“This groundbreaking discovery demonstrates, for the first time, that studying large numbers of individual stars in a distant galaxy is possible,” says astrophysicist Fengwu Sun from the University of Arizona.
Importantly, observing more individual stars will also help us better understand dark matter in the lensing plane of these galaxies and stars, which we couldn’t do with only the handful of individual stars observed previously.”
Gravitational lenses have been used previously to resolve individual stars in the distant Universe.
It was an exciting find because it was the first time we were able to see so many individual stars so far away.”
Further JWST observations are expected to reveal even more stars hiding in the blurry light of the Dragon Arc, billions of light-years away.
Across the gap of time and space that separates us from the early Universe, our view is limited. From sources so far away that it can be difficult to see something as bright as a galaxy glowing in the dark, light that travels across billions of light-years is produced.
More than 40 individual stars on the outskirts of a galaxy whose light has traveled through space-time for nearly 6.5 billion years have been resolved by human endeavor using JWST, breaking through those boundaries.
Astrophysicist Fengwu Sun of the University of Arizona says, “This revolutionary discovery shows, for the first time, that studying large numbers of individual stars in a distant galaxy is possible.”.
“Although earlier Hubble Space Telescope studies discovered about seven stars, we can now resolve stars that were previously unknown to us. More individual star observations will also help us better understand dark matter in these galaxies’ and stars’ lensing planes, something we couldn’t do with just the few individual stars that have been observed so far. “.”.
Because of a peculiarity of space-time that general relativity explains, we occasionally see outliers even though stars from far-off galaxies are typically too small to see individually.
Space-time itself warps and curves around sufficiently large masses with strong gravitational fields, much like a trampoline mat warps beneath a bowling ball. Gravitational lensing is the phenomenon that causes any light that passes through this twisted space-time to be distorted, duplicated, and magnified.
The head and tail of the Dragon Arc are distinct images of the same distant spiral galaxy, forming a smear of light across the sky that resembles a Chinese dragon.
Only 4 billion light-years away, a massive cluster of galaxies known as Abell 370 is the source of the illusion due to the gravitational warping of space around it. Scientists can reverse-engineer the gravitational lensing process to view the background galaxies as they would have appeared without the smearing, with the added benefit of magnification, even though the more distant light appears to us as a bit of a jumbled mess.
However, that is not all. In the Abell 370 cluster, several solitary stars float in the void between the galaxies. Microlensing is the ability of each star to produce an extra lensing effect of its own.
In the past, individual stars in the distant Universe have been resolved using gravitational lenses. A group led by astronomer Yoshinobu Fudamoto of Chiba University in Japan was able to resolve an unprecedented 44 individual stars in the smeared light of the Dragon Arc by using the microlensing of rogue intracluster stars.
Sun explains, “We were actually searching for a background galaxy that is lensing-magnified by the galaxies in this massive cluster when we discovered these individual stars.”.
Upon processing the data, however, we discovered what seemed to be numerous individual star points. Since it was the first time we had ever seen so many separate stars so far away, it was an exciting discovery. “.”.
Equipped with this knowledge, the team discovered that a large number of the stars in the Dragon Arc are red supergiants, which are enormous, red stars nearing the end of their lives that have puffed up as their fuel runs out. These stars are redder and cooler than the large, bright, hot blue and white giants that are usually resolved over great intergalactic distances.
The evolution of galaxies that are very distant from our own is somewhat clarified by this information. Red supergiant stars are typically harder to see than hot ones due to their lower temperature. The advantage of JWST in locating objects beyond the reach of other instruments is its ability to see red light.
It is anticipated that additional JWST observations will uncover additional stars concealed in the hazy light of the Dragon Arc, which is located billions of light-years away.
