NGC 1309 is helping us measure the expansion rate of the universe. How? It is home to a particular type of star called a Cepheid variable and they vary in brightness at regular intervals. By comparing their variation rate to how bright they appear, the distance to them can be worked out pretty accurately (so they say). By knowing the distance to the Cephid, we know the distance to the galaxy. It so happens there was a cataclysmic explosion in the galaxy, a “Type 1a” supernova whose light reached us in 2002; by comparing that to other Type 1a supernovae, scientists can tell the universe is not only still expanding but is expansion is accelerating. How can this be, the expansion accelerating part? I could see the expansion happening at a constant rate but to have acceleration? Sounds like a job for Astroprof; if anybody can explain it so it is easily understandable he can.

Galaxies like NGC 1309 provide much more than a stunning vista for those who look up at dark skies. Having said that, NGC 1309 isn’t too bright at around a magnitude 13 to 14; then it is a whopping 30 megaparsecs away! That’s better than 100 million light-years distant; the supernova whose light we could see in 2002 had to travel over 100 million years to get to Hubble or here. Having tried to get astrophoto’s I can tell you it isn’t as easy as the typical daytime photo. It is actually very difficult and then to see something like this – boy. If you got time click the image and have a look at some of the detail, I’d love to know more about the galaxies in the background, they must be at staggering distances.

If you go to the source of the image on this post you can also get wallpaper versions, I have one.

Credit: NASA, ESA, The Hubble Heritage Team, (STScI/AURA) and A. Riess (STScI)