Astronomers have determined the cause of the dramatic dimming of one of the brightest stars in the night sky.
A colossus called Betelgeuse started dimming last year and has continued this year as it appears to be on its way toward a violent death.
The star's strange behaviour had led to theories that it would soon explode in an enormous supernova that would have been visible from Earth.
But based on Hubble Space Telescope observations, scientists said they now believe Betelgeuse ejected a huge hot, dense cloud of material into space that cooled to form dust.
This dust cloud is shielding the star's light and making it appear dimmer from the perspective of viewers on Earth.
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Betelgeuse is classified as a red supergiant, the largest type of star. It is more than 10 times the mass of our sun.
If it resided at the centre of our solar system, its surface would extend to the planet Jupiter.
Scientists suspect Betelgeuse – pronounced "beetle juice" – is nearing the end of its life cycle when it will use up its nuclear fuel and explode, relatively soon in cosmic terms, in an event known as a supernova.
"Frankly, we don't know for sure how soon Betelgeuse will go supernova," astrophysicist Andrea Dupree, director of the Solar Stellar Planetary Sciences Division at the Harvard-Smithsonian Center for Astrophysics and leader of the research published this week in the Astrophysical Journal, said on Friday.
"It is likely not in our lifetimes. But, we do not know how a star behaves the week before, the night before it explodes," Dupree added.
In a supernova, huge stars like Betelgeuse expel large amounts of heavy elements, including carbon, oxygen, calcium and iron, into space that become building blocks of new generations of stars.
Betelgeuse is located relatively near our solar system, about 725 light-years away. A light year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km).
Its dimming began last October and by mid-February had lost more than two-thirds of its brilliance.
It returned to its usual brilliance by April but may be dimming again, which researchers are working to confirm.
Scientists are still unable to explain how the dust cloud was formed, and hope to study it further to better understand what could be going on with Betelgeuse.
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