Astronomy Central

Wednesday 16th May 2012

All times are GMT+1 hour

 

Get yourself outside tonight if it’s clear, pull up a deck chair, and scan the star clusters, nebulae, and even see other galaxies with your binoculars. Their lower power makes them just perfect for objects such as the larger open clusters, giving you great views and of course as you get to use both eyes, providing almost a 3D view. Just taking in the whole night sky scene and aimlessly wandering along the band of the Milky Way is also very enjoyable, who says astronomy has to be all scientific and technical? If you have binoculars up to 10 x 50 then they’re ideal for the job, portable, and easy to hold. Anything over this size will usually need a tripod. All the objects listed here are at their best in dark skies, ideally with the bright Moon not around.

But if old crater face is about, you will get amazing views of the lunar landscape through your binoculars. It’s best to look along the terminator, the boundary between light and dark as shadows are cast across craters and mountains making them easy to pick out.

 

The Moon for tonight…  waning crescent 5% full, setting in the west at 6.45 pm, and rising in the east beyond midnight at 4.12 am

Next new Moon, Sunday 20th of May

Next full Moon, Monday 4th of June

 

 

The Coat Hanger

“Hey that’s a coat hanger!” That’s the first thing I thought when I first spotted this star cluster through binoculars…and it’s not actually a real cluster, but we’ll come to that later. Lying in the constellation of Vulpecula is Brocchi’s Cluster,  Collinder 399, Al Sufi’s Cluster, or more commonly the Coat hanger. People will know exactly what you mean when you say the Coat Hanger. So now I think we’ve both established what this thing looks like…it looks like a coat hanger.

But all is not what it seems as the Coat Hanger is actually an asterism, just like the Plough/Big Dipper is an asterism. It is a collection of stars that are not physically related to each other, but happen to group together along your line of sight to look like a regular open cluster. Ten of these stars are responsible for forming the recognisable coat hanger shape, six of them make a straight line, then four more make the hook shape coming from the mid point of the line of stars. This is a large cluster, perfect for your low power binoculars being 1.5 degrees across, 3 times the diameter of the Moon. This nice looking object lies in the band of the Milky Way, and you may even see it with the unaided eye from a dark place.

The Coat Hanger lies between constellations Cygnus and Aquila, but an easy way to find it is to locate the bright star Altair in Aquila about 20 degrees south-west of the head of the swan in Cygnus. See the very bright star Vega north of the head of the swan? Now draw an imaginary line from Altair to Vega, and the Coat Hanger lies one third of the way up from Altair to Vega.

Tonight you’ll see the Coat Hanger rising from the north-east after dark, it then climbs high to the east by late evening, and even higher to the south-east by daybreak. See the constellation of Cygnus, and you’ll always know the Coat Hanger lies nearby.

How long will it be around for? The Coat Hanger will be visible for some considerable time, eventually going out of view in the setting Sun’s glow at the beginning of February 2013. 

 

 

The Coma Cluster

The Coma Cluster is an open star cluster in constellation Coma Berenices. It is not to be confused with the Coma Galaxy Cluster. It is actually a small open cluster, but you see it quite large in the sky as it’s quite close to Earth at just 288 light years away. This cluster is also visible with the un aided eye in dark skies. It is much closer than the Pleiades Cluster (440 light years), and further than the Hyades Cluster (151 light years). You’ll see this nice collection of around 40 stars with your naked eye in relatively dark skies. High power is not the way to go with this one as you’ll want to get as much of the cluster in your field of view. The Coma Cluster is a big one, spanning roughly 5 degrees of sky, about 10 times the angular diameter of the Moon.

Coma Berenices is a faint constellation lying between Bootes, Leo, and Virgo, and if you have any light pollution you’re going to have trouble seeing it. But to find the Coma cluster, first locate the star Denebola that marks the end of the tail of the lion of Leo. Now draw a line up from Denebola to the end star, Alkaid, on the handle of the Plough. About one third up from Denebola along this line is the Coma Cluster.

Tonight the Coma Cluster is visible rising high in the south after dark, where it climbs to its maximum height above the horizon at 9.50 pm. It later moves over to the north-west, where it sets after daybreak.

How long will it be around for?  The Coma Cluster will be visible until around the start of September 2012, where it sinks into the glare of the setting Sun in the west.

