Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Big black holes cook flambeed stellar pancakes

02.05.2008
According to two astrophysicists from Paris Observatory, the fate of stars that venture too close to massive black holes could be even more violent than previously believed. Not only are they crushed by the black hole’s huge gravity, but the process can also trigger a nuclear explosion that tears the star apart from within. In addition, shock waves in the pancake star carry a brief and very high peak of temperature outwards, that could give rise to a new type of X-ray or gamma-ray bursts.

Scientists have long understood that massive black holes lurking in galactic nuclei and weighing millions of Suns can disrupt stars that come too close. Due to intense tidal forces, the black hole’s gravity pulls harder on the nearest part of the star, an imbalance that pulls the star apart over a period of hours, once it gets inside the so-called “tidal radius”.

Now, Matthieu Brassart and Jean-Pierre Luminet of the Observatoire de Paris-Meudon, France, say the strain of these tidal forces can also trigger a nuclear explosion powerful enough to destroy the star from within. They carried out computer simulations of the final moments of such an unfortunate star’s life, as it penetrates deeply into the tidal field of a massive black hole.

When the star gets close enough the black hole (without falling into), the tidal forces flatten it into a pancake shape. Previous studies already performed by Luminet and collaborators twenty years ago had suggested this flattening would increase the density and temperature inside the star enough to trigger intense nuclear reactions that would tear it apart. But other studies had suggested that the picture would be complicated by shock waves generated during the flattening process, and that no nuclear explosion should occur.

The new simulations investigate the effects of shock waves in detail, and find that even when their effects are included, the conditions favour a nuclear explosion which will completely destroy the star, and which will be powerful enough to hurl much of the star’s matter out of the black hole’s reach.

Stellar fireworks

The tidal disruption of stars by black holes may already have been observed by X-ray telescopes such as GALEX, XMM and Chandra, although at a much later stage : several months after the event that rips the star apart, its matter starts swirling into the hole, heats up and releases ultraviolet light and X-rays. However, if pancake stars really do explode, then they could in principle allow these events to be detected at a much earlier stage. Future observatories, such as the Large Synoptic Survey Telescope (LSST), which will detect large numbers of supernovae, could turn up some explosions of this type.

But this might be not the only hazard facing the doomed star. Brassart and Luminet calculated that the shock waves inside the stellar pancake carry a brief (The rate of such "flambeed pancake stars" is estimated to about 0.00001 event per galaxy. Since almost every galaxy – including our own Milky Way – harbors a massive black hole in its centre, and since the universe is transparent to hard X and gamma radiation, several events of this kind per year should be detectable within the full observable universe.

Conclusion

The planned high-energy, all-sky surveys are the best suited to detect more flares of this type because of their large sky coverage. By providing a quick localization of flambeed stellar pancakes, followed by the detection of the corresponding afterglows in the optical, infrared, and radio bands, these missions could bring as much to the understanding of stellar disruptions by black holes as the Beppo-Sax and Swift telescopes did for the comprehension of gamma-ray bursts.

Jean-Pierre Luminet | alfa
Further information:
http://www.obspm.fr/actual/nouvelle/may08/crepe.en.shtml

More articles from Physics and Astronomy:

nachricht Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst

nachricht Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>