Discovering Distant ExplosionsSo how do we find objects on the other side of the Universe? The answer is simply by looking! The latest instruments enable us to scan large areas of sky. Using Cerro Tololo's Blanco 4m telescope and the Canada-France-Hawaii 3.5 metre telescope, we are able to scan a piece of sky larger than the size of the moon every 5 minutes to a faintness level which allows us to find Type Ia supernovae halfway across the Universe. Type Ia supernovae are very rare - but each image we take contains 50000 galaxies. With these telescopes we can survey more than a million galaxies in a night, and find tens of supernovaeAt the Canada-France-Hawaii telescope, we sometimes scan the sky 10 ten times slower, and look 4 times fainter. This allows us to find even more distant objects such as SN 1999fv (a.k.a. Dudley DoRight), which at 9 billion light years - it is receding at 80% of the speed of light - is the most distant supernova yet detected from the groun. To be fair, our competitors, the Supernova Cosmology Project, have an object at an almost identical distance. But both these ground discovered objects have been eclipesed by another object, discovered by Ron Gilliland and Mark Phillips with the Hubble Space Telescope, and discussed Fully in the main body of text. 
Because we are looking to such faint levels, the sky is packed with galaxies, and we
typically find up to 4 supernovae in one patch of sky 1/2 the size of full moon. These
objects are uncovered by comparing an image with an image taken of the same region of
sky taken a month earlier. After careful alignment, and adjustment to make the two
images as identical as possible, we subtract the first image from the second, to reveal any
new objects. Most of the objects we find are not easily seen by your eye without the
subtraction. |