The Hubble Space Telescope has shed light on why the Orion star flared up in the 1930s and has remained bright ever since.

Several decades ago, the once unremarkable FU Orionis became hundreds of times brighter and has remained nearly the same ever since. Recently, astronomers used the Hubble Space Telescope to observe how this star, much like a black hole, is absorbing the surrounding material.

2024-11-26 10:00:34https://naked-science.ru/article/astronomy/habbl-pomog-razobratsya-p

Located 1360 light-years away from us in the constellation Orion, there exists a star that is invisible to the naked eye, and without telescopes, we would have never discovered its unusual "behavior."

In 1937, astronomers observed that its visible magnitude (brightness level) increased from 16.5 to 9.6 — the smaller the number, the brighter the star. As astronomers explained, such a jump indicates that the star has become 250 times brighter.

The first suspicion was a so-called supernova explosion: the end of a star's primary life cycle when it sheds all its outer layers. However, such a final burst should fade away in at least a few months. It cannot last for decades. Yet, the visible magnitude of the flaring star has remained approximately at the level of 9 to this day.

The object was designated as FU Orionis (FU Ori), and when other similar cases were discovered, they also came to be known as FUors. It turned out that these are very young, still "forming" stars, surrounded by vast gas-dust clouds known as protoplanetary disks. Someday, new worlds will form from this material.

There are quite a few of these "future solar systems" observed in space, but FUors have an interesting characteristic. Typically, the surrounding disk does not come into direct contact with the star: it is kept at a distance by the magnetic field of the star itself. FU Orionis appears to be one of the exceptions to this rule: it seems to be actively consuming material. This process is called accretion.

Recently, using the Hubble telescope, astrophysicists from the USA and China managed to determine how intensely FU Orionis emits ultraviolet light. In their article for the publication The Astrophysical Journal Letters, the scientists reported that in this spectrum, the star shines several orders of magnitude brighter than previously thought.

This indicates a very high temperature. Researchers calculated that it should be around 16,000 Kelvin. This is roughly three times hotter than the surface of the Sun. According to the researchers, the material is crashing onto the star with such force that a shock wave is generated.

Interestingly, this system actually contains two stars. One is estimated to have a mass of about 0.6 solar masses, while the other has 1.2. The smaller star is considered the central one. It is presumed to be the one absorbing the material and has already consumed around two dozen Jupiter masses. Calculations suggest that from 1936 to 1937, the accretion rate increased by about 10,000 times. This likely occurred due to the immense abundance of accumulated material around and the gravitational influence of the second star.