[Author’s Note:  This article is in error. I somehow misread the information provided in the Astronomer’s Telegram post stating that the star was decreasing in size. I discovered the error a few days after I posted the article. Since the premise of the article is incorrect, the entire article can be disregarded. Rather than delete the article, I am posting this announcement and leaving the original article intact. I apologize for any confusion or misunderstanding this article may have caused.]

Betelgeuse Collapsing? Think Again

The buzz about Betelgeuse is about its sudden and historic fainting (dimming.) Those who have a knowledge of the star and of supernovas have received the news with anticipation. Is this the great moment of Betelgeuse going supernova? Many people already know that immediately before the supernova, the progenitor star (the original star before a supernova) collapses in on itself. Betelgeuse is dramatically dimming, so it must be collapsing. Not true. Betelgeuse is expanding.

Dimming and Expanding Betelgeuse on 22 January 2020

Expanding Betelgeuse

Betelgeuse is dimming, but it is also cooling. Down approximately 100°K (180°F) in the past four months. This is an issue of physics. Temperature increases with increased pressure and the temperature decreases as the pressure decreases. The collapsing mass of a star increases pressure and temperature [¹SEE:  Primer on Combined and Ideal Gas Laws below.] The expansion of a star would cause a decrease in temperature. Betelgeuse temperature is decreasing, therefore astronomers believe it is expanding, not collapsing.

…Betelgeuse is currently the coolest and least luminous yet observed. Since September 2019, the star’s temperature has decreased by ~100 K while its luminosity (inferred from the C-band/m-bol observations) has diminished by nearly 25%.

Edward F. Guinan and Richard J. Wasatonic
Posted in The Astronomer’s Telegram 20 January 2020

No Joy On A Neighborhood Supernova?

Does this mean that Betelgeuse is not about to go supernova? Nobody knows. This could be the last big push outward before the finale we’ve been anticipating. It could also be another step toward the end but not the last gasp of Betelgeuse.

Betelgeuse in the Orion constellation

It is unusual behavior and worthy of constant monitoring. This may be one part of the process that will help us understand the last days, weeks, months, and years of a supergiant red star. Stars don’t suddenly brighten or dim without reason and now we have the opportunity to discover something new and visibly intriguing about the process of a star’s death.

What’s happening? Something wonderful.

[¹Primer on Combined and Ideal Gas Laws ].]