Solar System Notes, January 2015
January Moon & Planet data for 2015
All dates and times are NZDT (UT +13 hours) unless otherwise specified. 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 January 31 morning evening morning evening Sun rise: 5.48am, set: 8.59pm rise: 6.22am, set: 8.45pm Twilights Civil: starts: 5.17am, ends: 9.31pm starts: 5.54am, ends: 9.14pm Nautical: starts: 4.34am, ends:10.14pm starts: 5.15am, ends: 9.52pm Astro: starts: 3.43am, ends:11.04pm starts: 4.33am, ends:10.34pm
The Earth is at perihelion, its closest to the Sun for the year, on January 4 when it will be 0.983 Astronomical Units, 147 million km, from the Sun.
January Phases of the Moon (times as shown by guide) Full Moon: January 5 At 5.52 Pm ( 04:52 Ut) Last Quarter: January 13 At 10.47 Pm ( 09:47 Ut) New Moon: January 21 At 2.14 Am (Jan 20, 13:14 Ut) First Quarter: January 27 At 5.48 Pm ( 04:48 Ut)
The Planets in January
Venus and Mars are visible for a short time after sunset. Mercury will also be close to Venus in the first part of the month, but will be lost to view by about the 20th. Jupiter rises in the opposite side of the sky a little later in the evening at first. It rises at sunset at the end of January. Saturn remains a morning object although rising earlier as the month progresses.
MERCURY will be briefly visible in the evening sky, near Venus, during the first half of January. It will set just over an hour after the Sun up to mid January. During the first part of January, Mercury will gradually move closer to Venus as they both move to the east through the stars. They are less than 1Â° apart from the 8th to the 13th. But Mercury will never quite catch up to Venus as its motion slows. With a magnitude of -0.7 Mercury will be easy to see, especially in binoculars, to the lower left of the much brighter Venus.
After mid January Mercury will fall behind Venus again as the innermost planet's motion drops away. Mercury is stationary on the 14th when it stops moving to the east. It will then be 19Â° east of the Sun. Over the next few days the planet will move increasingly rapidly to the west and towards the Sun, until it is at inferior conjunction between the Earth and Sun on the 30th. At conjunction it will be nearly 3.5Â° north of the Sun; the planet will be 98.6 million km, 0.659 AU, from the Earth and half this distance from the Sun.
Obviously Mercury will be lost to view several evenings before conjunction.
VENUS is also an early evening object, setting just over an hour after the Sun all month. It starts January in Sagittarius but moves into Capricornus on the 3rd and on into Aquarius on the 25th. On the 22nd the brightest star in Capricornus, delta Cap mag 2.85, will be 1Â° above Venus.
By the end of the month Venus will be 10Â° to the lower left of Mars. As noted above, Venus and Mercury will be close during the first half of the month, less than 3Â° apart up to the 18th. Mercury will always be to the lower left of Venus and visible before any star.
On the evening of the 22nd the 5% lit crescent moon will be 7Â° to the lower right of Venus. The moon will set about 50 minutes after the Sun, so will be very low.
MARS is the third early evening planet of the month. It sets about two and a quarter hours after the Sun on the 1st, but only 90 minutes later on the 31st. Thus it will gradually get a little lower during the month. Mars starts January in Capricornus but moves on into Aquarius on the 9th.
In Aquarius Mars will catch up with and pass Neptune which moves much more slowly. The two will be closest on the 20th when Neptune will be only 20 arc-minutes (two-thirds the diameter of the full moon) below and a little left of Mars. Neptune's magnitude will be 8.0. Thus it should be readily visible in binoculars once the sky is sufficiently dark. There are no stars between the planets likely to be mistaken for Neptune. But the two planets will be low with an altitude of only 6Â° one hour after sunset. On the 19th Mars will be 40 arc-minutes left of Neptune, on the 21st, 1Â° to its upper right.
On the 23rd the moon, the crescent now 11% lit, will be just over 5.5Â° to the lower right of Mars.
JUPITER rises 2 hours after sunset on the 1st and at the time of sunset on the 31st. Thus it is the fourth planet visible in the evening sky, albeit later than the other three. It will spend the month moving slowly to the west through Leo, situated 8 to 12Â° to the left of Regulus, magnitude 1.4.
The 90% lit waning moon passes Jupiter on the 8th when the moon will be 5Â° to the upper right of the planet as seen late evening shortly after they rise.
