The Hubble Space Telescope has joined up with the Spitzer Space Telescope and the duo have produced images of some of the earliest galaxies from when the Universe was peaking with star-forming activity. The study was led by Brian Siana from University of California, Riverside. The results were presented this week at the 223rd Meeting of the American Astronomical Society. 

The galaxies are seen as they appeared an astonishing 10 billion years ago, when the young Universe was buzzing with star formation. Hubble isn’t quite strong enough to see the faint light from these early galaxies on its own, so it requires a partnership with Abell 1689; a galaxy over 2.5 billion lightyears away. Abell 1689 allows Hubble to take advantage of a phenomenon called gravitational lensing. 

Gravitational lensing occurs when a very large object, like a galaxy or black hole, is curved and can bend light around it. Essentially, the galaxy acts like a giant natural telescope. It stretches the light, distorting the image, but it also amplifies light considerably. The amplification of light is what allowed Hubble to detect these faint galaxies and correct for the distortions. 

These early galaxies are not like what we are used to seeing. They were considerably smaller, with the largest ones only one-tenth of the mass of our Milky Way and a fraction of the width in light years.  They did not exist in recognizable shapes, such as our own spiral, but are irregularly-shaped clusters of stars. The masses were determined by the Spitzer Space Telescope by analyzing their luminosity.

NASA is set to begin a three-year-long survey of these galaxies from the young Universe. It will seek to explore the earliest galaxies through the use of deeper gravitational lensing than has been utilized before from six distant galaxies. The James Webb Space Telescope, set to launch in 2018, will continue to study these early galaxies. Through infrared spectroscopy, it will be able to discern more information on how these earliest stars formed and even determine their chemical composition.

Among these amazing discoveries were four 13-billion-year old galaxies that were about 10-20 times brighter than the others. It is estimated that this bright light is due to rapid formation, on the order of 50 times faster than the Milky Way. These are believed to be extremely dense, with over a billion stars packed into an area only one-twentieth the size of our galaxy. These are the most distant galaxies to have their respective masses determined.

Telescopes are able to see so far back in time due to reionization, which occurred during the first billion years of the Universe. Prior to this, space appeared opaque due to the large quantity of neutral hydrogen which scattered photons. Bright stars that kicked off large amounts of radiation were able to ionize the hydrogen. This gives empty space the clarity needed for light to travel great distances and are why astronomers are able to get a glimpse of activity so far back in the past.