Scientists using the Hubble Space Telescope have found a very distant single star or star system that exists around 900 million years after the Big Bang, which occurred 13.8 billion years ago.
The amazing discovery—described by NASA as “record-breaking”—was published today in Nature today.
At 12.9 billion light-years distant it’s the farthest individual star ever seen to date though a galaxy called GN-z11 was discovered in 2017 at 13.4 billion light-years away.
This ancient far-off star has been nicknamed “Earendel,” which comes from an Old English word meaning “morning star” or “rising light.” It’s catalogue name is WHL0137-LS.
Earendel is far more distant than previous observations of similar systems. In 2018 an enormous blue star nicknamed Icarus became the farthest individual star ever seen at nine billion light-years.
Earendel is estimated to have a mass greater than 50 times the mass of the Sun.
It was found using the Hubble Space Telescope as part of the Reionization Lensing Cluster Survey (RELICS) Program, which images massive galaxy clusters with the aim of finding the brightest distant galaxies for the James Webb Space Telescope (JWST) to study.
The research will tell us more about our cosmic origins, but how Earendel was found is incredible.
Led by Brian Welch at the Johns Hopkins University, Baltimore, the team used a galaxy cluster as a natural “magnifying glass,” something called “gravitational lensing.”
Gravitational lensing is the best way to discover incredibly far-off stars.
It describes the effect of the gravity of a foreground star or galaxy bending the light from a background star or galaxy. That occurs because mass bends space (as predicted by Einstein), so light from the background star takes a different path.
In Earendel’s case a distant star was magnified by a closer object in the foreground, a massive galaxy cluster called WHL0137–08 (also called WHL J24.3324-8.477 and nicknamed the ‘Sunrise Arc”), which Hubble has photographed before as part of the same RELICS Program:
Gravitational lensing revealed Earendel to be either an individual star or double star system.
Astronomers are excited because Earendel has a redshift of 6.2.
So is Earendel a red giant star? No—it’s just that when we detect very old light it is red because it’s been stretched over time as it travels through space. Red light has the longest wavelength.
Since the Universe is expanding, very distant stars and galaxies appear to move away from us at greater speeds than closer galaxies. Their light is therefore redder.
The redness of its light is how the researchers can estimate the distance of Earendel because the redder its light is, the earlier in the history of the Universe it must exist.
“We almost didn't believe it at first, it was so much farther than the previous most-distant, highest redshift star,” said Welch. “The galaxy hosting this star has been magnified and distorted by gravitational lensing into a long crescent that we named the Sunrise Arc.”
To put it in perspective, the previous record for spotting a star using gravitational lensing was at much smaller redshifts of around 1–1.5.
The researchers hope that they will soon be able to use the Webb telescope—a full-fledged and sensitive infrared telescope that is specifically created to find redshifted objects—to measure Earendel’s temperature, mass and spectral properties.
“With Webb we expect to confirm Earendel is indeed a star, as well as measure its brightness and temperature,” said co-author Dan Coe at the Space Telescope Science Institute (STScI) in Baltimore. “We also expect to find the Sunrise Arc galaxy is lacking in heavy elements that form in subsequent generations of stars. This would suggest Earendel is a rare, massive metal-poor star.”
It’s thought that the Webb telescope may even discover that magnified stars like Earendel are common.
Wishing you clear skies and wide eyes.
