University of Chile Postdoctoral fellow & first autor of the paper - Lixin Dai, – that will be released tomorow in the paper edition of Astrophysical Journal Letters- explains what is the discovery and why is important for science.

What is the discovery?

Our research is on modeling how a star could be destroyed by a very massive black hole through tidal forces using Einstein‘s theory of General Relativity. An example of the tidal force is the tides on Earth made by the Moon. If this force is too big, it will not only make tides of the oceans, but also change the shape of the Earth or even totally destroy it. The scale of the tidal force from black holes is huge since black holes are very massive, so stars passing by close can be totally destroyed.

What we did differently from others is: Others used Newtonian mechanics to study the topic, but given the huge gravity from black holes, it is important to consider General Relativity in the models. We are among the first to do that - we put the star in an elliptic orbit around the black hole, and then used general relativistic simulations to see how the star is destroyed and how the black hole "eats" the star.

How long have you been working on the research?

Prof. Andrés Escala of U. de Chile, Prof. Paolo Coppi of Yale University, and I have started collaborating and worked on this specific research topic for about 10 months.

Why is this discovery important for astronomy? (what‘s next, etc.)

Tidal disruption events are relatively rare (we have about 20 candidates so far), but they are nonetheless intriguing, as they are the brightest events in the sky. Some of the tidal disruption events, for example the event (Swift J1644+57) observed by Swift in 2011, outshines its galaxy for weeks. The study of these events can help us discover black holes that are dormant otherwise, test if intermediate mass black holes exist, and understand better how materials accrete onto black holes and how jets and radiations are produced. With the launch of the Large Synoptic Survey Telescope (LSST) in the upcoming decade, we expect to see around 2000 such events! So it is very important and timely for us to understand the details of the temporal behavior of tidal disruption flares.

Our project is still on-going. Our simulation shows that happens when a star is disrupted in a relativistic elliptic orbit, but it is rather hard for the stellar tidal streams to collide with each other and eventually feed the black hole, unless the black hole is not rotating around its own axis. However, in nature, black holes are in general spinning, so there ought to be other ways for the black hole to "eat" the star after the disruption. It is not totally clear yet to astrophysicists what is the most effective mechanism for doing so, however, it is possible that the shocks and the magnetic flux in the stellar material contribute to the feeding of the hole. We will continue to investigate on these aspects.

What kind of equipment’s did you use in order to do your research?

The simulation we have done so far only requires a single desktop computer to run. But we will employ a cluster soon for bigger and more extensive simulations.

In order to see the animation that explains the phenomena, please click here

Picture source: NASA/CXC/M.Weiss