New space telescope, new questions about cosmic history
On July 12, 2022, the world caught its first glimpses through humanity’s new set of infrared eyes, the James Webb Space Telescope (JWST). That day, NASA released images of previously unseen celestial wonders: baby stars born inside interstellar gas clouds; the death throes of a star in its final hurrah; and the deepest image of the universe ever taken showing a crowded neighborhood of galaxies so massive that light coming from the even more distant universe is distorted and magnified by the warped fabric of space-time itself.
While these pictures captivated the imaginations of young and old alike, the astronomers who’ve waited much of their careers on the precious data now streaming from JWST are scratching their heads at what they see. In fact, their findings are causing us to rethink things from the beginning — I mean the very beginning — when the universe we call home was a mere infant.
JWST is NASA’s latest flagship mission, joining the ranks of luminaries like the Hubble Space Telescope, which launched in 1990 and is still delivering groundbreaking discoveries to this day (this columnist just received some fresh Hubbledata last week). But while JWST may be almost seven times bigger than Hubble, it is not just size that matters when studying the history of the universe.
Because light does not instantly move from one place to another but takes some time to travel, the light we observe coming from stars and galaxies over astronomical distances had to leave those objects sometime in the past. The further we look, the longer ago that light left. Also, things that are far away are not as bright; imagine staring at the headlights of a car when it is five feet in front of you versus a quarter-mile away. So, to study the first stars and galaxies as they formed more than 13 billion years ago, we must look very far away. Here is where the huge size of JWST comes in handy.
But there is another wrinkle. The space itself over which light from the distant universe must travel is expanding, stretching out the light waves and turning the bright blue light of baby stars within baby galaxies in the baby universe into infrared light that human eyes cannot see. JWST is specially tuned to pick up this infrared light, while Hubble is more sensitive to bluer colors. So JWST literally sees different light than Hubble, critical for studying conditions while the universe was in its infancy.
Astronomers expected to see hundreds of baby galaxies in the very first pictures when JWST opened its infrared eyes, but they did not expect to see such big babies! Over the years, Hubble had shattered its own records again and again for seeing further and further into the past, taking censuses of galaxies much like those we take of the population every few years. The numbers and sizes of galaxies we’d counted seemed consistent with cosmology, our theory of how galaxies formed and the universe evolved.
After what JWST has seen, we are not so sure. The cosmological theory is astonishing, as it predicts a storyline from the Big Bang to the modern day with major characters such as dark matter and dark energy. Dark matter holds galaxies and groups of galaxies together while dark energy pulls space apart. How much of a starring role each of these characters plays over the course of history determines how many and how massive galaxies can form. With existing data, we have studied the contributions of dark matter and dark energy, and the story they tell seems to inconveniently leave out JWST’s big babies.
These newly discovered galaxies with the mass of 100 billion suns only 400 million years after the Big Bang (the universe is 13.7 billion years old) are so massive and there are so many of them that our current accepted cosmology says that there shouldn’t have been enough material around to form them. This has left theorists considering alternative cosmologies, including one where dark energy played an outsized role in the early universe. On the flip side, it also has observational astronomers scrutinizing the data and measurement techniques used to calculate the galaxy masses.
It is an extremely vibrant time in the scientific community as we welcome challenges to our understanding of the cosmos, which has held up quite well until now. It could very well be that issues exist with the data analysis we don’t yet understand — we just opened these infrared eyes after all — and the galaxies are not as big as they might seem. Either way, the data continue to roll in and more and more baby galaxies are discovered every day. Any rethinking of our cosmology will also have to stand up to the observational facts we learn and we must constantly ask ourselves if we are really seeing what we think we are seeing. But this is the fun part. It’s what science is all about.
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Joseph Burchett is an assistant professor of astronomy at NMSU. He can be reached at jnb@nmsu.edu.
This article originally appeared on Las Cruces Sun-News: Star News: New space telescope, new questions about cosmic history
