Kaboom, indeed

Michael D. Lemonick has a Time article, and another one, about the stars:

Astronomers can make a surprising amount of hay over relatively small observations. That faint hiss in your AM radio that just seems like spotty reception? It’s actually the cosmic background radiation pouring in from all over the universe. That subtle red-shift in the light from distant stars? Turns out the universe is expanding.
Now investigators may be ready to turn a small discovery into big science again. Researchers at the Kavli Institute for the Physics and Mathematics of the Universe in Japan have discovered an exploding star known as a type 1a supernova at the edge of the cosmos, and while 1a’s aren’t that common — stars like the sun don’t blow up that way, for example — they’re not all that uncommon either. Still, this particular 1a could help solve the mysteries of both dark matter and dark energy — huge stuff by any measure — and all thanks to a single optical illusion that has Albert Einstein‘s fingerprints all over it.
One weird prediction of the great physicist’s General Relativity theory is that massive objects like stars and galaxies should warp the space around them, bending the paths of light rays that stream by. They act as a “gravitational lens,” distorting or magnifying the image of another object farther in the background. In this case, the background object was the 1a supernova, known awkwardly as PS1-10afx; the massive foreground object is probably a huge cluster of galaxies.
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Supernovas like PS1-10afx are valuable tools not just because they’re bright, but because they’re uniformly bright; all 1a’s put out pretty much the same amount of visible energy. This constant, known as a standard candle, makes it easy for astronomers to determine how distant the supernovas are because they can calculate how bright any one of them should look from Earth at any particular distance.  Significantly, this also allows them to calculate how fast the universe is expanding, simply by watching the rate at which the brightness falls off. Back in 1998, two teams of astronomers looking at Type 1a’s discovered, to their astonishment, that the most distant supernovas weren’t moving as fast as they expected — or to put it another way, nearby supernovas were moving too fast. Somehow, the universe was expanding faster and faster as it aged.
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The Nobel-prizewinning explanation: some mysterious force, a sort of antigravity, was speeding the expansion. The force, now known as dark energy, has Einstein’s fingerprints on it too: he predicted it in 1916, then retracted it in the 1920’s as the crude observations of the day seemed to rule it out.
In order to understand what dark energy actually is — and astronomers aren’t nearly there yet — it’s crucial to find more, and more distant, Type 1a’s. That’s why the new discovery is so important: PS1-10afx, is easily the most distant supernova seen. The explosion happened more than nine billion years ago, when the universe was only about five billion years old, and its light has been racing toward us ever since. If scientists can find several more from around that time, they’ll be able to nail down the cosmic expansion rate when the universe was young. That will flesh out their understanding of how dark energy behaves — whether it changes in strength over time, for example — and ultimately help them figure out what the heck it is.
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Not only that: the foreground cluster of galaxies that magnified the supernova’s image is undoubtedly filled with dark matter, the invisible, still-unidentified stuff that makes up 80 percent of the mass of the cosmos. Dark matter has the opposite effect of dark energy — pulling the universe together  rather than apart. The more of it there is in the foreground mass, the more powerful the gravitational-lensing effect — so by figuring out how much the supernova was magnified, astronomers can get a handle on exactly how much of the mysterious stuff the cluster holds.
The Kavli Institute is not alone in its interest in scouring the remote cosmos for 1a’s that could be lensed. The ground-based Large Synoptic Survey Telescope, slated to go online in 2018, and the space-based Euclid mission, planned for a 2020 launch, will almost certainly add significantly to astronomers’ stash of magnified supernovas. Those could help answer some questions that even Einstein himself didn’t know to ask.

