ZTF makes first discovery of rare cosmic 'lunch'

ZTF makes first discovery of rare cosmic ‘lunch’

Newswise – The universe can be a violent place. Stars die or collide and black holes devour anything that gets too close. These and other events produce flashes of light in the night sky that astronomers call transients. The Zwicky Transient Facility is currently one of the largest transient surveys astronomers use to study the ever-changing universe. The survey is also a treasure trove of rare, strange and unusual events that astronomers often discover by chance.

“Our new search technique helps us quickly identify rare cosmic events in ZTF survey data. And since ZTF and larger upcoming surveys such as Vera Rubin’s LSST scan the sky so frequently, we can now expect to discover a host of rare or previously unknown cosmic events and study them in detail,” says Igor Andreoni, postdoctoral associate in the Department of Astronomy at UMD and NASA’s Goddard Space Flight Center.

AT2022cmc is a special case of what is known as a tidal disturbance event or TDE. TDEs occur when a star approaching a black hole is violently torn apart by the black hole’s gravitational tidal forces – similar to how the Moon pulls the tides on Earth but with greater force. Then pieces of the star are captured in a rapidly spinning disk orbiting the black hole. Finally, the black hole consumes what’s left of the doomed star in the disk.

In some extremely rare cases like AT2022cmc, the supermassive black hole launches “relativistic jets” – beams of matter moving at near light speed – after destroying a star. Discovered in February 2022, astronomers led by Andreoni tracked AT2022cmc and observed it with multiple setups at multiple wavelengths. The analysis is now published in the journal Nature.

“The last time scientists discovered one of these jets was more than a decade ago,” said Michael Coughlin, assistant professor of astronomy at the University of Minnesota Twin Cities and co-lead. of the item. “From the data we have, we can estimate that relativistic jets are launched in only 1% of these destructive events, making AT2022cmc an extremely rare event. In fact, the flash of light from the event is among the brightest ever observed.

The new data processing method – equivalent to searching a million pages of information every night – allowed Andreoni and his colleagues to perform rapid analysis of ZTF data and identify the AT2022cmc TDE with relativistic jets. They soon began follow-up observations which revealed an unusually bright event across the entire electromagnetic spectrum, from x-rays to millimeter and radio.

ESO’s Very Large Telescope revealed that AT2022cmc was at a cosmological distance of 8.5 billion light-years. Optical/infrared images from the Hubble Space Telescope and radio observations from the Very Large Array identified the location of AT2022cmc with pinpoint accuracy.

Researchers believe that AT2022cmc was at the center of a galaxy that is not yet visible because light from AT2022cmc has passed it, but future space observations with the Hubble or James Webb Space Telescopes may uncover the galaxy when the transient will eventually disappear.

It’s still a mystery why some TDEs throw jets while others don’t. Based on their observations, Andreoni and his team concluded that the black holes in AT2022cmc and other similar jet TDEs are likely spinning rapidly in order to power the extremely bright jets. This suggests that a rapidly spinning black hole could be a necessary ingredient for launching a jet – an idea that brings researchers closer to understanding the physics of supermassive black holes at the center of galaxies billions of years away. -light.

Prior to AT2022cmc, only a few possible jet TDEs were known, mostly discovered by gamma-ray space missions, which detect the higher energy forms of radiation produced by these jets. With their new method, astronomers can now search for these rare events in ground-based optical surveys.

“Astronomy is changing rapidly,” Andreoni said. “Other optical and infrared surveys of the whole sky are now active or will soon be online. Scientists can use AT2022cmc as a model to know what to look for and find more disturbing events from distant black holes. This means that more than ever, Big Data Mining is an important tool for advancing our knowledge of the universe.

The article, “A very bright jet from the disruption of a star by a massive black hole”, is published in Nature on November 30, 2022.
DOI: DOI: 10.1038/s41586-022-05465-8

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