The Solar System in October 2015

Dates and times shown are NZDT (UT + 13 Hours) unless otherwise stated. Rise and set times are for Wellington. They will vary by a few minutes elsewhere in NZ.

Sunrise, sunset and twilight times in October

                    October  1  NZST                 October 31  NZDT
                    morning  evening                 morning  evening
       SUN: rise:   6.54am,  set:  7.28pm    rise:   6.07am,  set:  8.02pm
Twilights
  Civil:    starts: 6.29am,  ends: 7.54pm    starts: 5.40am,  ends: 8.30pm
  Nautical: starts: 5.56am,  ends: 8.26pm    starts: 5.04am,  ends: 9.06pm 
  Astro:    starts: 5.23am,  ends: 9.08pm    starts: 4.26am,  ends: 9.45pm

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

  Last quarter:  October  5 at 10.06 am (Oct  4, 21:06 UT)
  New moon:      October 13 at  1.06 pm (00:06 UT)
  First quarter: October 21 at  9.31 am (Oct 20, 20:31 UT) 
  Full moon:     October 28 at  1.05 am (Oct 27, 12:05 UT)

Lunar occultations of planets

An occultation of Venus by the moon on the morning of October 9 will be visible from New Zealand. Despite being a day time event, the occultation should be readily visible in binoculars or a small telescope and probably with the unaided eye for those with good vision.

Later in the month, on the evening of October 26, the moon, only one day short of full, will occult Uranus, again visible from most of New Zealand.

More information on these events is given in the section for the planet.

The planets in October

Only Saturn is visible in the evening sky, best viewed following sunset as the sky darkens. Mercury remains too close to the Sun to observe all month, while Venus, Mars and Jupiter have a get together in the dawn morning sky,

Mercury is at inferior conjunction between the Earth and Sun on the morning of October 1 at about 4 am. At conjunction the planet will pass about 2.4° south of the Sun and as seen from the Earth. Mercury will be 0.656 AU, 98 million km from the Earth and 0.347 AU, 52 million km from the Sun.

After conjunction, Mercury becomes a morning object rising before the Sun. At its best, in mid October, the planet will rise 30 minutes before the Sun; by the end of October only 20 minutes earlier. In effect Mercury will not be visible at any time during the month.

Venus, MARS and JUPITER in the morning sky during October.

The three planets will start the month well spread out in the dawn sky.

Venus will be readily visible as a brilliant point of light in the dawn sky throughout October. It rises 2 hours before the Sun on the 1st, reducing to about 105 minutes earlier by the 31st. It will be the furthest of the three from the Sun at the start of October.

Mars rises some 75 minutes before the Sun on the 1st, and 100 minutes earlier on the 31st, so then little different to Venus.

Jupiter rises 1 hour before the Sun on the 1st, almost 2 hours earlier on the 31st. So it starts October as the closest of the 3 planets to the Sun and ends the furthest.

As a result of these changing positions there will be some close passes during the month. On the morning of October 18.Mars and Jupiter will be 24' apart, a little less than the diameter of the full moon. Mars, magnitude 1.7 will be to the lower left of the far brighter Jupiter (-1.8). The planets will be low while the sky is still dark enough to see them. Half an hour before sunrise Mars will be just 9° up as seen from Wellington. At magnitude 1.7 Mars is likely to be difficult to see but Jupiter should be fairly easy to spot, at an azimuth nearly 20° to the north of east. Binoculars will then show Mars if it is not visible to the eye. The elongation of the planets, 40° from the Sun, means the worst of the glare should be to the right of the planets

Eight mornings later, on the 25th, Venus will be 1° above Jupiter. Half an hour before sunrise Jupiter will be some 12° up, so now a little better placed. The brightness of Venus will make locating the pair simple.

Finally the last morning of October will find Mars some 1.7° to the lower right of Venus. This is not their closest approach: that will be on October 3.

The crescent moon will pass Mars and Jupiter on the morning of October 10 when it will be at the apex of a triangle formed by it and the two planets defining its base. The moon, 9% lit, will be just under 3° from each of the planets. The three will be low with the moon a little over 7° up 40 minutes before sunrise.

OCCULTATION of VENUS, morning of October 9, NZDT

In NZ the occultation takes place well after sunrise. Even so both phases of the occultation will be observable with binoculars or a small telescope. The light intensity of Venus will exceed that of the sunlit edge of the moon making the disappearance against the moon's lit limb observable. For New Zealand the occultations will take place fairly centrally round the moon's limb. The moon will be a 15% lit crescent

It will take about 90 seconds for the moon to cover the full diameter of Venus (30 arc second). But Venus will be only 40% lit, with the moon covering and exposing the unlit half first. Hence from the observer's point of view the occultation will start at about the time given in the table below for the mid event. The lit portion of Venus will be hidden or exposed to view over the following three-quarters of a minute.

