James Webb keeps breaking records for most distant galaxies ever seen


Even though it hasn't been collecting data for very long, the James Webb Space Telescope keeps breaking its own records for peering deeper into space and time. The telescope has now detected a galaxy candidate that lies 35 billion light-years from Earth, which if confirmed would make it the most distant galaxy ever found. At least, for now.

To look into space is to look back in time. We see things as they appeared when the light first left them, and since the speed of light in the vacuum of space is constant, the farther away an object is the further back in time we’re effectively looking. A star 100 light-years away, for example, appears to us now as it was 100 years ago. Taking advantage of this, if we look at extremely distant objects we can get a glimpse into the early stages of the universe.

James Webb was designed to look farther back in space and time than any other telescope before it, so it’s no surprise that it may have detected the most distant galaxy ever observed. Known as CEERS-93316, the galaxy – if it is confirmed to be a galaxy – is about 35 billion light-years away. We’re seeing it as it was just 235 million years after the Big Bang, which is close to when the first galaxies were thought to have started forming, and only about 135 million years after the first stars were born.

CEERS-93316 is the most distant galaxy discovered so far, at around 35 billion light-years from Earth


But that raises an apparent paradox – if the universe is 13.8 billion years old, how can anything be farther away than that? The light shouldn’t have had enough time to reach us. But the key is that the universe has expanded greatly since the light first left the galaxy about 13.6 billion years ago, so that the “proper distance” to CEERS-93316 now is 35 billion light-years.

The expansion of the universe stretches light waves out, shifting them towards the red end of the spectrum, and astronomers measure this “redshift” through what are known as z values. Anything with a z value higher than 10 exists within the first few hundred million years of the universe, and so far the only confirmed galaxy in that range is GN-z11, which was measured by the Hubble and Keck I telescopes to have a z of around 11. CEERS-93316 however blows it out of the water, with a z of 16.7.

James Webb is particularly well suited to look for these distant galaxies. It’s packing a huge mirror that picks up more light, as well as infrared instruments that can see these faint red galaxies better than any other observatory so far.

Perhaps the best demonstration of its abilities is how quickly it keeps breaking its own records, even though observations only began a few months ago. CEERS-93316 is just the latest and current record holder, but two other studies released earlier in July revealed galaxies with redshifts of z = 12.3 and 13. Either of these alone would have been records in their own right, if they hadn’t been outdone so quickly.

That said, none of these candidates have been confirmed as galaxies yet, and their distances will need to be confirmed as well. However it all plays out, it’s unlikely that CEERS-93316 will hold onto the record for very long anyway – as James Webb continues to stare deeper into the cosmos with more and more observation time, it will uncover even fainter galaxies and objects that will help us understand the early stages of the universe.

The study hasn’t yet been peer-reviewed or published in a journal, but has been submitted to arXiv (PDF).

Source: University of Edinburgh


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