The Solar System In July 2017

Dates and times shown are NZST (UT + 12 hours) unless otherwise stated.

The Earth is at aphelion, its greatest distance from the Sun for the year, on July 4 just before midday. The apparent diameter of the Sun will then be 31.46 arc-minutes, and its distance 152.1 million km, 1.016 astronomical units.

Sunrise, Sunset and Twilight Times in May

Times are for Wellington. They will vary by a few minutes elsewhere in NZ.

                    July  1  NZST                     July 31  NZST
       SUN: rise:   7.45am,  set:  5.04pm    rise:   7.27am,  set:  5.27pm
  Twilights     morning       evening            morning       evening
  Civil:    starts: 7.16am,  ends: 5.33pm    starts: 7.00am,  ends: 5.55pm
  Nautical: starts: 6.42am,  ends: 6.00pm    starts: 6.27am,  ends: 6.20pm
  Astro:    starts: 6.08am,  ends: 6.41pm    starts: 5.55am,  ends: 7.00pm

July Phases of the Moon (times NZST, as shown by GUIDE)

          First quarter: July  1 at 12.51 pm (00:51 UT)
  Full moon:     July  9 at  4.07 pm (04:07 UT)
  Last quarter   July 17 at  7.26 am (Jul 16, 19:26 UT)
  New moon:      July 23 at  9.46 pm (09:46 UT)
  First quarter: July 31 at  3.23 am (Jul 30, 15:23 UT)

The Planets in July 2017

The second part of July will provide an excellent opportunity to view Mercury in the early evening sky. Jupiter is also best observed early evening, while Saturn is well placed all evening. Venus remains the obvious brilliant morning "star". Mars is too close to the Sun to see all month.

Mercury is an evening object and will be best placed for viewing at the end of the month. It sets 45 minutes after the Sun on the 1st, so will then be rather low for viewing as the sky darkens. By mid July the planet will set just after 7 pm, nearly 2 hours after the Sun. At 6 pm, 45 minutes after sunset, Mercury, magnitude -0.2, will be almost 10° above the horizon in a direction some 30° to the north of west.

By the end of July, Mercury will be even easier to see, some 15° up 50 minutes after sunset. Regulus, at 1.4 a magnitude fainter than Mercury, will be about 6° below the planet. On the 25th Mercury, now at magnitude +0.2, will be 1.2° to the left of the star, with the latter slightly higher. On that evening the crescent moon, 4.4% lit, will be less than 3° below Mercury. The following evening, the 26th, will find Mercury just over 1° from Regulus now slightly higher than the star. The moon will be 10° above the pair.

Venus remains an easy morning object during July. It rises about 3.5 hours before the Sun on the 1st, reducing to 2.5 hours earlier on the 31st. During July, Venus makes its way across Taurus, passing between the Pleiades and Aldebaran. At their closest, on the morning of the 14th, the planet will be 3° to the lower left of the 1st magnitude star. Venus will of course completely outshine Aldebaran, by 5 magnitudes.

On the morning of the 21st, the crescent moon will be just under 5° to the lower right of Venus. The previous morning the moon will be a little less than 3° to the left of Aldebaran. The end of July will find Venus in the most northerly part of Orion, some 15° to the lower left of Betelgeuse.

Mars is not observable during July. It finally reaches conjunction with the Sun on the 27th of July. It will then be 1.64 AU beyond the Sun and 397 million km, 2.66 AU, from the Earth.

Jupiter will remain a prominent early evening object during July. It sets at 1am on the 1st and a few minutes after 11pm on the 31st, so will then be getting a little low and to the west by mid evening. The planet will be a few degrees below Spica.

The moon, at first quarter, will be 3° to the lower right of Jupiter on the 1st. It passes Jupiter again on July 28/29. As seen from NZ, the moon will be just over 8° below Jupiter on the 28th and some 6° to the upper right of the planet on the 29th. Their closest approach is a few minutes before noon on the 28th, when the two are 3° apart. This will be about the time Jupiter rises for NZ.

Saturn will be well placed for evening viewing during July. It rises at 3.45 pm on the 1st and two hours earlier by the 31st, giving it a good altitude an hour after sunset. The planet will be moving rather slowly to the west through Ophiuchus. The moon, two days short of full, will be 4° from Saturn as seen early evening in NZ. The separation of the two will increase during the evening as the moon moves away to the east.

Outer Planets

Uranus is a morning object in Pisces during July. It rises about 2 am on the 1st and at midnight on the 31st. The planet is at magnitude 5.8 throughout the month.

Neptune rises at 10.15 pm on July 1 and two hours earlier on the 31st. It is in Aquarius at magnitude 7.9.

The 80% lit waning moon occults Neptune on the morning of July 14 for NZ. The event is visible from NZ, although the disappearance of Neptune behind the moon will be at the sunlit limb, so not readily observable.

The reappearance from behind the moon is at the unlit limb but occurs shortly before sunrise particularly for the North Island. The South is better placed, with the Sun 7° below the horizon at Christchurch. The reappearance will not be instantaneous as for a star, the disk of the planet taking about 7 seconds to emerge from behind the moon.

Some times of the reappearance are:

  Invercargill 07:10:08 am  Sun below -12°
   Dunedin      07:13:37 am  Sun -10°
   Christchurch 07:19:01 am  Sun  -7°
   Nelson       07:22:07 am  Sun  -5°
   Wellington   07:24:12 am  Sun  -4°
   Auckland     07:27:15 am  Sun  -2°

A modest telescope would be necessary to see the event, but the sky is likely to be too bright in the North Island to see the planet.

Pluto, magnitude 14.4, is at opposition on July 10. It will then rise close to the time of sunset and set close to the time of sunrise. The planet will remain in Sagittarius and will be 1.3° from the magnitude 2.9 star, pi Sgr, by the end of the month.

Minor Planets

(1) Ceres in the morning sky, starting July in Taurus only 14° from the Sun, too close for observation. It moves into Gemini on the 11th and by the end of the month 2° from the 3.0 magnitude star epsilon Gem. Ceres, with a magnitude 9.0, will then rise 100 minutes before the Sun

(4) Vesta is in Leo during July at magnitude 8.2. Its path through Leo takes the asteroid past Regulus. The two are just over 4° apart at their closest on July 18. Vesta sets at 10.30 pm on July 1 and 7.40 pm on the 31st.

(6) Hebe, in Ophiuchus, fades from magnitude 9.3 to 9.7 during July. It rises just before sunset on the 1st.;10

(7) Iris is in the morning sky with a magnitude 9.7 on the 1st and 9.2 on the 31st. The asteroid is in Pisces and rises at 12.30 am on the morning of July 31.

(10) Hygiea in Sagittarius, fades from magnitude 9.2 to 10.0 during July. On the 1st it rises 20 minutes before sunset and is less than a degree from M22.

Brian Loader  
New Zealand

Solar System notes for July, 2017 sky-solar201707 2017-06-21 12:00:00