May sky highlights

May 16 2012 By Ninian Boyle

May's Highlights

Although it is not getting dark until quite late now, there are still plenty of things you can see in the night sky... 

The planet Venus has to be the highlight of this month. It is extremely bright and through binoculars or a small telescope will show a lovely crescent phase. It is moving steadily nearer to the Sun from our point of view here on Earth, ready for its transit across the disc of the Sun in June.

A beautiful crescent Moon will occult or pass in front of, the open star cluster Messier 67 on the 26th of the month. The best way to view this is through binoculars or a small telescope with a fairly low power eyepiece. The start of the occultation is around 21:00BST which means that it will still be twilight, so it might be tricky to see. 

It will be easier to see the end of the occultation when M67 reappears from behind the Moon at around 22:50BST when the sky will be much darker. Because the Moon has no atmosphere the stars will seem to instantly disappear behind the dark portion of the Moon at the beginning of the occultation and pop into view again from behind the brightly lit side of the Moon at the end. Occultations of stars by the Moon are used to obtain the exact position and also the shape of the edge of the lunar disc. 

Saturn is now the dominant planet in our night sky.

The Moon This Month

The Moon gives us a waxing gibbous phase on 1st May. It is 73% illuminated and lies a little to the south-east of planet Mars in Leo. Mars is still bright enough to be seen near the brightly lit lunar landscape. 

Full Moon occurs on the 6th. It will be quite low in the sky compared to other times of the year and is moving through the constellation of, Libra The Scales and will drift into that of Scorpius the Scorpion. 

The 13th May brings us a last quarter Moon. This shows as the illuminated eastern half of the Moon. You can only see a last quarter Moon in the early hours of the morning. The phase is now waning towards New Moon... 

And New Moon occurs on 20th May. New Moon and the few nights either side of this are of course the best time to observe the many deep sky delights which can be found all over the heavens. At other time the bright Moon has a tendency to 'drown out' the fainter and more difficult objects to see and image. 

The Planets This Month

Venus is now the brightest object in the sky 

Because Venus is getting nearer to us it is starting to appear larger as well as brighter, this is in spite of the fact that at the beginning of the month it is only showing a fairly slender crescent. It is a truly lovely sight through a small telescope. Venus is so bright because it is so reflective. 

Venus will transit the face of the Sun in June, an event which only occurs once every 124 years and then again 8 years after this. We saw a transit in 2004 and so we are due the second viewing this year. I'll be explaining a lot more about it and how you might see it, next month. 

Mars is still on view in the constellation of Leo, The Lion. However, we are moving away from the planet quite rapidly now and so it will appear dimmer and, if you plan to observe it through a telescope, much smaller than it did a few weeks ago. 

The small apparent size of the disc of Mars will mean that any features on its surface will be difficult to see. However, you may still be able to detect a polar cap or the bright Hellas Basin. 

Saturn is now past opposition and is heading lower into the western skies as the month progresses, so view it with a telescope earlier in the month rather than later. The famous rings are tilted towards us and are nicely on display. You should be able to see the shadow of the body of the planet cast onto the rings. You will need a fairly high power to see this well, anything from 80-150x magnification.

Naked Eye Astronomy

A fun thing to do if you don't have any optical aid such as a telescope or even binoculars, is to use certain stars and groups of stars to help you navigate your way around the night sky. 

There are several bright stars which can act a 'jumping off points' for you. This month I would like to draw your attention to the group of stars known as 'The Plough'. This group is often referred to as a constellation, but strictly speaking, is an asterism. This is a group of stars which are easily recogniseable and which may be a part of a constellation, or made up from two or more constellations. The Plough is in fact part of the Constellation of Ursa Major, The Great Bear. The seven stars of The Plough look a bit like a 'Saucepan' with a bent handle. If you follow the stars of the handle in an arc away from the 'bowl' of The Plough, the next bright star you come to is a distinctly orange coloured star called Arcturus. 

The star Arcturus, lies in the constellation of Bootes, The Herdsman. The name Arcturus means 'follower of the bear'. Bootes is a constellation which looks a bit like a child's kite. In fact this 'kite' shaped part of the constellation is a well known asterism itself. 

If you keep moving from the handle of The Plough, through the star Arcturus and keep going in an arc, the next brightest star which you come to is that of Spica in the constellation of Virgo, The Virgin. So you can 'arc to Arcturus and speed on to Spica'. During this month this way of finding the star Spica will also help you to find the planet Saturn. Saturn lies above (north) of Spica and has a slight 'straw' colouring and is a little brighter than Spica.

Deep Sky Highlights of May

May starts to bring the summer constellations back into our skies and many deep-sky treats with them... 

Rising higher in the south-eastern skies this month is the constellation of Hercules. Hercules was the son of Zeus and Alcmene a mortal woman, so he was a demigod. The constellation is most famous for the stunning globular star cluster known as Messier 13 or M13. This can be found between the two stars on the right hand side of the 'keystone' asterism. 

From a dark sky sight on a clear night, M13 can just be made out with the naked eye as a small fuzzy patch of light. Through binoculars or a small telescope it take on a distinctly spherical appearance and with a larger telescope of say around 6-inch aperture you can start to resolve the stars in this cluster. Globular clusters contain some of the oldest stars in the Universe and M13 it is thought contains up to a million stars, tightly packed together. Globular clusters orbit their parent galaxy unlike the stars that make up the majority of the galaxy itself. 

There is one other lovely globular cluster to be found in Hercules and which is often overlooked for its brighter sibling M13. This is M92. This globular star cluster forms an equilateral triangle with the two stars at the top of the 'keystone' asterism. Of course a good star chart will help you find these wonderful objects. If you would like to buy such a chart, then please take a look at my suggestions on my website which you can buy on Amazon 

Finally....

If you are on Facebook, please come and be 'fan' of my page 'Astronomy Know How with Ninian Boyle'. I'm planning to use it for lots of free information and tips on how to observe the night sky and also post up interesting events as they are set up. It will mean that you'll be the first to know about really useful things connected to your hobby, so join me on facebook 

Oh! and you can follow me on Twitter too www.twitter.com/astroknowhow