Way back in the first ages of the universe the first galaxies were born. Astronomers want to know more about them. They are especially interested in knowing exactly when these distant galaxies formed and what their stars looked like. Now that JWST is a working observatory, astronomers are excited to use its data to explore those early epochs. They are eager to see more distant objects and, as seems likely, reset the cosmic timeline after the Big Bang.
July 13, 2022 was a momentous day. He marked the first images released from the telescope; a set called Early Departure Observations. Many call it the first day of a new era of astronomy. They are not wrong, even if it sounds great. Since then, astronomers have been digging into the images and data to learn more about the universe.
JWST will answer many questions astronomers have been asking about the earliest times 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 reveals about the early universe. And a group of astronomers from the US, Israel and China propose to use the JWST data to search for primitive galaxies. They want to observe objects that exist at redshifts beyond z~11. That was when the newborn universe was about 420 million years old.
How the Webb Telescope studies distant galaxies
His instrument of choice aboard JWST is the near-infrared camera (NIRCam) and the images of very distant objects it produces. It should be able to extend our view to a time just tens of millions of years after the Big Bang. It would be then that the first galaxies (if they existed) began to take shape. They would look like when the Reionization Epoch began. That is a period after the Cosmic Dark Ages when light could travel freely through the infant universe.
Of course, NIRCam cannot make this observation on its own. Get cosmic assistance. In particular, the telescope relied on gravitational lensing to capture images of the earliest possible galaxies. That target is the nearby galaxy cluster SMACS 0723-73, and is part of the ongoing Early Launch Observations program at JWST. This group is massive. Thanks to the gravitational influence of its great mass, it is recognized as a good cosmic “magnifying glass”. It is a gravitational lens that amplifies the view of distant galaxies that populate the distant Universe. Fortunately, NIRCam’s field of view is large enough to be able to study both the cluster and a lateral field not driven by gravitational lensing. It’s so sensitive that the flanking field also sees far beyond what HST could do.
The international team has searched for a field of candidate galaxies, using ERO data from SMACS.
0723-73 observations. They have identified 88 candidate galaxies at very large distances (redshift z>11). They expect that some can lie up to z~20. That could be a time less than 100 million years after the Big Bang. If these galaxies are confirmed to be found so early in cosmic time, that would be amazing. It would mean that the timeline of the Universe after the Big Bang might have to be changed. For one thing, it would mean that the start of the Epoch of Reionization would be much sooner than we expected.
Astronomers currently believe that it began about 370,000 years after the Big Bang. Before then, the Universe was in a hot, dense state, populated with a soup of ionized gas. Eventually, it got cool enough for the protons and neutrons to combine and form neutral atoms. And it was then that light from the first galaxies and their stars was finally able to move freely throughout the expanding Universe.
However, if, as expected, the first galaxies can be seen only a few tens of millions of years after the Big Bang, then perhaps the Cosmic Dark Ages did not last as long as everyone thought. NIRCam and spectroscopic observations of those early galaxies will ultimately confirm their ages, helping to 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.