Saturday, 28 April 2007

The Largest Telescope

Here is a view through the largest telescope ever. It is the Astronomy Picture of the Day for May 24, 2006.

The telescope was big. Bigger than the whole Earth. Bigger than our Solar System. Bigger even than the whole Milky Way galaxy!

This image uses an entire cluster of galaxies as a massive gravitational lens, that bends light so as to magnify the even more distant galaxies and quasar beyond it.

The image was taken by the Hubble Space Telescope with 16 hours of exposure time, and was released on May 23, 2006. The cluster that forms the lens is at a distance of 7 billion light years; and the quasar is at about 10 billion light years. As is always the case with a gravitational lens, there are multiple images visible of the same magnified galaxies. This was the first ever case where a lens gave five images of the same quasar.

One of the galaxies which is being distorted into an arc by the lens is at a distance of about 12 billion light years. The whole image is about 2 arcminutes wide. To put that in perspective, the full moon is roughly 30 arcminutes across. Under conventional cosmological models, this kind of image gives a view of the universe when it was something like 10% to 15% of its current age.

For more details, including annotated images and a diagram of how this kind of gravitational lens works, see the Hubble Press Release. See also heic0606: Hubble captures a ‘five-star’ rated gravitational lens from the European home page for NASA/ESA Hubble Space telescope, for more details, images and video.

These are exciting times for anyone interested in cosmology!