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.

Outer planets

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.

Brighter asteroids:

(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