The European Space Telescope Euclid is supposed to explore the “dark side” of the cosmos – dark matter and dark energy. But in the recordings of his test phase, astronomers have discovered a rare and spectacular light phenomenon: a light Einstein ring. This ring -shaped light wreath arises when the light of a distant object is distorted and distracted by the gravity of a foreground object. In this case, a “only” 590 million light year -old galaxy creates an exceptionally strong and clear gravitational lens effect. Their removal and the clear expression of the Einsteinring, which are low after cosmic standards, make this discovery a rare find, as the astronomers report. It could help measurement of the invisible dark matter and its gravity effect.
According to Albert Einstein’s general theory of relativity, the gravity also affects radiation: Mass oak objects in space bend space -time and also steer light from the straight track. If a massive object passes like a galaxy directly in front of another, much further away, a special optical phenomenon can occur: the foreground galaxy acts like an magnifying glass and reinforces and distorts the light of the background object. If both objects are aligned in a certain way, the unlocked light forms a bright ring. According to Albert Einstein, this effect is referred to as Einsteinring. “Both Einstein rings and point-shaped lens effects have an enormous scientific value,” explain Conor O’riordan from the Max Planck Institute for Astrophysics in Garching and his colleagues. “Strong gravitational lenses can be used as ‘cosmic telescopes’ to check the general theory of relativity and to research the properties of dark matter.” Einstein rings generated relatively close to galaxies are particularly suitable for this, but they are rare: “So far, only five such systems have been known,” report the astronomers.
Heller light ring around near galaxy
Now the team around O’riordan has discovered a sixth, particularly well -distinguished case of such a close galaxy as the author of an Einstein ring – according to cosmic standards. She tracked down the space telescope Euclid of the European Space Agency ESA on July 1, 2023. This should map the distribution of matter and the expansion of the universe in the course of its six -year mission. But before the telescopic space probing started her sky through the sky, it first went through a test phase in autumn 2023 in which the instruments were calibrated and tested. During this time, Euclid initially broadcast some of them, in which Bruno Altieri from the ESA evaluation team believed to recognize references to an Einstein ring. “Already with this first observation it looked for me,” reports Altieri. After the telescope had delivered further, sharper recordings of the object in question, this was confirmed: “We could then see a perfect Einstein ring,” says the astronomer.
The newly discovered Einstein ring is generated by the Galaxy NGC 6505, which has been known since 1995, which is around 590 million light years away from us – according to cosmic standards, this is a “stone’s throw”. “But the Einsteinring caused by this galaxy was unknown until observation by the Euclid telescope,” explain the astronomers. “This is the first strong gravitational lens that Euclid discovered and the first created by NGC galaxy.” However, the real peculiarity of this discovery lies in the extraordinary clarity and clear expression of the Einsteinring. The foreground galaxy distorts the light of a background galaxy of around 4.42 billion light years away to a very bright, almost perfect ring. “The Euclid recording represents one of the best signal-to-noise relationships that have so far existed from a strong gravitational lens in the optical and near-infrared area,” observe O’riordan and his colleagues. “According to simulations, the discovery of this object was extremely unlikely: such a large galaxy with such a low red shift has a chance of only 1: 2000, such a bright source,” explain the astronomers.
Only the beginning of the Euclid discoveries
However, the newly discovered Einstein ring is also important because it allows the team to calculate the mass and the proportion of dark matter in the foreground galaxy more precisely. Because with relatively nearby galaxies as gravitational lenses, this ring forms around the densest, inner part of the star disc. “This type of object is incredibly useful to examine the substructures of dark matter in the lens galaxy,” says O’riordan. According to initial calculations, the dark matter has a share of around 11.1 percent in the total mass of the galaxy area enclosed by the Einstein ring. However, the evaluations of this data have only started. According to the team estimates, the Euclid probe could discover thousands of other strong gravitational lenses in the course of its mission. “Euclid will revolutionize the field with all of these data that we have never seen before,” says O’riordan. Such astonishing discovery at such an early stage of his mission means that Euclid is on the way to ventilate many more secrets. The astronomers “Altieri’s Linse” have baptized the first Einsteinring now described – in honor of their discoverer Bruno Altieri.
Source: Conor O’riordan (Max Planck Institute for Astrophysics, Garching) et al., Astronomy & Astrophysics, DOI: 10.1051/0004-6361/202453014