X-Ray Pulse Casts Black Holes in a New Light

This picture of a galaxy nicknamed JO204, taken with the MUSE instrument on ESO’s Very Large Telescope in Chile, shows how material is streaming out of the galaxy in long tendrils to the lower-left. Red shows the glow from ionized hydrogen gas and the whiter regions are where most of the stars in the galaxy are located. Some more distant galaxies are also visible. (ESO/GASP collaboration)

(CN) – Astronomers have noticed an X-ray pulse near a black hole that was recently observed tearing apart a star, uncovering new information about the physical properties of black holes.

In November 2014, astronomers observed a giant black hole in a galaxy 300 million light years away tearing apart a star.

Since then, they have been collecting data about the event, called a “tidal disruption flare,” in an attempt to learn more about black holes.

Researchers from the Massachusetts Institute of Technology reported their findings Wednesday in the journal Science.

The newly published study shows that certain events can help calculate the spin of a black hole.

When the black hole tore apart the star, it created a “pulse” of X-ray activity near the center of the distant galaxy, according to the astronomers.

The researchers found that the pulse brightened and faded every 2 minutes and 10 seconds, and lasted for at least 450 days. The pulse appeared to come from the “event horizon” of the black hole, which is the part where it completely swallows all matter.

With the gathered data the researchers calculated that the black hole is spinning at around 50 percent of the speed of light.

“That’s not super fast,” study author Dheeraj Pasham said in a press release from the American Astronomical Society. “There are other black holes with spins estimated to be near 99 percent the speed of light.”

“But this is the first time we’re able to use tidal disruption flares to constrain the spins of supermassive black holes,” Pasham explained.

Calculating the speed is difficult, and the team hopes these findings can help them learn more about how black holes function.

“Events where black holes shred stars that come too close to them could help us map out the spins of several supermassive black holes that are dormant and otherwise hidden at the centers of galaxies,” Pasham said.

“This could ultimately help us understand how galaxies evolved over cosmic time,” he added.

Pasham had developed a code to detect patterns in astrophysical data. Though he did not specifically create the code for tidal disruption flares, he used it for this study.

The team looked at data from two of NASA’s observatories, as well as one from the European Space Agency.

While they don’t know for sure what is causing the pulse, the team theorized that a different kind of star, called a white dwarf, may be responsible.

If the white dwarf was orbiting the black hole at the same time as the tidal disruption flare, the hot material of the torn-apart star could have illuminated it each time the dwarf orbited, they theorized.

Pasham noted there is still more to learn from the data and data like it.

“Estimating spins of several black holes from the beginning of time to now would be valuable in terms of estimating whether there is a relationship between the spin and the age of black holes,” he said.

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