Considered one of the brightest stars within the night sky has been getting oddly brighter, prompting speculations that it would soon explode in a supernova. Should we actually stay up for such a blinding celestial spectacle?
The star in query is Betelgeuse, an enormous red-tinged star that sits on the left shoulder of the unmissable constellation Orion. Some 650 light-years from Earth, Betelgeuse often ranks because the tenth-brightest star within the night sky. Since early April, nevertheless, the star has climbed to the seventh spot and currently shines at over 140% its “usual” brightness, in response to the Twitter account Betelgeuse Status, which tracks the star’s behavior.
Betelgeuse is a red giant, an infinite star that has burned up all of the hydrogen fuel in its core and expanded a whole bunch of times beyond its original envelope. Astronomers imagine the star is now fusing helium into carbon and oxygen, a phase in a star’s life that lasts tens to a whole bunch of 1000’s of years and precedes the star’s demise in a supernova explosion. Betelgeuse’s recent antics, the start of which date back to 2019, have led some to take a position that the moment of its spectacular death may be near. If Betelgeuse were to go boom it will be the closest supernova explosion in greater than 400 years and it will be so vivid it will be visible even in daylight.
Related: This recent supernova, the brightest in years, could help astronomers forecast future star explosions
The nice dimming
Betelgeuse is a variable star known for normal oscillations between brighter and dimmer periods. For greater than 100 years, astronomers have observed Betelgeuse loosen up every 400 days, then drop to about half of its peak brightness and brighten up again. But in December 2019, the star unexpectedly dimmed beyond what had ever been seen before, hitting a low 2.5 times fainter than its usual dimmest shine. The explanation for the event, since dubbed the Great Dimming, was later traced to an infinite expulsion of fabric from the star’s interior that created an enormous dust cloud that subsequently obscured our view of the star.
End of life
Although Betelgeuse has since recovered its usual brightness, the star has not been quite its old self for the reason that Great Dimming. Its 400-day brightness oscillation period has halved to 200 days and, on top of that, the star now appears to be going through the additional brightening that excites skywatchers. The astronomers that Space.com spoke to, nevertheless, are tempering the supernova expectations.
“Our greatest models indicate that Betelgeuse is within the stage when it’s burning helium to carbon and oxygen in its core,” Morgan MacLeod, a postdoctoral fellow in theoretical astrophysics at Harvard University and lead creator of a recent study about Betelgeuse’s Great Dimming, told Space.com. “Which means it’s still tens of 1000’s or perhaps 100 thousand years from exploding, if those models are correct.”
While a star’s regular life ends when it runs out of hydrogen and begins to fuse helium in its core, its expanded life as a red giant lasts beyond the helium-burning stage, explained MacLeod. With helium gone, the star will sustain itself by burning carbon and oxygen into neon and magnesium, then burning those into silicon. Eventually, the star’s core fills with iron. And that is when the fireworks begin.
“Adding helium nuclei to an iron atom actually extracts energy somewhat than gives off energy,” said MacLeod. “So rapidly, somewhat than a response which is releasing tremendous amounts of energy, the middle of the star starts to soak up energy. And when that change happens, the middle of the star collapses on itself type of from the within out, after which that results in what we call the core-collapse supernova.”
The timescale of stellar death
While the hydrogen-burning phase of a star’s life can last billions of years, each subsequent phase is shorter and shorter.
“The helium-burning phase is several hundred thousand years long,” Miguel Montargès, an astronomer on the Laboratory of Space Studies and Instrumentation in Astrophysics on the Paris Observatory and one in all Europe’s leading experts on Betelgeuse, told Space.com.
“Then you might have the subsequent phase that lasts like 10,000 years, then 1000’s of years, after which it is a century, and the ultimate one is simply some days and hours just before the explosion.”
Like MacLeod, Montargès thinks that Betelgeuse still has many 1000’s of years of life ahead of it and is somewhat unconcerned by the recent unexpected brightening. Actually, the star has been this vivid previously, he said, albeit just for temporary periods of time.
“If we compare the present brightening to the Great Dimming, it’s really quite negligible,” Montargès said. “In the course of the Great Dimming, the magnitude [a measure of a star’s brightness that is logarithmic and inversely proportional to the visible brightness] went from 0.8 all the way down to 1.75. The same old peak brightness, however, is about 0.3, and now we’re only at about 0.1.”
