To peer through a telescope is to look back in time. The light reaching the lens has taken millions or even billions of years to travel through the vastness of space, which means every image is a snapshot of the distant past. And NASA's Hubble Space Telescope is a glorious time traveler, spotting galaxies over 13 billion years old that formed around when the universe began.
These distant galaxies often appear rather fuzzy. But now, thanks to a trick of gravity, the space telescope captured an exceptionally detailed image of galaxy that existed 13.3 billion years ago, just 500 million years after the Big Bang, reports Paul Rincon at the BBC.
The impressive detail in the new image of the galaxy is due to a process called gravitational lensing. A massive object, like a large galaxy, can bend space and cause the images of objects behind them to appear brighter and warp them into slightly larger shapes, according to a NASA press release. In this case, a massive galaxy cluster in the foreground of an image amplified the light from a very distant ancient galaxy and smeared it into a small arc.
“Pretty much every galaxy at that distance is an unresolved dot... it's kind of a matter of luck to get a galaxy that's lensed in just the right way to stretch it out and get that much detail—it's a pretty nice find,” Brett Salmon, lead author of the study and researcher at Baltimore’s Space Telescope Science Institute, tell Rincon. “By analyzing the effects of gravitational lensing on the image of this galaxy, we can determine its actual size and shape.” They recently presented their work at the 231st Meeting of the American Astronomical Society.
By combining data from Hubble and the Spitzer space telescope, Salmon and his colleagues attempted to “unsmear” the galaxy to learn more about it. A preliminary assessment suggests that it’s pretty small, weighing in at around 3 billion solar masses—about 1/100th the size of our Milky Way galaxy, according to NASA's press release. It is also around 2,500 light-years across—only half the size of the Small Magellanic Cloud, a dwarf galaxy that orbits the Milky Way. The galaxy is likely similar to many other small galaxies that formed soon after the Big Bang.
As Amber Jorgenson at Astronomy reports, the new galaxy is called SPT0615-JD. And finding it was no accident. The researchers were studying galaxies using Hubble and Spitzer as part of the RELICS program to find extremely distant galaxies using gravitational lensing. The team examined 41 massive galaxy clusters, and located the new galaxy while observing a cluster called SPT-CL J0615-5746.
One thing Salmon and other investigators are trying to figure out is how and when galaxies formed into the orderly shapes we see today. “We don't really know how the first galaxies in the universe assembled those nice rotating discs in those beautiful images we see," he tells Rincon. "So when did those discs actually start to form?”
This latest study, along with past work, is helping scientists tease out an answer. As Rincon reports, another study presented at the meeting focused on galaxies that formed just 800 million years after the Big Bang. It suggests that at this early date they were already rotating, which is what likely leads to disc formation. “Once the galaxy settles into a disc, that sets in motion the rest of the evolution of the galaxy. So finding out when that turbulent phase starts to settle down is a key initial condition,” Salmon says.
As Jorgenson reports, studying ancient galaxies is challenging to do with the aging Hubble telescope. But it might become easier when the James Webb Space Telescope launches in 2019. The Webb will include a more advanced spectroscope capable of peering even deeper into time. According to NASA, while Hubble is able to see “toddler galaxies” the Webb’s infrared will allow it to see “baby galaxies.”