Milky Way Grew by Swallowing Other Galaxies

[Ichingcarpenter]

The motto "E Pluribus Unum" ("out of many, one") could be applied to the Milky Way. Astronomers have obtained new evidence that our home galaxy contains pieces of many former galaxies. The findings strengthen the idea that large galaxies don't emerge whole from single, gigantic clouds of dust and gas. Rather, they grow by swallowing their neighbors.


The clues come from globular clusters--spherical concentrations of up to millions of stars, orbiting the galactic center as self-contained neighborhoods. Aside from our galaxy's huge spiral arms, globular clusters constitute some of its most striking features. Astronomers have long thought they formed from concentrated clouds of gas and dust in the early Milky Way. But two papers in tomorrow's issue of Nature paint an entirely different portrait.


In one paper, a team of Korean astronomers measured the calcium content of stars in 37 of the Milky Way's 158 known globular clusters. About half contained significant amounts of the element, indicating that they had formed from the remnants of supernovae, the titanic explosions of giant stars that once manufactured calcium and other heavy elements in their cores. This finding is significant, says lead author Jae-Woo Lee of Sejong University in Seoul, because it indicates the globular clusters must have once been much larger than they are today. Otherwise, they wouldn't have exerted the gravitational force needed to trap the supernovae remnants so that they could condense into new stars. "This led us to believe that many of the globular clusters we studied are most likely the relics of more massive, primeval dwarf galaxies that merged with ," he says.


http://sciencenow.sciencemag.org/cgi/content/full/2009/1125/2?rss=1




A "Lego" Model of the Universe

The model most widely accepted for the evolution of our universe, and the galaxies that populate it, is that they formed from smaller galaxies which eventually coalesced, to form larger combined galaxies. We have seen recently reports of one galaxy eating another, and for a day or so we were led to believe that our Solar System was indeed from another galaxy all together.

This model has once again been confirmed, as nine galaxies – termed as “Lego-like” – have been found through a joint effort of the Hubble Telescope and its cousin observatory, NASA’s Spitzer Space Telescope.
First identified by James Rhoads of Arizona State University, USA, and Chun Xu of the Shanghai Institute of Technical Physics in Shanghai, China, the nine galaxies are believed to be “…among the lowest mass galaxies ever directly observed in the early Universe,” according to Nor Pirzkal of the European Space Agency/STScI.

http://www.dailygalaxy.com/my_weblog/2007/09/a-lego-model-of.html

[XemaSab]

1. NOM!

n/t

[Warpy]

2. In my gloomier moments, when I consider the usual spiral galaxy

composed of billions of stars around a supermassive black hole, all I can think of is that we're all circling the drain.

That analogy probably explains a lot about how glaxies are constructed in our particular few seconds of time in the universe.

It seems the oldest galaxies were globular clusters without black holes at the core.

I say "were" because most of them are probably long gone, chewed apart by galaxies like our own.

"My black hole can beat up your black hole, nyah!"

[imdjh]

3. Galactic imperialist!

[wroberts189]

4. How can you have a party without a lot of guests :). nt

[Itchinjim]

5. Jezz, Wal-Mart is everywhere