NASA Finds Possible Black Hole Behind Mysterious Repeated Explosions Of Giant Star

Astronomers have discovered what causes a giant star to repeatedly become brighter and then dim again. Using NASA's Chandra X-ray Observatory, researchers found that the star has a hidden companion that pulls material away from it at regular intervals, according to NASA.

The discovery is based on a new study published in the latest issue of The Astrophysical Journal. Researchers found that the companion passes close to the star every 113 days as the two objects orbit each other. The companion could be a black hole or a neutron star, which is the dense core left behind by a massive star.

This is the first time astronomers have detected X-rays from this type of erupting star. It is also the first discovery of such a star with a black hole or neutron star as its companion.

The star, named AT 2016blu, is located in the spiral galaxy NGC 4559, about 30 million light-years away from Earth. Researchers estimate that it has a mass at least 33 times greater than the Sun.

For 15 years, astronomers had observed the star becoming very bright before dimming again at regular intervals. However, they could not identify the reason behind this behaviour until they received data from the Chandra telescope at the right time.

Mojgan Aghakhanloo of the University of Virginia, who led the study, explained that astronomers had been observing these changes for years but could not understand their cause without the right Chandra observations.

AT 2016blu belongs to a group of stars known as luminous blue variables. These are hot, massive stars that regularly change in brightness. A well-known example of this type is Eta Carinae.

However, AT 2016blu is a special type of luminous blue variable because it shows repeated and rapid increases in brightness. These bright bursts look similar to supernova explosions, in which a massive star collapses and sends material into space.

Unlike a real supernova, AT 2016blu survives these repeated eruptions. Because of this, it is also called a supernova impostor.

Between 2012 and 2026, astronomers recorded at least 27 bursts of visible light from the star. These bursts occurred roughly every 113 days.

Co-author Nuria Torres-Alba of the University of Virginia said the star's behaviour was difficult to understand because it repeatedly appeared like a supernova but survived each eruption. Researchers realised that they needed X-ray observations during one of these bright periods to find the reason.

Chandra Telescope Helps Explain Repeated Outbursts

Researchers used the Chandra X-ray Observatory because it is the only X-ray telescope with clear enough vision to separate AT 2016blu from another bright X-ray source located nearby.

They believed that the repeated flashes of visible light could be caused by regular bursts of powerful X-rays. These X-rays heat the thick gas around the star, making it glow in visible light.

In March 2026, Chandra observations showed that the star was at least 100 times brighter in X-rays than it had been in observations from 2001 and 2002, before the repeated outbursts began.

Researchers believe the most likely explanation is that material from the star is pulled towards its companion when the two objects come closest in their oval-shaped orbit.

During this close approach, the black hole or neutron star captures material released by AT 2016blu. This material moves at extremely high speeds, close to the speed of light. As it becomes very hot, it produces bright X-rays.