Wed July 18, 2012
Using Hubble, Astronomers Spot Oldest Spiral Galaxy Ever Seen
Originally published on Wed July 18, 2012 5:29 pm
Astronomers made a surprising announcement today: They have found a spiral galaxy that existed very early in the universe — the oldest spiral galaxy ever seen.
The galaxy is special because such a well-formed spiral wasn't thought to have existed this early on, when the universe was tumultuous.
"As you go back in time to the early universe, galaxies look really strange, clumpy and irregular, not symmetric," Alice Shapley, a UCLA associate professor of physics and astronomy, and co-author of the study, said in statement. "The vast majority of old galaxies look like train wrecks. Our first thought was, why is this one so different, and so beautiful?"
The galaxy, which has been named BX442, was observed using the Hubble Space Telescope as it existed 3 billion years after the Big Bang. Think about that: It means the light from that part of the universe took 10.7 billion years to get here.
But back to that big central question. Why does this "grand design" galaxy — with its well-formed spiral arms — exist?
In its press release, UCLA reports:
"[David Law, lead author of the study] and Shapley think the answer may have to do with a companion dwarf galaxy, which the OSIRIS spectrograph reveals as a blob in the upper left portion of the image, and the gravitational interaction between them. Support for this idea is provided by a numerical simulation conducted by Charlotte Christensen, a postdoctoral scholar at the University of Arizona and a co-author of the research in Nature. Eventually the small galaxy is likely to merge into BX442, Shapley said.
"'BX442 looks like a nearby galaxy, but in the early universe, galaxies were colliding together much more frequently,' she said. 'Gas was raining in from the intergalactic medium and feeding stars that were being formed at a much more rapid rate than they are today; black holes grew at a much more rapid rate as well. The universe today is boring compared to this early time.'"
The findings are published in the July 19 issue of the journal Nature.
Update at 6:20 p.m. ET. Why A Rendering:
Some of you may be wondering why we needed to use a rendering, instead of the actual image of the galaxy. The answer is that at that distance this is the image you get from Hubble:
And even that image is a false color composite. When the astronomers got the images from Hubble, they explain that they thought the spiral was an illusion. So they went to the W.M. Keck Observatory atop Hawaii's Mauna Kea volcano to make more observations. Using a special instrument they determined BX442 was really a rotating spiral.