October astronomy highlights

Oct 4 2012 By Ninian Boyle

It's official! We have now passed the Autumn Equinox and so the hours of darkness outnumber the hours of daylight for observers in the northern hemisphere anyway. Those who reside in the southern hemisphere have it the other way around and have moved into 'Spring'.

A lovely sight which is often missed in the Autumn sky, is the star 'Formalhaut'. It is the brightest star in Pisces Austrinus or the Southern Fish. You will need a clear southern horizon to see it well. This star is interesting because it lies only(!) 25 light years away and is one of the brightest in the entire sky. Not only that, we know that is surrounded by a disc of dust and certainly at least one planet. The planet was imaged by the Hubble Space Telescope in 2008.

The 'Square of Pegasus' is riding high in mid-evening during the month of October. If you take the two left hand or eastern-most stars of the 'square', and drop a line down southward for the same distance again you will be in the right area to find the faint planet Uranus. You'll see it in binoculars as a small but distinctly round little pale green 'star'. Go and take a look...

As I write this, there is breaking news of a new comet which has just been discovered which looks as though it will become very bright towards the end of next year. It's called comet ISON and in November 2013 it could become as bright as the full Moon! Comets are notoriously unpredictable though, so I am urging caution about over-excitement. I will of course keep you up to date with information about this comet in future 'Newsletters' as I hear it.

I mentioned this last month and it still holds true...As the Sun heads towards its peak of activity next year there is the likelihood of more sunspots to see on its surface, with the proper filters of course, and also the likely increase of auroral activity. October skies are often dark enough to start observing this phenomenon at the start of the season. If you live in northern parts of the UK or Europe then your chances of seeing the Aurora increase dramatically, but with solar activity high, your chances of seeing the Northern Lights also increases further south. If you have never seen the Aurora Borealis before, it is a magnificent sight, but you will need dark clear skies to see it at its best advantage. I will be posting some information and images on my blog soon all about the Aurora.

Deep Sky Highlights of October

This month I thought I would point out a few interesting things to see in the 'watery' constellations of Pisces the Fish, Aquarius the Water Bearer and Capricorn the Sea Goat (whatever that is?)...

Pisces is a constellation which is not particularly distinct, but occupies the area of sky to the bottom left (south-east) of the Square of Pegasus which rides high in the south on October evenings. The brightest Deep Sky Object in this region of sky is Messier 74, a pretty face on spiral galaxy, visible in binoculars as a faint smudge of light and which looks more substantial in a telescope. You'll find it about half way along the eastern-most of the two fish.

While you are in Pisces, take a look at the 'circlet' asterism marking the head of the western-most fish. It is worth getting familiar with it as an easy way to find the constellation. The planet Uranus is currently quite nearby.

Head west into the constellation of Aquarius and forming a triangle with the stars alpha (Sadalmelik) and beta (Sadalsuud) Aquarii is the attractive globular star cluster Messier 2. It is quite obvious in binoculars and larger apertures will start to resolve the outer stars in the cluster. The planet Neptune is currently residing in Aquarius; you will need a telescope of at least 75mm aperture to see it clearly.

Among the deep sky delights of Aquarius is the 'Saturn Nebula'. It has nothing to do with the planet other than looking vaguely like it. It is in fact a planetary nebula (even more confusing!). This is where a star has shed its outer shell of gas into a kind of bubble. It was thought that this kind of nebula looked a little like a planet and so hence the name. You'll find the Saturn Nebula near the south of Aquarius near to the constellation of Capricorn.

This constellation lies fairly low in the south from mid-northern latitudes, so you'll need a fairly flat horizon without trees or buildings in the way to see all of it. The brightest Deep Sky Object in this constellation is M30 another bright globular cluster. Compare and contrast this one to M2 in Aquarius. M30 is probably the only Deep Sky Object in the constellation visible to amateur astronomers with small scopes. Even though Capricorn is a Zodiacal constellation it is surprisingly unremarkable but still worth getting to know.

The Orionid Meteors

It's that time of year again when we move into the season of some good meteor showers...

The Orionids are a reliable regular shower of fast moving 'shooting stars'. The particles of dust which give rise to this shower originate from the tail of the famous Halley's Comet. Every year in October the Earth passes through this stream of debris left by the comet.

The shower is active right throughout the month, but it reaches its peak around the 21st October. Good nights to observe it are on the 20th the 21st and the 22nd. The number of meteors we are likely to see is measured by something called the ZHR or Zenithal Hourly Rate, which for the Orionids are 25 meteors per hour. However, you are not likely to see this many due to the fact that the ZHR assumes perfect conditions which we never have!

As the name suggests, the meteors will appear to emanate from a point in the sky in the constellation of Orion the Hunter. This is not the best place to look at though as the meteors streaks will be very short at this point, so look some distance away although it doesn't really matter exactly where you look. Having said that, direct your gaze towards the constellation of Taurus the Bull, above and to the right of Orion and you should have a good chance of seeing a few of these lovely meteors.

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 here Twitter too.