Night Sky Notes – May 2018

Night sky notes for May 2018         Geoff Mitchell

The May night sky shows the summer constellations rising  mid evening and the spring constellations heading into the western twilight  The bright planet Jupiter is now low in the south by early evening, reaching opposition in the constellation of Libra on May 9th.  Binoculars show a tiny disk and the four Galilean moons Io, Europa, Ganymede and Callisto changing position evening to evening as they orbit the giant planet. Telescopes reveal the most prominent cloud belts in the equatorial region and the subtle straw coloured `Great Red Spot`. At favourable times the Galilean moons cross in front of Jupiter (as seen from Earth) , these transit events can also produce shadows cast onto the cloud tops . To observe these shadow transits requires a moderate telescope (20cm aperture or larger) and moderate magnification (x 150).

The bright planet Venus can now be seen low in evening twilight, small telescopes show a disk with a phase of around 80%.

The late spring night sky contains many fine objects to view but also has a few notable events of special interest.   From late May onwards Look to the NW  some 90 to 120  minutes  after sunset  or to the NE before sunrise  i.e. when the Sun just below the horizon during the summer months when extremely high clouds at 80 km altitude known as Noctilucent Cloud (NLC) may be seen. NLC’s show a bluish colour and also show filamentary structure.

The constellation of  Virgo due south as twilight fades contains a large cluster of Galaxies , the Virgo Super cluster , visible as faint misty patches in moderate sized telescopes – the bright late evening skies however makes observing these quite a challenge . Our own Milky Way galaxy stretches from the constellation of Auriga [The Charioteer], marked by the bright star Capella and through the constellations of Perseus and Cassiopeia all now positioned low in the north.  In the south the night sky looks outward to the distant galaxies of the Virgo and Coma cluster.

In the east the summer constellation of Cygnus [The Swan] now rises by late evening. The bright star Vega in the adjacent constellation of Lyra [The Lyre] is seen low above the north east horizon and Altair in the constellation of Aquila low in the east. Vega, Altair and Deneb, in the constellation of Cygnus form the `Summer Triangle` asterism, a useful sign post for the summer skies.  Adjacent to  Lyra the familiar `keystone asterism ` of the constellation  Hercules is noted for the Globular clusters  M13 and M92 the former containing some 750,000 stars, a nice view in a small telescope .

Scorpius [The Scorpion] in part is visible low in the south use binoculars to see the myriad of stars in these rich star clouds, best seen on clear dark moonless evenings from darker locations outside the town. The red star Antares, the name means `rival to Mars ` the characteristically deep red in colour is easily seen in binoculars. Look low in the SE late evening in late May to find a yellowish star in Scorpius which is in fact the ringed planet Saturn which reaches opposition in late June. Although rather low as seen from the UK, its ring system is now wide open, a classic view of this gem of the solar system. Small telescopes will show the rings and the brightest moon Titan. Larger telescopes show up to six or so fainter moons and any white oval features on the planets disk.

The familiar asterism of the plough in the constellation of Ursa Major, The Great Bear is seen high overhead with its handle or tail pointing upwards mid evening. Use the right hand pair of stars Dubhe and Merak (The pointers) to find the faint pole star Polaris and the position of North.

High in the east the bright orange star Arcturus in the constellation of Bootes [The Herdsman] is the brightest star in the northern hemisphere of the sky.  Between Arcturus and the Keystone asterism in Hercules lies the `U` shaped constellation of Corona Borealis [Northern Crown]. The faint 11th magnitude star T Coronae Borealis ` Blaze Star` is a  reoccurring nova  (eclipsing binary star system)  that periodically sheds material and brightens to 2nd or 3rd magnitude; the last two outbursts were in 1866 and 1946.

Mars is located on the border of Capricornus / Sagittarius, rising by early morning and is unmistakably red in colour .The apparent size of the disk increase from 11 to 15 arc second during May as the planet approaches opposition in late July.

Comet 2016 R2 Panstarrs is faint at12th magnitude located in the constellation of Auriga. The comet reaches perihelion on May 9th at a distance of 387 million km from the Sun and is a long period comet with an orbital period of around 20,800 years.



