This red supergiant has been watched with interest for the last 10 years. At first it became brighter, then it began to fade and now it is not visible at all. Moreover, a supernova explosion, which is expected in such cases, did not occur.

When astronomers began to compare sky images from different years, they discovered an interesting phenomenon: some missing stars had disappeared. In fact, a large-scale study was recently conducted on this subject, and many images were analyzed by a neural network.

As a result, the absolute majority of the 150,000 differences in the images were deemed to be erroneous detections: dust particles, scratches accidentally hitting the optics, etc. But apparently there are about a hundred cases left where a real star actually disappeared.

Experts have proposed different versions of the nature of this phenomenon. For example, the effect of gravitational lensing: A very powerful object, such as a black hole, acts as a “lens” and distorts the light of the object behind it, as a result of which something forms next to it for a while and then disappears.

Recently, scientists found another mysterious example like this, but this time they understood what they were dealing with. Since 2014, they have observed the star M31-2014-DS1 in the Andromeda galaxy, where they recognized a red supergiant – a very massive and old star that is about to “die”. As a reminder, the Andromeda galaxy (M31) is the Milky Way’s closest large neighbor and is located approximately 2.5 million light-years away.

Any star begins to explode at the end of the main cycle of its “life”, that is, when its core runs out of hydrogen for thermonuclear reactions. The core is compressed, causing it to flare and the surrounding mantle to overheat. The outer shell of the star expands to incredible sizes: the luminary becomes hundreds of times larger than the Sun. This shell then leaves the star forever. The mantle of solar-type dwarf stars slowly descends from them, but is ejected from massive stars in a spectacular flash called a “supernova explosion.”

The ejected matter remains as a picturesque cloud in the surrounding space, and the core contracts and becomes one of three: In the case of Sun-like and other low-mass luminaries – a white dwarf about the size of a planet in diameter. and if the star is a weightlifter – either a pulsar (neutron star) or a black hole

The extinct star in the Andromeda galaxy was many times larger than the Sun. Therefore, it was logical to expect a farewell supernova explosion from it. But he wasn’t there. Instead, the star initially became brighter during the first two years of observations, then dimmed to its original level over the next year and continued to gradually weaken.

After all, in 2023 it was no longer trackable not only in the optical but also in the near-infrared range. But until recently it was still difficult to see something barely perceptible in the presence of a supergiant star.

According to a team of US astrophysicists, what was until recently considered impossible has happened: A star “collapsed” and turned into a black hole without a supernova explosion, that is, without throwing almost anything into space. This event is called a failed supernova. In the article (available on the preprint server) arXiv.org) scientists have put forward a scenario of the possible development of events, which explains exactly why this is happening.

They believed that the star “during its lifetime” had a mass of about 20 Suns, but at the time it mysteriously disappeared it “weighed” only about seven Suns. That is, it did not shed its shell for the simple reason that there was nothing to discard: the star had long ago lost almost all of its outer mantle. The reason is not specified, but in relation to other such “robbed” stars it has been established that they are “robbed” by a companion star: it drags the essence of the victim into itself. Note that supergiant stars are mostly found in binary systems.

In any case, according to astrophysicists, the star that became “invisible” in the Andromeda galaxy was an almost “bare” core surrounded by a very thin shell. It was these remnants of the once luxurious mantle that glittered as the star grew brighter and brighter.