 

Open Cluster M103

The great W of Cassiopeia is still moderately high in the north by night fall, and is a rich hunting ground with your binoculars. The plane of the Milky Way runs right through Cassiopeia, and so this is where open clusters can be found. One of these stellar jewels is open cluster M103 or NGC 581, one of the more distant of the open clusters at up to 9,000 light years away. It’s really easy to find, as it is close to the star that makes the left point in the W of cassiopeia. You’ll see it as a small hazy patch of nebulosity unresolved into stars, averted vision may be needed to get it to emerge out of the darkness, and a tripod for your binoculars would always be useful. This cluster has around 40 member stars, is 15 light years across, and a younster at only 25 million years old. Open clusters like M103 were formed from the same ancient cloud of gas and dust, with most of the cloud’s raw materials condensing down into stars…and very likely planets. Any remaining gas would have been blown away millions of years ago by the newly formed stars’ fierce ultra violet light and stellar winds.

To find M103 simply imagine a line drawn from the right point star of the W (Shedir), across to the left point star of the W (Ruchbah). Now continue on this straight line to a distance of 1 degree past the left point star to find this open cluster…1 degree is the width of your little finger held at arm’s length.

Tonight you’ll see the great W of Cassiopeia still moderately high in the north after dark. As the night progresses it drops closer to the northern horizon and then starts climbing again beyond midnight. It rises higher in the north-east by daybreak.

Open cluster M103 is at magnitude 7.4

How long will it be around for? Cassiopeia is a circumpolar constellation from northern latitudes, meaning it never sets below the horizon. The constellation will be at its lowest point in the sky at around the end of April 2012, when it will be a little more than a handspan at arms length above the northern horizon.

 

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The Beehive Cluster

The Beehive Cluster, Praesepe, M44, or NGC 2632 is a very nice and attractive open star cluster to look at through your binoculars, and does kind of look like a swarm of bees. The Beehive is another open cluster close to Earth, at 577 light years away in the constellation of Cancer. This puts it slightly further away than the Pleaides. M44 is now in the south-east by early evening. This cluster lies in the fainter constellation of Cancer, in between Leo, and Gemini. The stars that make up the head of Leo the Lion look like a large backwards question mark. You’ll find M44 with your naked eye roughly half way between this “question mark”, and the two twin stars of Castor and pollux in Gemini. The Beehive actually has over 1,000 stars, and is around 600 million years old.

Tonight the Beehive Cluster is visible quite high in the south-west by night fall, it then moves over to the north-west where it sets at 2.00 am.

This object is at magnitude 3.7

How long will it be around for? The Beehive Cluster will now be in the sky until the beginning of June 2012, where it will be low in the west before eventually moving into the Sun’s glare. During the coming months it will gradually rise earlier and earlier, and climb higher into the night sky to make a nice binocular target.

 

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Double Star Albireo

If you look at the constellation Cygnus tonight and find the star that marks the “head of the swan” you’ll have the star Albireo, and it does actually look to your unaided eye as one faint single star. But this is probably the best known double in the sky, two stars seperated by 35 arc seconds. Get your binoculars on it and you’ll see straight away that there’s actually two different colour suns there (colours will be more subtle than image above), a brighter yellowish star called Albireo A at magnitude 3.1, and its fainter bluer companion star Albireo B at magnitude 5.1. It seems counterintuitive but colours red/orange/yellow are far cooler than blue when it comes to the temperature of stars. So fainter blue Albireo B is quite a lot hotter than its brighter yellow companion, with blue Albireo B also being a “Be star”, rotating at a speed of 250 kilometres per second at its equator.

The yellow star in the double actually is a double in itself with an orbiting companion star, but they’re much too close together to see with your binoculars.

Look towards the north-east/east in mid to late evening and you’ll see Cygnus lying low rising from the horizon, with Albireo rising at 7.52 pm. Cygnus manages to climb quite high in the south east by day break. The figure of the swan appears to be flying away from Cassiopeia, so it’s easy to find the head star Albireo.

How long will it be around for? Double star Albireo will be visible for some considerable time, eventually going out of view in the setting Sun’s glow at the beginning of February 2013. 