Back to normal
Within the paper, posted on the net repository Arxiv on May 16, MacLeod and his colleagues, somewhat than expecting a supernova, predict that Betelgeuse will return inside the subsequent five to 10 years to its usual ways, slowing its cycle of brightening and dimming to the conventional 400 days.
“We expect the change within the cycle duration is linked to the event that caused the Great Dimming,” MacLeod said. “We expect that the large bubble that burst from the star’s interior before the dimming caused the star’s envelope and its interior to maneuver in opposite directions, and, in consequence, the star is now pulsating twice as fast in comparison with its normal cycle.”
Betelgeuse is an infinite star. If we were to position it at the middle of our solar system, it will extend all of the strategy to Jupiter. The star’s size, combined with its position in our galaxy, the Milky Way, allows astronomers to check Betelgeuse in higher detail than most stars.
“Most stars apart from our sun can’t be studied in any detail in any respect,” MacLeod said. “We see them only as point sources of sunshine. But Betelgeuse is sufficiently big that we are able to resolve it with the Hubble Space Telescope and with radio telescopes.”
Those images reveal a striking body quite unlike our sun. Relatively than a single smooth sphere of superhot plasma, Betelgeuse is a lumpy clump of boiling gas bubbles, a few of them as large as a small star. Huge plumes of hot material rise from Betelgeuse’s core to its surface, then cool down and disappear back contained in the interior. It’s just like the sun’s cycle on very high doses of steroids. Once every few centuries, Betelgeuse burps out a bubble so large that a Great Dimming ensues. But all that does not imply the star is about to blow up. Unless, in fact, the astronomers’ assumptions are unsuitable.
If Betelgeuse were about to go supernova, would we all know?
Because of the skills of our greatest telescopes, astronomers can see what’s happening in Betelgeuse’s outer layers so well that they will measure the chemical composition of the star’s atmosphere. They, nevertheless, don’t have any way of knowing what is admittedly occurring contained in the star’s core. Is it really burning helium? Or has it switched to fusing carbon already? And if it did so, how would we all know?
Montargès said that loads of our assumptions about Betelgeuse come from our observations of other red giant stars. For instance, one other Milky Way red giant often known as VY CMa, situated 3,900 light-years away from Earth within the constellation Canis, is considered much closer to the moment of its death than Betegeuse. But unlike the brightening Betelgeuse, that star has been consistently dimming over the past 100 years.
“100 years ago, VY CMa was once visible to the naked eye,” said Montargès. “However it has expelled a lot material that we are able to now only see it in infrared. This expelling of fabric is what we expect to see when the star nears the supernova explosion. VY CMa has already removed about 60% of its original mass, while Betelgeuse still has 95% of its initial material.”
The astronomer added that, in response to historical records, Betelgeuse was once described as a yellow star up until 2,000 years ago, when poets began describing it as red. That, Montargès thinks, might indicate that Betelgeuse is simply within the earliest stages of its life as a red giant.
Second sun
But Montargès understands the joy about Betelgeuse’s possible death. When the star ultimately explodes, it is going to make front-page news for months.
“When it happens, the star will turn out to be as vivid as the complete moon, except that it is going to be concentrated in a single point,” Montargès said. “For perhaps two months, it is going to be so vivid that when you shut down all of the lights in a city and don’t have any clouds, you’d give you the option to read a book in the sunshine of the supernova. It’s going to be so vivid that it is going to be visible within the daylight, too. There might be one other star shining within the sky through the day.”
Fortunately, although close enough to offer such a spectacle, Betelgeuse is simply too distant from Earth for its explosion to be dangerous to us. Astronomers think that a large star would must blow up inside 160 light-years from our planet for us to feel the explosion’s effect, in response to EarthSky.
The last known supernova to have exploded within the Milky Way galaxy was SN 1604, also often known as the Kepler supernova. It was named after astronomer Johannes Kepler, who described it in his book “De Stella Nova.”
In line with historical records, that supernova, 30 times more distant from Earth than Betelgeuse, remained visible through the day for over three weeks.
Montargès expects Betelgeuse to soon return to inside its limits. For the subsequent few months, the star won’t be visible, as it is going to get too near the sun. Astronomers may have to attend until the top of the summer to envision on its progress.
“If in September it’s still as vivid as now, or brighter, then we should always start wondering what’s happening,” said Montargès. “But from my perspective, I do not think it’s that interesting at this stage.”