New Galactic Neighbor

Dan Yocum writes "The Sloan Digital Sky Survey reveals a new Milky Way neighbor: a galaxy so big we couldn't see it before. A huge but very faint structure, containing hundreds of thousands of stars spread over an area nearly 5,000 times the size of a full moon, has been discovered and mapped by astronomers of the Sloan Digital Sky Survey."

Comments

So

[Mikkeles]

Can't see the galaxy for the stars, eh?

Re:How do they define a galaxy?

[Travoltus]

"What happens if a black hole eats another black hole?"

It becomes Congress?

What happens if a black hole eats...?

[fredistheking]

Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.

Not very long ago...

[ian_mackereth]

... in a galaxy surprisingly not so far away...

Could this be...

[idonthack]

Could this be what's warping the Milky Way, previously thought to be Dark Matter?

Re:How do they define a galaxy?

[FalconZero]

What makes this a galaxy rather than just some random swirl in the cosmos?

If I remember my Physics elective from uni, Galaxies are internally gravitationally bounded, that is the entire 'clump' of things is held rougly in equalibrium with gravity providing the contracting forces.

does this galaxy have a black hole to call its own in the middle?

The jury is out on the existance of supermassive holes at all galactic centers (partly due to obvious impossibility of direct detection).

What happens if a black hole eats another black hole?

Black hole collisions are theoretically possible, and has been simulated on a Cray (pretty pictures included).

Some SDSS info

[Michael Woodhams]

I was a graduate student at the Astrophysical Sciences deptarment at Princeton when they were planning and starting to build the SDSS. A few interesting facts:

Some very clever optics (designed by James Gunn) went into the telescope. Normal telescopes do not produce the large field of view required. There were existing specialized telescopes which did (Schmidt cameras) but they have the imaging plane in the wrong place.

The main camera uses 30 2k x 2k CCDs, cooled by liquid nitrogen. At the time (early '90s) these cost on the order of $200k per chip.

The camera works in "drift scan" mode: the telescope moves such that the images of the stars drift along the columns of detectors in the CCDs. The packets of charge are shifted along the CCDs at the same rate - so instead of producing distinct individual frames, it continuously outputs data along an ever-lengthening strip along the sky. As I recall, the data rate is about 8Mbyte/s.

The camera spends rather more time on spectroscopy than imaging. (The imaging is primarily about selecting targets for the spectroscopy.) The spectrograph does 640 objects at a time. A computer-drilled plate is (manually) plugged with fibre optic cables in the right positions for that field of sky.

like looking at the milky way through 3d glasses

[themysteryman73]

"It's like looking at the Milky Way with a pair of 3-d glasses," said Princeton University co-author Robert Lupton.

I wonder where he got 3d glasses that make stuff look 3d in real life? I could use some of them to stop walking into walls so much!

Re:5000 times the size of a full moon?

[Quixote]

Moon = .5 degree
FTFA: nearly 5,000 times the size of a full moon

So naturally it is 5000*0.5 = 2500 degrees, silly!

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;-) for the ;-) -impaired