Archive for the ‘astrophysics’ Category

Scientists spot two massive stars creating a pinwheel of dust

November 20th, 2018
Image of a complex pinwheel-shaped structure.

Enlarge / An image of Apep taken in the infrared. (credit: University of Sydney/European Southern Observatory)

Figuring out what powers the Universe's largest explosions can be a real challenge, as the explosion wipes out evidence of what caused it. Archival data can sometimes provide hints of what was in the area where things went boom, but a lot of the progress we've made comes down to physicists modeling some of the more extreme objects out there and seeing if they can recapitulate the details of the explosion.

That's where we're at with long gamma ray bursts (where "long" in this case means a couple of seconds). We've seen them happen, and astrophysicists have calculated that they could be emitted from a rapidly rotating, massive star. But we don't have a lot of examples of this sort of star to study in order to see if the physics of their explosions match up with our models. Now, a team of researchers thinks it has spotted one that, in combination with a second massive star, created the fantastic-looking pinwheel shown above. But detailed observations of the system suggest that the pinwheel is formed by materials that originated on a single star yet are moving at two different speeds—something we can't explain.

The serpent god

Technically, the new object goes by the absurdly memorable name 2XMM J160050.7–514245. Surveys spotted it because it was an oddity: unusually bright at certain infrared wavelengths. Follow-up observations revealed its sinuous form, which led the researchers to rename it from the "cumbersome" 2XMM J160050.7–514245 to Apep, which is the name of a serpent deity in Egyptian mythology.

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Atoms may come apart as the Universe’s biggest stars explode

October 24th, 2018
This is what a quark-gluon plasma looks like when you don't have several Suns' worth of mass crushing it back together.

Enlarge / This is what a quark-gluon plasma looks like when you don't have several Suns' worth of mass crushing it back together. (credit: Brookhaven National Lab)

The building blocks of atoms, protons and neutrons, are composed of a collection of particles called quarks and gluons. Shortly after the Big Bang, however, the Universe was too energetic and dense for the quarks and gluons to form stable interactions. Instead, the Universe was filled with a form of matter called a quark-gluon plasma, where the particles could interact with each other promiscuously.

Billions of years later, a bunch of primates figured out how to re-create a quark-gluon plasma by smashing heavy atoms together. It was the first time the material is known to have existed since the Universe's first moments. But a group of astrophysicists is now suggesting that the biggest stars in the Universe also form something like a quark-gluon plasma as they explode, and these researchers use this to explain why we see so many distinct-looking supernovae.

It goes boom

Physical models of stellar explosions have done remarkably well at explaining what we see out in the Universe. They have helped us understand the amount of mass needed before a star will explode (as opposed to forming a white dwarf) and can describe the differences among a number of classes of supernovae. But something rather embarrassing happens as we move on to larger stars. For blue supergiants, with dozens of times the Sun's mass, the models stop exploding.

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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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