The Mainichi Shimbun answers some common questions readers may have about recent reports that Betelgeuse, one of the stars that forms the constellation Orion, may be on the brink of exploding and eventually disappear.
Question: Is it true one of the stars of Orion has suddenly gotten a lot darker?
Answer: You're referring to Betelgeuse, one of the first-magnitude stars in the Orion constellation, which is often thought of as a winter constellation in the northern hemisphere due to its visibility in the cold months of the year. Much online attention has been paid to its luminosity following a report by the U.S. news outlet CNN that the star has been observed at its dimmest in the last 100 years. News reports included claims that Betelgeuse is close to the end of its life, which would be caused by the collapse of its core and lead to a supernova, but among experts, the current consensus is that there are no indications it is set to explode.
Q: What kind of star is it?
A: It has a mass about 20 times that of our own sun, and an estimated lifespan of around 10 million years. Already 9 million years are believed to have passed since it formed, making it an old star. Generally, the greater a star's mass, the shorter its lifetime. It's referred to as a red supergiant star due to its red color from expanding to around 1,000 times the size of our sun. Due to its relatively low density, it is easy for the star to expand and contract, which in turn causes a wide variance in its brightness.
Q: Why would a star explode?
A: A star's high pressure and high temperature core leads to nuclear fusion, producing gradually heavier elements from helium, oxygen, magnesium, up to iron. This gradually results in a dense iron core, the mass of which eventually cannot be sustained by the star, resulting in a supernova explosion.
Q: Wouldn't it be scary if Betelgeuse exploded?
A: Although a supernova would involve a star with a mass eight times or more than that of our sun, Betelgeuse exploding still would not be enough to have an effect on us here. If Betelgeuse did explode, it would be moderately bright for around 100 days, and after a few years it would no longer be visible. Hitoshi Yamaoka, an associate professor at the National Astronomical Observatory of Japan, said, "We want people to enjoy looking up at the night's sky and seeing changes in celestial bodies."
(Japanese original by Ayumu Iwasaki, Science & Environment News Department)