Milky Way Destined To Be Andromeda's Tasty Snack

[Buster's Uncle]

Milky Way Destined To Be Andromeda's Tasty Snack
Forbes
Brid-Aine Parnell  9/19/2014 @ 2:00AM



The Universe’s most massive galaxies have stopped making their own new stars and are now just snacking on smaller nearby galaxies instead, according to a new study.

Astronomers have figured out that the Milky Way will chow down on two nearby dwarf galaxies in the next four billion years or so – the Large and Small Magellanic Clouds. But our solar system won’t have long to savour its dominance, since our nearest neighbour Andromeda is likely to be the one snacking off us a billion years later.

“All galaxies start off small and grow by collecting gas and quite efficiently turning it into stars,” explained lead author Dr Aaron Robotham of the University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR).

“Then every now and then they get completely cannibalised by some much larger galaxy.”



English: Artist’s conception of the Milky Way galaxy. (Photo credit: Wikipedia)


The Milky Way is currently at the tipping point and scientists expect any further growth for the galaxy to come from eating up smaller neighbours, rather than collecting gas.

“The Milky Way hasn’t merged with another large galaxy for a long time but you can still see remnants of all the old galaxies we’ve cannibalised,” Robotham said in a statement.

“We’re also going to eat two nearby dwarf galaxies, the Large and Small Magellanic Clouds, in about four billion years.

“[But] Andromeda will eat us because it’s the more massive one,” he added.

Star formation slows down in really massive galaxies because of extreme feedback events in the very bright region at the centre of the star cluster, known as an active galactic nucleus.

“The topic is much debated, but a popular mechanism is where the active galactic nucleus basically cooks the gas and prevents it from cooling down to form stars,” Dr Robotham said.



Some of the many thousands of merging galaxies identified within the GAMA survey. (Credit: Professor Simon Driver and Dr Aaron Robotham, ICRAR)


Eventually, gravity will cause all the galaxies in the Universe to bunch together and blend into just a few remaining super-giant galaxies.

“If you waited a really, really, really long time that would eventually happen but by really long I mean many times the age of the Universe so far,” he added.

The study, which was published in the Monthly Notices of the Royal Astronomical Society, used data which was collected with the Anglo-Australian Telescope in New South Wales as part of the Galaxy and Mass Assembly (GAMA) survey. The survey took seven years to complete and involves more than 90 scientists.


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