One of the design goals of the James Webb Space Telescope was to provide the ability to image the Universe at wavelengths that would reveal its first stars and galaxies. Now, just a few weeks after its first images surfaced, we’re getting a strong hint that it’s a success. In some data released by NASA, researchers have discovered five galaxies from the distant Universe that existed only a few hundred million years after the Big Bang. If confirmed to be as far away as it appears, one of them will be the most distant galaxy ever observed.
Opening
For many of its observatories, NASA allows astronomers to submit bids for observations and gives those users exclusive access to the data after a period of time. But for its newest instrument, NASA has a number of goals that will make the data immediately available to the public for anyone to analyze as they please. Some of these include similar locations is one of the first images releasedwhere the large foreground galaxy cluster acts as a lens to magnify more distant objects.
(You can see the details one of the datasets used for this analysisIt’s called GLASS, which uses the Abell 2744 cluster to magnify distant objects that are further magnified by a telescope.)
The images in this database were long exposures made in different parts of the infrared spectrum. The full range of wavelengths covered by the NIRCam instrument was divided into seven parts, and each part was imaged for anywhere from 1.5 to 6.6 hours. A large international team of researchers used these parts to perform an analysis that will help them identify distant galaxies by looking for objects present in some parts of the spectrum but missing in others.
The search was based on the notion that most of the Universe was filled with hydrogen atoms hundreds of millions of years after the formation of the Cosmic Microwave Background. These would absorb any light at or above wavelengths sufficient to ionize hydrogen, rendering the Universe opaque to those wavelengths. At that time, this cutoff was somewhere at the UV end of the spectrum. But in the intervening time, the expansion of the Universe has moved this cross section into the infrared part of the spectrum – one of the main reasons Webb is sensitive to these wavelengths.
At first you don’t see it (left), then you do. Contrast images show the appearance of the object in the region of space highlighted by the crosshairs, but at longer wavelengths.
So the team looked for objects that were present in images of the lowest-energy parts of the infrared spectrum imaged by Webb, but not in the higher-energy parts. And the exact point at which it disappears indicates how far redshifted the cutoff for that galaxy is, and thus how far away the galaxy is. (You can expect future research to take a similar approach.)
This method generated five different objects of interest, and the draft manuscript focused on the two most distant: GLASS-z13 and GLASS-z11. First, it is farther than the farthest confirmed distance of anything detected in the Hubble Deep Field; If confirmed, this would make it the most distant object we know of, and therefore the closest object in time to the Big Bang.
