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A black hole lunch: star spaghetti



Astronomers call it “spaghettification,” and it’s not a pretty idea: it’s what happens when you venture too close to a black hole and fall. Tide forces stretch you and break you like a noodle, then your strips circulate the black hole until they collide and knock each other in.

On the upside, the energy released by your long fall and the collapse of what were once your atoms could possibly produce a flash – a cosmic funeral bonfire, if you will – that can be seen all over the universe.

In a case reported last week, it was just an anonymous star in a distant galaxy that met its doom. Thanks to luck and ever-increasing vigilance in the sky the whole world watched as the star went down.

“It was actually a great party,” Matt Nicholl, an astrophysicist at the University of Birmingham in England, said in an email. He led a team of astronomers who described this star’s apocalypse in the monthly announcements from the Royal Astronomical Society on Monday.

“This black hole was a messy eater,” added Kate Alexander of Northwestern University and a member of Dr. Nicholls team in an email. Eventually, she said, only about half of the star was consumed by the black hole. The rest of its dissolved material was blown outward into space at a tremendous speed a few percent of the light.

Tension began on September 19, 2019, when the Zwicky Transient Facility, a telescope on Palomar Mountain in California, and other sky-monitoring networks discovered a flare in the middle of a galaxy 215 million light-years from Earth in the constellation Eridanus.

The flame had the characteristics of a tidal disturbance, the technical name for when a black hole tears a star to pieces and eats it.

Astronomers rushed to their ground- and space-based telescopes to monitor AT2019qiz when the flame was named. (“AT” stands for “astronomically transient.”)

Over the next few weeks, the flare lit up quickly. At its peak, it burst about a billion times as much energy as our sun. In the following five months, the flare slowly disappeared.

The result was a unique and multidimensional appearance – based on radio emissions, X-rays and gamma rays as well as old-fashioned observations of visible light – on the complexity of death at black holes.

Black holes are gravitational holes in space-time predicted by general relativity, Albert Einstein’s theory of gravity. They are so deep and dense that nothing, not even light, can escape them. Our Milky Way galaxy, and presumably most galaxies, is filled with black holes produced when massive stars died and collapsed into themselves. In addition, any galaxy appears to have a supersize version of one of these monsters millions or billions of times as massive as the Sun.

“We know that most galaxies have a supermassive black hole in their centers,” wrote Dr. Alexander in an e-mail. “But we still do not understand exactly how these black holes grew to be as large as they are, or how they shape their host galaxies.” Studying stellar perturbations, she said, could help understand how these black holes eat, grow, and interact with their environment.

The black hole in the Eridanus galaxy weighs about one million solar masses. As reconstructed by Dr. Nicholl and his team migrated a star the size and mass of our own sun into the center of the galaxy and came too close – about 100 million miles – to the black hole.

It is approximately the distance from the earth to the sun. At that time, gravity from the black hole exceeded gravity from the star’s core, and the star was “spaghettified” in a long stream around the hole. Eventually, the current flowed all the way around the black hole and collided with itself, “that was when the black hole started to suck it in,” said Dr. Nicholl.

He added: “If you were to imagine the sun stretching out in a thin stream and crashing towards us, then the black hole.”

Astronomers have recently documented other such disturbances in black holes, but such events rarely occur so close to our own galaxy, and their inner dynamics are often obscured by dust and gas kicked up by the fatal collision. In this case, astronomers could look behind the curtain and observe that it was made of bits from the shredded star.

“Because we caught it early, we could actually see the curtain of dust and dirt being pulled up as the black hole launched a powerful outflow of material,” said Dr. Alexander.

Most of the light they saw came from this material that was blown out into space at speeds of about 6,000 miles per second. Spectral studies showed that the material flowing outward from the black hole was identical to that which fell in – evidence that it was crumbs from the clumsily eaten star.

The flare AT1910qiz could serve as a “Rosetta stone” for understanding other star-crushing events, said Dr. Alexander. AT2019qiz was special, she added, because astronomers began observing it very early, right after the star was torn apart, collecting so much data from many different kinds of telescopes.

New telescopes like the Vera Rubin Observatory and the European Extremely Large Telescope, both under construction in Chile, were to pull in even more of these Instagram cosmic foods.

Enjoy your meal.


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