Earendel, the farthest known star, is a massive B-type star more than twice as hot as our Sun, and about a million times more luminous, according to an analysis of data from Webb’s Near-Infrared Camera (NIRCam) instrument.
This Webb image shows Earendel, a massive B-type star more than twice as hot as our Sun, and about a million times more luminous. Image credit: NASA / ESA / CSA / D. Coe, STScI, AURA, ESA & Johns Hopkins University / B. Welch, NASA’s Goddard Space Flight Center & University of Maryland, College Park / Z. Levay.
Earendel, also known as WHL0137-LS, is a very massive star located in the constellation of Cetus.
The star is so far away that its light has taken 12.9 billion years to reach Earth, appearing to us as it did when the Universe was only 7% of its current age.
Earendel was first identified in 2022 in Hubble images taken as part of the Reionization Lensing Cluster Survey (RELICS) program.
The star was nicknamed after the Old English word for ‘morning star’ or ‘rising light.’
Earendel’s parent galaxy, WHL0137-zD1, was nicknamed ‘Sunrise Arc,’ because gravitational lensing distorted its light into a crescent.
Both Hubble and Webb were able to detect Earendel due to its lucky alignment behind a wrinkle in space-time created by the massive galaxy cluster WHL0137-08.
While other features in the galaxy appear multiple times due to the gravitational lensing, Earendel only appears as a single point of light even in Webb’s high-resolution infrared imaging.
Based on this, astronomers determined that Earendel is magnified by a factor of at least 4,000, and thus is extremely small — the most distant star ever detected, observed 1 billion years after the Big Bang.
Icarus, the previous record-holder for the most distant star, was detected by Hubble and observed around 4 billion years after the Big Bang.
Another team using Webb recently identified a gravitationally lensed star they nicknamed Quyllur, a red giant star observed 3 billion years after the Big Bang.
Stars as massive as Earendel often have companions. Astronomers did not expect Webb to reveal any companions of Earendel since they would be so close together and indistinguishable on the sky.
However, based solely on the colors of Earendel, astronomers think they see hints of a cooler, redder companion star.
This light has been stretched by the expansion of the Universe to wavelengths longer than Hubble’s instruments can detect, and so was only detectable with Webb.
NIRCam also shows other notable details in the Sunrise Arc, which is the most highly magnified galaxy yet detected in the Universe’s first billion years.
Features include both young star-forming regions and older established star clusters as small as 10 light-years across.
On either side of the wrinkle of maximum magnification, which runs right through Earendel, these features are mirrored by the distortion of the gravitational lens.
The region forming stars appears elongated, and is estimated to be less than 5 million years old.
Smaller dots on either side of Earendel are two images of one older, more established star cluster, estimated to be at least 10 million years old.
“We determined this star cluster is gravitationally bound and likely to persist until the present day,” Webb astronomers said.
“This shows us how the globular clusters in our own Milky Way might have looked when they formed 13 billion years ago.”
