|Events during May
The Moon: Full – 2nd, Last quarter – 10th, New moon – 16th, First quarter – 23rd.
This snapshot shows Mercury setting close to the 28 hour-old crescent Moon in the north-west on the 17th May, about 1h 21m after
the Sun has set and 2h 10m before Venus sets.
The deepsky objects shown are:
M1 (Crab nebula) - the most famous and conspicuous supernova remnant. Around the year 5246BC a star in the constellation of
Taurus exploded, about 6,300 light years from Earth. The explosion was eventually observed in 1054AD as a very bright supernova, which today has
developed as the Crab Nebula. It shines as a nebula of magnitude 8.4 near the southern "horn" of Taurus.
The Crab Nebula can easily be seen under clear dark skies, but can equally easily be lost in background light under less favourable conditions.
With 7x50 or 10x50 binoculars, M1 is just visible as a dim patch. With a little more magnification, it is seen as a nebulous oval patch, surrounded
by haze. In telescopes starting with a 4-inch aperture, some detail in its shape becomes apparent, with mottled patches and streaks towards the
inner part. Under excellent conditions and with larger telescopes, from about 16 inches aperture, suggestions of the filaments and fine structure
M36 – is one of three bright open clusters in Auriga. It lies at a distance of 1,400 light years and has a magnitude of 6.3.
This cluster has at least 60 member stars and is thought to be quite young at about 25 million years.
M37 – at 6.2 magnitude, this is the brightest open cluster in Auriga. It has over 500 stars, a distance of 4,400 light years
and an estimated age of 300 million years.
M38 – is the third open cluster in Auriga at 7.4 magnitude. It has a distance of 4,200 light years and is about 220 million
M44 (Beehive cluster or Praesepe) – an open cluster in Cancer at 3.7 magnitude. Easily visible to the naked eye, this cluster
has about 350 stars, is about 577 light years distant and is estimated at 730 million years old.
Also indicated on the snapshot are some of the brightest stars in the area:
Betelgeuse – in Orion, is among the brightest stars in the night sky. It is a red super giant with a magnitude varying between
0.3 to 1.2 and is about 430 light years distant. Physically it is one of the largest stars visible to us and, if placed at the centre of our Solar
System, would extend to between the orbits of Mars and Jupiter.
Capella – is the brightest star in the constellation Auriga, at a distance of 42 light years. Although it appears as a single
star to the naked eye, it is actually a pair of close bright binary stars (about 60 million miles apart – two thirds the distance between Earth and
the Sun) next to a second fainter binary pair. The brighter binary is composed of two yellow stars whilst the dimmer has two dwarf red stars.
Pollux – is a red-orange giant star in Gemini with a magnitude of 1.2 and a distance of 34 light years. It was the first star
visible from Earth that was discovered to have a planet in orbit. The planet is nearly three times the mass of Jupiter. Gemini has at least two
other stars with orbiting planets.
||Mercury is at superior conjunction on the 3rd, reappearing in the evening sky and fading from –1.1
magnitude in mid-May to 0.4 magnitude by the end of the month when it sets 2 hours after the Sun. As seen on the May snapshot, a thin crescent Moon
just over 1 day old, will set near Mercury in the north-west on the 17th.
The best times to observe Mercury are when it is an evening star in the spring and a morning star in the autumn. In midsummer the lighter skies make visibility difficult near the horizon.
||Venus moves from Taurus into Gemini at a spectacular bright –4.2 magnitude, shining in the sky long
after the Sun has set, setting itself at about 01.30h throughout May. This is a treat of an opportunity to see Venus in a dark sky. As from June,
Venus will move closer to the Sun and will become a morning object during August and for the remainder of 2007. The Moon is nearby on the 19th.
On the 8th June 2004, Venus was at inferior conjunction and transited the sun. Transits of Venus are rare, taking place at greater
than 100 year intervals and usually in pairs. The last two transits of Venus were in 1874 and 1882. June's transit
began at 7.20h and lasted 6 hours until 13.20h, the total event visible from Europe as a small black disc crossing
the lower part of the sun from left to right. The next transit will be in late June 2012. After that, transits of Venus
won't occur again until 2117 and 2125.
