The James Webb Space Telescope has made new observations of Earendel, the most distant single star ever seen, and it seems like it has a cooler companion star.
The most distant individual star ever seen, called Earendel, may not be a single individual star after all. Instead, it seems to be a pair – one extraordinarily bright, hot star and another cooler one that we can’t see directly.
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| The most distant star ever seen is within the Sunrise Arc NASA, ESA, CSA, Dan Coe, Brian Welch, Zolt G. Levay |
The Hubble Space Telescope first spotted Earendel in 2022 using a phenomenon called gravitational lensing. A massive galaxy cluster lies just between Earth and Earendel, and its gravity warps and magnifies the light of the star, making it bright enough for us to spot even though it is located about 28 billion light years away.
Earendel’s extreme distance, along with the time its light took to travel to our telescopes, means that it was one of the earliest stars in the universe: it formed less than 1 billion years after the big bang. New observations with the James Webb Space Telescope (JWST) have begun to unveil some of the mysteries of this cosmic early bird.
Those observations have shown that Earendel is a massive star more than twice as hot as the sun and a million times brighter. Its colour is predominantly blue, which is typical of hot stars, but the spectrum of its light also has an unexpected peak right around the transition between the ultraviolet and visible wavelengths.
This particular peak usually occurs in relatively cool stars, which hints that we might be seeing the light from a pair of stars, one hot and one cool. “The data… cannot definitively rule out a single star model,” says Brian Welch at NASA’s Goddard Space Flight Center in Maryland. “But the two-star version is currently a better fit.”
The apparent presence of a second star wasn’t a huge surprise to the researchers. “Most massive stars that we know of have a companion, so we expected to see some evidence of that for Earendel,” says Welch. “But it is more common for one star to be much fainter than the other, so we expected to have to dig a bit more to find evidence of a companion.” The unexpected peak in the light made the companion star much more obvious than expected.
Researchers are now analysing the JWST data further in hopes of learning more details about Earendel and its home galaxy, which is nicknamed the Sunrise Arc because of how its light is warped by gravitational lensing. Such distant objects are some of our best windows into the very early universe.