Abell2744 Y1, one of the oldest galaxies ever seen by humans, has recently been discovered by astronomers, using the Spitzer, Chandra and Hubble Space Telescopes. This galaxy is so distant that the light reaching Earth now from the island of stars left their source over 13 billion years ago.
Because of the finite speed of light, distant objects are seen as they were long ago. The image we see today from Abell2744 Y1 shows how the object looked when the Universe was only 650 million years old. Astronomers currently estimate the age of the Universe at around 13.8 billion years.
The nearly-discovered galaxy is 30 times smaller than our own Milky Way. Like many early galaxies, Abell2744 Y1 is seen producing stars at a rate 10 times faster than our own galaxy.
The Hubble Space Telescope records images in visible and near-infrared light, while the Spitzer space observatory extended vision further into the infrared portion of the electromagnetic spectrum. Additional data was collected by the Chandra observatory, which recorded the distant galaxy in X-ray wavelengths. By combining data from these three space telescope, astronomers are able to see galaxies up to 100 times more distant than any of the observatories could resolve on their own.
Frontier Fields, a program that combines images from multiple space telescopes, was utilized to merge the images. A total of six galaxy clusters will be photographed during the course of the program.
"Just a handful of galaxies at these great distances are known. The Frontier Fields program is already working to find more of these distant, faint galaxies. This is a preview of what's to come," Jason Surace, of NASA's Spitzer Science Center at the California Institute of Technology, said.
Observations of Abell2744 Y1 are aided by a phenomenon known as gravitational lensing. Images from distant galaxies are focused by galaxies closer to Earth, the same way a magnifying glass bends sunlight. This natural telescope to view the most distant objects in the Universe was first predicted by Albert Einstein, in the General Theory of Relativity.
Galaxies for the study are first detected using the Hubble telescope. Instruments aboard the Spitzer spacecraft are then used to determine the distance to the target, as well as measure how many stars are contained in the galaxy. The study is led by astronomers from the Instituto de Astrofísica de Canarias (IAC) and La Laguna University in Spain.
"[W]e expected to find very distant galaxies close to the cluster core... However, this galaxy is very close to the edge of the Hubble image. We are really lucky that we could find it in the small field of view of Hubble... [Other] galaxies are analyzed but none is more distant than Abell2744 Y1," Nicolas Laporte, IAC researcher, said.
Details of the research have been accepted for publication in the the journal Astronomy and Astrophysics Letters.
