Astronomers have spotted what may be the two most distant galaxies ever seen hidden in early-release images from NASA’s newest space telescope.
He James Webb Space TelescopeEarly scientific work includes a program called the Grism Lens-Amplified Survey from Space, or GLASS. Through GLASS, astronomers are examining the galaxy cluster Abell 2744, which is so massive that its gravity is able to distort the space around it and act as gravitational lens to zoom in on images of much more distant galaxies behind them.
Astronomers led by Rohan Naidu of the Harvard–Smithsonian Center for Astrophysics discovered the two candidates. galaxies, named GLASS-z11 and GLASS-z13, in the first batch of GLASS data. The galaxy designations come from the fact that astronomers have measured their “redshifts” to be 11 and 13, respectively.
Gallery: First photos from the James Webb Space Telescope
Red shift is a measure of how much a galaxy’s light has been stretched expansion of the universe; the higher the redshift, the further away (and further back in time) we see the source. The redshifts of 11 and 13 mean that we see these two galaxies as they existed more than 13.4 billion years ago, just 400 and 300 million years after the big bang respectively.
The findings are still inconclusive; Galaxies’ redshifts have only been measured based on the color of their light using Webb’s Near Infrared Camera (NIRCam). By confirming their redshifts, astronomers will analyze each galaxy’s spectrum, the “barcode” that measures how much light is present at each wavelength, and determine how much light emitted by specific atoms and molecules is has shifted to red.
by Webb Near infrared spectrograph (NIRSpec) is already scheduled to conduct these studies. If this work confirms the apparent redshifts, then the two galaxies will be a surprise to astronomers. The area of the sky studied by GLASS so far amounts to 50 arcminutes square (the full moon measures 31 arcminutes in diameter), and yet in this area it has already discovered two galaxies with a redshift d ’11 or higher.
This abundance would indicate that the luminous galaxies in the same early universe are more common than expected. The detection also implies, Naidu’s team wrote, that Webb will discover many more galaxies like these, and perhaps even more distant ones, in future observations.
GLASS-z13, candidate for the most distant known galaxy, as seen by the James Webb Space Telescope. (Image credit: Naidu et al. 2022. Image: Pascal Oesch (University of Geneva & Cosmic Dawn Center, Niels Bohr Institute, University of Copenhagen). Raw data: T. Treu (UCLA) and GLASS-JWST. NASA /CSA/ESA/STScI)
Locating these bright early galaxies is important because their rapid formation suggests they can be used to trace regions of galaxy formation in the early universe. And because galaxies form where matter is most concentrated, mapping these early galaxies will also tell us about the distribution of normal galaxies and dark matter only a few hundred million years after the Big Bang.
Another surprising discovery is that GLASS-z11 shows signs of being elongated, with a growing spiral disk. The most distant current confirmed galaxy, GN-z11, also appears to have a disc. Although most galaxies discovered at high redshift tend to appear lumpy, GLASS-z11 and GN-z11 show that it was possible for the galactic structure to develop quite rapidly.
GLASS-z11 and GLASS-z13 are modest galaxies compared to ours Milky Way Galaxy, which is about 100,000 light-years across and contains approximately 200 billion stars. GLASS-z11 and GLASS-z13 are, however, large for their time, with diameters between 3,000 and 4,500 light-years, and containing stars with a total mass equivalent to the order of a billion suns, many of ‘they very bright.
According to our theories of galaxy formation, in the time since the images we see of them, both GLASS-z11 and GLASS-z13 will have grown substantially through mergers with other galaxies, and may have turned into giants elliptical galaxies. Meanwhile, cosmic expansion has pushed GLASS-z11 and GLASS-z13 away from us, and today they are more than 32 billion light-years away, far beyond the reach of any telescope.
The findings are reported aa preprint published on arXiv.org on Tuesday (July 19); the research has also been submitted to the Astrophysical Journal Letters.
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