In the wake of the recent fluctuations in the brightness of the Betelgeuse, astronomers scrutinized the star’s stellar statistics, and found little surprise.
According to a team led by researchers at the Australian National University (ANU), the results have changed some important things about our favorite red giant.
“The actual size of the physical Betelgeuse has become a mystery – previous studies have suggested that it may be larger than Jupiter’s orbit,” says astronomer László Molnár from the Konkoly Observatory in Hungary.
“Our results say that Betelgeuse only reaches two-thirds of it, with a radius of 750 times the radius of the Sun.”;
Betelgeuse is always a bit difficult to map accurately. Forget the picture book in the star book, which rotates smoothly as a fairly smooth sphere, and picture something more like a pulbating blob with blurry edges.
In 1920, patterns of interference with its light waves were used to produce an angular diameter – the width of the starlight of the Betelgeuse while hanging in our sky – close to 47 milliarcseconds.
Based on an estimated distance of about 180 light years, the red star was previously thought to have a diameter equal to about two and a half times the distance between Earth and the Sun.
Since then there have been many other attempts to drag a metaphorical tape measure around Betelgeuse’s buttocks.
Revisions of its location over the past few years have pushed it back to a distance of 724 light years away, where those 47 milliarcseconds represent something more than 1,300 times the width of the Sun; a diameter that can see Betelgeuse swallowing almost any planet in the orbit of Jupiter.
Such figures, including many stabs to its general mass, paint a picture of a supergiant star approaching a stage in its life when it is theoretically collapsed and exploded into a shining ball of wonder -exciting eye sight.
The unexpected dimming of the star’s radiance in recent years still gets excited whispers if it is a kind of Betelgeuse death, making us all stars in a bad mood in the bed of a rich aunt at the hospital.
It is now believed that dust clouds are responsible for at least one of the events. And another, it seems, shows how healthy our old Aunt Betelgeuse is.
“We found the second smaller event was probably due to star pulsations,” said ANU astrophysicist Meridith Joyce, who led the study.
Pulses as observed at Betelgeuse are usually the result of pressure drops flowing through the burning courtyard of a star. Our own Sun has waves moving all over its body, saying a lot about its beauty inside.
Using the information collected in the space-based Solar Mass Ejection Imager before Betelgeuse’s radiance, the research team developed stellar activity models to produce a better sense of how close retirement really is.
“It’s burning helium in its core right now, which means it’s nowhere near exploding,” Joyce says.
“We can look around 100,000 years before an explosion occurs.”
The results also allow researchers to reduce the radius of the giant, shaving a third from the previous girth. Based on this new figure, Betelgeuse could not be more than 700 light years away, either.
“Our results show that this is only a 530 light year from us – 25 percent closer than previously thought,” Molnár said.
See, we are all a bit disappointed. Four centuries have passed since a supernova was spotted by the naked eye, and we think we owe a decent burial star.
Now that we know that the Betelgeuse is closer to us than we thought, it is sure to be a heck of a display when it eventually collapses. If you are worried about the new seating arrangements, in 530 light years we are still not close to feeling the heat of its radiation.
For any pass for a scientist in 100,000 CE, these row seats would certainly be a coincidence.
“It’s still a big deal when a supernova dies. And this is our closest candidate. It gives us a rare opportunity to study what happens to stars like this before they explode,” Joyce said.
This research was published in The Astrophysical Journal.