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New Galactic Neighbor
Posted by
samzenpus
on Wed Jan 11, 2006 08:55 PM
from the there-goes-the-neighborhood dept.
from the there-goes-the-neighborhood dept.
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."
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So (Score:5, Funny)
Re:So (Score:3, Funny)
3 blind scientists
How do they define a galaxy? (Score:3, Interesting)
Re:How do they define a galaxy? (Score:5, Funny)
It becomes Congress?
Parent
What happens if a black hole eats...? (Score:5, Funny)
Parent
Re:What happens if a black hole eats...? (Score:2)
Re:How do they define a galaxy? (Score:3, Insightful)
it's a strucured group of stars. our galaxy is very roughly a flat disk of stars, this new one is a sphere of stars intersecting it.
Re:How do they define a galaxy? (Score:5, Insightful)
Parent
Re:How do they define a galaxy? (Score:5, Interesting)
Yes, this is offtopic, but what is really wild is that they simulated that in 1994 on a Cray C90, which has a floating point speed of 16 gigaflops. Back here in 2006: the Playstation 3, a TOY, has a floating point speed of 2 teraflops.
Parent
Re:How do they define a galaxy? (Score:3, Interesting)
I disagree. The orbits of stars that get very close (while moving very fast!) to our galaxy's central mass have been directly observed, as shown on this page [wolaver.org], which includes an amazing movie of stars whipping around the central mass. Likewise, we have observed strong x-ray variability of that region on a time scale of hours, implying a source no larger in size a few li
Re:How do they define a galaxy? (Score:3, Informative)
Re:How do they define a galaxy? (Score:3, Interesting)
Re:How do they define a galaxy? (Score:3, Insightful)
Re:How do they define a galaxy? (Score:3, Informative)
Correct, except this in itself provides a means to differentiate a black hole from something with a surface in the case where the black hole has a companion star. Material from the companion is pulled towards the black hole. If there were a surface the material hits the surface and releases a burst of X-rays periodically. A black hole will never have these burst since it does not have
Re:How do they define a galaxy? (Score:3, Funny)
Because if it wasn't bound by gravity it would be an open cluster nebula.
what really matters though is isf this cluster has 100 billion stars or not. if it only has 99,999,999,999 stars it's not a galazy at all. I assume someone counted before declaring this collection of distant stars a galaxy, but some
Re:How do they define a galaxy? (Score:3, Interesting)
Re:How do they define a galaxy? (Score:3, Informative)
Think of a backyard trampoline. Golf balls and marbles [planets and suns] will sit quietly on it and if a marble gets close enough to a golf ball it will slide towards it down the little hill created by the golf ball.
Not very long ago... (Score:5, Funny)
Galaxy?! (Score:2, Funny)
Re:Galaxy?! (Score:4, Interesting)
Actually, on an intergalactic scale, this thing is freakishly close. According to TFA this dwarf galaxy is 30,000 light years from Earth. The distance from Earth to the center of the Milky Way galaxy is roughly 27,700 light years (according to Wikipedia [wikipedia.org]). This thing is nearly right on top of us.
BTW, if you're preparing to shoot it, the quote you're looking for is "It's coming right for us!"
Parent
Could this be... (Score:5, Interesting)
Re:Could this be... (Score:4, Informative)
Parent
*in warbly voice* (Score:4, Funny)
Dwarf galaxy (Score:3, Insightful)
It's a "dwarf galaxy" and yet so big we couldn't see it before?
Re:Dwarf galaxy (Score:2)
I don't really pay attention to these guys and type of work, so I could be wrong.
Re:Dwarf galaxy (Score:5, Informative)
That's right. It's a dwarf galaxy because its actual size is small (compared to other galaxies) but its apparent size is 5,000 times that of the Full Moon because it's so close, as galaxies go.
In case that's not enough to explain it to you, consider that the Moon is much smaller than Jupiter, but appears to be larger because it's much nearer.
Parent
Hmm (Score:5, Funny)
Sounds an awful lot like witchcraft, if you ask me. I think we should burn you and the moon, just to be sure.
