Astronomers have exposed an object posing as a supernova

The distant massive star AT 2016blu has been showing flares for several years that astronomers took to be harbingers of a supernova explosion. However, new observations have shown that the reason for the unusual behavior was another space object. About what is really happening in the system, see the "Izvestia" article.

Why was the star mistaken for a future supernova

AT 2016blu is located about 29 million light-years from Earth. It is a huge star with about 33 times the mass of the sun. Such massive stars end their lives with powerful supernova explosions, so scientists have suggested that the observed activity may be a sign of an approaching catastrophe.

However, over time, this version began to raise doubts. Studies in 2023 and 2025 suggested that there may be a binary system behind the behavior of AT 2016blu and that the star is not preparing for an imminent explosion at all. At the same time, the mechanism of what was happening remained unclear.

The researchers note that between 2012 and June 2026, AT 2016blu recorded 27 quasi-periodic outbreaks that occurred approximately every 113 days. It was assumed that they could be associated with the passage of the components of the binary system through the nearest point of the orbit.

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What the new observations showed

To test the hypothesis of a binary system, scientists conducted new X-ray observations AT 2016blu. The researchers knew in advance when the next outbreak was going to occur, so they were able to organize observations at exactly the right moment. The results of the work are published in the journal Phys.org .

The observations culminated in March 2026, when AT 2016blu was at the peak of another outbreak. To do this, the researchers used the "Chandra" space X-ray Observatory, which temporarily interrupted the planned observation program and sent the telescope to the star. Astronomers who observed the object from other telescopes, as well as more than 30 astronomy enthusiasts, also participated in the work.

"Chandra" detected the X-ray source during the expected flare. The comparison with archived data turned out to be especially important: observations of the observatory in 2001-2002 did not reveal X-ray radiation when the system was stable and had not yet demonstrated such outbursts.

X-ray radiation occurs when a star transfers matter to its companion. The falling substance heats up and begins to emit in the X-ray range. The researchers calculated the required accretion rate and found that the data obtained corresponded to the presence of a compact companion.

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Who actually causes starbursts

The new data allowed scientists to conclude that the AT 2016blu flares were caused not by preparations for a supernova explosion, but by interaction with another object in a binary system. A companion of a massive star may be a compact remnant, such as a black hole or a neutron star. As the objects approach, some of the star's matter begins to flow into the compact object. This process is accompanied by heating of the substance and the appearance of X-rays.

Thus, AT 2016blu is a massive X-ray binary system. The researchers call AT 2016blu the first known case of a luminous blue variable star that has a compact companion. At the same time, the star gradually loses matter in favor of a compact object, and during certain stages of the orbit, the system becomes especially active.

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Why the discovery is important for astronomy

AT 2016blu became an example of the so—called supernova impostor, an object whose behavior resembles the deathbed activity of a massive star, but does not end with an immediate supernova explosion. Now scientists want to find out if other similar objects can behave in the same way.

"Scientists" have received additional time for observations at the Chandra Observatory to study other "impostors." In addition, the Vera Rubin Observatory's ten-year sky survey will reveal a large number of new objects with short-term flares. The authors of the study note that the discovery of the binary system AT 2016blu links it to a broader class of models in which the interaction of massive stars with compact objects can explain various short-term phenomena preceding supernovae.

Massive stars play an important role in the evolution of the universe: they form heavy chemical elements, which then spread out into space and can participate in the formation of new stars and planets. Therefore, studying such objects helps scientists to better understand their life cycle.