Mercury reaches superior conjunction on January 18th and is positioned on the far side of the Sun as seen from Earth. Hence, the planet remains close to our star throughout January and is therefore unsuitably placed for observation.
The current morning apparition of Venus is now fast coming to an end. Our inner neighbour remains a brilliant object at the start of the month, but rises no more than 90 minutes or so before sunrise. As always, magnitude –3.9 Venus is easy to spot due its brilliance, although the planet is currently about as faint as it gets when seen from Earth.
Venus elongation from the Sun continues to steadily decrease during the month and by the last week of January the planet will be unobservable from northern temperate latitudes. However, observers located in the tropics and more southerly latitudes may still be able to glimpse the planet low down towards the eastern horizon in the dawn twilight sky until the end of the month.
During January the phase of Venus increases from 94 to 97%, with the planets apparent size about 10 arc seconds. On January 10th, the thin waning crescent Moon is located just 3 degrees north of Venus.
At the start of the month Venus is located in Ophiuchus before moving into Sagittarius on January 6th.
Mars remains a very difficult early evening object located towards the western / southwestern horizon. Although the planet sets just under two hours after the Sun it is positioned inconveniently low down, shines at only magnitude 1.2 and is located just a few degrees above the horizon in the evening twilight sky.
At the start of January, the "Red planet" is located in Capricornus before moving into Aquarius on January 29th.
On January 13th, the thin waxing crescent Moon will pass 6 degrees north of Mars.
Jupiter was at opposition at the beginning of last month, and continues to be visible for most of the night. Despite the planet fading from magnitude -2.7 to -2.5 during January, it remains a brilliant unmistakable object that is far brighter than any of the surrounding stars.
Jupiter starts the year moving retrograde in Taurus, close to the northern arm of the sprawling V-shaped Hyades open cluster and located just north of first magnitude orange/red star Aldebaran and just to the southeast of the famous open cluster, M45 - The Pleiades. It then reaches its stationary point on January 30th before resuming direct motion once more.
The current northern declination of Jupiter favours northern hemisphere observers, but even from southern hemisphere latitudes, where the planet appears lower down, it is still unmistakable due to its brightness. The apparent diameter of Jupiter remains large, although this month it decreases from 47 to 43 arc seconds. Even when viewed through a small telescope, a wealth of surface details are visible, including cloud bands, twists, knots and storms; including the most famous of all "The Great Red Spot". Also easily visible, but not always at the same time are the four bright Galilean moons: Io, Europa, Ganymede and Callisto.
On January 22nd, the waxing gibbous Moon passes 0.5 degrees south of Jupiter and an occultation is visible from central South America.
Saturn is now a morning object amongst the stars of western Libra, positioned well to the east of mag. 1.0 Spica, the brightest star in Virgo. At the start of January, Saturn rises up to 5 hours before the Sun with the period of visibility improving as the month progresses. By months end Saturn rises just after midnight.
During January, the magnitude of Saturn is 0.7 and the apparent tilt of the rings, as viewed from Earth, almost 19 degrees. At such an angle, the ring system is beautifully displayed and a wonderful sight in all types of telescopes. On January 15th, the distance between the Earth and Saturn dips below 10 AU and continues to decrease, closing the month at 9.75 AU. On this date, the apparent size of Saturn is 17 arc seconds.
On January 7th, the waning crescent Moon passes 4 degrees south of Saturn.
A good time to look for Saturn’s largest moon Titan (magnitude 8.6) is on mornings of January 4th and 20th when it is near greatest western elongation and on January 12th and 28th when it is near greatest eastern elongation.
Uranus is an evening object visible that now sets before midnight. The planet shines at magnitude 5.9 and is located in Pisces just south of the "Great Square of Pegasus".
It is now moving direct and heading back towards star 44 Piscium, which at magnitude 5.8 is of almost equal brightness and currently positioned only a few degrees to the east of Uranus.
On January 17th the waxing crescent Moon passes 5 degrees north of Uranus.
Neptune is an early evening object that is visible for a few hours as soon as it gets dark. The planet is located in in Aquarius and at magnitude 8.0 requires at least a pair of binoculars or a small telescope to be seen.
