Why so many globulars?

[badgerchap]

Realised the other night that there are so many globulars available at this time of year. Anyone have any ideas why this is? I'm guessing that since the Milky Way's galactic core is in view at the moment, it must be due to the idea that globulars orbit centered on the core? Or am I just imagining this whole thing, and there are just as many visible throughout the year?

[acey]

Your first guess is correct!

[badgerchap]

Lol - I'm not as thick as I thought! Always good to know...

[Chris H]

Globular clusters are tiny satelites of the Milky way galaxy there are thought to be around 150 globs orbiting our galaxy.

[badgerchap]

Yeah, I was aware of that lol. Doing a degree in astronomy, my hopes would not look too good if I didn't! Just never really noticed their abundance at this time of year before.

[acey]

The distribution of globulars was what enabled Shapley to deduce the location of the galactic centre. Extract from his obituary:

"That the distribution of such clusters in the sky is highly asymmetric (most of them are situated in one hemisphere) was known long before Shapley's time: as well as the fact that many of them contain large numbers of cepheid variables whose absolute brightness can be estimated from the periods of their light changes. Armed with this evidence, Shapley embarked on systematic study of the distribution of the globular clusters in space; and found its center to be located some 50,000 light years from us, in the direction of the galactic longitude 325o in the constellation of Sagittarius. This point Shapley boldly identified with the centre of our entire Galaxy; and he was indeed right. As a result of his work, our Galaxy began to emerge for what it actually is: a stellar system at least ten times as large as all earlier estimates - from Herschel to Kapteyn - made it out to be; with our Sun located eccentrically some 15 thousand parsecs from its centre."

`Great Debate:' Obituary of Harlow Shapley

[Macavity]

An interesting notion:

Milky Way Grew by Swallowing Other Galaxies - ScienceNOW

[badgerchap]

Yeah, it seems to be a pretty standard idea that large galaxies through mergers. A lot of the data from GalaxyZoo and other surveys suggests that galaxies start out as dwarves, and after a few mergers, gain their spiral arms. As the mergers continue though, they lose the spiral again and end up as giant ellipticals. I think that was from GalaxyZoo anyway. Is it only me that would love to be in alive when the Milky Way and M31 collide? I think that would be sweet! Of course, theorists predict that individual stars would not actually be disturbed by the interaction, so although it might look pretty cool, it could be relatively uneventful for an observer on Earth. If Earth stood a chance of still being habitable at the time that is lol.

[Macavity]

Is it only me that would love to be in alive when the Milky Way and M31 collide? I think that would be sweet!.

I think it might be truly fascinating! A few more "close stellar companions" - Or even being "flung into (DSO) space"? Assuming we survive, astronomy would certainly be uhm... different!

[ollypenrice]

I'm glad Shapley got his due on this thread. Both he and Herzprung found a way to calibrate the variables and so get a distance to the globulars. Peak season was a month or two ago when the southern Milky Way was in full glory.

Olly