Night Sky Notes – May 2017

Night Sky Notes for May 2017             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, the red planet Mars slips into western twilight by late May . Comet 2015 V2 Johnson is a binocular object moving southward from the constellation of Hercules, down through the constellation of Bootes during May. Comet 41P (Tuttle- Giacobini- Kresak ) is a telescopic / binocular object  on the borders of Lyra and Hercules  low in the east , mid evening.

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 mid 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.  Observe the Seeliger Effect from late May to late June around the date of opposition and note any brightening of the ring system due to the ring particles angle of illumination changing causing the apparent brightening.

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.

Comet C/2015 ER61 Panstarrs, a long period (P ~ 18000 years) comet from the Oort cloud reaches perihelion on May 9th at a distance of 1.04 AU from the Sun. It is currently brighter than expected 6.5m (binocular object as a round coma 8 arc min diameter – low surface brightness ) but from UK is poorly placed i.e. very low in predawn skies at 04:00 BST just before dawn twilight interferes   Also see Venus low in the east in dawn twilight.

Planets in May 2017

Mercury is placed in dawn skies reaching greatest elongation on May 17th

Venus is visible in dawn skies low in the east, Venus and 18% waning crescent moon May 22nd.

Mars sets an hour after the Sun by late May but is poorly placed in evening twilight in May.

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

Saturn rises late evening by late May, low in Sagittarius – rings remain wide open in 2017 – Nice.

Uranus reached conjunction in early 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

New Moon          May 25th             Moonless, best time for deep sky observing.

First Quarter     May 3rd               Best days to see shadow details in lunar craters (early evening) **

Full Moon           May 10th             Best days to see bright ray craters like Copernicus / Tycho.

Last Quarter      May 19th              Moon visible in daytime skies.  Do not look directly at the Sun.


Meteor showers       η Aquarids – peak May 5th, range April 24th to May 20th – ZHR 40/ hour

α Scorpiids maxima April 28th – May 12th, low rates only ZHR 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 late evening  , rings open at 26° DE [tilt] showing Saturn’s North Pole.

Comet 2015 V2 Johnson low in east late evening (telescopic – see notes) – difficult in bright twilight by late May

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

Thin 2% waxing crescent Moon visible after sunset on May 26th and May 27th, note the dimly lit Earthshine.

May 7th Jupiter close to the Moon tonight.

Venus shines brightly and Comet C/2015 ER61 Panstarrs a binocular object low in dawn 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.