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NATO announces major changes coming to American movie theaters over next 3 years

I clicked on it hoping it would tell me who Lana Del Ray is…

PhD candidate =f*cking grad student

I’m fond of saying that the cosmos is like a clock, with many objects and events undergoing cycles that can be measured and understood. Our calendars and clocks, after all, really are based on astronomical processes, such as the turning of Earth and its orbit around the sun.

Some other objects keep a calendar, too, but maybe they don’t check their watch often enough. They run late.

That seems to be the case for the star system T Coronae Borealis, or T Cor Bor for short. Every 80 years or so it dramatically brightens, going from obscurity to one of the 200 brightest stars in the sky in just a matter of hours. That cadence makes each of its flare-ups truly a “once-in-a-lifetime” event. The last time it did this was in 1946, so you might expect that it won’t again until 2026, two years from now. This particular object started showing signs of an impending blowout more than a year ago, however, so astronomers updated their own appointment books for it.

And then nothing—at least, not yet. It’ll blow, of that we’re certain, but it may not do so for another year. Or it could go tonight.

T Cor Bor is a binary star, or two stars that orbit each other. One, usually the brighter of the two, is a red giant, a star that is a little more massive than the sun and at the end of its life. Complicated processes in the star’s core cause the outer layers to swell up and cool. It becomes far more luminous as it grows—emitting much more light—but the cooler gas of its expanding outer layers turns the star red. It’s estimated to be about 75 times wider than the sun, making it more than 100 million kilometers in diameter—big enough that if it was swapped out for our own star, it would stretch nearly to the orbit of Venus.

The other star is far more dead. It, too, started off much like the sun and went through a red giant phase. Over time it blew off its outer layers, revealing the white-hot core—a white dwarf. Only the size of Earth but with more mass than the sun, it’s extremely hot and dense, yet its small stature makes it much fainter than its swollen companion.

Despite its Lilliputian nature, the density of the white dwarf gives it immense gravity. The two stars are so close together, separated by only about 75 million kilometers, that the white dwarf can physically pull material away from the red giant. This puts T Cor Bor in a second stellar category: it’s not just a binary star system but also a symbiotic one.

The red giant’s siphoned-off material moves toward the white dwarf but cannot simply plunge onto it. Because the two stars orbit each other, the infalling material has angular momentum, the tendency of a rotating object to continue rotating. As it moves toward the smaller star, it speeds up that sideways motion, just like water accelerates as it streams down a bathtub drain. This material forms a flattened disk around the white dwarf called an accretion disk. Matter—mostly hydrogen—then falls onto the white dwarf’s surface from the disk’s inner edge.

But all that added material poses a problem. Over time, the hydrogen spreads out over the white dwarf’s surface and piles up. The amount falling in is small in astronomical terms, just a few billionths of the mass of the sun every year (in more human terms, about one seventh the mass of the moon!). But remember that the gravity of a white dwarf is fierce, 100,000 times that of Earth’s. As the hydrogen accumulates, it gets extremely hot and eventually is compressed so much it undergoes catastrophic nuclear fusion. That is, it explodes like a thermonuclear bomb—or, really, several trillion of them.

The blast from the explosion expands rapidly, releasing huge amounts of energy. At its peak the explosion puts out more than 1,000 times as much light as the two stars combined, and they’re already several hundred times more luminous than the sun, so this is a big deal indeed.

Seen from Earth, the result is a “new” star, what’s called a nova, suddenly shining in the sky. But there’s more. Once the explosion ebbs, and the white dwarf settles down, the process repeats itself. The red giant starts feeding the white dwarf, and matter accumulates, gets squeezed and explodes again: lather, rinse, repeat.

Astronomers have witnessed T Cor Bor blowing its top at least twice in the past, in 1866 and 1946. (There are also less conclusive earlier reports of a remarkably bright star suddenly appearing suspiciously close to T Cor Bor’s location in 1217, as well as in 1787.) This repetition makes the system a subclass of nova called a recurrent nova.

But T Cor Bor has some behaviors that are still frustrating the best predictions astronomers can presently offer. In 1938, about eight years before it erupted the last time, the system got somewhat brighter, entering what astronomers sometimes call an excited state. That happened again in 2015, pushing the expected eruption date forward to 2023. Then again, it dipped in brightness a little more than a year before it blew in 1946, and that same dip was seen last year. Given that, astronomers readjusted the expected date to early 2024, though possibly as late as September.

Well, as I write this in October, I’ll speak up for all astronomers involved: oops. But we really don’t have anything to apologize for—the estimate for T Cor Bor’s explosive brightening is statistical in nature, so it’s subject to considerable uncertainty. It could just as easily blow before the end of the year or maybe early next year. Either way, it should happen soon.

And when it does, astronomers will point telescopes on the ground and in space at the event, hoping to glean as much information as they can to better figure out how and why T Cor Bor brightens and then dims before exploding.

How bright will it get when it finally decides to deliver? Right now it’s hovering around magnitude 10.0, far too faint to see without big binoculars or a telescope. It should brighten to magnitude 2.0, roughly the same brightness as the stars in the Big Dipper. That would make it easy to see even in mildly light-polluted skies.

How can you spot it when it finally blows? It’s in the constellation of Corona Borealis, the northern crown. This is far enough north in the sky that everyone in the Northern Hemisphere has a shot at seeing it. For the next month or so, you can find the constellation by going outside after sunset once it’s dark and facing west. The bright orange star Arcturus will be low to the horizon. Corona Borealis will be a curved arc, like the letter C, about 20 degrees above it (the equivalent of twice the size of your outstretched fist). Once T Cor Bor blows, it should be brighter than any of the stars in the immediate constellation, just outside the curve of stars.

Unfortunately, starting in November, Corona Borealis will be below the horizon after sunset. To see it, you’ll have to get up before sunrise, around 4 A.M., when it will be low to the horizon in the north-northeast. As time goes on, it’ll get higher before sunrise, making it easier to see.

I’ll note that a lot of news I’ve seen about T Cor Bor gives the impression this star will blaze into glory and be a gasp-worthy sight in the night sky. In reality it will only get as bright as a fair-to-middling star. This is still cool and worth watching, though! Only a handful of recurrent novae are known in our galaxy, and fewer still get bright enough to spot without optical aid. So while it might not rival Venus in the heavens, just knowing the reality behind what you’re seeing—two dead and dying stars locked in a dance that leads to a soul-vaporizing explosion that outrivals anything you can imagine—makes this worth a look.