morning of October 1.
Venus was at inferior conjunction mid August, so September find it moving up into the morning sky. It rises nearly 100 minutes before the Sun on September 1. On the 5th Venus is stationary, after which it will start moving east towards the Sun. But the Sun itself will be moving to the east through the stars a little more rapidly. As a result the time Venus rises before the Sun will continue to slowly increase, up to almost 2 hours earlier on the 30th.
Venus starts the month in Cancer. Its easterly motion takes it into Leo on the 24th. Before that on the morning of the 10th the 11% lit crescent moon with be 7° to the left of Venus.
Mars is also a morning object, but rather lower than Venus. It rises just under an hour before the Sun on the 1st and 70 minutes before the Sun on the 30th. Mars will be at magnitude 1.8 all month.
Like Venus, Mars starts the month in Cancer, moving on into Leo on the 6th. In Leo it will move towards Regulus, alpha Leo, and is closest to the magnitude 1.4 star on the morning of September 25, when the two will be about 50 arc-minutes apart. Mars, at magnitude 1.8 will be slightly fainter than Regulus and to the lower left of the star.
The moon, a 6% lit waning crescent, will be just under 4° above Mars on the morning of the 11th, one day after it passes Venus.
Jupiter is the third planet in the morning sky that rises shortly before sunrise. It is in Leo all month, moving away from Regulus. It was at conjunction with the Sun on August 26, so will rise only 3 minutes earlier than the Sun at the beginning of September. By the end of the month this will have increased to nearly an hour before the Sun, but the planet will be only 5° above the horizon twenty minutes before sunrise making it a difficult object to see.
Saturn will be the only naked eye planet left in the evening sky once Mercury has slipped out of it. It sets at 12.40 am at the beginning of September and 11.56 pm (NZDT) on the 30th. Hence it will be readily visible in the earlier part of the evening. It will be in Libra about 12° below Antares all month, Saturn moving slightly closer to Antares as the month progresses.
The moon a 29% broad crescent will be some 3.5° to the right of Saturn on September 19.
Uranus remains in Pisces during September. It rises around 9.14 pm on the 1st and 8.15 pm (NDST) on the 30th. The planet will be at magnitude 5.7 so readily seen in binoculars.
OCCULTATION OF URANUS. On the morning of September 2 an occultation of Uranus by the moon will be visible in NZ for places just north of Auckland southwards. A grazing occultation occurs just south of Wellsford. The disappearance will be at the bright limb of the of the 88% lit moon so difficult to observe. The reappearance at the unlit limb will be a lot easier to see using a small telescope.
Unlike stellar occultations, the occultation of Uranus will not be instantaneous due to the angular diameter of the planet. In the South Island the reappearance will take about 6 seconds, but this time will increase further north, nearer the graze path, to almost 20 seconds at Auckland.
The time of the reappearance is near 5 am; for most places a little before, but for Wellington and places near the east coast of the North Island Uranus will reappear shortly after 5am. Users of Occult will be able to generate accurate times for their position.
A second lunar occultation of Uranus occurs on September 29. It is only visible from the south of South Africa, the ocean areas to the south and parts of Antarctica.
Neptune is at opposition on the 1st. It then rises 15 minutes before sunset and sets a few minutes after sunrise. By the end of the month Neptune sets an hour before sunrise. The planet remains in Aquarius at magnitude 7.8, so is quite easily seen in binoculars. The near full moon is closest to Neptune on September 26.
Pluto continues to be in Sagittarius all September with a magnitude 14.3 to 14.4.
(1) Ceres is in Sagittarius during September fading a little from magnitude 8.2 to 8.7 during the month. The dwarf planet will be slow moving in Sagittarius, being stationary on the 15th. It will then be about 3.5° from the M55 globular cluster.
(4) Vesta is in Cetus throughout September brightening from magnitude 6.7 to 6.3 during the month. The asteroid rises at 8.16 pm on the 1st. By the end of September it will rise about 40 minutes before sunset and set nearly an hour after sunrise.
(9) Metis is in Aquarius, starting the month at magnitude 9.2. It will then rise at the time of sunset but not set until well after sunrise. The asteroid is at opposition on September 6. By the end of the month it will have dimmed slightly to magnitude 9.6
(15) Eunomia starts September in Andromeda with a magnitude 8.4. It moves into Pegasus on the 22nd. Opposition is at the end of September when Eunomia will have brightened to 7.9. It will then be the second brightest asteroid in the sky. , having crossed into Pegasus on the 22nd.
(29) Amphitrite starts September at magnitude 9.9. It is in Aries and stationary on the 7th. By the 30th it will have brightened to magnitude 9.3 and be just under 5° from the star beta Ari.
Brian Loader New Zealand
Solar System notes for August, 2015
The Solar System in August 2015
Dates and times are NZST (UT + 12 hours) unless otherwise specified. Rise and set times are for Wellington. They will vary by a few minutes elsewhere in NZ.
