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

The Solar System in July 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.

The Earth is at aphelion on July 7 at about 4 am. It will then be 1.0167 AU, 152 million km from the Sun.

Sunrise, sunset and twilight times in July

                       July  1  NZST                July 30  NZST
                    morning  evening                 morning  evening
            rise:   7.45am,  set:  5.04pm    rise:   7.28am,  set:  5.26pm
Twilights
  Civil:    starts: 7.16am,  ends: 5.33pm    starts: 7.01am,  ends: 5.54pm
  Nautical: starts: 6.42am,  ends: 6.08pm    starts: 6.28am,  ends: 6.27pm 
  Astro:    starts: 6.08am,  ends: 6.41pm    starts: 5.55am,  ends: 7.00pm

July PHASES OF THE MOON (times as shown by GUIDE)

  Full moon:     July  2 at  2.20 pm (02:20 UT)
  Last quarter:  July  9 at  8.24 am (June  8, 20:24 UT)
  New moon:      July 16 at  1.24 pm (01:24 UT)
  First quarter: July 24 at  4.04 pm (04:04 UT) 
  Full moon:     July 31 at 10.43 pm (10:43 UT)

The planets in July

Venus and Jupiter will be a spectacular pair the first few evenings of July, closest on the 1st, gradually separating during the rest of the month. Mercury may be briefly visible in the morning before sunrise early in July, and possibly just visible in the evening at the end of July.

Saturn is easily visible all evening, setting well after midnight. Mars remain too close to the Sun for observation.

Mercury may be briefly visible in the morning sky shortly before sunrise early in the month. On the morning of the 1st, 45 minutes before sunrise the planet will a low 8° above the horizon in a direction a little east of northeast. The planet's magnitude will be -0.1. A week later Mercury will be half a magnitude brighter, but less than 5° up at the same time.

The planet closes in on the Sun until it is at superior conjunction on the morning of July 24. At conjunction its angular distance from the Sun as seen from the Earth will be about 1.5°. It will actually be 200 million km from the Earth, 48 million km beyond the Sun.

After conjunction Mercury will become an evening object. By the end of July it will set just over half an hour after the Sun. On the 31st the planet will be very low almost directly below Venus. Its magnitude will be -1.2, but it is not likely to be visible in the bright twilit sky.

Mercury starts July in Taurus, it enters Gemini on the 9th and moves on into Cancer on the 23rd.

Venus and JUPITER start July as a close pair just under 20 arc-minutes apart (two-thirds the diameter of the full moon) on the 1st. Venus will, of course, be much brighter than Jupiter. The spectacular conjunction is likely to be a little subdued due to the full moon but the latter will be on the opposite side of the evening sky to the pair of planets.

Both planets spend the month in Leo. In the evenings following their conjunction Jupiter will rapidly fall behind and get lower than Venus. At first Venus will look to be moving towards Regulus but will turn away from the star, being stationary on the 23rd. Jupiter will move much more slowly but steadily towards the star. It will be August before they are at their closest.

On the July 18 the moon as a very thin crescent will be just over 6° to the left of and slightly lower than Jupiter. The following evening will find the moon close to Venus with the two about 1.6° apart. Regulus will be about 3° from them.

On the 19th the moon will occult Venus, an event visible in daylight from Queensland. The path of the occultation passes to the north of New Zealand.

Mars will be a nominal morning object during July. On the 1st it rises only 6 minutes before the Sun. So the planet will be far too close to the Sun to see. Things are little better at the end of July. Mars will then rise about 45 minutes before the Sun, but be so low in the morning twilight that at magnitude 1.7 it will not be visible.

Saturn will be well placed in the evening sky throughout July. It will be moving slowly to the west in Libra, not moving very close to any bright stars. It is joined by the 71% lit, gibbous moon on the 26th. The latter will be about 2.5° to the lower right of Saturn mid evening.

Saturn's north pole will be tilted 24° towards the Earth so that the ring system is well open for viewing.

Titan, Saturn's largest moon, at magnitude 8.6, should be visible as a faint object in binoculars given a dark sky. It is best observed when Titan is at is greatest distance from Saturn, about 3 arc-minutes. Its greatest elongations to the east (left) of the planet are on the July 3 and 18, to the west (right) of Saturn on July 11 and 26. On the first and last dates moonlight may make Titan difficult to see in binoculars. July 3 is only a day beyond full moon, on the 26th our moon is close to Saturn.

Outer planets

Uranus is in Pisces all July. It rises shortly after midnight on the 1st and some 90 minutes before midnight of the 31st. With a 5.8 magnitude it is readily seen in binoculars. The planet is stationary on the morning of July 27 after which it will start moving in a retrograde sense to the west.

Neptune rises just before 10 pm on July 1 with its rise time advancing to just before 8 pm on the 31st. The planet remains in Aquarius at magnitude 7.9 to 7.8, so is quite easily seen in binoculars.

Pluto is in Sagittarius all July and at opposition on the 6th. It will then be nearly 32 astronomical units from the Earth and near 33 from the Sun with a magnitude 14.3.

Brighter asteroids: (to do)

(1) Ceres is in Microscopium much of July, but moves into Sagittarius in the 25th. It rises an hour and a half after sunset on the 1st and nearly as much before sunset on the 31st. It does not pass close to any bright stars during the month. The asteroid is at opposition on July 25 and brightens to magnitude 7.5 for a few nights near that date.

(4) Vesta is essentially a morning object in Cetus throughout July. It rises just after midnight on the 1st and at 10.30 on the 31st. Its magnitude brightens from 7.6 to 7.2 during the month.

(15) Eunomia starts July on the border of Pegasus and Pisces at magnitude 9.7. The asteroid rises half an hour after midnight on the 1st and at 11.15pm on the 31st.It is in Pisces for the rest of the month within a few degrees of the magnitude 2.8 star gamma Peg. At their closest on the 14 the two are 1.5° apart. By July 31 Eunomia will have brightened to magnitude 9.1

Brian Loader  
New Zealand