In a small galaxy about 1.8 billion light-years away, a supermassive black hole was observed gorging on a large star, ripping it to shreds and spitting out debris. Bright X-rays radiated from the location as material that fell into the black hole was heated to millions of degrees, a process that lasted a full decade, more than 10 times longer than any previously observed star's death by means of a black hole.
When a star wanders too close to a black hole, the tidal forces become so intense that the star is ripped apart in a tidal disruption event, or TDE. Tidal forces are a measure of the difference between gravitational forces acting on different parts of a star, planet or other celestial object. The moon's tidal forces regularly tug the oceans around the Earth, but a black hole's tidal forces are great enough to rip a star clear in half.
"We have witnessed a star's spectacular and prolonged demise," lead researcher Dacheng Lin from the University of New Hampshire said in a press release. "Dozens of tidal disruption events have been detected since the 1990s, but none that remained bright for nearly as long as this one."
The extraordinary length of time that it took for the star to be completely devoured likely means that this was the most massive star we have ever seen destroyed by a TDE. However, the extended bright phase of the TDE could possibly mean the opposite: that this was the first time we have seen a smaller star torn apart by a black hole, a process that requires more intense tidal forces than with a larger star.
A trio of space telescopes—NASA's Chandra X-ray Observatory and Swift satellite, as well as ESA's XMM-Newton—were used to monitor the bright TDM. The source of the X-rays was first detected in 2005, and it has been observed many times since. The TDE reached peak brightness in 2008—about 100 times brighter than when first observed. The findings were detailed yesterday in Nature Astronomy, and the study can be viewed online on arXiv.
The data from the research may help scientists learn about how black holes in the early universe grew to sizes much larger than we see today—up to one billion times the mass of the sun. (The black hole at the center of the Milky Way is thought to be about 3 million solar masses.)
"This event shows that black holes really can grow at extraordinarily high rates," says co-author Stefanie Komossa of QianNan Normal University for Nationalities in China. "This may help understand how precocious black holes came to be."
How they came to be, and what they ate.
Source: Chandra X-Ray Observatory