Science News checks back on the big star that suddenly went dim (as regular readers here will remember) a couple of months ago, prompting some speculation that we were about to see a massive explosion. Well, they’ve got a clearer idea of what’s making the red giant go dim – and it might just be a big cloud of dust:
“I think some people wanted this to be seen as the death throes of the star, and it’s very much not,” says astrophysicist Emily Levesque of the University of Washington in Seattle.
When people think about stars that are visible in our sky that could explode soon, Betelgeuse is near the top of the list,” she says. “So when people said this star is doing something weird, it caught people’s attention.”
Levesque and astronomer Philip Massey of the Lowell Observatory in Flagstaff, Ariz., decided to investigate more mundane possibilities than an imminent supernova that could explain the dimming.
The pair observed the star on February 14 — when it was nearly at its dimmest — looking for signs of titanium oxide molecules in the star’s outer layers, a clue to its temperature. Comparing those observations with similar ones that Levesque had taken in 2004 showed that the temperature had dropped by about a measly 50 degrees Celsius.
“To our surprise, Betelgeuse didn’t look that different,” Levesque says. “The temperature couldn’t explain how much dimmer Betelgeuse had gotten in the last few months.”
That leaves the dust explanation, the scientists report in a study to appear in the Astrophysical Journal Letters. “It’s partly process of elimination,” Levesque says. Red supergiants like Betelgeuse are known to puff out clouds of gas which condense into dust. And the star did dim uniformly over all wavelengths of light that Levesque and Massey measured, which supports the idea that dust from the star is to blame. By contrast, dust that lies in the spaces between stars would block certain wavelengths of light more than others.
You can read their research here.