Planets in May 2018

Mercury reached greatest elongation on April 29th and in May is poorly placed in UK dawn skies

Venus is visible in evening twilight and is located north of the crescent Moon on May 17th.

Mars rises early morning in May but will feature prominently in our evening summer skies at opposition in July.

Jupiter is now low in the south in the constellation of Libra late evening with good telescopic views.

Saturn rises by midnight by late May, low in Sagittarius – rings remain wide open in 2018 – Nice.

Uranus reached conjunction in April, visible again in autumn evening skies.

Neptune reached conjunction in March, visible again in autumn evening skies.

Dwarf planet Pluto reaches opposition on early July (Mag 14.1) in Sagittarius.

Moons phases in May  2018

New Moon         May 15th             Moonless, best time for deep sky observing.

First Quarter     May 22nd            Best days to see shadow details in lunar craters (early evening)

Full Moon            May 29th             Best days to see bright ray craters like Copernicus / Tycho.

Last Quarter      May 8th               Moon visible in daytime skies.  Do not look directly at the Sun.


Meteor shower s       η Aquarids – peak May 5th, range April 24th to May 20th – ZHR 40/ hour (low in UK skies)

α Scorpiids maxima April 28th – May 12th, low rates only ZHR  just 5


The highlights of the month

Jupiter is low in the south by late evening with cloud belt features and moons visible in modest telescopes.

Saturn low in south east by midnight  , rings open at 26° DE [tilt] showing Saturn’s North Pole.

Noctilucent cloud – from late May watch the NW skies 2 hours after sunset (see text)

Thin 8% waxing crescent Moon visible below Venus  after sunset on May 17th , note the dimly lit Earthshine.

May 9th Jupiter at opposition but just 20° elevation due south by late evening in UK skies. .

Crescent Moon visibility,

A very thin 2.7% waxing crescent Moon is located low in western skies after sunset from around 21:10 until moonset is 21:59 on May 16th but is difficult to see in bright twilight.


More detailed sky notes and LAS Newsletters, Finder charts are available to LAS members via the Members` page on the LAS Website  Artificial satellite and International Space Station visible passes and bright Iridium flares – check the  home page for posting s of details of favourable observing times.


Sky looking south at 11pm British Summer Time (BST), mid May 2018

Low in the south the planet Jupiter shines brightly in the constellation of Libra, high in the south the orange star Arcturus in the constellation of Bootes.

Looking  at Virgo we look outside our own Milky Way galaxy towards the external galaxies of the Virgo Cluster , look  to Sagittarius  to into the spiral arm of our own galaxy, the centre of our own galaxy is however too far south to see from the UK  .  Markarian’s chain is a line of brighter galaxies between the stars Vindemiatrix and Denebola.

The orange star Arcturus is found by following the curve of stars in the handle of the Plough down. The constellation of Bootes, resembles a `kite` or `Club ` in shape.   The star Izar is a beautiful orange/ blue double star visible in small telescopes. To the east of Bootes find the `horseshoe` shaped constellation of Corona Borealis (Northern Crown) and the `Keystone` Asterism in the constellation of Hercules. Hercules also has M13 the famous Globular Cluster, visible to the unaided eye as a misty patch; telescopes show the true wonder of this cluster with over 750,000 stars. Likewise another nice globular is M92 in Hercules.



Sky looking east at 11pm BST mid May 2018


In May the summer constellations of Lyra and Cygnus are rising by late evening, the Milky Way may be visible on moonless evenings from a dark site.  Constellation of Hercules high in the east contains two fine Globular Clusters M13 and M92 visible to small telescopes as fuzzy patches; moderate telescopes resolve the clusters into a myriad of stars.



Sky looking north at 11pm BST mid May 2018

The Plough asterism (Constellation of Ursa Major) follow the pointer’s Dubhe and Merek to find the polestar Polaris. The `W` shaped constellation of Cassiopeia is at its lowest point in the north late evening.  The Milky Way follows the galactic equator and stretches from east through the constellations of Cygnus, Cassiopeia, Perseus and down into the north western  horizon.


Sky looking west at 11pm BST mid May 2018



Venus shines brightly low in the NW in evening twilight