The Solar System In September 2016

Dates and times shown are NZST (UT + 12 hours) until the start of NZDT (UT + 13 hours) on Sunday 25 September at 2 am when clocks should be put forward 1 hour.

The southern spring equinox is on September 23 at 2:22 am.

Rise and set times are for Wellington. They will vary by a few minutes elsewhere in NZ.

Sunrise, sunset and twilight times in September

                            September  1  NZST               September 30  NZDT
                    morning  evening                 morning  evening
       SUN: rise:   6.43am,  set:  5.58pm    rise:   6.54am,  set:  7.27pm
Twilights
  Civil:    starts: 6.18am,  ends: 6.24pm    starts: 6.29am,  ends: 7.53pm
  Nautical: starts: 5.46am,  ends: 6.56pm    starts: 5.56am,  ends: 8.26pm
  Astro:    starts: 5.14am,  ends: 7.28pm    starts: 5.23am,  ends: 9.00pm

September phases of the moon (times as shown by Guide)

          New moon:      September  1 at  9.03 pm (09:03 UT)
  First quarter: September  9 at 11.49 am (11:49 UT)
  Full moon:     September 17 at  7.05 am (Sep 16, 19:05 UT)
  Last quarter   September 23 at  9.56 pm (09:56 UT)

The planets in September 2016

Mercury, Venus and Jupiter start the month as a close group low to the west after sunset. Mercury will disappear after a few days and Jupiter after a few more days as they move into conjunction with the Sun.

Saturn and Mars remain prominent throughout the evening in the vicinity of Antares.

Mercury Venus and Jupiter

Mercury starts September as an evening object setting an hour and forty-five minutes after the Sun on the 1st. That evening, three-quarters of an hour after sunset, the planet at magnitude 1.4, will be almost due west and some 10° above the horizon. Finding it will be made easier by the presence of Venus 6.5° to its right and a little higher. Jupiter will also be present below Venus and slightly to its left.

Two evenings later the moon will join the group with the thin crescent of the two day old moon between Venus and Jupiter.

Over the next few nights Mercury will rapidly get lower in the evening sky to disappear in the twilight. On the 13th it is at inferior conjunction between the Earth prior to becoming a morning object. Towards the end of September, Mercury will rise about half an hour earlier than the Sun so remaining more or less unobservable.

Jupiter will also continue to get lower in the evening sky to be at conjunction on the far side of the Sun on the 26th. It will then be 5.45AU, 8.15 million km beyond the Sun.

Venus on the other hand will get a little higher in the evening sky, setting just over two and a half hours after the Sun on the 30th.

Mars and SATURN will also be in the evening sky forming a fairly close group with Antares at the beginning of the month. During September Mars will move away from Antares while the much slower moving Saturn will remain about 6° from the star.

Mars starts September in Scorpius, joins Saturn in Ophiuchus on the 3rd but moves on into Sagittarius on the 22nd. The moon, near first quarter, will join the two planets in Ophiuchus on September 9.

Outer Planets

Uranus, at magnitude 5.7, is in Pisces. By the end of September it will rise just over an hour after the Sun sets making it observable late evening.

Neptune is at opposition on September 2 when it will be 4330 million km, almost 29 astronomical units, from the Earth. The planet is in Aquarius at magnitude 7.8.

Pluto at magnitude 14.4 is also in the evening sky during September setting well after midnight. The planet remains in Sagittarius some 1.5° from the magnitude 2.9 star pi Sgr and less than half a degree from the magnitude 3.7 star omega Sgr.

Minor Planets

(1) Ceres is in Cetus during September and brightens from magnitude 8.4 to 7.8 making it the brightest asteroid. It is at its best as a morning object, although it will rise close to 10 pm on the 1st and close to 9 pm on the 30th.

(18) Melpomene is also in Cetus and close to Ceres, the two being less than a degree apart between September 6 and 10. Melpomene starts the month at magnitude 9.0 and ends it at 8.3, similar to Vesta.

(2) Pallas, in the evening sky, starts September at magnitude 9.3 in Equuleus. It moves into Aquarius on the 26th, dimming a little to 9.7 by the end of the month.

(4) Vesta rises close to 4 am on September 1, remaining in Gemini throughout the month. On the morning of the 3rd it will be only 10 arc-minutes from the 4th magnitude star zeta Gem. The asteroid brightens slightly during the month from magnitude 8.5 to 8.3. By the end of September it will rise about 3.40 am NZDT.

(11) Parthenope is another asteroid which brightens during September, from magnitude 9.8 to 9.2 when at opposition at the end of the month. It is also in Cetus although over 20° from Ceres and Melpomene.

Brian Loader  
New Zealand