Astronomy Now - January 2021

Highlights: Remote Uranus in the evening

When: evenings throughout January

What’s special: At the turn of the year, the remote ice-giant Uranus is in good shape in the evening
sky among the stars of Aries. It’s only two months past opposition and so offers a decent amount of
twilight-free time throughout January in which to observe it. Under a pristine ultra-dark sky,
Uranus, shining at magnitude +5.7, can be detected without optical aid, though a pair of 10 × 50
binoculars makes its detection a piece of cake.

How to observe: A small telescope operating at low magnication clearly shows Uranus as non-
stellar, with its characteristic green-blue tint. A 80–100mm (~three- to four-inch) telescope at a
power around 100× should be able to resolve its 3.6-arcsecond-sized disc. Uranus crawls slowly
retrograde (east to west) through Aries until 16 January, when it reaches its second stationary point.
Look for the planet between magnitude +5.5 xi (ξ) Arietis, 3.3 degrees to the south-east, and the
magnitude +5.7 star 19 Arietis, some 2.3 degrees to the north-north-west.

At mid-month, it crosses the southern meridian (culminates) at around 6.30pm, when it attains at
its highest altitude (around 52 degrees, from London).

e red planet Mars, moving faster east to west, has been closing in on Uranus since the start of the
year; by 10 January the pair should lie within the ve-degree eld of view of 10 × 50 binoculars.
ey 0° lie closest together, with Mars just 1.7’ north, on the evening of 21 January. A near rst-
quarter Moon lies around six degrees south-east of the pair at this time.

Uranus lies in Aries throughout 2021; on the evening of 21 January Mars sits just 1.7 degrees north, with the Moon is close
attendance too.

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Highlights: Remote Uranus in the...

January 2021

Astronomy Now