We do not fully understand what the first stars of the universe were like. We know that they must have formed from hydrogen and helium because most heavy elements are formed only after stars have formed. We know that the lack of those heavier elements changed the dynamics of star formation, meaning that the first stars must have been much larger. But how big it is remains an unanswered question.
Now, researchers report that one of those stars may be one step closer to direct observation. Thanks to an accidental alignment between a distant star and an interstellar galaxy, gravity lensing magnified an object that existed within a billion years after the Big Bang. The object can be a single star or a small system of two or three stars. Its discoverers say it has already recorded time for tracking observations by NASA’s latest space telescope.
The lenses work by aligning objects so that light travels through them in a curved path. Gravitational force, which distorts space-time itself, performs a similar function, changing space and traveling in a curved path of light. There are numerous examples of how the gravitational influences of objects on the front create a lens-like effect and amplify and / or distort light from distant objects behind them.
This success prompted the formation of the group Reionization Lensing Cluster Survey, or RELICS. The team points to space telescopes in large clusters of galaxies, where strong gravitational fields are more likely to produce lensing effects. When light from the first stars begins to remove electrons from the hydrogen in the interstellar medium, the team searches for pre-ionizing objects.
Due to the random distribution of matter in the natural world, gravity lenses are random and often produce funhouse effects and duplicate images. Using these effects, it is possible to create an approximate map of where the lensing effects are strong, with information about the distribution of the object on the front.
This map may have a “lensing critical curve” that can be identified because most background objects are displayed as two images on either side of the curve. But a few objects will end in a curve and experience strong magnification.
As you can see in the image above in this article, most objects in the lens critical curve appear to extend along with it, indicating that they may be large structures such as galaxies or star clusters. The exception indicated by the arrow is WHL0137-LS. Researchers have named Earendel, the Old English word for the morning star, because it appeared from the morning of the universe, about 900 million years after the Big Bang.
Various models of lensing effects suggest that Earendel magnified by at least 1,000- and 40,000 factors. Based on that, the size limits of the lensed object can be set. These limitations indicate that its maximum possible size is smaller than the clusters we have previously observed, i.e. Earendel may be a small star system with three or fewer stars. It could also be a single star.
Although Earendel is a multi-star system, most of these systems end up in one of the stars. The researchers, who worked under the assumption that most of what they saw was a single star, guessed its properties based on the light first emitted in the UV range. They found that the mass of the iridescent sun was 40 to 500 times greater. It contains only 10 percent of the heaviest elements found in the sun.
More precise details are currently not possible. But researchers say they will use the Webb telescope to pinpoint exactly what kind of star it is.
Based on Earendel’s estimated time and the existence of at least some heavy elements, we can say that it is not one of the first stars in the universe. But during the web launch, the scientists pointed out that the telescope would be capable of capturing previous stellar populations with sufficient lenses.
We will hear more about this imaging technique in the future.