and

When our Sun finally dies, some five billion years from now, the end will come quietly, the conclusion of a long, uneventful life. Our star will, in a sense, go flabby, swelling first, releasing its outer layers into space, and finally shrinking into the stellar corpse known as a white dwarf.
Things will play out quite differently for a supermassive star like Eta Carinae (photo), which lies 7,500 light-years from Earth. Weighing at least a hundred times as much as our Sun, it will go out more like an adolescent suicide bomber, blazing through its nuclear fuel in a mere couple of million years and exploding as a supernova, a blast so violent that its flash will briefly outshine the entire Milky Way. The corpse this kind of cosmic detonation leaves behind is a black hole.
For Eta Carinae, that violent end might not be long in coming, according to a report in the latest Nature. "We know it's close to the end of its life," says astronomer Armin Rest of the Space Telescope Science Institute and the lead author of the paper. "It could explode in a thousand years, or it could happen tomorrow." In astronomical terms, a thousand years might as well be tomorrow; as for a supernova blowing up literally tomorrow, well, that's almost unheard of.
In 1843, Eta Carinae gave a hint that the end might be near when the hitherto nondescript body flared up to become the second brightest star in the sky, after Sirius. It stayed that way for twenty years or so, then faded and left behind a majestic, billowing cloud of gas known as the Homunculus Nebula. Eta Carinae lost some ten percent of its substance in this event, which astronomers now call a "supernova impostor", after which it has returned to relative quiet, or what passes for quiet in such an unstable object.
Astronomers back in the day did the best they could to observe the twenty-year flare but, without modern instruments, they couldn't really learn much. That has frustrated investigators now just as it did then, since studying Eta Carinae in detail could tell them a lot about what caused the outburst, and maybe even help them figure out when the inevitable supernova explosion is going to occur.
But as the Nature report makes clear, that understanding may now be at hand. Using a fiendishly clever new observing technique, Rest and his colleagues have been able to take readings of the original blast in real time. "We can look directly at the eruption," says Princeton astrophysicist Jose Prieto, a co-author of the report, "as it's never been seen before."
To understand how they did that, start with the basic fact that light from the outburst sped away from Eta Carinae in all directions. Some of it headed straight toward Earth to wow nineteenth century astronomers. But some of it took a detour, reflecting off dust clouds in interstellar space in what astronomers call a "light echo". At least a bit of that echo was redirected toward Earth. The dust clouds were so far from the star that the long-delayed light is only now reaching us and, unlike in 1843, we now have the instruments to study it.
It gets even better. The 1843 flare-up played out over twenty years, which means the light-echo version will do the same. "We took observations nine months ago," says Rest, "and we were looking at 1843. Now we're looking at 1844. It's like a movie. It's really cool." (Of course, the images are from 7,500 years before 1843 and '44, since that's when the stellar event occurred; it just took 7½ millennia for the light to reach us.) Better still, astronomers can see light echoes from a variety of dust clouds, at varying distances from the star. That creates detours of varying lengths, so they can see different phases of the eruption all at once.
"The big puzzle," says Prieto, "is what caused the outburst. This star has been studied to death with all sorts of telescopes, but no one theory has ever been able to tell us what happened." It might have been some sort of instability deep within the star itself, or the blast might have been triggered by matter dumped on Eta Carinae by a stellar companion.
The good news is that the light-echo observations will give theorists a trove of information to work with and, in the next few years, says Rest, "we'll be getting more observations, and they'll keep getting better."
If Eta Carinae is going to blow imminently, the obvious question is whether Earth is in mortal danger. Fortunately, the answer is no. At 7,500 light-years, the intense radiation from even a powerful supernova would lose its punch by the time it reaches us. All we'll experience is the most spectacular light show in many centuries. The last confirmed supernova explosion in the Milky Way happened in 1604, a teasingly close five years before Galileo pointed his first, primitive telescope skyward.
It is, in short, about time for another big blast, and even though the theorists haven't weighed in, Rest has reason for hope. "There was one of these 'supernova imposters' in another galaxy," he says, something similar to Eta Carinae's 1843 outburst. "And then, a few years later: kaboom!"

Rico says it's nice we get to see this stuff from a safe distance. Hopefully we'll have migrated to some other solar system by the time the Sun gets around to self-destructing...