Maybe it is the most juvenile part of our fascination with science, but sometimes it seems that our most interesting observations of the universe around us are also the most destructive. So when astronomers capture images of a black hole tearing apart a star the size of the Sun, people want to hear about it.
Events like this are relatively unusual because the phenomena themselves are both rare and typically short-lived … occurring over a period of months, occasionally years, and then fading rapidly.
Astronomers have employed the use of the ROTSE IIIb telescope (short for 'Robotic Optical Transient Search Experiment') to identify nearby supernovae, when one such an event was detected in early 2009. The project, called the ROTSE Supernova Verification Project (RSVP), has turned up a number of transient observations which have mimicked, in some respects, supernovae. But this one, which astronomers dubbed “Dougie” (purportedly named after the South Park character), was different.
At first, the team believed they had glimpsed a supernova — a “super luminous supernova,” for that matter — But as they began to investigate the source of the burst, the details they uncovered began to diverge from the classical picture of a supernova explosion.
Specifically, neither the X-ray nor the optical signatures matched the expected values of a superluminous supernova event. Nor did it fit the template for a cataclysmic variable star or gamma ray burst: two relatively common transients detected by the survey. Slowly, as the data came in from other sources trained on Dougie, the conclusion became clear: the astronomers were witnessing a tidal disruption event — a massive flare generated when a medium=mass star is eaten by a supermassive black hole.
In addition to the impressive visual nature of the spectacle, some researchers also think that the sudden injection of mass into the supermassive black hole, which was dormant at the time, likely has the “consequence of bringing life back to an otherwise quiescent galactic nucleus."
Scientists first posited the likelihood of tidal disruption events in 1975 as an inevitable consequence of the existence of supermassive black holes in galactic nuclei.
However, as it turns out, Dougie wasn't eaten by a particularly massive black hole: further models show that the black hole was hitting the Eddington Limit in an attempt to ingest the star — whereby the radiative luminosity of the mass was exceeding the gravitational force and actually blowing gas away from the hole, rather than sucking it in. That factor accounted for much of Dougie’s brightness, and it also demonstrated that the black hole involved was relatively small, weighing around one million solar masses.
Rather than swallowing the star whole, the small black hole creates tidal forces which were stronger on one side of the star than the other. These forces act to shear away the mass of the star, stretching it out into something resembling a butterfly noodle. Extraordinarily, it made it look as though the star were fighting back.
The team feels that this puts Dougie into a relatively rare class of super-Eddington tidal disruption events, a rare glimpse that gives astronomers a clear picture of the inner workings of black holes, and how they shape galactic nuclei.
WATCH: "Formation of a Debris Disk After the Tidal Disruption Of a Star by a Supermassive Black Hole"
Regardless of how small the black hole might realistically be, the forces at play remain sublimely intense. In addition to providing good research material, epic battles between stars and black holes out in the cosmos will continue to attract attention and fascination among the scientifically-minded.