‘
What are those two images? Not much to look at, are they?
Appearances can be deceiving. Astronomers are actually pretty excited about these two guys. They are dwarf galaxies, collections of stars that are like our own Milky Way Galaxy, but far smaller. The Milky Way has about 200 or so billion stars in it. These two dwarfs only have about 100,000 stars in them (which is why they are called dwarf galaxies of course). They appear to be companions to the Milky Way, orbiting it at a distance of a little over 600,000 light years. For comparing, the Milky Way is about 100,000 light years across.
Why is this exciting? We already know of several galaxies orbiting our own, like moons orbiting a planet. But so far, they have all been more massive, closer, and brighter than these two punks. These two (which are not yet officially named) are the most distant known, which helps astronomers understand how the Milky Way formed, and what it’s made of. Theories suggest that there might be a hundred satellites like these, but they are so faint they are really hard to find. Any time one is discovered, it’s a big deal.
These two were found in the Sloan Digital Sky Survey — a project to map out a quarter of the sky with incredible precision: they’ll map 100 million celestial objects, and determine distances to a million galaxies. An astronomer noticed the one on the left as a slight over-dense cluster of stars in the constellation Canes Venatici. He emailed an astronomer friend who started looking at the data, and found the second galaxy a few hours later!
This makes me wonder just how many more of these things are floating out there. With projects like Sloan going on, we’ll be finding many more such treasures, sitting in our own back yard.’
May 8th, 2006 at 3:26 pm
I’ve got the perfect names for the Milky Way’s newly-discovered friends, Phil and Lil.
May 8th, 2006 at 3:40 pm
This discovery reminded me of the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC).
Reading present blog topic led me to this image:
http://antwrp.gsfc.nasa.gov/apod/ap980203.html
May 8th, 2006 at 3:49 pm
This discovery reminded me of the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC).
Just how many more groups of Stars, that are yet to be discovered, will certainly provide job security for the entire Sloan Digital Sky Survey team. Nevertheless, in order for NASA to return human beings to the lunar surface by Year 2020 some of these “bean counting” projects will have to be cut back.
May 8th, 2006 at 4:15 pm
So how do these things get named anyway? Is it by some exaulted committee like that which decides if something is a planet? (BTW, were those two KBO asteroids declared planets?)
Cheers…
May 8th, 2006 at 5:15 pm
Geeze, the universe is looking more and more fractal-like. Moons orbit planets, planets orbit stars, stars orbit galactic centers, satellite galaxies orbit galaxies. The same basic patterns operate at larger and larger scales. Wouldn’t this be like a version of the Kuiper belt operating at the several-galaxy level? We already know about the small dim stars orbitting at large distances from the Milky Way center, which would seem roughly similar to the kuiper belt at galactic scales. Next we will be finding satellite galactic clusters.
Is there a name for a galaxy and its satellites? We have a galaxy, then we have a galactic group, is there any name for the structural level in-between that just includes a galaxy and its satellites? This discovery indicates there probably should be.
May 8th, 2006 at 6:08 pm
Funny that I happend to see that before I headed out today, because there was a guy getting off the metro with that exact same image in his hand on 8×10 cardstock and I knew exactly what it was and had a vauge insight as to just who he may be.
May 8th, 2006 at 6:45 pm
This is great information. Thanks. I actually found your blog by doing a search with the word gold on blogger.
Cool.
Cheers!
May 8th, 2006 at 9:57 pm
The “naming” is done through The International Astronomical Union or IAU, same with planets.
For objects like Comets, there are astronomical designations for each comet as well as up to 3 last names of the discoverers.
May 9th, 2006 at 2:59 am
If you want to be remembered, look’s like a team of three is max. But then of course you have to FIND something!
icemith.
May 9th, 2006 at 4:31 am
So, what’s the difference between a “dwarf galaxy” with ~100,000 stars and a globular cluster the same size, besides density and symmetry?
May 9th, 2006 at 4:36 am
icemith,
Comets are not named for teams of discoverers, but for up to three independent discoverers. And only if the reports are received within 24 hours of each other.
May 9th, 2006 at 4:59 am
This is why I love astronomy. There is so much over our own heads still waiting to be discovered. So much knowledge just waiting for the right person to uncover it.
May 9th, 2006 at 6:17 am
I love looking up also! I am always amazed by what you can’t see.
May 9th, 2006 at 8:26 am
Phil, I think you lost a zero in that second paragraph:
Ray Gray, you might want to read some more of this site to find out attitudes toward these “bean counting” projects vs. returning to the moon. The Pres gave us the agenda, now he needs to cough up the cash to fund it.
May 9th, 2006 at 9:19 am
“The Pres gave us the agenda, now he needs to cough up the cash to fund it.”
Yes, there is quite a lot of stuff the Pres needs to cough up.
May 9th, 2006 at 12:59 pm
DJ, I’m sure the Pres. is quite as familiar with the benefits of cough syrup as any other narcotic,,,
GAry7
May 9th, 2006 at 9:38 pm
technical question for Phil (or any other astronomers reading):
what exactly are the demarcation points between a dwarf galaxy, a globular cluster and an open cluster? If I didn’t know otherwise, I would have characterized these two as open clusters.
I’d be interested to know what the criteria might be…
May 10th, 2006 at 12:35 am
Our old Ford Galaxy was quite roomy inside, despite its being much smaller than your average globular. Today’s compacts might be a better comparison.
Jess Tauber