 

Open Cluster M39

Open cluster M39, or NGC 7092 is a nice little collection of stars right in the band of the Galaxy, giving you a backdrop of more distant suns. It is in Cygnus (see position of M39), a great constellation in its own right to spend time in as the Milky Way goes along its length. Look for the distinctive shape of this constellation, it resembles the shape of a cross, or of course what it’s meant to be…a swan. Unlike a lot of constellations it does actually resemble what it’s meant to be, a swan as it flies away from Cassiopeia. From the tail star of the swan (Deneb), along the body, to the head (Albireo) forms roughly a straight line. The back of your fist held at arm’s length makes 10 degrees of sky. The open cluster M39 lies just under the width of your fist from the tail star of the swan (Deneb) in the direction of Cassiopeia, then about 3 degrees lower.

Open cluster M39 is 800 light years distant, and its stars are about 300 million years old. It has between 30 and 50 stars forming an attractive triangular shape.

Tonight open cluster M39 is rising in the north-east after sunset, to the west of the tail of the swan in constellation Cygnus. As the night progresses it rises, climbing in the north-east during the early hours, and high into the east as day breaks.

M39 is at magnitude 5.5

How long will it be around for? This cluster is circumplolar from northern latitudes meaning it never actually sets. As darkness falls right now during early summer M39 is low to the north, but through the coming weeks and months it will slowly climb in the eastern sky.

Galaxies M81 & M82

These two galaxies 12 million light years away are one of the best sights you’ll see through a telescope. Two island universes in the same view, separated by 130,000 light years.  But they can actually be glimpsed with binoculars in dark skies. They are the “grand design” spiral galaxy M81 at 36,000 light years across, and smaller irregular starburst galaxy M82. They are in Ursa Major, and their proximity to each other is causing them to gravitationally interact. This interaction is causing intense star burst in M82, just at the galaxy’s centre new suns are being born 10 times faster than in our entire Milky Way.

They’re not really close to any easy marker points in the sky. But if you  draw a line from the bottom left star of the bowl of the “Big dipper” (Phad) to the top right star at the bowl edge (Dubhe), then carry that imaginary line about the same distance again, you’re in the place in the sky for M81 and M82.

In your binoculars they will appear as two small fuzzy shapes close by each other, and you should notice they are different shapes. Spiral M81 is the brighter of the two at magnitude 7.0, and the irregular star burst galaxy M82 is slightly dimmer at magnitude 8.4, M82 is also called “The Cigar galaxy” for its shape. It takes practise to find these, and yes they will appear as two small fuzzy smudges. But those two fuzzy smudges are entire galaxies in interstellar space, and you’re seeing them with your own eyes with just a pair of binoculars. The star light from two stellar systems 12 million light years away.

By nightfall Ursa Major is very high in the east, during the evening it climbs higher, eventually getting to virtually directly overhead by the pre dawn hours.

How long will it be around for? Galaxies M81 and M82 are circumpolar in the northern sky, meaning they will always be above the horizon never setting. The best time to see them are when the bright Moon is not around, and under dark skies away from light pollution.

M13, The Hercules Cluster

This famous globular cluster at 25,000 light years away is a classic of the northern skies, and if your first view of it is from a really dark site with a larger pair of binoculars, I promise you will not forget it. It’s well worth getting away from light pollution to see it. In clear dark skies through your binoculars you should see a quite bright, fuzzy, but crisp, glowing “ball of suns”, although individual stars will not be resolved. This globular cluster contains over a million stars all packed into a region of space 145 light years wide. Space is so limited here that stars are thought to collide in the centre, producing bluer suns called “Blue stragglers”. Globular clusters like M13 are not actually part of the Milky Way’s disk, but reside far above and below the spiral arms, surrounding the Galaxy in a halo. Their stars are known to be very old, and in 1974 a message was sent to the Hercules Cluster in the hope that an intelligent civilisation might live there.

The way to locate M13 is to find the Hercules “keystone”, this is four stars making a rough square 5 or 6 degrees across, at the centre of the Hercules constellation. In this map you’ll see M13 marked about a third of the way between the two right hand, (or uppermost right now) stars of the square. Look at Ursa Major, or “The Plough” and the first two stars of the handle that are attached to the “bowl”, make a straight line. This line points to the centre of Hercules. The keystone can be slightly difficult to find at first especially in more light polluted skies but once you get the hang of it, it becomes easy.

