Betelgeuse is a star nearing the end of its life. Because it is creating heavier and heavier elements in its core that could be used for stars after it dies, a NASA story once dubbed the red giant a workaholic.
The star is a famous one among amateur astronomers not only for its size and brightness, but also because it is part of Orion, a bright winter constellation in the Northern Hemisphere.
Professional astronomers also keep a close eye on the star, as it is notoriously variable: its diameter changes from anywhere between 550 to 920 times the sun's diameter. In 2013, astronomers said Betelgeuse is likely to crash into a "cosmic wall" of interstellar dust in a few thousand years.
When astronomers say Betelgeuse is expected to explode soon, they mean shortly in astronomical terms: within a million years, according to several sources. Predicting exactly when it will turn into a supernova is difficult, however, as it depends on precise calculations of its mass as well as an understanding of what is going on inside the star.
Betelgeuse is so vast — its size would extend beyond Jupiter's orbit if it were placed in the sun's position in the solar system — that several telescopes have captured images of the star and spotted it shedding mass. Starting in 1993 and continuing for at least 15 years, its radius shrank by 15 percent, an astonishing amount for so short a time.
As the star prepares for what could be a large explosion, another challenge awaits: it is expected to crash into a wall of interstellar dust in the next few thousand years.
An infrared Herschel Space Observatory image released in 2013 suggested it would crash into the dust at a speed of 66,960 miles per hour (107,761 kilometers per hour.)
The crash would take a while to complete: the solar wind is expected to touch the line around 5,000 years from now, with the heart of the star crashing into the bar 12,500 years after that.
Observations of the red giant revealed that gas that is leaving the star is colder than astronomers thought it would be. Scientists aren't sure how so much mass left the star, while not generating a lot of heat, they said in a 2016 study. Possible explanations include magnetic fields, or shock waves, but more work will be needed to confirm the models. Astronomers are also doing comparison studies with another red supergiant star, Antares, to better understand the situation.
The Atacama Large Millimeter/submillimeter Array, known as ALMA, has given the astronomy community the highest-resolution image of Betelgeuse to date.(Image credit: ALMA (ESO/NAOJ/NRAO)/E. O'Gorman/P. Kervella).
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