Mutual Events of Jovian Satellites
There are about 26 mutual events of Jupiter's Galilean satellites observable from NZ during January. The events involve either occultations or eclipses of one satellite by another. Visually, mutual occultations are the more interesting to watch as satellites can be seen to merge and separate over a period several minutes. Eclipses are normally partial events with fairly small magnitude changes of the eclipsed satellite. Consequently they are mostly difficult to detect visually. Total eclipses are rare.
Useful observations and timings of both types of event can be made by those set up for the video observation of minor planet occultations.
For more details refer to the IMCCE web site, <http://www.imcce.fr/phemu/> where predictions and requirements for observing and reporting information are available. Users of Dave Herald's Occult program can generate their own predictions.
SATURN is a morning object throughout January. It rises some 2 hours and 20 minutes before the Sun on the 1st and nearly 5 hours earlier on the 31st. The planet starts the month in Libra, moving into Scorpius on the 18th when it will be 10Â° to the left of Antares. At the end of January, Saturn will be 1Â° from the star beta Sco. The magnitude 2.6 star has a fainter companion, magnitude 4.5, some 13.8" from it. Binoculars will show the pair.
On the morning of January 17 the waning moon, 19% lit, will be a little less than 4Â° below Saturn.
URANUS remains in Pisces as an evening object magnitude 5.8. By the end of January it will set soon after 11pm. The 30% lit moon will be 2Â° below Uranus on January 25. An occultation of the planet will be visible from a large part of northeast Asia
NEPTUNE is an early evening object in Aquarius at magnitude 8.0. On January 31 it will set at the same time as Venus, a few minutes before 10 pm. It will then be a little under 2Â° to the right of Venus. The conjunction of Mars and Neptune on the 20th (see Mars above) will give an opportunity to easily find the fainter outer planet using binoculars.
PLUTO is in Sagittarius at conjunction with the Sun of the 3rd. It will then be 32.8 astronomical units beyond the Sun and just over 5 billion km from the Earth. Light from Pluto takes about 4hours and 40 minutes to reach the Earth.
(1) Ceres rises an hour before the Sun on January 1, some three and three quarter hours before it on the 31st. The asteroid is in Sagittarius, it will dim slightly during the month from magnitude 8.9 to 9.2 during January.
(3) Juno is at opposition on January 27 with a magnitude 8.1. This makes it the brightest asteroid currently observable. The asteroid is in Hydra.
(4) Vesta is at conjunction with the Sun on January 11. At conjunction it will be 35 arc-minutes from the Sun as seen from the Earth. Its distance from the Sun will be 2.20 AU, from the Earth 3.16 AU, 473 million km.
(6) Hebe, in the evening sky, dims from magnitude 9.0 to 9.6 as the Earth's distance from the asteroid increasing during January. The asteroid will be in Eridanus at first but moves into Taurus on the 11th.
The follwing table lists various solar system object events during January. A list of astronomical terms used in may be found after the table.
|January 2||Aldebaran 1.4 degrees south of the Moon|
|January 3||Moon northern most declination (18.7 degrees)
Pluto at conjunction
|January 4||Earth at perihelion|
|January 5||Moon full|
|January 8||Jupiter 4.8 degrees north of the Moon
Regulus 3.9 degrees north of the Moon
|January 9||Moon at apogee|
|January 13||Moon last quarter
Spica 3.0 degrees south of the Moon
|January 14||Mercury greatest elong E(19)|
|January 16||Saturn 1.8 degrees south of the Moon|
|January 18||Moon southern most declination (-18.6 degrees)|
|January 19||Pluto 2.8 degrees south of the Moon|
|January 20||Mars 0.2 degrees south of Neptune
|January 21||Mercury stationary
Mercury 2.9 degrees south of the Moon
Moon at perigee
|January 22||Venus 5.4 degrees south of the Moon
Neptune 3.7 degrees south of the Moon
|January 23||Mars 3.8 degrees south of the Moon|
|January 25||Uranus 0.6 degrees south of the Moon Occn|
|January 27||Moon first quarter|
|January 29||Aldebaran 1.2 degrees south of the Moon Occn|
|January 30||Mercury inferior conjunction|
|January 31||Moon northern most declination (18.5 degrees)|
- apogee: Furtherest point in the orbit of a body orbiting the Earth
- conjunction: Two astronomical objects are 'lined up' (have the same right ascension) when viewed from Earth. If only one object is mentioned the Sun is generally the other object.
- declination: 'Latitude' for celestial objects. The distance in degress above (north) or below (south) the celestial equator.
- inferior conjunction: Conjunction where a solar system object is between the Earth and the Sun
- perigee: Nearest point in the orbit of a body orbiting the Earth
- perihelion: Nearest point in the orbit of a body orbiting the Sun