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Tour: NASA's Chandra Finds Source of Star's Mysterious Outbursts
(Credit: NASA/CXC/A. Hobart)
[Runtime: 02:40]
With closed-captions (at YouTube)
Astronomers using NASA’s Chandra X-ray Observatory have discovered what is triggering repeated outbursts from a giant, unstable star.
The new study has unearthed a previously hidden companion object that keeps pulling material away from the massive star every 113 days as they orbit one another.
This partner is either a stellar-mass black hole, or the dense collapsed core of a massive star called a neutron star. This is the first X-ray detection of one of this class of erupting stars. It is also the first one of these objects found with a black hole or neutron star companion.
The volatile star, known as AT 2016blu, is in the spiral galaxy NGC 4559 that is located about 30 million light-years from Earth. Astronomers estimate the mass of this star is at least 33 times that of the Sun.
Astronomers have been watching this star get really bright and then dim again in optical light on a regular basis for over 15 years. But until they were able to get Chandra data at the right time, they were unable to figure out what was making this happen.
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 for this 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 to be considered an ultraluminous X-ray source, or ULX, which is a special class of bright X-ray objects. The discovery of this system may also help studies of stars that change in brightness before they undergo supernova explosions. Astronomers suspect that much of this behavior may be caused by systems containing a massive star orbiting a compact object or another massive star.
(Credit: NASA/CXC/A. Hobart)
[Runtime: 02:40]
With closed-captions (at YouTube)
Astronomers using NASA’s Chandra X-ray Observatory have discovered what is triggering repeated outbursts from a giant, unstable star.
The new study has unearthed a previously hidden companion object that keeps pulling material away from the massive star every 113 days as they orbit one another.
This partner is either a stellar-mass black hole, or the dense collapsed core of a massive star called a neutron star. This is the first X-ray detection of one of this class of erupting stars. It is also the first one of these objects found with a black hole or neutron star companion.
The volatile star, known as AT 2016blu, is in the spiral galaxy NGC 4559 that is located about 30 million light-years from Earth. Astronomers estimate the mass of this star is at least 33 times that of the Sun.
Astronomers have been watching this star get really bright and then dim again in optical light on a regular basis for over 15 years. But until they were able to get Chandra data at the right time, they were unable to figure out what was making this happen.
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 for this 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 to be considered an ultraluminous X-ray source, or ULX, which is a special class of bright X-ray objects. The discovery of this system may also help studies of stars that change in brightness before they undergo supernova explosions. Astronomers suspect that much of this behavior may be caused by systems containing a massive star orbiting a compact object or another massive star.
Download this video (MP4)
Quick Look: NASA's Chandra Finds Source of Star's Mysterious Outbursts
(Credit: NASA/CXC/A. Hobart)
[Runtime: 00:46]
With narration (video above with voiceover)
A giant star in a distant galaxy has been mysteriously erupting for at least 15 years.
New data from NASA’s Chandra explains what is causing these huge outbursts.
A small black hole or neutron star in orbit with this star and yanking material away.
This is leading to repeated flares that are as bright as a supernova every 113 days.
(Credit: NASA/CXC/A. Hobart)
[Runtime: 00:46]
With narration (video above with voiceover)
A giant star in a distant galaxy has been mysteriously erupting for at least 15 years.
New data from NASA’s Chandra explains what is causing these huge outbursts.
A small black hole or neutron star in orbit with this star and yanking material away.
This is leading to repeated flares that are as bright as a supernova every 113 days.
Return to: NASA's Chandra Finds Source of Star's Mysterious Outbursts (November 9, 2026)
Revised: November 09, 2026