Sky Notes May 2015

Sky Notes for May 2015                                                   Geoff Mitchell

The May night sky shows the spring constellations well but twilight skies mean later observing hours as we head into the summer months.  The bright planet Jupiter is well placed high in the south by early evening.  The spring night sky contains many fine objects to view with both binocular and small telescopes and this month has a few notable events of special interest. The constellations of Leo and Virgo contain a large cluster of Galaxies , the Virgo Super cluster , visible as faint misty patches in moderate sized telescopes – Galaxy hunting season is now `open` . Our own Milky Way galaxy  stretches from the constellation of  Auriga , marked by the bright star Capella overhead  through the constellations of  Perseus  and Cassiopeia and down into the north west . This faint band of stars is best seen on clear dark moonless evenings from darker locations outside the town.

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 towards the horizon 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.

Look to the west early evening to see the brilliant planet Venus shining brightly setting some four hours after the Sun. Telescopes shows Venus has phases (like our Moon).  Currently Venus shows 60% phase in May approaching 50% (Dichotomy) at greatest elongation in early June and then increasing in apparent size and reducing to a thin Crescent as the planet moves towards inferior conjunction. Between May 7th and May 11th, Venus is positioned close to M35 in Gemini, lying just 1.6° north of the star cluster on May 9th.

Mercury makes an appearance low in the west after sunset, Mercury lies close to the Pleiades on April 30th as it heads towards greatest elongation on May 7th and then rapidly moves back towards the Sun becoming lost in daytime skies from May 19th. A thin crescent Moon is 9° away from Mercury low in twilight (9.45pm May 19th). Lunar Libration in May favours best views of the southern polar region e.g. Newton crater visible 1 day after first quarter in the evening skies or around last quarter at dawn.

Jupiter moves from the constellation of Cancer (The Crab) towards Leo and the bright star Regulus and is past opposition but is still well placed for observing / imaging this month. Small telescopes show the four bright moons discovered by Galileo in 1610 and the famous cloud belts. The Great Red Spot is currently more subtle and straw coloured and has been fading recently.  Jupiter’s Galilean moons show shadow transits and go into eclipse behind the planet. A 21cm aperture or larger telescope is recommended to see the tiny dark shadow disks of the Galilean moons cast onto the cloud tops of Jupiter turbulent atmosphere.

The spring constellation of Leo is due south by mid evening, the brightest star Regulus and the `reversed question mark ` shaped star asterism of `The Sickle` makes this an easily recognisable constellation. Leo stretches eastward and is marked at the tail end by the star Denebola.  Leo contains some moderately bright galaxy pairs visible in moderate sized telescopes on moonless evenings.  M65/M66 and NGC 3628 form the famous galaxy triplet, all three galaxies being visible in the same telescopic field of view.  The galaxy rich constellations of Virgo and Coma Berenices can now be seen in the south by late evening. The Virgo cluster of Galaxies has many relatively bright galaxies visible in moderate sized telescopes on moonless clear evenings.

Saturn positioned low in the constellation of Scorpius now rises by late evening in May, reaching opposition on May 23rd. It is however rather low as seen from the UK, but has its ring system 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.  Look at Saturn over a few nights around May 23rd and you may note the apparent brightening of the rings due to the Seeliger effect from dust particles in the rings.

The bright star Vega in the constellation of Lyra is seen low above the northern horizon, rising high in the east by the late evening and already heralds the summer constellations of Lyra and Cygnus low in the NE.

From late May when the Sun just below the horizon late evening is the start of the few months when extremely high clouds at 80 km altitude known as Noctilucent Cloud (NLC) may be seen. Look around 2 hours after sunset in the NW or 2 hours before sunrise in the NE, NLC’s show a bluish colour and also show filamentary structure.

Planets in May

Mercury is placed low in the west after sunset in our evening skies early in the month. Mercury lies close to M45 on April 30th and reaches greatest elongation east on May 7th, lost to daytime skies from May 19th, Inferior conjunction May 30th.

Venus shines brightly and is positioned low in the west after sunset visible in evening twilight.  Venus is positioned close to the open star cluster M35 on May 9th.

Mars is lost to daytime skies in May, reaching conjunction in mid June.

Jupiter shines brightly in the south west on the border of Leo / Cancer (The Crab) early evening and is at well passed opposition but offers some good views in May.

Saturn now rises by late evening and will be at opposition in May 23rd low in SE evening skies.

Uranus is placed in our daytime skies – best views in autumn skies.

 Neptune is placed in our daytime skies – best seen in autumn skies

Moons phases in May

New Moon         May 18th               Moonless, best time for deep sky observing.

First Quarter     May 25th              Best days to see shadow details in lunar craters (early evening) **

Full Moon            May 4th                Best days to see bright ray craters like Copernicus / Tycho.

Last Quarter      May 11th               Moon visible in daytime skies.  Do not look directly at the Sun.

Meteor shower’s:     Eta Aquarids, unfavourable maxima is on May 6th , Full Moon May 4th

The Highlights of the Month

Venus dominates the evening twilight, showing characteristic phase (60%) during May

Jupiter in the south west evening skies, cloud belts and four of Jupiter’s moons visible in a small telescope.

Saturn at opposition on May 23rd, low in south east, rings open at 24° DE [ tilt] showing Saturn’s North Pole.

Mercury reaches greatest elongation (21°E), best time to see Mercury May 7th 9.30 pm BST (see notes)

Moon, very thin crescent visible (difficult) in evening twilight May 19th very low in NW (see notes)

Lunar Libration, best view of the southern lunar polar area e.g. Newton crater at first **and last quarter Moon.

Pleiades (Seven Sister’s) star cluster (M45) and Mercury low in the evening twilight good binocular view May 1st.

Beehive cluster (M44) visible to the unaided eye but best seen with binoculars.

Comet 2014 Q2 Lovejoy fades but remains telescopic in the constellation of Cepheus / Ursa Minor (see notes)

Telescopic triplet of galaxies M65/M66/NGC3628 in the constellation of Leo

Virgo cluster of Galaxies, brighter members of the cluster can be seen with small telescopes or binoculars.

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

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.