Thought I'd use today's Object of the Day to introduce our many new Zooites to some of the things we get up to here. Galaxy Zoo Get-Togethers
have been a tradition for a little over a year; our most recent was to Astrofest
, where some of us attended some excellent lectures. One, by Johan Knapen
, was about barred spirals, one of the questions we get asked in Galaxy Zoo 2
Bars are present in more than half of all spiral galaxies. It is not clear why they form. While it seems logical that a star should travel around in a circular orbit, the stars in bars travel round more in a boxy or sausage-shaped orbit - which is perfectly stable. In fact, stars can orbit in all kinds of crazy patterns, and once they're there, they'll keep doing it. What makes them leave the circular or oval path and head into a more rectangular one in the first place is less obvious. It seems to be some instability in the galaxy itself.
According to the lecture, a timeline of the evolution of the bar in a spiral galaxy would go something like this:
The galaxy starts of as a smooth disk-like spiral; then gradually the bar grows and grows, the arms emerging from its ends. But, of course, we don't know this for certain - because a bar would take several million years to form. This is one of the ways in which Galaxy Zoo comes in handy. We can't watch evolution taking place, but we can map the fossil record; and, similarly, we can use the massive amounts of data and our eyes to look at many, many galaxies and one day see if we can place them on such a sequence. Maybe the above is right, and maybe it's wrong.
If you found this interesting, you can see a more detailed write-up of my lecture notes here
. I personally think we can get several very informative Objects of the Day out of that talk; anyone like to find some examples (or indeed counterexamples) and write more?
You can check out lots more beautiful barred spirals here
P.S. For an authentic look at my lecture notes, here some of them are along with my devoted assistant Cassie. Note messy piles of astronomy related stuff all over the table.