The Solar System In January 2017

Dates and times shown are NZDT (UT + 13 hours).

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

Sunrise, sunset and twilight times in January

                            January  1  NZDT                 January 31  NZDT
                    morning  evening                 morning  evening
       SUN: rise:   5.48am,  set:  8.59pm    rise:   6.22am,  set:  8.44pm
Twilights
  Civil:    starts: 5.18am,  ends: 9.31pm    starts: 5.54am,  ends: 9.13pm
  Nautical: starts: 4.35am,  ends:10.14pm    starts: 5.16am,  ends: 9.51pm
  Astro:    starts: 3.44am,  ends:11.04pm    starts: 4.34am,  ends:10.33pm

January phases of the moon (times as shown by guide)

          First quarter: January  6 at  8.47 am (Jan  5, 19:47 UT)
  Full moon:     January 13 at 12.34 am (Jan 12, 11:34 UT)
  Last quarter   January 20 at 11.13 am (Jan 19, 22:13 UT)
  New moon:      January 28 at  1.07 pm (00:07 UT)

The Earth is at perihelion, its closest to the Sun for the year, on January 4 at 11 pm (NZDT), 10 hours UT. The Earth will then be 0.9833 AU, 147.1 million km, from the centre of the Sun, which will have an apparent angular diameter of 32.53 arc-minute.

The planets in January 2017

Venus remains the obvious bright planet in the evening sky with Mars, much fainter, only a few degrees higher. Mercury will be a morning object visible an hour before sunrise during the second half of the month. Jupiter and Saturn are also morning planets. Jupiter rises just before midnight by the end of January. Saturn will be readily visible to the east by the end of the month.

Evening Planets

Venus will remain brilliant in the evening sky throughout January reaching magnitude -4.7 by the 31st. It will get a little lower in the western sky, setting by 10.30 pm at the end of January. The planet starts January in Aquarius moving on into Pisces on the 23rd.

On the 13th Venus will pass Neptune, magnitude 7.9. At their closest their separation will be 21 arc-minutes, less than the diameter of the full moon. By 10 pm, when the sky should be dark enough to see Neptune in binoculars, the two planets will be 36 arc-minutes apart with Neptune to the left of and slightly higher than Venus

The crescent moon will be a couple of degrees below Venus on January 2.

Mars is a little higher than Venus throughout January, its brightness fading slightly from magnitude 0.9 to 1.1 during the month. It is 12° from Venus on the 1st, the separation decreasing to 5.5° by the 31st. On January 19 Mars will move into Pisces from Aquarius.

Early in January, Mars and Neptune are very close, the separation being only 4.9 arc-minutes on the 1st about 1-6th of the diameter of the full moon. Neptune is then to the lower left of Mars with a magnitude 7.9 so visible in binoculars. There will be no star nearby which could be confused with Neptune.

Mars will move away from Neptune during the following evenings but on the 3rd the two, now 1.5° apart, will be joined by the 25% lit crescent moon. By the time the sky is dark enough to see the planets, the moon will have just moved past them and be about 1° from Mars. A few hours earlier the moon will occult first Neptune and then Mars, events visible from the parts of the north Pacific.

Morning Planets

Jupiter is the brightest planet in the morning sky, it will be joined there by Saturn and Mercury during the month. On the 1st Jupiter rises at 1.25 am, almost 2 hours earlier by the 31st, that is shortly before midnight. In Virgo, Jupiter starts the month 4.4° from Spica. Its slowing, easterly movement brings it to just over 3.5° from the star by the end of the month.

On the morning of the 20th, the moon at last quarter, will be just over 5° from Jupiter and 7° from Spica.

Saturn, emerging into the morning sky after its December conjunction, will rise about 80 minutes before the Sun on the 1st and more than three and a half hours earlier than the Sun on the 31st. The planet is in Ophiuchus at magnitude 0.5.

On the morning of the 25th, the crescent moon will be just over 5° below Saturn as seen from New Zealand.

Mercury also emerges from the Sun into the morning sky following its inferior conjunction at the end of December. At first it will be too close to the Sun to see. The westerly retrograde motion of the planet will move it quite rapidly away from the Sun, so that when stationary on the 9th, it will rise 75 minutes before the Sun. Mercury will also have brightened from magnitude 2.9 to 0.4, so it May be briefly visible very low to the east-south-east before the sky gets too bright to see the planet. It will then be some 6.5° to the lower right of Saturn.

Mercury’s distance from the Sun continues to increase for another 10 days until it reaches its greatest elongation on the morning of the 20th. It will then be 24° from the Sun at magnitude -0.2, rising 100 minutes before the Sun and so readily visible, if low, up to an hour or less before sunrise. The planet continues to be briefly visible at this sort of time for the rest of the month.

The moon, as a very thin crescent, will be 5° to the left of Mercury on the morning of the 26th.

Outer Planets

Uranus, at magnitude 5.8, remains in Pisces and is observable all evening. It will set after midnight, about 12.30 am by the 31st. The moon, just past first quarter, will be just over 4° to the upper right of Uranus on the 6th.

Neptune is in Aquarius at magnitude 7.9 throughout January. It conjunctions during the month with Mars, on the 1st, and Venus, on the 13th are described in the notes for those planets.

Pluto is at conjunction with the Sun on January 7, so is not observable during the month. At conjunction Pluto will be over 33 astronomical units from the Sun and over 34 AU, 5.1 billion km, from the Earth.

Minor Planets

(1) Ceres starts the month in Cetus but moves into Pisces on the 8th. The asteroid fades a little during the month from magnitude 8.6 to 9.0. Its distance from Uranus increases from 7.2 to 9.5° during the month. The asteroid sets just after midnight at the end of January.

(4) Vesta starts January in Cancer moving on into Gemini on the 19th. It ends the month about 3.5° above and to the right of Pollux, beta Gem, mag 1.2. Vesta is at opposition on the 18th when its magnitude will be 6.2

(18) Melpomene is also in Cetus between 11 and 15 degrees from Ceres. The asteroid continues to fade from magnitude 9.7 to 10.3 during January. Melpomene is on the opposite side of Ceres to Uranus. The asteroid is also a few degrees from comet Harrington-Wilson during January.

(9) Metis and (14) IRENE are both in Leo, about 6° apart. Their magnitudes brighten to 9.5 and 9.4 respectively on the 31st. Metis will then be just over 12° to the right of Regulus, mag 1.4, in a direction towards delta Leo, mag 2.5. Irene will be below Metis. They rise about 10.30 pm.

(15) Eunomia also brightens to magnitude 9.5 by the 31st. It will then be in Sextans, 2.5° to the right of alpha Sex, mag 4.5. Eunomia rises just before 9pm.

Comets.

Two reasonably bright comets should be visible in binoculars during January.

P/Honda-Mrkos- Pajdusakova (45P) at magnitude 7.7 is 16° to the lower left of Venus on the 1st. The 9% lit crescent moon will be 5.5° to the right and slightly lower than the comet. At 10 pm the comet will have an 8° altitude, the moon being a degree lower. Subsequent evenings the comet will get lower in the evening sky and soon be lost to view.

D/Harrington-Wilson (D/1952 B1) is in Cetus, magnitude 8.9 on the 1st and 8.6 on the 31st. It will be quite close to the asteroid (8) Melpomene, their separation being about 6° on the 1st, 4° mid month and just over 6° by the 31st. On the 23rd the comet is less than a degree below the star Menkar, alpha Cet, mag 2.5.

Brian Loader  
New Zealand