To locate Neptune, imagine a line connecting stars Ancha (θ Aquarii) mag. 4.2 and ι Aquarii (mag. 4.3). Just over halfway along this line is e Aqr (38 Aquarii), a mag. 5.4 star. Positioned just east of e Aqr is Neptune.
On January 14th the waxing crescent Moon passes 6 degrees north of Neptune.
Solar System Data Table January 2013
|Date||Right Ascension||Declination||Mag.||Size||Illum. (%)||Distance (AU)||Constellation|
|Sun||5th Jan 2013||19h 03m 30.7s||-22d 38m 03.0s||-26.8||32.5'||100||0.983||Sagittarius|
|Sun||15th Jan 2013||19h 47m 00.0s||-21d 09m 41.1s||-26.8||32.5'||100||0.984||Sagittarius|
|Sun||25th Jan 2013||20h 29m 22.8s||-19d 00m 56.1s||-26.8||32.5'||100||0.985||Capricornus|
|Mercury||5th Jan 2013||18h 29m 21.2s||-24d 28m 12.4s||-0.8||04.7"||98||1.420||Sagittarius|
|Mercury||15th Jan 2013||19h 39m 19.2s||-23d 24m 23.7s||-1.3||04.7"||100||1.430||Sagittarius|
|Mercury||25th Jan 2013||20h 50m 05.9s||-19d 51m 55.9s||-1.3||04.9"||99||1.381||Capricornus|
|Venus||5th Jan 2013||17h 36m 31.5s||-22d 47m 44.1s||-3.9||10.7"||94||1.565||Ophiuchus|
|Venus||15th Jan 2013||18h 30m 59.4s||-23d 08m 33.5s||-3.9||10.4"||96||1.599||Sagittarius|
|Venus||25th Jan 2013||19h 25m 15.8s||-22d 18m 40.2s||-3.9||10.3"||97||1.628||Sagittarius|
|Mars||5th Jan 2013||20h 41m 27.3s||-19d 27m 41.0s||1.2||04.2"||98||2.234||Capricornus|
|Mars||15th Jan 2013||21h 13m 20.6s||-17d 14m 29.3s||1.2||04.1"||98||2.257||Capricornus|
|Mars||25th Jan 2013||21h 44m 30.2s||-14d 43m 10.3s||1.2||04.1"||99||2.280||Capricornus|
|Jupiter||5th Jan 2013||04h 22m 08.4s||20d 49m 56.9s||-2.7||46.4"||100||4.248||Taurus|
|Jupiter||15th Jan 2013||04h 19m 14.1s||20d 45m 21.9s||-2.6||45.2"||99||4.360||Taurus|
|Jupiter||25th Jan 2013||04h 17m 42.4s||20d 44m 01.5s||-2.6||43.9"||99||4.491||Taurus|
|Saturn||5th Jan 2013||14h 32m 05.0s||-12d 28m 24.7s||0.7||16.3"||100||10.168||Libra|
|Saturn||15th Jan 2013||14h 34m 39.6s||-12d 38m 36.7s||0.7||16.6"||100||10.012||Libra|
|Saturn||25th Jan 2013||14h 36m 39.4s||-12d 45m 45.8s||0.7||16.9"||100||9.849||Libra|
|Uranus||5th Jan 2013||00h 18m 10.3s||01d 12m 02.7s||5.9||03.5"||100||20.204||Pisces|
|Uranus||15th Jan 2013||00h 19m 00.9s||01d 17m 55.3s||5.9||03.5"||100||20.371||Pisces|
|Uranus||25th Jan 2013||00h 20m 08.4s||01d 25m 35.3s||5.9||03.4"||100||20.527||Pisces|
|Neptune||5th Jan 2013||22h 13m 03.2s||-11d 41m 16.6s||8.0||02.2"||100||30.661||Aquarius|
|Neptune||15th Jan 2013||22h 14m 12.4s||-11d 34m 47.3s||8.0||02.2"||100||30.775||Aquarius|
|Neptune||25th Jan 2013||22h 15m 28.9s||-11d 27m 37.9s||8.0||02.2"||100||30.867||Aquarius|