The Solar System In September 2017

NZDT starts at 2am on the morning of September 24 when clocks should be advanced by 1 hour, bringing NZ time to UT + 13 hours. Dates and times shown are NZST (UT + 12 hours) until September 23 and then NZDT for the rest of the month, unless otherwise stated. The southern spring equinox is on September 23, NZ time, with the Sun crossing the celestial equator at about 8am.

Sunrise, Sunset and Twilight Times in September

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

                    September  1  NZST               September 30  NZDT
       SUN: rise:   6.43am,  set:  5.58pm    rise:   6.54am,  set:  7.27pm
  Twilights     morning       evening            morning       evening
  Civil:    starts: 6.18am,  ends: 6.24pm    starts: 6.29am,  ends: 7.53pm
  Nautical: starts: 5.46am,  ends: 6.56pm    starts: 5.57am,  ends: 8.26pm
  Astro:    starts: 5.15am,  ends: 7.28pm    starts: 5.23am,  ends: 8.59pm

September Phases of the Moon times (NZST/NZDT), as shown by GUIDE

          Full moon:     September  6 at  7.03 pm (07:03 UT)
  Last quarter   September 13 at  6.25 pm (06:25 UT)
  New moon:      September 20 at  5.30 pm (05:30 UT)
  First quarter: September 28 at  3.54 pm (02:54 UT)

The Planets in September 2017

The three terrestrial planets, Mercury, Venus and Mars, are all morning objects rising shortly before the Sun. Venus should be observable, especially early in the month. Mercury and Mars are not likely to be observable at any time.

Mercury rise 38 minutes before the Sun on September 1. The planet is at its greatest elongation 18° west of the Sun on the 12th but still rises only 39 minutes before the Sun. At the end of September, Mercury rises only 6 minutes before the Sun.

Venus starts off a little better than Mercury, rising nearly an hour and a half before the Sun. Half an hour before sunrise it will be some 9° up so easily visible as a low brilliant object. It will be well round to the north from east, The planet gets closer to the Sun as September progresses, so that by the 30th it will rise 50 minutes before the Sun. As a result, Venus will be then very low shortly before the Sun rises, and not as far to the north of east as at the beginning of the month.

Mars rises 23 minutes before the Sun on September 1. By the end of the month it will rise about 40 minutes earlier than the Sun and be 3.5° to the lower right of Venus. At magnitude 1.8 Mars and only a degree or two up half an hour before sunrise it is not going to be observable.

In the middle of the month the three terrestrial planets will form quite a tight group in Leo fairly close to Regulus. On the 18th they are joined by the Moon. In a period of just under 24 hours, the Moon will occult Venus, Regulus, Mars and Mercury as seen from some part of the Earth. The Venus event is visible, as a day time event, from all of Australia and New Zealand. At Wellington the time of disappearance is about 1:27 pm and the reappearance at 2:40 pm. The moon will be only a 6% lit crescent about 28° from the Sun. Binoculars are likely to show up the event, but the very thin crescent moon May be difficult to find.

Jupiter is visible in the early evening during September. It sets three and a half hours later than the Sun on the 1st, about 100 minutes later on the 30th so by then will be a low object to the west following sunset. Jupiter is in Virgo, close to Spica. At their closest on the 12th, the 1st magnitude star will be 3° to the left of the planet.

On the 22nd, the crescent moon will join the pair, when it will be just over 4° to the lower right of Jupiter. By then it would be best to be looking by 7pm or soon after. An hour later the three will be very low.

Saturn at least is visible all evening during September, although it will set about 1.40 am (NZDT) on the 30th. Saturn will be in Ophiuchus. Its encounter with the moon will be on the 27th, the moon being a day short of first quarter, about 5° to the right of Saturn mid evening.

Outer Planets

Uranus rises just before 10pm (NZST) on the 1st and close to 9 pm (NZDT) on the 30th. The planet is in Pisces at magnitude 5.7 throughout the month.

Neptune rises close to the time of sunset on September 1. By the 30th it will rise just after 5pm (NZDT) over 2 hours before the Sun sets. So it will then be well placed for viewing in the evening sky. The planet is in Aquarius at magnitude 7.8.

Pluto, magnitude 14.4, remains in Sagittarius. It will be just under a degree from the 2.9 magnitude star pi Sgr.

Minor Planets

(1) Ceres, a morning object starts the month at magnitude 9.0 in Gemini. On the 18th it will cross into Cancer brightening slightly during the month to magnitude 8.8.

(2) Pallas is in Eridanus rising at 10.20 pm on the 1st. During September it brightens from magnitude 9.0 to 8.5.

(4) Vesta is in Leo at first and then Virgo during September. As an evening object it will set too soon after the Sun for observation.

(7) Iris is in Aries throughout September, brightening from magnitude 8.5 to 7.7 during the month. It rises at 11:12 pm on the 1st and 10.33 pm on the 30th. It is quite close to Hamal, alpha Ari magnitude 2.0. Their separation is 2.1° on the 1st, increasing to 3.7° on the 24th after which Iris starts moving back towards Hamal.

(89) Julia is in Pegasus all month. It is at opposition at the beginning of September. For a few nights it will reach magnitude 9.0. On the 2nd it will form a near equilateral triangle with the stars zeta Peg (mag 3.4) and xi Peg (mag 4.2). Julia?s motion will take it past zeta, the two being 8 arc-minutes apart on the 8th. By the end of September Julia will have faded to magnitude 9.4.

Near Earth Object (3122) FLORENCE rapidly fades in early September as its distance from the Earth increases. On the 1st it will be at mag 8.9, 7 million km from the Earth and moving at about 24 arc-minutes per hour. The next two nights finds it in Delphinus, magnitudes 9.1 and 9.3 respectively. It is in Vulpecula at magnitude 9.6 on the 4th and in Cygnus at 9.9 on the 5th. By then Florence will be 8.4 million km away with an apparent speed 17 arc minutes per hour.

Brian Loader  
New Zealand