Located regarding 250 million light years from Earth at the center of another galaxy, it was the fifth-closest example of a star-destroying black hole ever observed.
Once the gravity of the black hole completely broke the starastronomers saw a dramatic increase in high-energy X-ray light around the black hole. This indicated that as the stellar material was drawn towards its doom, formed an extremely hot structure on top of the black hole called the corona. NASA’s NuSTAR satellite is the most sensitive space telescope capable of observing these wavelengths of light, and the proximity of the event provided an unprecedented view of the formation and evolution of the corona.
The work demonstrates how the destruction of a star by a black hole, a process formally known as a tidal disruption eventmight be used to better understand what happens to material captured by one of these giants before it is completely devoured.
most of black holes that scientists can study are surrounded by hot gas that has accumulated over many years, sometimes millennia, and forms disks billions of kilometers wide. In some cases, these disks outshine entire galaxies. Even around these bright sources, but especially around much less active black holes, a single star stands out, tearing itself apart and consuming itself. And from start to finish, the process often takes just a few weeks or months. The observability and short duration of tidal disruption events make them especially attractive to astronomers, who can decipher how the black hole’s gravity manipulates the material around it, creating incredible light shows and new physical features.
“Tidal disruption events are a kind of cosmic laboratory“said study co-author Summer Gezari, an astronomer at the Space Telescope Science Institute in Baltimore. “They are our window into a real-time feed into a massive black hole lurking at the center of a galaxy.”.
a startling sign
The focus of the new study is an event called AT2021ehbwhich took place in a galaxy with a central black hole regarding 10 million times the mass of our Sun. During this tidal disruption event, the side of the star closest to the black hole was torn apart more strongly than the far side of the star, pulling everything apart and leaving nothing but a long noodle of hot gas.
Scientists believe that the stream of gas is whipped around a black hole during such events, colliding with itself. This is believed to create shock waves and gas flows outwards that generate visible light, as well as wavelengths not visible to the human eye, such as ultraviolet light and X-rays. The material then begins to settle into a disk that rotates around the black hole like water flowing through it. a drain, and friction generates low-energy X-rays. In the case of AT2021ehb, this series of events took place over just 100 days.
The event was first seen on March 1, 2021 by the Zwicky Transitional Facility (ZTF), located at the Palomar Observatory in southern California. It was later studied by NASA’s Neil Gehrels Swift and Neutron star Interior Composition Explorer (NICER) telescope (which observes longer X-ray wavelengths than Swift).
Then, around 300 days following the event was first detected, NASA’s NuSTAR began observing the system. Scientists were surprised when NuSTAR detected a corona, a cloud of hot plasma or gas atoms stripped of electrons, since coronas typically appear with jets of gas flowing in opposite directions from a black hole. However, with the tidal event AT2021ehb, there were no jets, making the corona observation unexpected. The coronas emit higher-energy X-rays than any other part of a black hole, but scientists don’t know where the plasma comes from or how it gets so hot.
“We’ve never seen an X-ray emitting tidal disruption event like this without the presence of a jet, and that’s really spectacular because it means we can potentially tease out what causes jets and what causes coronas.“, said Yuhan Yao, a graduate student at Caltech in Pasadena, California, and lead author of the new study. “Our observations of AT2021ehb agree with the idea that magnetic fields have something to do with how the corona forms, and we want to know what is causing that magnetic field to get so strong.“.
Yao is also leading an effort to look for more ZTF-identified tidal disruption events and then observe them with telescopes like Swift, NICER, and NuSTAR. Each new observation offers the potential for new insights or opportunities to confirm what has been observed at AT2021ehb and other tidal disruption events. “We want to find as many as we canYao said.
NASA in Spanish