The predicted times (NZDT am) for a number of places in NZ are given below, D = Disappearance and R = Reappearance:

Auckland:      D 8:11:59,  R 9:52:32
Hamilton:      D 8:14:35,  R 9:54:33
Palmerston N:  D 8:20:14,  R 9:57:26
Wellington:    D 8:20:34,  R 9:56:01
Nelson:        D 8:17:51,  R 9:52:16
Christchurch:  D 8:21:35,  R 9:52:01
Dunedin:       D 8:23:31,  R 9:48:01
Invercargill   D 8:21:44,  R 9:43:22

Times for other places will of course vary, even in different parts of the same city. Those who have the Occult program should generate their own predictions, otherwise Venus should be easily visible, weather permitting, a few minutes before the disappearance.

The occultation is also visible from the eastern half of Australia where the disappearance occurs in a dark sky and the reappearance around the time of sunrise.

Saturn will be the only naked eye planet in the evening sky. It sets just before midnight on the 1st and soon after 10pm on the 31st. So even it will be low especially by the end of the month when it will set an hour after the end of nautical twilight (Sun 13° below the horizon)..

The planet starts the month in Libra but crosses into Scorpius on the 17th. Saturn will be about 10° below Antares, getting a little closer as the month progresses.

The 10% lit crescent moon will be about 5° below Saturn on the 16th. The following night it will be 9° to the upper right of Saturn.

Outer planets

Uranus is in Pisces during October, being at opposition on October 12. It will then be 19.0 AU, 2840 million km from the Earth and 20 AU, 2992 million km from the Sun. Being at opposition mid October means it is in the dark sky all night throughout the month.

OCCULTATION OF URANUS. On the evening of October 26 an occultation of Uranus by the moon will be visible in NZ for places from just north of Auckland southwards. A grazing occultation occurs just south of Wellsford. The path of the graze is very close to the one for the graze of Uranus on the morning of September 2.

At the October graze the disappearance will be nominally at the unlit limb of the 98.3% sunlit moon, near its north pole. With the moon so near full, the disappearance of Uranus will be very close to the terminator of the sunlit region, especially in the northern half of the North Island.

Times of the disappearance vary from 11:09:17 at Auckland, the planet taking 36.2 seconds to completely disappear, to Hamilton 10:03:36 (21.4 seconds), Wellington 10:52:39 (12.8 seconds), Christchurch 10:46:54 (11.4 seconds), Dunedin 10:41:58 (10.4 seconds) and Invercargill 10:35:59 (10.4 seconds). The times are for the 50% occultation of the planet.

The reappearance takes place some time later ranging from 11:26:26 at Auckland where the planet will be behind the moon for just over 17 minutes to 11:30:54 at Invercargill with Uranus behind the moon for 55 minutes. This will be at the sunlit limb of the moon.

Neptune was at opposition at the beginning of September, so it will be visible all evening throughout October. The planet will continue to be in Aquarius at magnitude 7.8 to 7.9, so is quite easily seen in binoculars. The 77% lit gibbous moon is closest to Neptune on October 23 when the planet will be 6° to the right and rather higher than the moon. The following night the two will be 10.5° apart with Neptune to the moon's upper left.

Pluto continues to be in Sagittarius all October with a magnitude 14.4.

Brighter asteroids:

(1) Ceres is in Sagittarius during October its magnitude ranging from 8.7 to 9.1. Ceres will be moving to the east through Sagittarius towards the constellation's triple boundary point with Microscopium and Capricornus

(4) Vesta is in Cetus throughout October its magnitude ranging from 6.2 to 6.9 during the month. It is at opposition on October 3, when it is brightest. The asteroid will be moving to the west, 9 to 10° from beta Cet, Diphda (magnitude 2.0). On the 17th it will be on the line from beta Cet to iota Cet (3.5), with Vesta a little under 2° from the latter.

(15) Eunomia is in Pegasus during October its magnitude varying from 8.0 to 8.3 as the Earth moves away from the asteroid following its end of October opposition. The asteroid moves in an arc through Pegasus more or less centered on gamma Peg (2.8), 8.4° away.

(29) Amphitrite starts October at magnitude 9.3 in Aries. It is at opposition on the 23rd at magnitude 8.7 and crosses into Pisces 4 nights later. By the end of October its magnitude will be back to 8.9. During October, Amphitrite will be moving to the west about 3° from beta Ari (2.6). On the 23rd, gamma Ari (4.6) will be close to midway between beta and Amphitrite.

(471) Papagena will be at opposition in Cetus on October 21 with a magnitude 9.5. It will then be 1.5° from tau Cet (3.5) The two are closest on the 17th with Papagena 1.26° to the lower left of the star.

Brian Loader