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 Further Improvement of Qubit Lifetime for Quantum Computers
09.12.2016 | Forschungszentrum Jülich

nachricht Electron highway inside crystal
09.12.2016 | Julius-Maximilians-Universität Würzburg

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: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>