NASA's Hubble Space Telescope has broken the distance limit for galaxies and uncovered a primordial population of compact and ultra-blue galaxies that have never been seen before.
The deeper Hubble looks into space, the farther back in time it looks, because light takes billions of years to cross the observable universe.
This makes Hubble a powerful "time machine" that allows astronomers to see galaxies as they were 13 billion years ago, just 600 million to 800 million years after the Big Bang.
The data from Hubble's new infrared camera, the Wide Field Camera 3 (WFC3), on the Ultra Deep Field (taken in August 2009) have been analyzed by no less than five international teams of astronomers. A total of 15 papers have been submitted to date by astronomers worldwide. Some of these early results are being presented by various team members on Jan. 6, 2010, at the 215th meeting of the American Astronomical Society in Washington, D.C
The faintest galaxies are now showing signs of linkage to their origins from the first stars. They are so blue that they must be extremely deficient in heavy elements, thus representing a population that has nearly primordial characteristics.
The existence of these newly found galaxies pushes back the time when galaxies began to form to before 500-600 million years after the Big Bang. This is good news for astronomers building the much more powerful James Webb Space Telescope (planned for launch in 2014), which will allow astronomers to study the detailed nature of primordial galaxies and discover many more even farther away. There should be a lot for Webb to hunt for.
The deep observations also demonstrate the progressive buildup of galaxies and provide further support for the hierarchical model of galaxy assembly where small objects accrete mass, or merge, to form bigger objects over a smooth and steady but dramatic process of collision and agglomeration. It's like streams merging into tributaries and then into a bay.
These galaxies are as small as 1/20th the Milky Way's diameter, the masses are just 1 percent of those of the Milky Way. The results show that these galaxies at 700 million years after the Big Bang must have started forming stars hundreds of millions of years earlier, pushing back the time of the earliest star formation in the universe.
The teams are finding that the number of galaxies per unit of volume of space drops off smoothly with increasing distance, and also found that the galaxies become surprisingly blue intrinsically.
The ultra-blue galaxies are extreme examples of objects that appear so blue because they may be deficient in heavier elements, and as a result, quite free of the dust that reddens light through scattering.
Hubble's WFC3/IR camera was able to make deep exposures to uncover new galaxies at roughly 40 times greater efficiency than its earlier infrared camera that was installed in 1997. The WFC3/IR brought new infrared technology to Hubble and accomplished in four days of observing what would have previously taken almost half a year for Hubble to do.
