We do not fully understand what the first stars of the Universe looked like. We know that they must have formed from hydrogen and helium, as most heavier elements were produced only after star formation. And we know that the lack of these heavier elements changed the dynamics of star formation in a way that meant that the first stars must have been very large. But how big remains an unanswered question. Now, researchers announce that it may be one step closer to the immediate observation of one of these stars. Thanks to a random alignment between a distant star and an intermediate cluster of galaxies, the gravitational lens has magnified an object that was present less than a billion years after the Big Bang. The object is likely to be either a solitary star or a solid two- or three-star system. And his discoveries say he has already made time for subsequent observations with NASA’s latest space telescope.
Gravity lens
The lenses work by positioning the materials so that light travels in a curved path through them. Gravity, which distorts space-time itself, can perform a similar function, changing space so that light travels a curved path. There have been many examples of the gravitational effects of objects in the foreground creating a lens-like effect, amplifying and / or distorting light from a more distant object behind them. This success led to the formation of a group called the Reionization Lensing Cluster Survey, or RELICS. The team is directing space telescopes into large clusters of galaxies with the expectation that strong gravitational fields there are more likely to produce lens effects. The team is looking for objects dating back to the re-ionization period, when light from the first stars began removing electrons from hydrogen into interstellar material. Due to the uneven distribution of matter in the physical world, gravitational lenses are uneven and often create fun effects and double images. Using these effects, along with information on the distribution of matter in the foreground, it is possible to create a rough map of where the lens effects are strongest. This map may include a “critical lens curve”, which can be recognized because most background objects appear as two images, with one on each side of the curve. But a handful of objects will end up on the curve itself and experience the strongest magnification. Advertising
Lonely star
As you can see in the image at the top of this article, most of the objects in the lens’ critical curve appear to extend along it, indicating that they may be larger structures, such as galaxies or star clusters. The exception, indicated by the arrow, is WHL0137-LS. Researchers named it Earendel, the old English term for the morning star, because it appears to date from the morning of the Universe, about 900 million years after the Big Bang. Various models of lens effects suggest that Earendel is magnified by at least a factor of 1,000 – and possibly up to 40,000. Based on this, it is possible to set limits on the size of the object being lensed. These limits indicate that its maximum possible size is smaller than the star clusters we have previously identified, which means that Earendel is likely to be a small stellar system with three or fewer stars. It could also be a star. Even though Earendel is a multi-star system, most of the mass of these systems tends to end up in one of the stars. Working on the assumption that most of what they were looking at was a single star, the researchers concluded its properties based on the light that was originally emitted in the UV region. They found that Earendel could have a mass of 40 to 500 times the mass of the Sun. It also has only about 10 percent of the heaviest elements found in the Sun. More precise details are not possible at this time. But researchers suggest they will use the Webb telescope to determine exactly what kind of star it is. Based on both the estimated time of existence of Arendel and the presence of at least some heavier elements, we can say that it is not one of the first stars of the Universe. But during Webb’s launch, scientists indicated that the telescope would be able to image older star populations if they also had adequate lenses. We will hear more about this imaging technique in the near future. Nature, 2022. DOI: 10.1038 / s41586-022-04449-y (About DOIs).
