How can young galaxies in the early Universe have ancient stars? That\u2019s the question a team of astronomers set out to answer using JWST as a probe. They first spotted the massive objects in 2022 and are still working to explain what these things are.<\/p>\n
<\/p>\n The infrared-sensitive recently JWST zeroed in on three of these objects. Interestingly, it found them emitting light from stars that appear to be mysteriously old. The galaxies themselves were seen as they appeared about 700 million years after the Big Bang. They look nothing like the spirals and ellipticals we see in the more \u201cmodern\u201d universe. <\/p>\n \u201cWe have confirmed that these appear to be packed with ancient stars \u2014 hundreds of millions of years old \u2014 in a universe that is only 600-800 million years old. Remarkably, these objects hold the record for the earliest signatures of old starlight,\u201d said Bingjie Wang, a postdoctoral scholar at Penn State University and lead author on a paper describing the find. \u201cIt was totally unexpected to find old stars in a very young Universe. The standard models of cosmology and galaxy formation have been incredibly successful, yet, these luminous objects do not quite fit comfortably into those theories.\u201d<\/p>\n In addition to ancient stars, the data from JWST also reveal the existence of unexpectedly large supermassive black holes in the galaxies. \u201cIt\u2019s very confusing,\u201d said Joel Leja, assistant professor of astronomy and astrophysics at Penn State. \u201cYou can make this uncomfortably fit in our current model of the Universe, but only if we evoke some exotic, insanely rapid formation at the beginning of time. This is, without a doubt, the most peculiar and interesting set of objects I\u2019ve seen in my career.\u201d<\/p>\n Since JWST can easily see back to extremely early epochs of cosmic time, these results reveal what the earliest objects were like. It doesn\u2019t yet explain how such old stars exist so soon after the birth of the Universe. If they truly are several hundred million years old, then they started forming extremely early in cosmic time. It\u2019s possible they were born much sooner than astronomers think. Their formation, for now, is hidden from our view. So, it\u2019s tough to know exactly when the process of star birth first began. <\/p>\n That\u2019s one challenge JWST\u2019s infrared abilities should help explain, particularly as astronomers use it to probe deeper into the earliest cosmic epochs. It shows objects emitting non-infrared light (UV) stretched by the expansion of the Universe into the infrared. This so-called \u201cancient\u201d light streams from numerous objects, including stars, galaxies, and the active hearts of galaxies. As Wang notes, it\u2019s not clear what bits of the emitted light comes from different objects. It could be coming from early galaxies appearing unexpectedly old and more massive than our Milky Way Galaxy. If so, then they formed much earlier than astronomers suspect. It\u2019s also possible that the light comes from more normal-mass galaxies with \u201covermassive\u201d black holes. Those supermassive monsters could be about a hundred to a thousand times more massive than such a galaxy would have in the \u201crecent\u201d Universe.<\/p>\n \u201cDistinguishing between light from material falling into a black hole and light emitted from stars in these tiny, distant objects is challenging,\u201d Wang said. \u201cThat inability to tell the difference in the current dataset leaves ample room for interpretation of these intriguing objects. Honestly, it\u2019s thrilling to have so much of this mystery left to figure out.\u201d<\/p>\n If the light the JWST detects does come from regions around supermassive black holes, then you have to think about why they\u2019re so bright so early in history. Since these are luminous in infrared, it means the original emissions were in UV light. And, the brightness means there\u2019s a lot of activity going on to emit the light. That implies much more mass in the central SMBH than expected. And, according to co-author Joel Leja, it\u2019s confusing because these objects don\u2019t seem to fit existing models of the early Universe.<\/p>\n \u201cNormally supermassive black holes are paired with galaxies,\u201d he said. \u201cThey grow up together and go through all their major life experiences together. But here, we have a fully formed adult black hole living inside of what should be a baby galaxy. That doesn\u2019t really make sense, because these things should grow together, or at least that\u2019s what we thought.\u201d<\/p>\n By baby galaxies, Leja explained, these systems are only a few hundred light-years across. By contrast, our Milky Way Galaxy is about 100,000 light-years across (give or take). However, those tiny galaxies contain about the same number of stars as the Milky Way\u2014between 10 billion and a trillion stars. \u201cThese early galaxies would be so dense with stars\u2014stars that must have formed in a way we\u2019ve never seen, under conditions we would never expect during a period in which we\u2019d never expect to see them,\u201d he said. \u201cAnd for whatever reason, the Universe stopped making objects like these after just a couple of billion years. They are unique to the early Universe.\u201d<\/p>\n Clearly, JWST will need to do some more looking to help explain these anomalous objects in the infant Universe. In particular, astronomers will want to know more about how ancient stars appeared so early in history. Future observations should provide a deeper, longer spectral look at all these objects. That will allow astronomers to differentiate the light from stars and the light from the regions around supermassive black holes. Each of these objects has its own specific light \u201cfingerprint\u201d that tells astronomers what it is. The answers they get will help them understand not only the evolution of early stars and their galaxies but also the continuing questions surrounding the origins and growth of supermassive black holes so early in cosmic time.<\/p>\n Tiny Bright Objects Discovered at Dawn of Universe Baffle ScientistsWhat Gives with Such Galaxies and Ancient Stars?<\/h3>\n
More on those Unexpectedly Big and Early Supermassive Black Holes <\/h3>\n
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Need More Data about Ancient Stars and Baby Galaxies<\/h3>\n
For More Information<\/h4>\n
RUBIES: Evolved Stellar Populations with Extended Formation Histories at z ~ 7\u20138 in Candidate Massive Galaxies Identified with JWST\/NIRSpec<\/p>\nLike this:<\/h3>\n