Thursday, 29 October 2015

M3 - Globular Cluster

Type: Globular Cluster  Also known as: NGC 5272

The next item on Messier's vast list is another globular cluster but, despite looking somewhat less 'intense' than the previous example, is actually slightly closer to us at 30,000 light years, slightly larger than M2 at 200 light years across, and consists of substantially more stars - some 500,000, no less. Some of them are red giants (the yellowish ones here) but most are hotter blue giants, many of them variable.

There are actually, at present count, 274 variable stars in M3 which is considerably more than in any other globular cluster, and it's thanks partly to these that it has become one of the best-studied such clusters in our skies. It's not as old as M2 at a mere 8 billion years old (compared to 13) but it's probably a more interesting target for amateur astronomers with decent enough equipment.

Observation: Many consider M3 one of the best clusters in the northern skies for observations. While barely visible with the naked eye, even in superb conditions, it can be spotted with binoculars and observed quite well with an average telescope. It's located in the Canes Venatici constellation and can be found almost exactly halfway between Arcturus and Cor Caroli. While an impressive sight by itself, those with a good telescope may even spot some background galaxies as well.

Monday, 26 October 2015


Type: Moon  Also known as: Uranus V

Like all the giant planets Uranus has about a billion moons, but few of them are much more than irregularly-shaped asteroids or Kuiper Belt objects captured by the green planet's powerful gravitational field. One of the more substantial examples, though by far the smallest of the five that are sufficiently large to have been rounded by their own gravity, is Miranda, but it's definitely the most interesting.

Discovered by Gerard Kuiper and named by him after the character in Shakespeare's 'The Tempest', Miranda is only 480km in diameter and is the least dense of Uranus's rounded moons. This suggests a significant portion of it is made up of water ice, but far more notable is the incredibly chaotic nature of its terrain which makes it look as though it's been constructed from the spare parts of various other broken moons! All over the moon there are large sections which bear little resemblance to the sections immediately adjacent to them, but what could cause such strange terrain?

One obvious possibility is geological activity, although it would have to be on a scale not previously seen, but an even more dramatic theory is that the entire moon was shattered into several large segments as a result of a colossal impact, with the fragments coalescing over time but in a different arrangement to before. Whatever caused it, Miranda is definitely among the most unique moons in the Solar System as far as its appearance is concerned, and one with a very violent past as well.

Wednesday, 21 October 2015

The Bat and the Squid

Type: Nebula  Also known as Sh2-129 (bat) & Ou4 (squid)

As anyone with even the merest hint of interest in astronomy knows, our galaxy and the many others in the universe contain nebulae. A lot of them in fact. But these ones are part of a very select group, perhaps populated by no others, for they are actually two nebulae in one! No doubt you can see the nice puffy red/pink gas cloud here (called the Flying Bat Nebula) but you might also notice the smaller light blue shape inside it (known as the Squid Nebula) which is actually a separate nebula.

The Flying Bat is a fairly standard emission nebula but there is still some confusion as to what the Squid Nebula actually is. It was only discovered a few years ago and was initially thought to be a planetary nebula but is now believed to be a bipolar outflow from the bright blue star at its centre (HR 8119). One thing that seems very likely, however, is that it's actually within the Flying Bat rather than in front of it.

Observation: This unusual pairing can be found some 2,300 light years away in the constellation of Cepheus and, while large, is also rather faint. Actually, the Flying Bat isn't too hard to see - it can be made out with a mere pair of binoculars - but you'll need some pretty decent equipment to image the Squid (at least 200mm lens) which is extremely faint. Many think it worth the effort though!

Wednesday, 14 October 2015

M2 - Globular Cluster

Type: Globular Cluster  Also known as: NGC 7089

When most people think of astronomical objects, it's usually the varied shapes and colours of nebulae that they remember, but star clusters can be just as beautiful. Take this one, for example - the second object on Messier's list - which is a globular cluster. In fact, it's actually one of the largest such clusters currently known, and it's also one of the oldest detected at around 13 billion years old.

Its large size is down to the sheer number of stars it contains - somewhere in the region of 150,000, which makes it 175 light years in diameter - but it is also very distant at 37,500 light years. As such, it was originally thought to be a nebula when discovered in 1746 by Maraldi, then again in 1760 by Messier himself who thought it was a 'nebula without stars' as it is so densely packed.

Observation: M2 lies well beyond the Galactic Center within the constellation of Aquarius. Despite being so far away, it's just about bright enough to be made out with the naked eye in excellent conditions, though it will appear only as a point of dim light. A large telescope is required to make out any individual stars, however.

Monday, 12 October 2015

M1 - Crab Nebula

Type: Nebula  Also known as: NGC 1952, Taurus A

Whilst admittedly not looking very crab-like, the first object catalogued by Messier was the Crab Nebula, and it's one of the most familiar sights from beyond our solar system. It lies 6,523 light years away and its distinctive, colourful, and extremely explodey likeness is regularly seen in many astronomy-related books and media and has even graced a few TV shows such as Star Trek where it has been seen in the background on computer displays.

One obvious reason for its striking appearance is that it's a supernova-remnant, and a fairly recent one in astronomical terms as well, corresponding to one recorded by Chinese astronomers in 1054. Even with this in mind, however, it's still very bright, and the reason behind this was uncovered in the 1960's with the discovery of the Crab Pulsar which lies at its centre which would go on to prove very important to the scientific understanding of supernova remnants in general.

Observation: M1 lies in the constellation of Taurus. It can be vaguely made out with nothing more than a pair of binoculars and can be seen a little more clearly with a modest telescope, but seeing the brilliant colour and detail such as the filaments would require substantially larger and more complicated equipment.