The discovery of a compact galaxy shows the “incredible” power of the Webb telescope

By Will Dunham

WASHINGTON (Reuters) – The detection of a very compact galaxy that formed relatively soon after the Big Bang and displayed an impressive rate of star formation is the latest example of how the James Webb Space Telescope reshapes our understanding of the early universe.

Scientists said the galaxy, dating to 13.3 billion years ago, is about 100 light-years across – around 1,000 times smaller than the Milky Way – but is forming new stars at a pace very similar to that of our much larger galaxy today. A light year is the distance light travels in one year, 5.9 trillion miles (9.5 trillion km).

It existed approximately 510 million years after the Big Bang event marking the origin of the universe. The universe at the time was less than 4% of its current age.

The discovery is another example of how Webb Observations, which launched in 2021 and began collecting data last year, is transforming our knowledge of the nature of the early universe. The orbiting infrared observatory was designed to be much more sensitive than its predecessor, the Hubble Space Telescope.

“Our current understanding of galaxy formation in the early universe doesn’t predict that we would see so many galaxies at such early times in the life of the universe, so that’s really exciting,” said PhD student Hayley Williams. in astrophysics at the University of Minnesota. and lead author of the study published this week in the journal Science.

“As we observe more and more of these distant galaxies, we will be able to paint a more complete picture of how the earliest galaxies in our universe came to be,” Williams added. “We find that the galaxies that existed in the early universe are very different from the galaxies that exist today and that our usual assumptions about the properties of galaxies may not apply in the early universe.”

Webb looks at the universe primarily in infrared, while Hubble has examined it primarily at optical and ultraviolet wavelengths. Webb has a much larger light-gathering area, allowing it to look at greater distances, and therefore further back in time, than Hubble.

“The range of JWST (James Webb Space Telescope) in the first billion years of the universe has been incredible, and has given astronomers a lot to consider and try to figure out when and how many galaxies formed” , said University of Minnesota astronomy professor and study co-author Patrick Kelly said.

What’s seen in the newly described galaxy, Kelly said, could be a “globular cluster” — a tightly-knit collection of tens of thousands to millions of stars — forming.

This galaxy, Kelly said, is “absolutely tiny” in relative terms.

“Nevertheless, we found that it forms about two stars every year, which is similar to the rate at which the Milky Way forms stars,” Kelly added.

The researchers examined the chemical composition of this galaxy, finding, for example, an abundance of oxygen much lower than that typically found in galaxies today – and for good reason. Oxygen and other elements heavier than hydrogen and helium are forged in the thermonuclear furnaces inside stars, then blasted out into space when the stars explode at the end of their life cycle.

Because far fewer stars had lived and died at that time in the universe, these heavier elements were rarer.

Observing this galaxy has been aided by a phenomenon called “gravitational lensing” which occurs when an immense amount of matter, such as a group of galaxies, creates a gravitational field that distorts and amplifies light coming from distant galaxies behind her but in the same line of sight.

“The combined power of the James Webb Space Telescope and the magnification of the galaxy due to the gravitational lens allow us to study this galaxy in great detail,” Williams said.

(Reporting by Will Dunham, editing by Rosalba O’Brien)

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