SCIENTISTS FIND A BLACK HOLE SPAGHETTIFYING A STAR REMARKABLY CLOSE TO EARTH

With the black hole feeding in such close proximity to Earth, finer details of the tidal disruption event were revealed to astronomers

A stronomers have spotted the closest visiblelight example yet of a supermassive black hole ripping apart and devouring a star. This star’s gory death can be blamed on a black hole with a mass equal to around a million Suns. The event occurred in the active star-birthing galaxy NGC 3799, which is located about 160 million light years from Earth in the constellation of Leo. The scientists, who hail from the University of Hawaii Institute for Astronomy, discovered the stellar murder, referred to as a tidal disruption event, or TDE, when they spotted the sudden brightening and rapid fading of the barredspiral galaxy within which it occurred.

The discovery was made with the All Sky Automated Survey for SuperNovae (ASAS-SN) system on 22 February 2023. “While black holes destroying stars have been seen before, this is the first one we have seen this close using visible light,” Willem Hoogendam, Institute for Astronomy graduate student and research co-leader, said. “This could give us a much better understanding of how supermassive black holes grow and collect material around them.”

TDEs occur when stars venture too close to supermassive black holes, which dwell at the hearts of all large galaxies and have masses equal to millions or even billions of Suns. The immense gravitational forces of these monstrous black holes generate huge tidal forces that squeeze the doomed stars horizontally while also stretching them vertically. This turns the stars into cosmic noodles of stellar material that wrap around supermassive black holes like spaghetti on a fork.

After this process, aptly called ‘spaghettification’, each destroyed star is gradually fed to the supermassive black hole. This violent process generates extremely bright flares that can be seen with instruments here on Earth.

Though these events are fairly common, finding TDEs relatively close to Earth in this manner is rare. That makes this one, designated ASASSN-23bd, a prime target for follow-up investigations. “This discovery suggests that black holes ripping stars apart nearby could be more common than previously thought – we just haven’t witnessed it happening frequently,” said Hoogendam.

The team followed up its initial observations of the TDE in NGC 3799 with more observations using ground and space-based observatories, including the Asteroid Terrestrial Last Alert System (ATLAS) telescopes on the Hawaiian mountains of Mauna Loa and Haleakalā, as well as the W. M. Keck Observatory on Mauna Kea. The team discovered that ASASSN-23bd is remarkable among TDEs for reasons other than its proximity to Earth. This TDE brightened over the course of just 15 days and then rapidly dimmed, making it around twice as fast as other TDEs. Additionally, it produced much less energy than other TDES. This marks it out as part of a category of events called ‘low luminosity and fast TDEs’.

1 Up to one solar mass

The end result of stellar evolution for low-mass stars like the Sun, these consist of a dense plasma of atomic nuclei and electrons.

2 Around 1.4 solar masses

Formed from stars between 10 and 25 solar masses, these dead stars are composed almost solely of neutrons.

3 5 to 50 solar masses

Stars that are too heavy collapse all the way to a black hole, with all their mass concentrated into a single point.

4 100 to 100,000 solar masses

The most elusive kind of black hole, these are believed to exist in the centres of very small galaxies.

5 Over 1,000,000 solar masses

These are known to lurk in the centres of most large galaxies, with no theoretical limit to how large they can grow.