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