We don’t fully understand what the first stars in the universe looked like. We know they must have formed from hydrogen and helium because most heavy elements form only after stars form. We know that the lack of these heavier elements has altered the dynamics of star formation, which means that the first stars must have been much larger. But how big it is remains an unanswered question.
Now, researchers report that one of these stars may be one step closer to direct observation. Thanks to the accidental alignment between a distant star and an interstellar galaxy, a gravitational reversal inflated 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 time-tracked observations by NASA’s latest space telescope.
gravitational lens
Lenses work by aligning objects so that light travels through them in a curved path. The force of gravity, which distorts space-time itself, performs a similar function, changing space and traveling in a curved path of light. There are many examples of how gravity can affect objects in the foreground to create a lens-like effect and amplify and/or distort light from distant objects behind.
This success prompted the formation of the group Reionization Lensing Cluster Surveying, or RELICS. The team points to space telescopes at large groups of galaxies, where strong gravitational fields are likely to produce lensing effects. As the light from the first stars begins to remove electrons from hydrogen in the interstellar medium, the team looks for pre-ionized objects.
Due to the random distribution of matter in the natural world, gravitational lenses are random and often produce playful effects and repeating images. With these effects, it is possible to create an approximate map of where the lens effects are strong, with information about the distribution of the object in the foreground.
This map may have a “critical lens curve” that can be selected because most background objects will be displayed as two images on either side of the curve. But some things will end up in a curve and experience strong magnification.
Single star
As you can see in the image above in this article, most objects in the critical curve of the lens appear to be stretched with it, indicating that they may be large structures such as galaxies or star clusters. The exception that the arrow points to is WHL0137-LS. Researchers named Earendel, the Old English word for morning star, because it appeared in the morning of the universe, about 900 million years after the Big Bang.
Various models of lens effects indicate that Earendel was magnified by at least 1,000 and 40,000 factors. Based on this, the size limits of the object with the lens can be adjusted. These limitations suggest that its maximum possible size is smaller than the clusters we previously observed, i.e. Earendel may be a small star system with three or fewer stars. It could also be 1 star.
Although the Earendel system is multi-star, most of these systems end up in one of the stars. The researchers, working on the assumption that most of what they saw was a single star, guessed its properties based on the light emitted first in the ultraviolet 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 not currently possible. But the researchers say they will use the Webb telescope to determine the exact type of star.
Based on the estimated time of Earendel and the presence of at least some heavy elements, we can say that it is not one of the first stars in the universe. But during the launch on the Internet, scientists indicated that the telescope will be able to capture previous star groups with sufficient lenses.
We’ll hear more about this imaging technology in the future.
natural2022. DOI: 10.1038/s41586-022-04449-y (about DOIs)