Tuesday, 24 June 2014

Object of the Month - The Milky Way

Our telescope is pretty uniquely capable of capturing images of the milky way in all its splendour thanks to the wide field cameras you are able to request images from. The only difficulty is working out what to point at, as the milky way takes up quite a lot of the sky. (Or all of it you could argue).

The Milky Way

The Milky Way is of course our own Galaxy. The name is a translation of the ancient Greek name (more directly Milky Circle). Being the ancient Greeks, they had various myths around breast-feeding goddesses to explain this phenomenon. The Greek word used for milky was 'galaxĂ­as', from which we derive our modern world for all such objects, not just our own.

We now know much more about the true nature of the Milky Way. It is a collection of about 100 billion stars, bound together into a spiralling disk. The disk itself is about 100,000 light-years in diameter, with own solar system almost 30,000 light-years from the centre. At the centre we now know there to be a super-massive black hole about 4.5 million times more massive than our Sun.

All the stars in our sky are part of the Milky Way galaxy, but when most people think of the Milky Way they think of the bright central band stretching across our sky. This is our view looking through the disk of the galaxy, towards the core, where we can see a very high density of stars. And this is what the pale light we see is: not glowing gas but stars so numerous that we cannot resolve them as individual stars but just see one continuous glow.

The dark patches are not areas without stars but areas where dense bands of dust within our galaxy obscures the star-light from behind. Small bright pink areas on the image above are emission nebulae, where giant clouds of hydrogen gas are collapsing to produce new stars.

How to Observe

If you want to see the bigger picture of the Milky Way then Constellation Cam is perfect. As for targets, Scorpius, Sagittarius, Scutum and Aquila lie along the most prominent part, with Scutum and Aquila much higher in the sky. It starts to fade by the time you get to Cygnus but still worth a look. 
There are some Messier objects in the region you can centre your picture on too. The image above is centred on Messier 8 (which is the bright pink object in the very centre).

A cluster cam zoom-in of dust lanes
A colour filter works just fine at 60,000 ms but you can try a longer exposure of 120,000. If taking black & white images, a red filter gives good contrast between the bright areas and the dust lanes. The compromise is that the edges of the dome shows up more strongly in this channel. Use a green filter if you want black dome.

Cluster Cam can be used to look at the dust lanes in more detail, but with limited good targets you might need to resort to Ra Dec coordinates. I leave that as a challenge for the more advanced user.

One thing I would love to see is a panorama of the Milky Way made from stitching together multiple shots. I've never seen this done with our images before.

Happy observing!