Before and after inferior conjuction, when Venus is
the closest it comes to the earth, are the times at which the planet is most brilliant and can be seen setting or rising
4 hours after or before the sun. The dates of the next two inferior conjunctions are October 28th 2010 and October 26th 2018.
||Mars moves from Aquarius into Pisces, at 0.9 magnitude. It is in darker skies by late May, when it
rises by 04.00h. The Moon is closeby on the 13th.
At opposition on the 28th August 2003, Mars was only 56 million kilometres from the earth. It showed a
disc of 25.1 seconds of arc across which is almost as large as it can ever appear. Mars started 2003 at 310 million kilometres from
the earth at 4.5 seconds of arc and 1.6 magnitude. By opposition it brightened 50 times to reach -2.9 magnitude but faded to 0
magnitude by December. Even to the naked eye Mars was a striking object in the summer and autumn sky, easily identifiable by its
reddish hue in an area of sky poor in bright stars. Mars will not be as close again for another 15 years.
These favourable oppositions occur every 15 years but other oppositions occur at average intervals of 2 years 2 months. In general Mars is observable every other year, being too close to the sun for favourable conditions during other times. Brightness at opposition varies from -1.0 to -2.9 magnitude, and when furthest from the earth it fades to 1.7 magnitude. The planet can be identified by its orange-red colour.
||Jupiter in Ophiuchus at –2.6 magnitude, rises at about sunset by the end of May. The Moon is closeby
on the 5th.
Being 770 million kilometres from the sun, the difference in brightness between opposition and conjunction varies less than with Mars, from about -2.8 to -1.8 magnitude.
The 4 largest moons of Jupiter are easily visible through a small telescope, ranging from 4.6 to 5.6 in magnitude. The innermost, Io, takes 1.8 days to orbit the planet making its motion easily detectable within a few minutes.
||Saturn remains in Leo at 0.5 magnitude, setting about 02.00h by the end of the month. The Moon is
nearby on the 22nd.
Saturn crossed the equator into the northern hemisphere in 1996 where it will remain until 2010 with the southern side of the ring system facing the earth. Because of its distance, its brightness varies little between opposition and conjunction but is affected by the huge ring system. Seen edge on the rings contribute little or no light.
Every 15 years the plane of Saturn's rings passes through the sun, illuminating first the north and then the south side. For a few days the rings are edge on to the sun. About the same time the earth passes through the ring plane and, depending on the earth's position this may happen just once or 3 times. During 1995/96 there was a triple crossing and the next will be 2038/39. The next single crossings will be in 2009 and 2025.
Saturn's largest moon, Titan, is visible in small telescopes orbiting outside of the ring system.
||Uranus in Aquarius, rises about 03.00h by the end of May and the Moon is closeby on the 12th.
Brightness varies slightly reaching 5.6 magnitude at opposition. This is bright enough to see with the naked eye but identifying it against the stars is difficult.
||Neptune in Capricorn, rises about 02.00h by the 31st, is stationary on the 25th and has the Moon nearby
on the 10th.
Neptune has an average magnitude of 7.9 which varies little with changing distance.
||No longer an offical planet and never brighter than 13 magnitude, Pluto is only visible through powerful
telescopes and we therefore do not report on its position in the sky.
Full moon: 2nd
Last quarter: 10th
New moon: 16th
First quarter: 23rd
The Moon in 2007:
The Moon was seen unusually high and low in the sky during 2006 (see Moon). Although the extremities occurred last year, the Moon will still be seen very
high and very low each month this year, most noticeable around full Moon. It will be near full and high around the 2nd and 29th January, the 25th February
and the 24th March; and near full and low around the 1st and 28th June.
During each month of 2007, the Moon will pass through the Pleiades. This will mostly be in daylight but observable 01.00-04.00h 7th August,
0.00-03.00h 28th October and 22.00-01.00h on the 21st to 22nd December. Binoculars will give a clearer view.