Friday, 23 December 2011

How to Picture the Size of the Universe

It's Full of Galaxies

It's Full of Galaxies

NASA’s Hubble Space Telescope has produced the deepest image of the universe ever taken. Astronomers generated this picture by pointing Hubble at one small patch of the sky for several months and recording every tiny photon of light they could get. The entire image (below) contains nearly 10,000 galaxies, but here you can see a small sample of what’s out there.

Because looking back in space means we’re also looking back in time, these galaxies are seen as they would have appeared nearly 13 billion years ago, just short of the beginning of time. If you're more spatially inclined, this means that the objects are 30 billion light years away.

But because the universe is ever expanding, and our estimates of its size get more refined over time, astronomers have actually come up with a better way of stating distances. As the universe grows larger, the light waves within it get longer, like a slinky being pulled apart. The wavelength of the light moves toward the redder part of the electromagnetic spectrum, so astronomers talk about the “redshift” of an object, meaning the amount that light waves from that object have expanded since they were emitted.

The galaxies in this image would be more accurately described as being at a redshift of 7.9.

Images: 1) NASA, ESA, S. Beckwith (STScI) and the HUDF Team 2) NASA and the European Space Agency

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