James Webb Telescope detects highly compact galaxy – 04/16/2023 – Science

The detection of a highly compact galaxy that formed relatively shortly after the Big Bang and exhibited an impressive rate of star formation is the latest example of how the James Webb Space Telescope is reshaping our understanding of the early universe.

Scientists said the galaxy, which dates back 13.3 billion years, has a diameter of about 100 light-years – about 1,000 times smaller than the Milky Way – but forms new stars at a rate very similar to our current one. galaxy, much bigger. A light year is the distance that light travels in one year, or 9.5 trillion kilometers.

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

The discovery is yet another example of how observations made by Webb, which launched in 2021 and began collecting data last year, are transforming our knowledge of the nature of the early universe. The orbital 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 does not predict that we would see so many galaxies at such early times in the universe’s life, so it’s really exciting,” said Hayley Williams, a doctoral student 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 piece together a more complete picture of how the first galaxies in our universe came to be,” added Williams. “We are seeing that the galaxies that existed in the beginning are very different from the ones 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 the infrared, while Hubble has looked at it primarily in optical and ultraviolet wavelengths. Webb has a much larger light-gathering area, allowing it to look at greater distances, therefore further back in time, than Hubble.

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

What’s being observed in the newly described galaxy, Kelly explained, could be a “globular cluster” — a tightly bound collection of tens of thousands to millions of stars — in the process of forming.

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

“However, we found that it was forming about two stars each 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, a much lower abundance of oxygen than is normally found in galaxies today — and for good reason. Oxygen and other elements heavier than hydrogen and helium are forged in thermonuclear furnaces inside stars and then blown out into space when stars explode at the end of their life cycles.

Since far fewer stars lived and died at that time in the universe, these heavier elements were scarcer.

The observation of this galaxy was aided by a phenomenon called “gravitational lensing,” which occurs when an immense amount of matter, such as a cluster of galaxies, creates a gravitational field that distorts and magnifies light traveling from distant galaxies located behind it, but in the same line of sight.

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