Astronomers have used the combined power of the Hubble and Spitzer space telescopes to spot a rare distant galaxy whose light is coming all the way from 500 million years after the Big Bang, back when galaxies had just started forming.
The object is known as SPT0615-JD and is the furthest object seen through a gravitational lens. This phenomenon is caused by a massive object (in this case a galaxy cluster) warping space-time, which acts as a lens magnifying objects even billions of light-years behind it. Thanks to this, SPT0615-JD is stretched out giving researchers a lot more information than they usually get from these rare objects. The discovery has been submitted for publication and was presented at the American Astronomical Society meeting last week.
"No other candidate galaxy has been found at such a great distance that also gives you the spatial information that this arc image does," lead author Brett Salmon, of the Space Telescope Science Institute in Baltimore, said in a statement. "By analyzing the effects of gravitational lensing on the image of this galaxy, we can determine its actual size and shape.”
The team estimates that the galaxy is very small, about 3 billion solar masses, which is roughly 1 percent of the mass of the Milky Way. It is 2,500 light-years across, tiny compared to full-size galaxies, and forming only a modest number of stars. This object is a true protogalaxy.
The discovery was part of Hubble’s Reionization Lensing Cluster Survey (RELICS) and companion S-RELICS Spitzer program. The team has observed 41 massive galaxy clusters while looking for lensed galaxies, although they weren’t expecting something quite so distant. When the James Webb Space Telescope, Hubble and Spitzer's successor, launches next year we will be able to image these galaxies much better than we can now.
"This galaxy is an exciting target for science with the Webb telescope as it offers the unique opportunity for resolving stellar populations in the very early universe," Salmon added. The telescope should be able to even identify substructures within the newly identified object.
SPT0615-JD is not the furthest galaxy we have ever detected, but it is the first that looks like more than just a distant red dot. Soon we will have the tech to see how the very first galaxies formed.