[astro] The milky way is bigger than we thought, perhaps as big as andromeda!

[Eugen Leitl]

----- Forwarded message from Peter Langston <MiniFunPeople at psl.to> -----

From: Peter Langston <MiniFunPeople at psl.to>
Date: Wed, 07 Jan 2009 18:49:15 -0800
To: The MiniFunPeople List <MiniFunPeople at psl.to>
Subject: The milky way is bigger than we thought, perhaps as big as andromeda!
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MiniFunPeople........................................ISSN 1098-7649
Forwarded-by: Peter Langston <MiniFunPeople at psl.to>
[Get ready for some, er, astronomical numbers... no, really!  Would you 
believe the Sun is moving at 1,000 mph?  Okay, it's not.  So how fast is it 
really moving?  -psl]
Forwarded-by: David Michael <harp at olympus.net>

  The New York Times <http://www.nytimes.com/>
  January 6, 2009

  Data Uncover Bigger Galaxy in Cosmos, and It’s Ours
  <http://tinyurl.com/9zrvtu>
  By KENNETH CHANG


It turns out that Andromeda, previously thought to be the biggest galaxy in 
this part of the universe, may not have bragging rights over the Milky Way 
after all.

Astronomers said Monday that the Milky Way is more massive than earlier 
known, given new measurements showing that the Sun 
<http://tinyurl.com/8a8mfh> is moving at 600,000 miles per hour around the 
center of the galaxy, or 100,000 m.p.h. faster than past calculations 
suggested.

The higher speed of the Sun means the galaxy must have more mass — about 
50 percent more — so as to generate a stronger gravitational pull to keep 
hold of the Sun, as well as all its other stars. That expands the Milky Way 
to roughly the heft of Andromeda.

“We thought we were like a little sister of Andromeda,” said a member of 
the research team, Mark J. Reid, an astronomer at the Harvard-Smithsonian 
Center for Astrophysics. “Now we’re like fraternal twins.”

Determining the shape, size and mass of the Milky Way is difficult. Most of 
the mass is in the form of invisible dark matter 
<http://tinyurl.com/a736h5>, a component that far outweighs the ordinary 
matter in stars and gas clouds.

The astronomers, who reported their findings in Long Beach, Calif., at a 
meeting of the American Astronomical Society, used the Very Long Baseline 
Array, a system of 10 radio telescopes stretching from Hawaii to the Virgin 
Islands. The team looked at bright, star-forming regions within the Milky 
Way, then measured the motion of those regions against the background of far 
more distant objects as the Milky Way rotated.

In a second finding, another team of astronomers found something surprising 
at the center of the Milky Way: baby stars, still in the process of 
coalescing out of dust and gas.

Astronomers have known of young stars near the gigantic black hole at the 
center of the Milky Way, some 28,000 light-years from Earth, but there has 
been a mystery as to how they got there. The tidal forces induced by the 
black hole would rip gas clouds to shreds before they could coalesce and 
collapse into stars, astronomers believed. Yet it also seemed unlikely that 
so many stars would have formed elsewhere and then pulled inward.

Using a radio telescope array in New Mexico, Elizabeth M. L. Humphreys, a 
Harvard-Smithsonian astronomer, and her colleagues have now discovered two 
protostars — baby stars still in their cocoons of dust and gas — within 
a few light-years of the black hole.

The astronomers said that the gas clouds appeared to be 10 to 1,000 times 
denser than typical star-forming clouds and that this helped hold them 
together against the tidal forces.
_______________
A version of this article appeared in print on January 6, 2009, on page A13 
of the New York edition.

----- End forwarded message -----
-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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