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If you keep a close eye on the night sky in the weeks and months ahead, you may spot something new. It will shine as bright as Polaris, the North Star, for no longer than a week before fading back into darkness.<\/p>\n
This ephemeral lighthouse is T Coronae Borealis, often referred to as T CrB. It is a nova, a nuclear explosion bursting forth from the pallid corpse of a long-dead star. Some people might have seen it before \u2014 the same beguiling sight lit up our heavens almost 80 years ago \u2014 and future generations may see it in another 80 years.<\/p>\n
To any world nearby, a nova would be apocalyptic. But to stargazers in our world, some 3,000 light-years away, it \u201cis a fun and exciting upcoming cataclysm,\u201d said Bradley Schaefer, an astrophysicist at Louisiana State University.<\/p>\n
Here is everything you need to know about this event: what it is, when it will appear and where to glimpse it.<\/p>\n<\/div>\n<\/div>\n
There are more than 400 known novas in the Milky Way galaxy. They result from the explosive pairing between a normal type of star \u2014 for example, a main sequence furnace like Earth\u2019s sun or an elephantine red giant \u2014 and a white dwarf, a smoldering stellar core left behind after a star\u2019s demise. The two are gravitationally bound companions destined to unleash a fiery blast into the cosmos.<\/p>\n
White dwarfs are relatively small, but they are also so dense that their intense gravitational pulls steal hydrogen-rich matter from a nearby regular star. That volatile material tumbles onto the surface of the white dwarf and, begins to pile up after a while, squashing the lower layers and raising their temperature.<\/p>\n
Eventually, that compressed matter \u201cgets past the kindling temperature of hydrogen,\u201d Dr. Schaefer said. It ignites, raising the temperature of the accreted material even further. Past a certain point, a runaway nuclear reaction begins, setting off an apocalyptic blast.<\/p>\n
\u201cThese novae are basically hydrogen bombs,\u201d Dr. Schaefer said.<\/p>\n
But don\u2019t confuse a nova with its more violent sibling, the supernova, which permanently destroys a star and angrily casts off its outer layers. After a nova\u2019s nuclear embers dim, the cycle starts anew, with the white dwarf once again gorging its way toward another explosion.<\/p>\n
T CrB is a nova that results when a white dwarf peels off enough of the outer layers of a red giant star that is about 74 times the size of our sun.<\/p>\n<\/div>\n<\/div>\n
The nova last exploded in 1946. Astronomers also observed it erupting in 1866, and historical reports show that it was spotted in 1787 and 1217.<\/p>\n
Most novas have explosive cycles that last many millenniums. But T CrB is impatient \u2014 a voracious consumer of its red giant\u2019s stellar fuel. Past observations indicate that it erupts once every 80 years, which makes it a recurrent nova \u2014 one that flares up at least once per century.<\/p>\n
Previous observations of T CrB have also shown that he nova blazes and convulses in a particularly erratic manner in the years leading up to an eruption, and things appear to be no different this time around: Its activity over the past decade or so suggests it is gearing up for an imminent explosion, one that will take place anytime between now and September.<\/p>\n
T CrB will appear in the Corona Borealis constellation, which is bordered by Hercules and Bootes. When it \u201cblows its stack, it\u2019ll be as bright as the North Star and it will be visible for a few days,\u201d said Bill Cooke, the Meteoroid Environments Office lead at NASA\u2019s Marshall Space Flight Center in Huntsville, Ala.<\/p>\n
\u201cYou\u2019re going to notice a new star in the sky,\u201d he added, viewable with the unaided eye.<\/p>\n
Don\u2019t miss it. \u201cIt\u2019s a once-in-a-lifetime occurrence,\u201d Dr. Cooke said. \u201cHow often can people say that they\u2019ve seen a star explode?\u201d<\/p>\n<\/div>\n<\/div>\n