Sunrise, sunset and twilight times in August
August 1 NZST August 31 NZST morning evening morning evening rise: 7.27am, set: 5.27pm rise: 6.46am, set: 5.57pm Twilights Civil: starts: 7.00am, ends: 5.55pm starts: 6.21am, ends: 6.23pm Nautical: starts: 6.27am, ends: 6.28pm starts: 5.49am, ends: 6.55pm Astro: starts: 5.54am, ends: 7.01pm starts: 5.17am, ends: 7.22pm
August PHASES OF THE MOON (times as shown by GUIDE)
Last quarter: August 7 at 2.03 pm (02:03 UT) New moon: August 15 at 2.53 am (Aug 14, 14:53 UT) First quarter: August 23 at 7.31 am (Aug 22, 19:31 UT) Full moon: August 30 at 6.35 am (Aug 29, 18:35 UT)
The planets in August
Both Venus and Jupiter are at conjunction with the Sun during August, marking their return to the morning sky. Mercury will become well placed for evening viewing during the month. Mars moves up a little in the pre-dawn sky. Saturn, in the evening sky, will set before midnight.
Mercury will set some 40 minutes after the Sun on August 1 making it a very difficult object to see despite its -1.1 magnitude. On the evening of the 7th Mercury, Jupiter and the star Regulus will form a cluster in the western sky. Mercury will be half a degree to the lower right of Jupiter which itself will be a degree below Regulus. The group will be very low in the sky before it is dark enough to see them.
As a marker Venus will be about 7.5° to the left of the group only slightly higher than Regulus. Obviously finding Venus will be a guide. Binoculars will help show the other objects.
As the month progresses, Mercury will set increasingly later than the Sun, by the 16th 95 minutes later and on the 31st a good two and a quarter hours later. At the end of nautical twilight the planet at magnitude 0.2 will be 15° up and slightly to the north of west making it an easy visual object. Around this date will provide the best opportunity of the year to see the elusive innermost planet.
Mercury stars the month in Leo crossing into Virgo on the 23rd.
Venus, unlike Mercury, will be heading back towards the Sun. It sets 2 hours after the Sun on August 1, so will be readily visible for a while after sunset. The distance between the planet and the Sun will decrease over the next couple of weeks until Venus is at inferior conjunction between the Sun and Earth on the morning of the 16th (NZST).
At this conjunction Venus will pass the Sun at an angular distance of 7.5° south of the Sun as seen from the Earth. Also as seen from the Earth the planet will be barely 1% lit, yet despite that it will be at magnitude -3.9.
As a result of its southerly elongation it may be visible at conjunction shortly before sunrise on the morning of the 16th. That morning Venus will rise at 6.33 am, the Sun 35 minutes later. So the planet should be in view very low a little to the north of east. The time of conjunction is about 7 am
By August 31, Venus will rise into the morning sky more than 90 minutes before the Sun so will readily be visible before sunrise some way round towards the northeast.
Jupiter is also heading towards the Sun during August. Although it starts the month closer to the Sun than Venus, the faster moving inner planet overtakes the gas giant and get there first. Jupiter is at conjunction on the 27th (NZST). It will of course be beyond the Sun as seen from the Earth passing less than a degree south of the Sun. No hope of seeing Jupiter at conjunction!
At conjunction the planet will be 806 million km (5.388 AU) beyond the Sun and 957 million km (6.398 AU) from the Earth. After conjunction Jupiter becomes a morning object but with only 4 days of the month to go will not be visible.
On the other hand at the beginning of August Jupiter will set nearly 100 minutes after the Sun, so is likely to be briefly visible for the first few evenings of August with Venus a few degrees to its upper left. On the evening of the 11th, Jupiter will be less than half a degree from Regulus, but the two will be only 11.5° from the Sun so very difficult to see.
Saturn is very much an evening object in August, but only as an early evening object by the end of the month. It sets just after midnight on the 1st, and before 10.30 pm on the 31st. The planet will be in Libra moving slowly to the east towards beta Scorpii in the head of Scorpius.
On the evening of August 22, the moon will be some 6° degrees below Saturn. The moon will be nearly half lit, just before first quarter.
Mars will slowly move a little further up into the morning sky before sunrise . It rises 40 minutes earlier than the Sun on the 1st, just over an hour earlier on the 31st. But it will remain low in the dawn sky and at magnitude 1.8 very difficult to see in the twilight. The planet starts August in Gemini but crosses into Cancer on August 6.
Uranus is in Pisces all August. It rises around 11.20 pm on the 1st and 2 hours earlier on the 31st. The planet will be at magnitude 5.8 so readily seen in binoculars. The 67% lit moon will be 3° from Uranus on the night of 5/6 August.
Neptune rises just before 8 pm on August 1 with its rise time advancing to just before 6 pm on the 31st. The planet remains in Aquarius at magnitude 7.8, so is quite easily seen in binoculars. The moon passes Neptune twice in August. The first occasion is on the night of August 2/3, the second at the time of full moon on the 30th.
Pluto continues to be in Sagittarius all August with a magnitude 14.3.
(1) Ceres is in Sagittarius during August fading a little from magnitude 7.6 to 8.2 following its opposition late July. During August the asteroid moves further into Sagittarius; by the end of the month it will be between the kite shaped asterism containing omega Sgr and the wide pair of stars theta 1 and 2 Sgr.
(4) Vesta is in Cetus throughout August brightening from magnitude 7.2 to 6.7. The asteroid rises at 10.25 pm on the 1st and 8.20 pm on the 31st. It is stationary mid month.
(9) Metis starts the month at magnitude 10.0 but brightens to 9.2 by the 31st. The asteroid is in Aquarius about 11° from Neptune at the end of August.
(15) Eunomia starts August in Pisces at magnitude 9.7, rising at 11.10 pm. It is well north of the equator and moving further north. On the 25th it swings into Andromeda. By the end of August it will rise at 9.30 pm and be at magnitude 8.5, only slight fainter than Ceres.
Brian Loader New Zealand