Astronomers List 88 Distant Galaxies They Want to Look at With JWST. Some Are Less Than 200 Million Years Old. - by spacewriter
Their instrument of choice onboard JWST is the Near-infrared Camera and the images of very distant objects that it produces. It should be able to extend our view out to a time only tens of millions of years after the Big Bang. That would be when the first galaxies started to take shape. They’d look as they did when the Epoch of Reionization began. That’s a period after the Cosmic Dark Ages when light could travel freely through the infant Universe.
Of course, NIRCam can’t do this observing all by itself. It gets 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 it’s part of the ongoing Early Release Observations program on JWST. This cluster is massive. Thanks to the gravitational influence of its high mass, it’s recognized as a good cosmic “magnifying glass”.
0723-73 observations. They’ve identified 88 candidate galaxies at very great distances . They are hoping that some could lie as far as z~20. That could be a time less than 100 million years after the Big Bang. If these galaxies are confirmed to lie at such early epochs of cosmic time, that would be amazing. It would mean that the timeline of the Universe after the Big Bang may have to be changed.
Currently, astronomers think 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, that’s when light from the earliest galaxies and their stars was finally able to move freely across 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 didn’t last as long as everyone thought. NIRCam and spectroscopic observations of those early galaxies will eventually confirm their ages, which will help further refine the timeline of the early Universe.
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