The ASASSN-15lh supernova more powerful than ever – Le Point

A brightness of 570 billion times brighter than our sun. Incredulous, astronomers observed for several months a supernova, the explosion of a star at the end of life, a largely unrivaled power in the history of astrophysics. This observation may help better understand these extreme celestial phenomena still mysterious. This supernova, called ASASSN-15lh, is 200 times more powerful than the typical explosion of these objects among the brightest in the universe. It is more than double the previous record, say the scientists whose discovery was published Thursday in the journal Science .

“ASASSN-15lh is the most powerful supernova ever discovered in the history of humanity and the explosive mechanism and source of the power of the explosion and the energy released remains a mystery as no theory of physics really manages to explain, “said Subo Dong, professor of astronomy at the University of Beijing, one of the main authors.

At the height of the explosion, the light intensity equivalent to about twenty times that of all a hundred billion stars that make up our galaxy, the Milky Way, astronomers have calculated these. This record of explosive power is an exceptional example of “hyper-luminous supernova”, a rare variety of very high intensity explosions caused by certain dying stars. “Scientists are frankly in the dark about the nature of these stars and stellar mechanisms that could explain these extreme supernovas,” responsible for these researchers.

International collaboration

This supernova, which is about 3.8 billion light years from Earth (one light year is equivalent to 9461 billion kilometers) in a galaxy was first detected in June 2015 by telescopes at Cerro Tolol, Chile participating in “Automated Survey for SuperNovae”, an international collaboration that tracks supernovae in the universe. Then several more powerful telescopes around the world have stepped in to conduct observation campaign that continues today.

The analyzes indicate that the spectrum of this supernova unlike any of those of the 250 other supernovae discovered to date by this group since its inception in 2014. Observations have revealed that this supernova shows some exceptional characteristics for this type of object “hydrogen-poor” and that, contrary to most stars. Even compared to other supernovas in the category of the most powerful discoveries for ten years ASASSN-15lh is distinguished by being more warm and not just brighter.

Hubble to clarify the mystery
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The galaxy where the supernova is also known lies without precedent, say the astronomers. Until then, all “super supernovae” were observed in low light and small galaxies where stars form much more quickly than in the Milky Way. However, the galaxy in which seems to be ASASSN-15lh is larger and brighter than the Milky Way. To these scientists, this particular environment may explain the galactic superpower of this supernova stars by creating capable of generating these huge amounts of energy exploding.

To clarify these and other mysteries this supernova, the research team will make observations with the Hubble Space Telescope. Todd Thompson, a professor of astronomy at Ohio State University, it is possible that this supernova was a type of neutron star with an extremely rare, says magnétoile, which turns on itself at least a thousand times per second and created a very strong magnetic field, converting all the light rotational energy. This would be the most extreme example of a magnétoile scientists think physically possible.

But if we discover that this object is located in the very heart of a large galaxy, this one and gases surrounding it may actually not be a supernova, but rather a kind of unusual activity around a very massive black hole, the astronomers supputent. In this case, the very high light intensity could be signing a phenomenon never seen before in the center of a galaxy, notes Christopher Kochanek, astronomer at Ohio State University, a co-author of this discovery .