way back In the earliest ages of the universe, the first galaxies were born. Astronomers want to know more about them. They are particularly interested in knowing exactly when these distant galaxies formed and what their stars looked like. Now that JWST is a working observatory, astronomers look forward to using its data to study these early epochs. They are eager to see the most distant objects and – it seems likely – to rearrange the cosmic timeline after the Big Bang.
July 13, 2022 was a momentous day. It marked the first images released from the telescope; a set called Early Release Observations. Many are calling it the first day in a new era in astronomy. You’re not wrong, even if it sounds terrific. Since then, astronomers have dug into the images and data to learn more about the universe.
JWST will answer many of the questions astronomers have asked about the earliest epochs of the universe. In particular, they want to know more about the distant galaxies that exist “out there.” Thanks to its infrared sensitivity, the telescope will look beyond what the venerable and highly productive Hubble Space Telescope is revealing about the early Universe. And a group of astronomers in the US, Israel and China propose using JWST data to search for early galaxies. You want to look for objects that exist at redshifts beyond z~11. At that time, the newborn universe was about 420 million years old.
How the Webb telescope studies distant galaxies
Her instrument of choice aboard JWST is the near-infrared camera (NIRCam) and the images it produces of very distant objects. It should be able to extend our view to a time just ten million years after the Big Bang. This is when the first galaxies (if they existed) began to take shape. They would look like they did at the beginning of the epoch of reionization. This is a time after the cosmic dark ages when light was free to travel throughout the young universe.
Of course, NIRCam cannot perform this observation alone. It gets cosmic help. In particular, the telescope relied on gravitational lensing to capture images of the earliest possible galaxies. This target is the nearby galaxy cluster SMACS 0723-73 and is part of the ongoing Early Release Observations program at JWST. This cluster is massive. Thanks to the gravitational influence of its high mass, it is considered a good cosmic “magnifying glass”. It’s a gravitational lens that enhances the view of the distant galaxies that populate the distant universe. Fortunately, the NIRCam’s field of view is large enough to study both the cluster and a flanking field that has not been enhanced by gravitational lenses. It’s so sensitive that even the flanking field sees well beyond what HST could do.
The international team searched a field of candidate galaxies using ERO data from the SMACS
0723-73 sightings. They have identified 88 candidate galaxies at very large distances (redshift z>11). They hope some could be up to z~20. That could be less than 100 million years after the Big Bang. If these galaxies are confirmed to be in such early epochs of cosmic time, it would be amazing. It would mean that the timeline of the universe might have to be changed after the Big Bang. For one thing, it would mean that the beginning of the epoch of reionization would be much earlier than we had anticipated.
Astronomers currently believe it began about 370,000 years after the Big Bang. Before that, the universe was in a hot, dense state populated with a soup of ionized gas. Eventually it cooled enough for protons and neutrons to combine and form neutral atoms. And then the light from the earliest galaxies and their stars was finally free to move through the expanding universe.
However, if, as expected, the first galaxies are seen only a few tens of millions of years after the Big Bang, then the cosmic Middle Ages may not have lasted as long as everyone thought. NIRCam and spectroscopic observations of these early galaxies will eventually confirm their ages, which will help further refine the timeline of the early Universe.
This article was originally published on universe today by Carolyn Collins Petersen. Read the original article here.
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