Teach Astronomy - High Redshift Galaxies

Описание: http://www.teachastronomy.com/
When did the first galaxies form? The Milky Way has stars that are ten or eleven billion years old in the globular clusters, and there are galaxies in the nearby universe that are the same age. So we know that the first epoch of star formation must have occurred at least that long ago or at a redshift at five or greater. At even earlier epochs it becomes very difficult to detect individual galaxies because galaxies were still being assembled, and the first galaxies were rare in any region of space. The highest redshift galaxies known are at redshifts of six or seven, but astronomers anticipate that redshift of formation must have been around redshift ten. By redshift ten or at that time the universe was ten times hotter and a thousand times denser than it is now. Redshift ten galaxies have their light shifted so far into the infrared that they're almost impossible to detect with optical techniques. So astronomers are building sensitive infrared instruments to try and find them.