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tonyPick [soylentnews.org] writes:

At The Conversation is an article on how galaxies stop turning gas into new stars and effectively die [theconversation.com]. It also describes a scenario where a galaxy is running though hydrogen gas reserves; still managing to produce stars but at a reduced rate and it is effectively already dead - a so called "Zombie galaxy".

It raises the possibility that Andromeda, and possibly even our own galaxy, are in this state:

Like a zombie, the Milky Way galaxy may already be dead but it still keeps going. Our galactic neighbor Andromeda almost certainly expired a few billion years ago, but only recently started showing outward signs of its demise.
...
How and why galaxies “quench” their star formation and change their morphology, or shape, is one of the big questions in extragalactic astrophysics. We may now be on the brink of being able to piece together how it happens. And part of the thanks goes to citizen scientists who combed through millions of galactic images to classify what’s out there.

The article author is Kevin Schawinski (Assistant Professor of Galaxy & Black Hole Astrophysics at the Swiss Federal Institute of Technology) - one of the founders of Galaxy Zoo [galaxyzoo.org], and the article also covers the ways in which the crowdsourcing of galaxy classification helped the research project goals.

Original Submission