Nicknamed Quyllur, the newly-detected red supergiant candidate is so far away that its light has taken 10.7 billion years to reach Earth.
This Webb image shows the highly-magnified red supergiant candidate Quyllur (white, central circle). Image credit: NASA / ESA / CSA / Webb / Diego et al., arXiv: 2210.06514.
Red supergiants are the evolved descendants of massive stars with initial masses between 7 and 40 times the mass of the Sun.
These stars have the largest radius of all known stars, although they are not the most massive or luminous.
They have spectral types K or M and surface temperatures below 4,100 K — this is very cool for a star and makes them to shine with a red color.
Their brightness makes them easily detectable in the near infrared, making them useful probes of ancient star formation.
Betelgeuse and Antares are the brightest and best known red supergiants in our Milky Way Galaxy.
So far, all previous stars discovered at high redshifts have been hot and blue stars.
If Quyllur is confirmed to be a red supergiant, it would be the first example of many to come.
“Among the greatest achievements by the NASA/ESA Hubble Space Telescope in the last few years was its discovery of extremely magnified stars at high redshift. Such objects were first predicted in 1991,” said Instituto de Física de Cantabria astronomers Jose Diego and his colleagues.
“The discovery of Icarus, a blue supergiant star at a redshift of z=1.49, marks the starting point of this new field, which allows study not only of individual stars at z>1, but also compact star clusters. The discovery also opens the door to novel studies of dark matter structures.”
“After the discovery of Icarus, other examples followed, culminating with the recent discovery of Earendel at z=6.2 (Earendel emitted its light approximately 900 million years after the Big Bang).”
“The NASA/ESA/CSA James Webb Space Telescope is expected to see further than Hubble and possibly detect individual stars close to the beginning of cosmic reionization.”
The astronomers noticed a highly-magnified red object while studying Webb’s images of the massive galaxy cluster ACT-CL J0102-4915, also known as El Gordo.
“The most likely explanation for the source is a single, highly magnified, red supergiant star,” they said.
“We nickname it ‘Quyllur,’ which is the Quechua term for star.”
Quyllur was magnified by a factor of at least 4,000 by both El Gordo’s gravity and an additional microlensing event.
The star has a surface temperature of 3,500 K and existed when the Universe was about 3.1 billion years old.
“Very luminous stars are rarely found isolated and normally live near stellar groups,” the researchers said.
“A nearby, multiply-lensed pair is estimated to be at a distance of 33-49 light-years from Quyllur, depending on the magnification.”
“This bluer source could be a star-forming region, and Quyllur would be in its outskirts.”
“Quyllur would be the first red supergiant found at cosmological distances,” the authors concluded.
The team’s paper was posted on the arXiv.org preprint server in October 2022.
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Jose M. Diego et al. 2022. JWST’s PEARLS: a new lens model for ACT-CL J0102-4915, EL Gordo, and the first red supergiant star at cosmological distances discovered by JWST. arXiv: 2210.06514
