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This Star Looked Like It Would Explode. Maybe It Just Sneezed

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In an email, Edward Guinan of Villanova University, who has been tracking Betelgeuse, called the new Hubble data “fantastic,” and said Dr. Dupree’s theory was “a good working hypothesis.” He added: “But I don’t entirely agree that the ‘Mystery’ is now solved.”

He noted that alternative explanations could explain the dimming: giant sunspots, perhaps, or gigantic rising convection cells tens of millions of miles across, radiating away their heat and energy and then cooling, turning over and sinking again.

Adding to the mystery is that Betelgeuse, after regaining its normal luminosity this May, has started to dim again. Betelgeuse has long been known to vary in brightness — although not so extremely as this year — in accordance with a 420-day cycle of pulsation in its size, so this new fading is occurring early, for reasons unclear.

That the star will eventually blow up is certain. Betelgeuse, sometimes pronounced “beetle-juice,” and also known as Alpha Orionis, is at least 10 times and maybe 20 times as massive as the sun. If it were placed in our solar system, its fiery gases would engulf everything out to Jupiter’s orbit.

The star is a so-called red supergiant in the last violent stages of its evolution. It has already spent millions of years burning primordial hydrogen and transforming it into the next lightest element, helium. That helium is burning into more massive elements. Once the core of the star becomes solid iron, sometime within the next 100,000 years, the star will collapse and then rebound in a supernova explosion, probably leaving behind a dense nugget called a neutron star.

Whatever Betelgeuse is going to do, it might have already done; we are just waiting for the news. The star is some 725 light-years away, so the light visible from Earth today, whether rising or falling, left the star around the year 1300.



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