The region immediately surrounding a supermassive black hole shines brightly with x-ray radiation, much of which comes from a compact source called the corona. In a very rare event occurring over a period of just days, a corona shifted closer to a black hole known as Markarian 335, causing an extreme blurring and stretching of x-ray light. NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) captured it in remarkable detail.
"The corona recently collapsed in toward the black hole, with the result that the black hole's intense gravity pulled all the light down onto its surrounding disk, where material is spiraling inward," says Michael Parker of the Institute of Astronomy in a news release. The work was published in the Monthly Notices of the Royal Astronomical Society.
Supermassive black holes are enormously dense objects thought to exist at the center of most galaxies. While light falls into the black holes, coronas and the surrounding accretion disks of superheated material emanate high-energy light. But some black holes are more massive and rotate faster than others. Mrk 335 is about 324 million light-years from Earth in the direction of the Pegasus constellation. It’s one of the most extreme systems when it comes to mass and spin rate: It squeezes 10 million times the mass of our sun into a region only 30 times the sun’s diameter, and it spins so rapidly, space and time are dragged with it.
We don’t know the shape and temperature of coronas, but astronomers know that these clouds contain particles that move close to the speed of light. So, as this corona moved closer, the intense gravity of Mrk 335 exerted a stronger tug on the x-rays emitted, pulling the corona’s light into the inner portion of the superheated disk. This stretched the corona’s light to lower energies than observed before.
After a dip in brightness was observed by NASA's Swift satellite, NuSTAR took a look at those high-energy x-rays in the range of 3 to 79 kiloelectron volts, giving astronomers a look at the region around the black hole where light can no longer escape gravity, called the event horizon.
This plot shows x-ray light streaming from regions near Mrk 335. X-ray light from the corona is reflected off the accretion disk, which feeds the black hole. The reflected light and the corona’s direct light are mapped over a range of x-ray energies. The yellow line is a model that shows what the data are predicted to look like if x-ray light had been stretched, or blurred. The blue line represents what the plot would look like without the blurring effects. The dots show actual NuSTAR data, indicating that the light is extremely blurred.
Months after it had moved, the corona is still in this close configuration. Researchers don't know if and when the corona will shift back.
Images: NASA/JPL-Caltech (top) & NASA/JPL-Caltech/Institute for Astronomy, Cambridge (middle)