Compact galaxy's discovery shows Webb telescope's 'amazing' power
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[April 15, 2023]
By Will Dunham
WASHINGTON (Reuters) - The detection of a highly 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 is reshaping our understanding of the early universe.
Scientists said the galaxy, dating to 13.3 billion years ago, has a
diameter of approximately 100 light-years - about 1,000 times smaller
than the Milky Way - but forms new stars at a rate very similar to that
of our much-larger present-day galaxy. A light-year is the distance
light travels in a year, 5.9 trillion miles (9.5 trillion km).
It existed about 510 million years after the Big Bang event marking the
universe's origin. The universe at the time was less than 4% of its
current age.
The discovery is another example of how observations by Webb, which was
launched in 2021 and began collecting data last year, are transforming
our knowledge of the nature of the early universe. The orbiting infrared
observatory was designed to be far more sensitive than its Hubble Space
Telescope predecessor.
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"Our current understanding of galaxy formation in the early universe
doesn't predict that we would see this many galaxies at such early times
in the universe's life, so this is really exciting," said Hayley
Williams, a University of Minnesota doctoral student in astrophysics and
lead author of the study published this week in the journal Science.
"As we observe more and more of these distant galaxies, we'll be able to
put together a more complete picture of how the first galaxies in our
universe came to be," Williams added. "We are seeing that the galaxies
that existed in the early universe are very different from the galaxies
that exist today and that our usual assumptions about galaxy properties
may not apply in the early universe."
Webb looks at the universe mainly in the infrared, while Hubble has
examined it primarily at optical and ultraviolet wavelengths. Webb
possesses a much bigger light-collecting area, letting it look at
greater distances, thus farther back into time, than Hubble.
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Using first-of-their-kind observations
from the James Webb Space Telescope, researchers detected a unique
galaxy highly compact but with star formation still at a rate
similar to our much-larger Milky Way existing about 13.3 billion
years ago that could help astronomers learn more about galaxies that
were present relatively shortly after the Big Bang. ESA/Webb, NASA &
CSA, P. Kelly/Handout via REUTERS
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"JWST's (James Webb Space Telescope's) reach into the first billion
years of the universe has been amazing, and has given astronomers a
lot to consider and try to understand about when and how many
galaxies formed," University of Minnesota astronomy professor and
study co-author Patrick Kelly said.
What is being observed in the newly described galaxy, Kelly said,
might 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.
"Nonetheless, we found that it was forming about two stars each
year, which is similar to the rate at which the Milky Way is forming
stars," Kelly added.
The researchers examined this galaxy's chemical composition,
finding, for example, an oxygen abundance much lower than typically
found in present-day galaxies - and for good reason. Oxygen and
other elements heavier than hydrogen and helium are forged in the
thermonuclear furnaces at the interior of stars and then blown into
space when stars explode at the end of their life cycles.
Because so many fewer stars had lived and died at that time in the
universe, such heavier elements were more scarce.
Observing this galaxy was aided by a phenomenon called
"gravitational lensing" that occurs when an immense amount of
matter, like a grouping 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
galaxy's magnification due to gravitational lensing allows us to
study this galaxy in detail," Williams said.
(Reporting by Will Dunham, Editing by Rosalba O'Brien)
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