On March 30, 2022, Astronomers using the Hubble Space Telescope published a paper in Nature, announcing they had found a star they dubbed Earendel that was 12.9 billion light-years from Planet Earth. At 12.9 billion light years it would be not only the most distant star yet detected, but also the oldest.
Detection of the star was possible because it was at the focus of a Gravitational lens. Forbes magazine reported that the star was detected during the work of the Reionization Lensing Cluster Survey (RELICS) Program. RELICS job was to find distant galaxies worthy of further study by the new James Webb Space Telescope.
The official designation is WHL0137-LS, and it is at least 50 times the mass of Sol, our sun, and on the order of a million times as bright. The Guardian reports that it is a blue supergiant. The unofficial name, Earendel, is a word from the Old English language, meaning "first light", as this star shone within the first billion years of our Universe.
Earendel may be the first example of a Population III star. In spite of the name Population III stars would be the earliest stars, predating the Population II stars that populate old Globular clusters, and the most recent Population I stars, like Sol, our sun.
Ars Technica noting that the almost complete absence of elements heavier than Helium in the early Universe meant stars could be much more massive than stars today, reported the star might be 500 times the mass of Sol.
Brian Welch, the lead author of the study that announced the star, said "This finding gives us an opportunity to study a star in detail in the early universe". According to The Guardian Welch, is still working on his PhD.
Welch assembled a large team to analyze Earendel, and confirm that it was a star, or a pair of binary stars. That team studied the images for three and a half years, prior to publication. Magnification from gravitational lenses is lumpy, due to the lumpiness of the galaxies that form the lenses. This means some regions get much higher levels of magnification than nearby regions. Objects that are near the lens' critical curve, are particularly highly magnified. Earendel's closeness to the lens's critical curve meant the lens was magnifying it 1,000 to 40,000 times.
The star considered the most distant, prior to finding Earendel, was detected in 2018, and, at 9 billion lightyears, was over four times older.
- Charles Q. Choi. Hubble Space Telescope spots most distant single star ever seen: Meet Earendel, a star 12.9 billion light-years from Earth, Space.com, 2022-03-30. Retrieved on 2022-03-30.
- Jamie Carter. Meet ‘Earendel,’ Hubble’s Record-Breaking New Farthest Individual Star Ever Seen At 12.9 Billion Light-Years, Forbes magazine, 2022-03-30. Retrieved on 2022-03-30. “The amazing discovery—described by NASA as “record-breaking”—was published today in Nature today.”
- Hannah Devlin. Distant star found by Hubble telescope may be earliest we will ever see, The Guardian, 2022-03-30. Retrieved on 2022-03-30. “The observations have been hailed as hugely significant and been prioritised for the first cycle of observations using Nasa’s James Webb Space Telescope, due to begin in June.”
- Joel Achenbach. Hubble telescope detects most distant star ever seen, near cosmic dawn, Washington Post, 2022-03-30. Retrieved on 2022-03-30. “Earendel is part of an early, small galaxy whose light has been magnified and distorted in two curved strips as a result of such lensing. Astronomer Dan Coe of Johns Hopkins discovered and named the Sunrise Arc in 2016 as part of a Hubble observation program. Welch, Coe’s student, scrutinized a tiny speck — some kind of object — providentially located on the arc where the magnification was highest. Over the course of 3½ years, the object remained in that spot.”
- John Timmer. Hubble picks up the most distant star yet observed - Gravitational lensing has amplified the light of what may be a single star., Ars Technica, 2022-03-30. Retrieved on 2022-03-30. “Lenses work by arranging materials so that light travels on a curved path through them. Gravity, which distorts space-time itself, can perform a similar function, altering space so that light travels a curved path. There have been plenty of examples of the gravitational influences of objects in the foreground creating a lens-like effect, amplifying and/or distorting the light from a more distant object behind them.”
- Rafi Letzter. Meet Earendel, the most distant star ever detected: The star, imaged by the Hubble telescope, shone just 900 million years after the Big Bang, The Verge, 2022-03-30. Retrieved on 2022-03-30. “Earendel’s home galaxy, the Sunrise arc, takes its name from that gravitational lensing effect that made this discovery possible.”
- Welch, Brian, et al. (2022-03-30). "A highly magnified star at redshift 6.2". Nature 603: 815-818. DOI:10.1038/s41586-022-04449-y. Retrieved on 2022-03-30. Research Blogging.
- Andrea Gianopoulos. Record Broken: Hubble Spots Farthest Star Ever Seen, NASA, 2022-03-30. Retrieved on 2022-03-30.
- Michelle Starr. The Most Distant Single Star Was Just Detected, as Ancient as The Cosmic Dawn, ScienceAlert, 2022-03-30. Retrieved on 2022-03-30.