Tonight the Hercules Cluster M13 is visible quite high in the east after dark, it then climbs higher through the evening, moving over to the south by day break. Its highest point is in the south at 2.00 am. 

M13, or The Great cluster in Hercules is a magnitude 5.9 object, and it is even visible naked eye under very good skies.

How long will it be around for? The Hercules Cluster M13 is known as one of the classic objects of the spring and early summer sky. You have bags of time to see this famous globular cluster as it will be at its prime right through the rest of spring, moving to a beyond midnight object during summer.

The Andromeda Galaxy, M31

Now lying low in the north at nightfall is Andromeda, or M31, the main large neighbouring galaxy of the Milky Way. It is a huge spiral galaxy 2.5 million light years away, with up to one trillion stars, and a diameter of possibly up to 220,000 light years. It’s more than twice the size of our Milky Way some think, others disagree saying it’s around Milky Way size, Andromeda’s size is a debated subject. Now positioned well, high in the sky, you can quite easily see Andromeda naked eye as a fuzzy glow from a dark site. In fact if you know where exactly it is, you can pick it out even from an area that has some light pollution with averted vision.

There there are two main ways to find this island universe in the sky. One is to locate the large square of Pegasus with its four stars marking each corner. You’ll find Pegasus to the east of Perseus, and Cassiopeia. The star at the left of the square is called Sirrah (or Alpheratz), look to the left of Sirrah and you’ll see three stars in a line, a dimmer star and two  bright stars. The first bright star is Mirach. Now look above Mirach and you’ll see a dimmer star, look about the same distance above again from the dimmer star, and here is located the Andromeda Galaxy (M31). Another way to find M31 it is to use the right hand V of the W of Cassiopeia and imagine a line pointing down, this V points just to the left of Andromeda.

Get your binoculars on M31 and you’ll see the bright core of the galaxy as a small fuzzy blob. But keep studying and use averted vision, and you’ll soon start to make out the fainter shape of the galaxy’s disk extending out from the core. This is an object far outside the Milky Way, an entire ”island universe”. To be seen at its best Andromeda should be observed with the bright Moon absent under dark skies, but it’s still visible even from urban areas.

Unfortunately not at its best position right now during spring, but tonight you just may see M31 the Andromeda Galaxy very low in the north after nightfall, but a dark and clear horizon will be needed. Beyond midnight though Andromeda climbs slightly higher in the north-east up to daybreak. M31 the Andromeda Galaxy is circumpolar, meaning it never actually sets in northern latitudes. 

M31 is at magnitude 3.4

How long will it be around for? Right now the Andromeda Galaxy is lying very low towards the north after dark. This object is actually circumpolar from northern latitudes so never goes below the horizon. Although right now Andromeda is placed at it’s worst position to see, being very low to the northern horizon. But during the following weeks and months Andromeda will start to climb from the north-east again.

The Perseus Double Cluster

This cluster is one of my favourites, it looks stunning in a telescope at low power, but binoculars also show it well. The Perseus Double Cluster, NGC 884 and NGC 869, or H and X Persei are actually two seperate open star clusters close to each other in space at around 7,000 light years away. They are only a few million years old, much younger than the Pleaides. To find it I could tell you to find this star, draw a line to that star etc, but the easiest way I have found to locate the Perseus Double is just to look for a fuzzy irregular patch in the band of the Milky Way between Cassiopeia and Perseus, (cluster marked as H+X on Perseus map). Once you see it, get your binos on it and you’ll see two very attractive open clusters of sparkling stars set against the blackness of space. There’s also a nice line of stars that curves away from the upper most cluster, when you see this line of stars you’ll know you have this popular deep sky object in your view.

Tonight you’ll see the Perseus Double Cluster moderately high towards the north after dark, nestled between Pereus and Cassiopeia. During the night it moves lower to the north just beyond midnight, before rising slightly higher in the north-east into the early hours The Perseus Double Cluster never sets as it is circumpolar meaning, it’s always above the horizon from northern latutudes. 

This open cluster is a magnitude 4.00 object

How long will it be around for? Like Andromeda, the Perseus Double Cluster will always be above the horizon as it is circumpolar from northern latitudes. It is still placed for viewing right now, but is at its low point in the sky during spring. Soon enough this attractive star cluster will start to rise higher.

 

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