Archive for the ‘astrophysics’ Category

We may have caught supernova debris slamming into neighboring stars

August 17th, 2017

Enlarge / When the smaller star finally explodes, its companion will obviously get hit by the debris. (credit: Fermilab)

Supernovae are some of the most energetic events in the Universe, sending massive shock waves out into the interstellar medium. And there’s every reason to think those shock waves run into things before they’ve had much of a chance to dissipate. Many stars have companions, either planets or other stars that orbit in reasonable proximity. In fact, there’s an entire subtype of supernova that appears to require a nearby companion.

So what happens to these objects when the shock wave hits? With our improved ability to rapidly identify supernovae, we may be on the cusp of finding out. Several times recently, researchers have spotted an extra blue glow to the burst of light from a supernova. And, in the most detailed observations yet, they make the case this glow comes from the supernova debris slamming into a companion star.

A supernova explosion that envelopes a nearby star is an inevitability. Eta Carinae, for example, is a system with two stars that are at least 30 times the Sun’s mass, meaning they’ll both eventually explode as a type-II supernova. Whichever goes first will undoubtedly send debris into the second. But there’s a different class of supernova, type-Ia, which requires the presence of a nearby star.

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Hypothetical black holes could be eating neutron stars

August 10th, 2017

Enlarge (credit: NASA’s Goddard Space Flight Center)

Immediately after the Big Bang, the Universe’s matter was incredibly dense and rippled with random fluctuations. Is it possible that some portions of it reached densities high enough to collapse into black holes?

The idea of primordial black holes has been kicking around in theoretical circles for a while, in part because they could provide much of the dark matter that seems to dominate the Universe’s large-scale structures. But testing for their existence requires some sort of consequence that we could detect, and the theorists have largely come up short there. But now, a team of three physicists writing in Physical Review Letters has come up with a rather intriguing consequence: these black holes could swallow a neutron star that, under the right conditions, would spit out heavy elements.

Truth or consequences

Two things could distinguish primordial black holes from those formed in the collapse of a massive star. One is that they could be nearly any mass, from less than the mass of a star up to thousands of times heavier than anything formed during a supernova. The heavier end of the spectrum is appealing, since it could explain how supermassive black holes appeared so quickly (in astronomical terms) after the Universe’s birth.

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