Scientists find colossal star torn apart by giant black hole

NASA's Chandra X-ray Observatory and ESA's XMM-Newton detected the evidence of this turbulent event, designated ASASSN-14li.
Mrigakshi Dixit
Astronomers thoroughly studied a star torn apart near a giant black hole.
Astronomers thoroughly studied a star torn apart near a giant black hole.

NASA/CXC/Univ of Michigan/J. Miller et al.; Illustration: NASA/CXC/M.Weiss 

Certain massive stars meet their stellar demise explosively, exploding as a bright supernova. In contrast, smaller and medium-mass stars conclude their lives by shedding material, collapsing, and cooling into a compact core.

Nevertheless, a subset of stars faces unfortunate fates as they approach immense cosmic entities—black holes. This close encounter tears the star apart, ultimately being devoured by a voracious black hole.

This violent act is known as a tidal disruption event (TDE), in which a black hole gobbles a doomed star that ventures too close. The entire act is highly influenced by the tremendous gravitational forces of a supermassive black hole lurking at the center of galaxies. 

This force generates immense tidal forces, tearing the star into a gas jet and unleashing tremendous energy into space, which, in certain instances, might surpass the brilliance of the host galaxy.

Such occurrences emit strong, bright X-rays, which scientists may detect using powerful space and ground-based observatories. 

Astronomers have now documented the best evidence yet of the colossal star being ravaged by a supermassive black hole. The black hole fully destroyed the star, flinging its fragments into space, and consuming the rest.

“We are seeing the guts of what used to be a star,” said Jon Miller of the University of Michigan who led the study. “The elements left behind are clues we can follow to figure out what sort of star met its demise,” Miller added in the official release.

The study of a star’s element to estimate its mass 

NASA's Chandra X-ray Observatory and ESA's XMM-Newton detected the evidence of this turbulent event, designated ASASSN-14li. It was discovered in November 2014 and located 290 million light-years away from Earth, making it one of the closest tidal disruptions ever observed.

This proximity presented scientists with an unparalleled chance to glean critical insights about TDEs. 

The powerful X-ray observatories, which serve as "forensic tools in space", considered the amounts of star elements — carbon and nitrogen — around the culprit black hole. 

According to the statement, scientists deduced that these elements were once part of the core of the star before it met a terrible end. 

Moreover, the presence of these elements suggests that the ill-fated star originally possessed a mass three times greater than our own Sun. This makes it one of the largest stars ever documented to be disrupted by a black hole.

The determination of the star's mass, which has been difficult to ascertain, is what makes these observations significant. Previous research calculated that the star in ASASSN-14li had merely 0.6 times the mass of our sun. 

“ASASSN-14li is exciting because one of the hardest things with tidal disruptions is being able to measure the mass of the unlucky star, as we have done here. Observing the destruction of a massive star by a supermassive black hole is spellbinding because more massive stars are expected to be significantly less common than lower-mass stars,” explained Enrico Ramirez-Ruiz, a co-author of this study from the University of California, Santa Cruz. 

The "Scary Barbie" crime scene

In a recent development, earlier this year, an alternate group of astronomers made a surprising discovery. They witnessed a colossal star, with a mass approximately 14 times that of the Sun, being torn apart by a black hole. This crime scene has been playfully dubbed the "Scary Barbie".

According to the press statement, this revelation has been accompanied by uncertainty and is still awaiting confirmation as a tidal disruption event. This is mainly due to the fact that assessments of the star's mass were based on the brightness of the flare rather than the chemical makeup of the star located near the black hole, like ASASSN-14li.

However, this novel approach to determining the mass of the dying star has unveiled fresh opportunities for forthcoming investigations. For instance, astronomers may be able to detect the presence of star clusters around supermassive black holes in more distant galaxies using this method.

The study results were reported in the Astrophysical Journal Letters

Study Abstract:

The proximity and duration of the tidal disruption event ASASSN-14li led to the discovery of narrow, blueshifted absorption lines in X-rays and UV. The gas seen in X-ray absorption is consistent with bound material close to the apocenter of elliptical orbital paths, or with a disk wind similar to those seen in Seyfert-1 active galactic nuclei. We present a new analysis of the deepest high-resolution XMM-Newton and Chandra spectra of ASASSN-14li. Driven by the relative strengths of He-like and H-like charge states, the data require [N/C] ≥ 2.4, in qualitative agreement with UV spectral results. Flows of the kind seen in the X-ray spectrum of ASASSN-14li were not clearly predicted in simulations of TDEs; this left open the possibility that the observed absorption might be tied to gas released in prior active galactic nucleus (AGN) activity. However, the abundance pattern revealed in this analysis points to a single star rather than a standard AGN accretion flow comprised of myriad gas contributions. The simplest explanation of the data is likely that a moderately massive star (M ≳ 3 M⊙) with significant CNO processing was disrupted. An alternative explanation is that a lower mass star was disrupted that had previously been stripped of its envelope. We discuss the strengths and limitations of our analysis and these interpretations.

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