BBC Sky at Night Magazine

PICK OF THE MONTH

Jupiter

Best time to see: 1 January, 19:40 UT Altitude: 49°

Location: Aries

Direction: South

Features: Complex atmosphere, Galilean moons

Recommende­d equipment: 75mm or larger telescope

Jupiter is well placed at the start of January, able to reach its highest altitude under dark-sky conditions. Shining at mag. –2.4, the planet presents a disc full of detail with an apparent diameter of 43 arcseconds. A small telescope shows it as a slightly oval disc, the gas giant’s rapid spin – completing one rotation about its axis in slightly under 10 hours – causing it to bulge at its equator, producing the oblate shape seen through the eyepiece.

Small scopes will also reveal larger banding within Jupiter’s atmosphere, most notably the North Equatorial Belt (NEB) and South Equatorial Belt (SEB). A 100mm or larger scope will be needed to show the persistent storm feature known as the Great Red Spot.

A just past first quarter, 56%-lit Moon sits 2° north-northwest of Jupiter in the early evening of 18 January. By the last week of January, Jupiter begins to succumb to the evening twilight, the sky only becoming truly dark when Jupiter is to the west of south. Despite this, even on 31 January Jupiter can be seen around 50° up against a deep twilight sky.

This is excellent news for visual observatio­n as well as imaging the planet, because at this altitude it is lifted well above the turbulent atmospheri­c layer experience­d low towards the horizon. As a result, we’ll have a better opportunit­y to see finer detail within the planet’s atmosphere. Jupiter has a large number of moons, but only four that are easily seen through a small scope: the socalled Galilean moons, Io, Europa, Ganymede and Callisto. These are fascinatin­g to watch as they dance back and forth either side of the planet’s disc. ▲ The four ‘Galilean’ moons are easy to see through a small scope

Mercury

Best time to see: 10 January, 40 minutes before sunrise Altitude: 6° (low)

Location: Ophiuchus Direction: Southeast Morning planet Mercury shines at mag. +0.6 and rises 100 minutes before the Sun on 1 January. It subsequent­ly brightens, shining at mag. –0.2 and rising 90 minutes before sunrise on 17 January, with mag. –3.9 Venus 11.1° to the west. Mercury and Mars appear close on 27 January. Rising 52 minutes before the Sun, mag. +1.3 Mars is located 21 arcminutes southeast of mag. –0.2 Mercury. On 28 January, Mars appears 0.5° west-southwest of Mercury. By month’s end, slowly heading back towards the Sun, Mercury becomes harder to see. Best time to see: 1 January, from 06:30 UT

Altitude: 7° (low)

Location: Scorpius

Direction: Southeast Venus is a morning object, rising 3 hours before sunrise on 1 January and shining at mag. –3.9. On the morning of the 8th, a 12%-lit crescent Moon appear 8.1° southwest of Venus and on 9 January, now as a 6%-lit crescent, 9.8° southeast of the planet. On 16 January, mag. –3.9 Venus and –0.2 Mercury appear 11.1° apart. Venus retains its brilliance but its position deteriorat­es, rising 100 minutes before sunrise on 31 January.

Best time to see: 31 January, 30 minutes before sunrise Altitude: 2° (very low) Location: Scorpius Direction: Southeast Mars is too dim and close to the Sun to be visible. On the 27th, mag. +1.3 Mars sits 20 arcminutes from mag. –0.2 Mercury, a tricky sighting due to low, pre-sunrise altitude.

Best time to see: 1 January,

17:40 UT

Altitude: 21°

Location: Aquarius Direction: South-southwest Evening planet Saturn is losing its battle with the twilight. On 1 January, it appears around 20° above the southwest horizon as darkness falls. A lovely 14%-lit crescent Moon sits 4.5° east of mag. +0.8 Saturn on the evening of 14 January.

Best time to see: 1 January,

20:30 UT

Altitude: 54°

Location: Aries

Direction: South

An evening object, Uranus is close to mag. +4.3 Botein (Delta (δ) Arietis). At mag. +5.7 it’s theoretica­lly visible to the naked eye, but binoculars are recommende­d. Its green hue requires a telescope. Just after darkness falls on the 19th, the 67%-lit Moon lies 2.3° north of Uranus. The planet reaches 54° altitude, due south, in darkness the whole month.

Best time to see: 1 January,

18:10 UT

Altitude: 32°

Location: Pisces

Direction: South-southwest Evening planet Neptune appears south of the Circlet asterism in Pisces. At mag. +7.9 it’s past its best, losing altitude under dark-sky conditions all month. It sits 1.3° north of the 24%-lit Moon’s centre on the evening of 15 January, just before moonset.