Largest Hubble Mosaics Ever Assembled

bobtheowl2 writes "The Hubble Heritage team of astronomers, who assemble many of the NASA Hubble Space Telescope's most stunning pictures, is celebrating its five-year anniversary with the release of the picturesque Sombrero galaxy. One of the largest Hubble mosaics ever assembled, this magnificent galaxy is nearly one-fifth the diameter of the full moon. The team used Hubble's Advanced Camera for Surveys to take six pictures of the galaxy and then stitched them together to create the final composite image. The photo reveals a swarm of stars in a pancake-shaped disk as well as a glowing central halo of stars."

Comments

Dust, and a whole bloody lot of it

[ControlFreal]

Indeed, it's dust. In order to get just a rough idea of how much dust that is, picture the following:

The Messier 104 (Sombrero) galaxy contains anywhere between 210,000,000,000 and 800,000,000,000 stars (although the latter figure seems more likely to me, mostly because the estimate is newer). That is a whole lot of mass!

Look at the image: given that the galaxy is about 50,000 lightyear across, the dust-band must be about 1,000 lightyears across. Just, for the sake of argument, assume that the dust is located in a ring with a diameter of 50,000 lightyears, 1,000 lightyears high and 1,000 lightyears thick. Then this ring has a volume of 1,000*pi*(51,000^2-50,000^2) is about 3e+11 cubic lightyears, which is 2.5e+59 cubic meters.

Is there any astronomer out there who can shed some light on the density of these clouds? Think about it: even if you assume only 1 (hydrogen) atom per square meter, there are 2.5e+59 hydrogen atoms there, which weight 4e+34 kg, and that's a very, very low estimate!

To put that into perspective: the earth weights about 6e+24 kg.

Re:Dust, and a whole bloody lot of it

[EricWright]

When I was a grad student, I did numerical simulations of supernova remnant evolution. These blasts were simulated expanding into an interstellar region of H density 1 per cc. I imagine dust clouds would be anywhere between 100 to 1000 times more dense than the "normal interstellar medium".

1 per cubic meter is FAR too low of an estimate (a million times less dense than I used, and my figure was based on published articles in The Astrophysical Journal), meaning there is probably a billion times more mass tied up in the dust clouds of M104 than your estimate. That a whole bloody, freaking, massive, gigantic, tremendous, enormous lot of dust!