Astronomers using NASA's Chandra X-ray Observatory found that a black hole or neutron star companion pulls material from the massive star AT 2016blu every 113 days, triggering repeated brightening episodes.
NASA's Chandra X-ray Observatory has discovered what triggers repeated outbursts from the massive star AT 2016blu, located in the spiral galaxy NGC 4559 about 30 million light-years from Earth.
A new study published in The Astrophysical Journal details the discovery of a previously hidden companion object that pulls material away from the massive star every 113 days as they orbit one another. The companion is either a stellar-mass black hole or a neutron star, the dense collapsed core of a massive star.
This is the first X-ray detection of one of this class of erupting stars and the first of these objects found with a black hole or neutron star companion.
AT 2016blu is a luminous blue variable, a type of hot, massive star characterized by changes in brightness. It is a special type that undergoes rapid and repeated increases in brightness so extreme that they resemble supernova explosions. Because the star is not destroyed, it is also referred to as a "supernova impostor."
Astronomers estimate the mass of this star is at least 33 times that of the Sun. Between 2012 and 2026, astronomers detected at least 27 bursts of optical light from AT 2016blu roughly every 113 days.
"For 15 years, astronomers have been watching this star get really bright and then dim again on a regular basis," said Mojgan Aghakhanloo of the University of Virginia in Charlottesville, who led this study. "Until we were able to get Chandra data at the right time, we couldn't figure out what was making this happen."
The team used Chandra because it is the only X-ray telescope with sharp enough vision to distinguish AT 2016blu from another nearby bright X-ray source. Chandra data from March 2026 revealed that AT 2016blu was at least 100 times brighter in X-rays than in Chandra data from 2001 to 2002, which is before the outbursts began.
The best explanation is that material from the star is falling onto a neutron star or black hole during the closest approach in their oval-shaped orbit around one another. When they come close together, material ejected by the star gets captured by the black hole or neutron star. The material orbits at very high speeds close to the speed of light, getting so hot that it shines brightly in X-rays.
AT 2016blu is bright enough in X-rays to be classified as a candidate of ultra-luminous X-ray source. These are rare, bright X-ray sources found with telescopes like Chandra that astronomers have yet to fully understand.
These new observations suggest there could be a link between ultra-luminous X-ray sources and the kind of violent stellar eruptions seen in AT 2016blu. The discovery may also help studies of stars that change in brightness before they undergo supernova explosions, as astronomers suspect much of this behavior may be caused by systems containing a massive star orbiting a compact object or another massive star.
Sources
This article was drafted with AI assistance and checked against the sources above. Company claims are reported as claims. Cover image is AI-generated.
The day's checked news, by email
One short email a day with the top stories. Free, and you can unsubscribe in one click.
Or follow for the latest news:
No comments yet. Start the discussion.
Wildfires are contaminating streams and rivers that supply drinking water, with impacts lasting up to eight years. Las Vegas, New Mexico, received $148 million to rebuild its treatment plant after the 2022 Hermit's Peak/Calf Canyon fire.
Astronomers have linked a repeating radio signal flashing every 7.9 minutes to a binary system containing a white dwarf and a G-type star similar to the Sun, the first such pairing found for a long-period radio transient.