Parent
Futurama-o-rama (Score:2, Offtopic)
Hermes: I'm just glad my fat ugly Mama isn't around to see 'dis day...
Professor: Enough about your promiscious mother, Hermes...
5000 times the size of a full moon? (Score:4, Informative)
Interesting wording.
So that must mean 5000 full moons in the sky?
Moon = 1800 arc seconds
or 1800/60 = 30 arc minutes.
or 30/60 =
So what is that in degree of sky?
A fist at arms length is roughly 10 degrees.
Re:5000 times the size of a full moon? (Score:2)
So, if the diameter of the moon is about 0.5deg, this thing is about 70 x 0.5 = 35 deg in diameter (if circular, but mind you, the original article says it is not).
That's huge.
Re:5000 times the size of a full moon? (Score:5, Funny)
FTFA: nearly 5,000 times the size of a full moon
So naturally it is 5000*0.5 = 2500 degrees, silly!
Parent
Re:5000 times the size of a full moon? (Score:5, Informative)
The measurements you offered for the degrees of the moon concerns of course only one dimesnion of the moon.
Now, suppose we assume that that galaxy is roughly squarish, we just need to take the square root of 5000 and we get roughly 70 which means that in the sky the galaxy is 70 times bigger than the moon in any one dimension (lets say width).
Therefore, assuming your other calculations are correct, then the galaxy is about 70x0.5= 35 degrees in the sky. Which is pretty big if you think about it.
Parent
Star Question (Score:2, Interesting)
Re:Star Question (Score:5, Insightful)
Why?
Well, it has to do with the density. Even if there is a galaxy nearby, if the content of a galaxy is sparcely populated by ordinary stars (and they are, I RTFA), you ain't gonna see them. Just like you don't see "humidity" (water molecules) in your room.
Parent
Re:Star Question (Score:2)
You're an observer looking across a field covered in a fog of a certain turbidity. Now, I disperse a spherical cloud of smoke at some distance from you in that field.
Assuming similar colour and only slightly different turbidity, then you're most helpful factor in noticing the cloud is seeing the edges delineating it. If the cloud covers a very wide field of view, you'll tend to just look through it, unregistered. A combination of low contrast and minimal local variation in structure (
Some SDSS info (Score:5, Informative)
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 (Score:5, Funny)
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:like looking at the milky way through 3d glasse (Score:3, Informative)
Appearance from outside (Score:4, Insightful)
Well, now we know. Little did we know that we knew all along.
Very cool! (Score:4, Funny)
Why women are smarter than /.ers (Score:3, Funny)
Re:Why is this considered a galaxy? (Score:2)
Re:Why is this considered a galaxy? (Score:4, Funny)
Ah, a parliament or congress.
Parent
Re:Why is this considered a galaxy? (Score:2)
Re:Wrong priorities... (Score:5, Informative)
This work instead shows how invaluable ground observatories (esp the small ones) are. It's not a super-flashy job; it's a long, time-consuming, and slow-rewarding job. But once you've done it, you get your 15 minutes of fame (actually, in this case, you may make it into the history book).
Parent
Re:Wrong priorities... (Score:3, Funny)
We've been here a while now. We did the Veni, Vidi, Vici thing, you just don't know it yet, but, yea, all your base are belong to us.
Re:Wrong priorities... (Score:5, Interesting)
Optimistic, aren't you?
Even worse, if you consider that we are the aliens, and our species has simply invaded and conquered this planet an aen ago. We adapted, survived, and destroyed our own history. If you don't understand the destroyed part of that, go to a library and read some 6,000 year old books. Assuming you knew the language, you wouldn't find the books. They're lost, damaged, and/or intentionally destroyed over the years.
We are the aliens, and our brothern have forgotten about us. We will be stuck here, alone, for a long time.
Parent
Re:Wrong priorities... (Score:3, Informative)
Re:Wrong priorities... (Score:3, Interesting)
Yes, see Larry Niven's Protector [wikipedia.org].
Re:hmmm (Score:3, Funny)
Apparently they're now called vertically challenged galaxy overlords.
Think of the little people...