Wednesday, October 29, 2008

The Chesire Cat Gravitational Lens

I just found this gravitational lens from the Sloan Digital Sky Survey which has been dubbed the Chesire Cat.


Hopefully you can see the eyes and the smile near the center of the image.

The two eyes of the cat are two massive elliptical galaxies about 4.5 billion light years away. These galaxies are bending and distorting the light of more distant galaxies (at least two different galaxies have been identified) to form the smile. These more distant galaxies are about 8 billion light years away.

Gravitational lensing is one of those weird things predicted by Einstein. He said that a massive object (say a galaxy) could warp space. Light from a more distant object would follow this strangely curved space time and creates all kinds of interesting patterns such as arcs, crosses and circles.

Gravitational lenses are useful for mapping dark matter. By looking at the pattern we see, we can calculate how much matter is present and how it is distributed. We can also look at the matter we see and conclude that what we don't see is, well, dark matter!

You can see the Chesire Cat and a bunch of other gravitaitonal lenses from the SDSS at at the CASSOWARY Graviational Lens page.

Reprinted with permission from the Half-Astrophysicist Blog.
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8 comments:

  1. SEROctober 30, 2008 at 2:35 AM

    That's pretty cool...how do these people find this stuff. Their eyeballs must be about worn out at the end of the day...

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  2. kkditherOctober 30, 2008 at 6:46 AM

    I need to read more about Einstein. How in the world did he envision all of this before it existed? Did he also have some so-wild out there predictions that we either haven't realized them as of yet or was he pretty much right-on in all of his visions? You are making me think too much again, hale.

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  3. hale-boppOctober 30, 2008 at 11:24 AM

    Ser, they have computer programs that help them out searching for these things. They frequently have distinctive shapes and colors. Once the computer gives you a list of candidates, then you can check them out (the Sloan Digital Sky Survey database has a couple hundred million objects in it or so).

    kk, we are still looking for gravity waves that Einstein predicted and still trying to verify his prediction of frame dragging (although we have some evidence for both direct confirmation awaits). Both good topics to add to my list of future blogs.

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  4. kkditherOctober 30, 2008 at 1:22 PM

    I can verify frame dragging. My frame has been dragging for months. ;>

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  5. drewzepmeisterOctober 30, 2008 at 7:52 PM

    Nice pic,hale! That CASSOWARY site is really cool.Zooming in on pictures...wow!

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  6. OrbsCorbsOctober 30, 2008 at 10:57 PM

    I love the Cheshire cat pic. I also like information and discussion about exotic things like dark matter and subatomic particles and quantum physics and the Large Hadron Collider. I cannot "wrap my head around" that stuff.

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  7. AnonymousOctober 30, 2008 at 11:13 PM

    Is there a true balance in the universe????

    Douse "=" really exist, or is it relative?

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  8. hale-boppOctober 31, 2008 at 10:56 AM

    Not sure what you mean by balance in the universe, anonymous. The universe is definitely not static. It is expanding...and the rate at which it is expanding is increasing. We have named this stuff that speeds up the expansion "dark energy" even though we have no clue what it is or how it works...just that it accounts for about 70% of the energy in the universe! Figuring out what makes up dark energy is one of the hottest research topics going right now.

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