Solar System notes for JANUARY, 2016
The Solar System in January 2016
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 January
January 1 NZDT January 31 NZDT morning evening morning evening SUN: rise: 5.48am, set: 8.59pm rise: 6.21am, set: 8.45pm Twilights Civil: starts: 5.17am, ends: 9.31pm starts: 5.53am, ends: 9.14pm Nautical: starts: 4.34am, ends:10.14pm starts: 5.15am, ends: 9.52pm Astro: starts: 3.43am, ends:11.04pm starts: 3.33am, ends:10.34pm
January PHASES OF THE MOON (times as shown by GUIDE)
Last quarter: January 2 at 6.30 pm (05:30 UT) New moon: January 10 at 2.30 pm (01:30 UT) First quarter: January 17 at 12.26 pm (Jan 16, 23:26 UT) Full moon: January 24 at 2.46 pm (01:46 UT)
The Earth is at perihelion on January 3 at noon NZDT (Jan 2, 23 hrs UT). It will then be 147 million km from the Sun (0.9833 AU).
The planets in January
At the beginning of January only Mercury of the naked-eye planets will be in the evening sky. But, at best, it will be very difficult to see. After conjunction mid month, Mercury joins the other four naked eye planets in the morning sky. The early evening sky will then be bereft of naked eye planets. By the end of January, Jupiter will rise about 10.30 pm so be easily visible to the east by midnight.
Mercury starts January as an evening object setting some 80 minutes after the Sun. On the 1st its magnitude will be -0.3 but with an altitude only 3.5 degrees, 45 minutes after sunset, it will be a difficult object. The Sun will be 8 degrees below the horizon so the westerly sky will still be bright making the planet difficult to see.
During the next few days Mercury gets closer to the Sun, especially after it is stationary on January 5 when the planet will start moving to the west and so towards the easterly moving Sun. Inferior conjunction is on January 14 when Mercury will be just under 50 million km from the Sun with the Earth 100 million km further out.
After conjunction Mercury becomes a morning object rising shortly before the Sun. The planet's westerly movement will take it quite quickly further from the Sun making it visible in the dawn sky. It is again stationary on January 26 by which date its motion away from the Sun will have slowed. On the last morning of January Mercury will rise almost 2 hours before the Sun. An hour after it rises the planet will be 8 degrees above the horizon with Venus the same distance above and to its left. At magnitude 0.3 Mercury should be fairly easy to see especially with Venus to act as a guide. But this is at about 5.30 am.
Venus remains a morning object rising about 140 minutes before the Sun all month. It starts January in Scorpius but moves into Ophiuchus on the morning of the 6th. Venus moves into Sagittarius on the 21st. On January 8 Venus will be 6 deg from Antares and on the 30th 3 degrees from the 2.8 magnitude star lambda Sgr.
As it moves to the east through the stars, Venus will overtake Saturn on January 9. At their closest, at about 5 pm, the two planets will be just over 5 arc minutes apart, about 1/6th of the moon's diameter. From NZ on the 9th at 5 am the two planets will be just over half a degree apart with Venus to the left of Saturn. They will be a similar distance apart on the 10th but with Venus now on the right of Saturn.
The crescent moon is closest to the two planets on the morning of January 7 when it will be 5 degrees left of Venus and 7.5 degrees from Saturn. The following morning the moon as a thinner crescent will below and a little to the right of the planets.
Mars rises 4 hours before the Sun on January 1 and nearly 6 hours before it on the 31st. Mars will be considerably higher than Venus. The planet starts the month at magnitude 1.3 in Virgo, 6 degrees below Spica. On the 18th Mars moves into Libra where it ends month a little brighter, magnitude 0.8. The morning of the 31st finds Mars 1.5 degrees from the star alpha Lib, magnitude 2.73
The moon, 36% lit, is closest to Mars on the morning of the 4th. The moon will be 2.5 degrees to the left of Mars.
Jupiter starts January in Leo with the 65% lit moon less than a degree to its upper left. On the 1st Jupiter rises about 12.30 am, by the end of January it will rise just before 10.30 pm so becoming visible late evening.
The planet is stationary on the 9th so its position changes little during the month. It gets to within a quarter of a degree of the boundary of Leo with Virgo, but as it starts moving back to the west retreats from the latter constellation.
The moon, now 82% lit, returns to the vicinity of Jupiter towards the end of January. On the morning of the 28th the two will be close to 4 degrees apart just before sunrise. Later in the morning, well after they set, the two will be just over a degree apart
Saturn rises just under two hours before the Sun on January 1, over four hours before the Sun on the 31st. It is in Ophiuchus all month at magnitude 0.5. See the notes for Venus for further details.
Uranus remains in Pisces during January at magnitude 5.8 to 5.9. It is an evening object. By the end of January it will be setting about 11.30 pm.
Neptune is also an evening object throughout January, by the end of the month it will set at 10.00 pm. The planet, magnitude 7.9, is in Aquarius.
Pluto continues to be in Sagittarius throughout January at magnitude 14.4. It is at conjunction with the Sun on January 6, after which it becomes a morning object rising as much as 2 hours before the Sun by the 31st. At conjunction Pluto will be nearly 5.1 billion km, 34 AU from the Earth and just over 33 Au beyond the Sun.
BRIGHTER ASTEROIDS: (1) Ceres is an evening object setting just before midnight on the 1st. It starts January in Capricornus at magnitude 9.3; on the 15th it moves into Aquarius. By the 31st, when it sets at 10.18, Ceres will be just over 10 degrees from Neptune.
