The most powerful exploding stars in the universe are still cloaked in mystery, but some are now yielding the secrets of their origins, scientists say.
Research is also shedding light on gamma-ray bursts, the most powerful explosions in the universe, up to a million times brighter than a supernova,scientists added.
The most powerful star explosions are supernovas, which are bright enough to briefly outshine all the stars in their galaxies. There are two known ways supernovas occur — a Type Ia supernova arises when one star piles fuel onto a dying star known as a white dwarf, and a Type II supernova happens when the core of a massive star runs out of fuel, collapses to an extraordinarily dense nugget in a fraction of a second and then bounces and blasts its material outward.
Probably the most observed type of super-luminous supernova is the hydrogen-rich SLSN-II. They apparently typically emerge from stars that possess thick hydrogen envelopes, which veil their light and make it difficult to say what causes these explosions. They may get the boost in brightness from a number of culprits, such as newly formed black holes, which rapidly suck matter into themselves, or magnetars, which are rapidly spinning neutron stars with powerful magnetic fields — either of these possibilities might disrupt the hydrogen tremendously, with luminous effects.
"SLSN-II are technically Type II supernovae, but are unlikely to be the same as common Type II supernovae that come from exploding red supergiant stars," Gal-Yam said. "The properties of SLSN-II cannot be matched by any red supergiant we know — they must have different progenitors."
"They are indeed mysterious," Gal-Yam said.
One possibility is that they are hydrogen-poor stars that had inflated to very large diameters, dozens of times larger than our sun's. When they went supernova, they would radiate brightly and for a long time, but not be surrounded by much of a hydrogen envelope.
"The other option people have looked into is to have a more normal hydrogen-poor star which is only a few times larger than the sun — such stars are known in our galaxy and called Wolf-Rayet stars — and then pump it up with magnetic energy drained from an object called a magnetar, which is a rapidly rotating and highly magnetized neutron star, that was formed in the core of this Wolf-Rayet star when its core collapsed," Gal-Yam said. "The mystery here is that while we know that magnetars exist — we see them in our galaxy — it is not clear they rotate rapidly enough when they are born inside stars to power up such super-supernovae."
Investigating super-luminous supernovas can help better understand how heavy elements were created, "especially in the early universe," Gal-Yam told SPACE.com. In addition, "they are very bright and can serve as beacons, illuminating faint and obscure tiny dwarf galaxies at high redshifts — very far away, so the light was emitted a long time ago — allowing us to study [smyers1] the very early universe."
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