Astrophysicists at Stanford University made a breakthrough discovery when they spotted a dwarf galaxy some 4 billion light years from earth. The galaxy is less than 600 light years across, to put that into perspective, the Milky Way, our own medium sized galaxy, is 100,000 light years across.
The tiny galaxy was discovered as a mere halo companion of a galaxy many times larger. The breakthrough discovery was made using a phenomenon called “gravitational lensing.” Basically, gravity can bend the path of light, distorting it in a predictable manner. Scientists were able to use this observed effect to discover the dwarf galaxy hiding in the “shadow” of its larger neighbor.
The image was taken by the Atacama Large Millimeter/sub-millimeter Array (ALMA) and it is expected to pave the way for ALMA to find many more such objects, which among other things, could help astronomers address important questions on the nature of dark matter.
The process of calculating the size and distance of remote objects using gravitational lensing has only recently been made possible due to technological advances. Even after scientists were able to secure the data, it took thousands of cutting edge computers to actually process it. Without this processing power, the scientists would not have been able to discern the dwarf galaxy, which now ranks among the farthest know objects from Earth.
The discovery was a breakthrough not just due to the distance of the galaxy, but because it marks one of only a few occasions where scientists have been able to pin down the dwarf galaxies. These galaxies are essentially drowned out by their larger neighbors, making them extremely difficult to find. In fact, only about 40 have been found so far.
While 4 billion light years is an immense distance, too far for most people to comprehend, on the cosmic scale, many objects are much further away. The farthest known galaxy, the galaxy MACS0647-JD, is about 13.3 billion light years away. Given that the galaxy is believed to be about 13.7 billion light years away, this means that light from the galaxy has been traveling towards us for nearly the entire history of time.