Wednesday, 5 November 2014

Image of the Day --A Mega Galaxy 50 Xs Size of the Milky Way

10369106_10152706870024841_8751046184735977263_n (1)

The image above shows IC 1101, a supergiant elliptical galaxy of approximately 6 million light-years across, which makes it the largest known galaxy discovered to date. It lies about 1.07 billion light-years away from Earth in the constellation of Virgo (the Virgin), and is made up of more than 100 trillion stars (for comparison, our Milky Way has about 300 billion stars), this galaxy is the extremely bright object at the center of Abell 2029, a massive cluster of thousands of galaxies. Being one of the most luminous galaxies ever seen, IC 1101 emits more than one quarter of the total light from this galaxy cluster.

IC 1101 is more than 50 times the size of the Milky Way (which is some 100,000–120,000 light-years across) and 2,000 times as massive. If it were in place of the Milky Way galaxy, it would swallow up the Magellanic Clouds, the Andromeda Galaxy, and the Triangulum Galaxy. IC 1101 owes its size to many collisions of smaller galaxies about the size of the Milky Way and Andromeda galaxies. As expected, the huge galaxy is giving birth to very few new stars. Unless it continues to collide and join with other younger galaxies, IC 1101 will eventually fade away.

Massive galaxies in the Universe have stopped making their own stars and are instead cannibalising nearby galaxies, according to research by Australian scientists. Astronomers looked at more than 22,000 galaxies and found that while smaller galaxies were very efficient at creating stars from gas, the most massive galaxies were much less efficient at star formation, producing hardly any new stars themselves, and instead grew by eating other galaxies.

Ultimately, gravity is expected to cause all the galaxies in bound groups and clusters to merge into a few super-giant galaxies, although we will have to wait many billions of years before that happens. “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,” said Aaron Robotham based at The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR)

“All galaxies start off small and grow by collecting gas and quite efficiently turning it into stars,” said Robotham. “Then every now and then they get completely cannibalised by some much larger galaxy.”

Dr Robotham, who led the research, said our own Milky Way was at a tipping point and expected to now grow mainly by eating smaller galaxies, rather than by 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,” he said.

“We’re also going to eat two nearby dwarf galaxies, the Large and Small Magellanic Clouds, in about four billion years.”But Dr Robotham said the Milky Way would eventually get its comeuppance when it merged with the nearby Andromeda Galaxy in about five billion years. “Technically, Andromeda will eat us because it’s the more massive one,” he said.

Almost all of the data for the research was collected with the Anglo-Australian Telescope in New South Wales as part of the Galaxy And Mass Assembly (GAMA) survey, led by Professor Simon Driver at ICRAR.

The GAMA survey involves more than 90 scientists and took seven years to complete.

Dr Robotham said as galaxies grew they had more gravity and could therefore more easily pull in their neighbours. He said the reason star formation slowed down in really massive galaxies was thought to be because of extreme feedback events in a very bright region at the centre of a galaxy 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.

No comments:

Post a Comment

About Me

Designed ByBlogger Templates