Spectacular Venus is currently an evening object, shining at mag. –3.9. The planet’s position is improving due to the plane of the ecliptic making a steeper angle relative to the western horizon at sunset.
As the main planets appear close to this plane, it means that any such objects close to the western horizon after the Sun has gone down will appear higher and last longer before setting.
This is demonstrated by an increase in the setting time after sunset. At the start of the month Venus sets three hours after the Sun. By the end of the month this value will have extended to nearly four hours.
Being above the horizon for longer after sunset allows Venus to appear against a darker background sky and this is when, visually at least, the planet really is spectacular.
At the start of January this occurs when Venus is relatively low with just 5˚ of altitude.
By the end of January, things improve and Venus appears around 15˚ up when the sky becomes truly dark.
The phase and relative sizes of the planets in January 2020. Each planet is shown with south at the top, to show its orientation through a telescope. Credit: Pete Lawrence
Ironically, being so bright, looking at Venus through a telescope when it’s in a truly dark sky introduces problems of contrast, not to mention poor seeing due to low altitude.
The best views are either during the day or just as twilight is starting to darken the sky. Through a telescope Venus currently shows a gibbous phase, 81-% illuminated on 1 January, 73%-illuminated on 31 January.
The waxing crescent Moon sits near Venus on the evenings of 27 and 28 January.
On the evening of the 27th, Venus appears separated from Neptune by a little over 4 arcminutes; the Solar System’s brightest and dimmest planets together.
Venus will be at mag. –4.0 on this date with Neptune 52,500 times dimmer at mag. +7.9.
Observing Venus in the January night sky
Best time to see: 31 January, from 17:00 UT
Features: Phase, subtle disc shadings
Recommended telescope: 75mm or larger
How to see the rest of the planets this month
Best time to see: 31 January, 40 minutes after sunset
Altitude: 4.5˚ (very low)
Not visible until the last week of January when it appears low in the southwest sky after sunset. As seen from the UK, a thin waxing crescent Moon sits 2.5˚ below mag. –1.0 Mercury on 25 January but both objects are low.
Mercury sets 70 minutes after the Sun on 31 January shining at mag. –0.9 and 85%-lit. On the 31st Mercury will appear separated from Venus by 26˚.
Best time to see: 31 January, 18:00 UT
Altitude: 6˚ (low)
Orange Mars is currently a morning object located in the southern part of Ophiuchus. Telescopically, the planet isn’t much to look at but this will improve as the distance between Earth and Mars decreases.
On 1 January Mars shines at mag. +1.6 and presents a 4 arcsecond disc, 95%-lit through the eyepiece. On the 17th, Mars sits 4.8˚ north of the star Antares. A waning crescent Moon sits 6.7˚ west-northwest of Mars on the 20th.
Best time to see: 31 January, from 07:15 UT
Altitude: 3˚ (very low)
Jupiter is a morning planet that appears rather close to the Sun at the start of January. By the month’s end, mag. –1.7 Jupiter will rise 1.3 hours before the Sun.
A slender waning crescent Moon sits near Jupiter on the morning of the 22nd, the 6%-lit crescent appearing 9.7˚ to the west of Jupiter. On the morning of the 23rd, the now 2%-lit waning crescent Moon sits 3.3˚ to the east-southeast of Jupiter.
Best time to see: 1 January, 19:10 UT
Uranus is an evening planet, which appears well positioned at the start of January, able to reach its highest point in the sky, due south, in darkness early evening, around 19:30 UT. By the end of the month, the planet loses this ability, being slightly to the west of south as darkness falls.
At mag. +5.8, in theory at least it should be possible to see Uranus with the naked eye. You’ll need a good, dark sky to do this. Through a telescope it’s Uranus’s green tint that catches the eye: it’s rather striking.
Best time to see: 1 January, 18:20 UT
Lying 46˚ further to the west than Uranus, Neptune’s position in the January sky deteriorates. Where Uranus appears at its highest point due south in darkness at the month’s start, Neptune is to the west of south.
By the end of the month, mag. +7.9 Neptune is just 12˚ up above the west-southwest horizon as true darkness falls. A meeting between Venus and Neptune on the 27th sees both planets separated by just 4 arcminutes. You’ll need a scope, binoculars, or a camera to see this.
Saturn is not visible in the night sky this month.
This article originally appeared in the January 2020 issue of BBC Sky at Night Magazine. Pete Lawrence is an experienced astronomer and a co-presenter of The Sky at Night.