Your guide to the night sky this month
All Month
Comet C/2017 K2 PanSTARRS is expected to be around ninth magnitude, following a short monthly path in the northeast of Ophiuchus, the Serpent Bearer. The comet is expected to brighten through the month from mag. +9.6 to mag. +8.8.
Sunday 1
Mag. –2.0 Jupiter lies 22 arcminutes northwest of mag. –4.0 Venus as both planets rise. Spot them from around 05:00 BST (04:00 UT) low above the east horizon.
Monday 2
If you have a clear, flat northwest horizon, keep an eye out for a slender 3%-lit waxing crescent Moon, 3.2˚ left of mag. +0.9 Mercury (as seen from the UK). If skies are clear, it may also be possible to spot the Pleiades, 2.8˚ to the right of Mercury.
Tuesday 3
The Moon is absent at the start and end of May, leaving the sky unaffected by its glare, which is perfect for this month’s ‘Deep-Sky Tour’. The darkest skies will be at the start of the month, as the June summer solstice is further away.
Wednesday 4
Minor planet 13 Egeria reaches opposition today at mag. +10.0. Egeria will be in Libra, the Scales, less than 1º west-southwest of mag. +2.7 Zubenelgenubi (Alpha (α) Librae), at 01:00 BST (00:00 UT), having passed 20 arcminutes from the star on 1 May.
Thursday 5
Minor planet 18 Melpomene reaches opposition today. Shining at mag. +10.3, Melpomene is currently located in northern Libra.
Friday 6
This morning is a good opportunity to look out for Eta-Aquariid meteors, the shower reaching its peak under moonless conditions. Although well-suited for Southern Hemisphere observation, the best chance of seeing an Eta Aquariid is in the run up to dawn.
Saturday 7
Our ‘Moonwatch’ target for May is the dramatic Apenninus mountain range, which borders Mare Imbrium. Observing it this evening and over the next couple of days will slowly reveal its intricate beauty.
Tuesday 10
This evening look for the arc of light known as the Jewelled Handle, extending into the dark of the lunar night. This clair-obscur effect is caused when the peaks of the Jura Mountains around Sinus Iridum catch the lunar dawn’s light.
Friday 13
This morning the 87%-lit waxing gibbous Moon will occult the binary star Porrima (Gamma (γ) Virginis). Observe from 01:30 BST to 02:50 BST (00:30 UT to 01:50 UT).
Monday 16
There’s a total lunar eclipse this morning. The Moon enters Earth’s penumbral (weak) outer shadow at 02:32 BST (01:32 UT), encountering the darker umbra at 03:27 BST (02:37 UT). Totality begins at 04:29 BST (03:29 UT).
Wednesday 18
Mars and Neptune appear 32 arcminutes apart this morning. Mag. +7.9 Neptune will be extremely hard to see against a brightening morning sky, mag. +0.8 Mars less so. Mag. –2.0 Jupiter lies 6.5˚ to the east-northeast of Mars.
Sunday 22
The 57%-lit waning gibbous Moon lies 5.8˚ south of mag. +0.8 Saturn this morning.
Tuesday 24
As we reach the end of May, the door opens for noctilucent cloud (NLC) spotting. If present, these ‘night-shining’ clouds are normally seen 90–120 minutes after sunset, low above the northwest horizon, or at a similar time low above the northeast horizon before sunrise.
Wednesday 25
Mag. +0.7 Mars, mag. –2.1 Jupiter and a 25%-waning crescent Moon form a right-angled triangle low above the eastern horizon as the dawn gets underway.
Friday 27
As they rise above the east-northeast horizon, mag. –3.9 Venus appears 1.1˚ from the centre of the 10%-lit waning crescent Moon. Given a flat horizon, both objects will be visible from the centre of the UK at 04:00 BST (03:00 UT).
Sunday 29
Mag. –2.1 Jupiter and mag. +0.7 Mars appear 0.6˚ apart in this morning’s sky. Catch them rising in the east around 03:00 BST (02:00 UT).
Family stargazing
There’s a total lunar eclipse visible during the early morning on Monday 16 May. Plan an early night on
15 May, setting alarm clocks for 03:00 BST. It will pay to have warm clothing and drinks at the ready so you can all be outside and ready to watch the start of the event at 03:27 BST. The Moon will be low above the southwest horizon as the initial partial stage of the eclipse begins and it will remain in this general direction as totality is reached at 04:29 BST. The Moon sets at 05:10 BST so you can all get some more sleep afterwards!
bbc.co.uk/cbeebies/shows/stargazing
NEED TO KNOW
The terms and symbols used in The Sky Guide
Universal Time (UT) and British Summer Time (BST)
Universal Time (UT) is the standard time used by astronomers around the world. British Summer Time (BST) is one hour ahead of UT
RA (Right ascension) and dec. (declination)
These coordinates are the night sky’s equivalent of longitude and latitude, describing where an object is on the celestial ‘globe’
Family friendly
Objects marked with this icon are perfect for showing to children
Naked eye
Allow 20 minutes for your eyes to become dark-adapted
Photo opp
Use a CCD, planetary camera or standard DSLR
Binoculars
10×50 recommended
Small/ medium scope
Reflector/SCT under 6 inches, refractor under 4 inches
Large scope
Reflector/SCT over 6 inches, refractor over 4 inches
GETTING STARTED IN ASTRONOMY
If you’re new to astronomy, you’ll find two essential reads on our website. Visit http://bit.ly/10_easylessons for our 10-step guide to getting started and http://bit.ly/buy_scope for advice on choosing a scope