(4) Vesta is in Cetus during January. It fades a little during the month from magnitude 8.0 to 8.3. The asteroid will be 6 degrees from Uranus on the 31st when it will set just before midnight.
(15) Eunomia is an evening object in Pisces during January, its magnitude fading from 9.5 to 9.8. It sets just before 11 pm on the 31st.
(27) Euterpe starts January in Gemini at magnitude 8.8 and is in the sky almost the whole night. By the 31st it will be a magnitude fainter and sets by 3am. The asteroid moves into Taurus on January 6.
Brian Loader New Zealand
Solar System Notes for December, 2015
The Solar System in December 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. The southern summer solstice occurs on December 22 at 5.48 pm NZDT (04:48 UT) SUNRISE, SUNSET and TWILIGHT TIMES in December
December 1 NZDT December 31 NZDT morning evening morning evening SUN: rise: 5.40am, set: 8.39pm rise: 5.47am, set: 8.59pm Twilights Civil: starts: 5.10am, ends: 9.10pm starts: 5.16am, ends: 9.31pm Nautical: starts: 4.28am, ends: 9.51pm starts: 4.33am, ends:10.14pm Astro: starts: 3.40am, ends:10.40pm starts: 3.42am, ends:11.05pm
December PHASES OF THE MOON (times as shown by GUIDE)
Last quarter: December 3 at 8.40 pm (07:40 UT) New moon: December 11 at 11.29 pm (10:29 UT) First quarter: December 19 at 4.14 am (Dec 18, 15:14 UT) Full moon: December 26 at 12.12 am (Dec 25, 11:12 UT)
The Planets in December
Only Mercury will be an evening object during December and it will be difficult to see. The remaining naked eye planets will be spread across the morning sky. Saturn too close to the Sun for observation early in the month, all 4 spread widely across the easterly morning sky at the end of December.
Mercury, an evening object, will set some 40 minutes after the Sun on the 1st, only 10 minutes after the end of civil twilight. As a result it will be too low to observed despite a -0.8 magnitude The planet moves rather further from the Sun during December until it reaches its greatest elongation 20° east of the Sun on the 29th. Even then it will set only 75 minutes after the Sun at the end of Nautical twilight. 45 minutes after sunset, Mercury will be only 4.5° above a level horizon towards the west-north-west, so still not an easy object despite its -0.4 magnitude.
Venus, MARS, JUPITER and SATURN in the morning sky during December.
Saturn was at conjunction on the last day of November, so will be too close to the Sun to see during the early part of December.
On the 1st as seen at 5am, the other three planets will be spread out across the evening sky. Most obvious will be Venus, due east and just on 13° up. Mars, magnitude 1.5, will be 14° away to its upper left with an altitude 20°. Jupiter will be 20° beyond Mars and nearly 27° up. Mars and Venus will be in Virgo with the latter 4° below Spica. Jupiter will be in Leo.
During December all three planets will be moving to the east through the stars, Venus most rapidly and Jupiter the slowest. As a result they will spread further apart. Venus will be in Libra by the 12th while Mars will pass Spica on the 24th some 3.5° below the star. Jupiter will remain in Leo but be close to the constellation’s boundary with Virgo by the end of the month. Saturn, in Ophiuchus, will move further into the morning sky to become visible by the end of December.
On the morning of the 31st the 4 planets, from Saturn, through Venus and Mars to Jupiter will be spread across some 77° of sky. Added to that, the Moon, 74% lit, will be 13° beyond Jupiter making a spread of a full 90° in all. At 5am with the Sun just over 8° below the horizon (at Wellington), Venus will be 15.5° up and in a direction 10° south of east. Saturn at magnitude 0.5, will be some 9° up just over 10° to the lower right of Venus. Mars will be on the opposite side of Venus 33° away and 33° above the horizon. Jupiter will be another 35° beyond Mars and 41° above the horizon. Finally the moon will be another 13° beyond Jupiter but at the same altitude.
Earlier in the month, the moon passes the planets. On the morning of December 5 the moon, 37% lit, will be 5.5° from Jupiter, 2 mornings later the moon now 20% lit will be 7° from Mars and the next morning, the 8th, just over 1° from Venus.
Uranus remains in Pisces during December at magnitude 5.7. It is an evening object. By the end of December it will be setting about 1.30 am.
Neptune is also an evening object throughout December, by the end of December it will set at midnight. The planet is in Aquarius, magnitude 7.9 throughout the month.
Pluto continues to be in Sagittarius throughout December at magnitude 14.4. At the end of the month it sets a few minutes after the Sun.
BRIGHTER ASTEROIDS: (1) Ceres is in Capricornus during December with a magnitude 9.3. It is about 20° from Neptune and like the planet will set close to midnight at the end of December.
(4) Vesta is in Cetus during December although it crosses a corner of Pisces mid month. Its magnitude fades from 7.5 to 8.0 during December. Vesta will be about 15° from Uranus, and will set at a similar time to the planet.
(15) Eunomia starts December in Pegasus but moves into Pisces on the 23rd. Its magnitude fades from 8.9 to 9.4 during December. It is an evening object, by the end of December it will set just after midnight.
(27) Euterpe is in Gemini, it starts December at magnitude 9.4, its brightness peaks at magnitude 8.4 when at opposition on December 25 and drops back to 8.9 by December 31. Euterpe is close to two red stars during the month. On December 14, with a magnitude 8.9, it will be half a degree below mu Gem, mag 2.9. Eight nights later Euterpe, at 8.6, will be 43 arc minutes below eta Gem, mag 3.3. In both instances it will be the brightest object immediately below the star.
Brian Loader New Zealand