What's Up With Betelgeuse?

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Is it about to esplode?


Betelgeuse Looks Fainter Than Usual. Could It Mean It's About to Go Supernova?

Have you noticed that Orion the Hunter – one of the most iconic and familiar of the wintertime constellations – is looking a little… different as of late? The culprit is its upper shoulder star Alpha Orionis, aka Betelgeuse, which is looking markedly faint, the faintest it has been for the 21st century.

When will this nearby supernova candidate pop, and what would it look like if it did?

The story starts, as all good astronomy and space stories seem to, on Friday night going into a holiday weekend.

We started seeing discussion on Betelgeuse trending on social media on the evening of Friday, December 20th, and dug down to the source of the excitement: a December 8th paper on "The Fainting of the Nearby Red Supergiant Betelgeuse" by researchers at Villanova University.

Light curve estimates courtesy of the American Association of Variable Star Observers (AAVSO) verified the assertion that the star had indeed faded about one magnitude, or a little over one half from its usual magnitude +0.5 to +1.5.

Noticing the sky was clear, we headed up to our parking garage rooftop observing site in downtown Norfolk, Virginia to take a look. Betelgeuse was indeed noticeably fainter, about a shade dimmer than nearby +1st magnitude Aldebaran.

Now, a change in one magnitude isn't unusual for a variable star such as Betelgeuse… but such a large dip always gives the astronomical community pause.

A red giant star 12 times as massive as our Sun and about 700 light years distant, the variability of red-orange Betelgeuse was first noted by astronomer Sir John Herschel in 1836.

Physically, the star is currently bloated out to a radius of perhaps eight Astronomical Units (AU). If you plopped it down in the center of our Solar System, Betelgeuse might extend all the way out to past the orbit of Jupiter....

Betelgeuse is always worth keeping an eye on, as it's one of the closest candidates in our galaxy for a nearby supernova.

We see supernovae frequently in distant galaxies, but such an event has not been witnessed in our galaxy in the telescopic era: Kepler's Star in 1604 in the constellation Ophiuchus was the last supernova observed in the Milky Way, though a supernova in the nearby Large Magellanic Cloud put on a good show in 1987.

A red giant like Betelgeuse lives fast and dies young, exhausting its supply of hydrogen fuel in just under 10 million years. The star is destined to undergo a core implosion and massive collapse and rebound as a Type II supernova.

Such an explosion could occur 100,000 years from now… or tonight.

https://www.sciencealert.com/betelgeuse ... out-to-pop

Beetlejuice! Beetlejuice! Beetlejuice!

There! It’s out of my system.

Very interesting. I haven't really looked at Betelgeuse this season. Then again where I live I don't see the stars too often this time of year. But I shall look and ponder the next clear and frosty night. And no worries I said eciujelteeb! eciujelteeb! eciujelteeb! as a counter measure.

"soon" by celestial standards is...a very long time
not freaked out here

Don't be a denier!

Interesting, Darmok. Thanks for posting. I was just out looking at Betelgeuse.

Now that I want to do some star gazing the sky will probably remain overcast until Orion goes out of season.

I thought it was looking oddly dimmer the last few months, but there are so many more interesting objects to observe that I never really thought too much about it.

If you want to know the real technical story:


Updates on the "Fainting" of Betelgeuse

ATel #13365; Edward F. Guinan, Richard J. Wasatonic (Villanova University) and Thomas J. Calderwood (AAVSO)
on 23 Dec 2019; 20:24 UT

As reported earlier in ATel #13341, the luminous red supergiant (a core-collapse SN II progenitor) Betelgeuse (alpha Ori) has become unusually faint with a V ~+1.125 mag (measured on 2019 December 07.25 UT). Since that report Betelgeuse has continued to decrease further in brightness. The most recent measurements made on 2019 December 19.3 UT, 20.2 UT and 22.25 UT are V = +1.273, +1.294 and +1.286 mag, respectively. This appears to be the faintest the star has been measured since photoelectric observations have been carried out of the star. However, photoelectric photometry carried out during late-1926 / early-1927 by Joel Stebbins (1931: Pub. Washburn Obs., 15, 177) indicates that Betelgeuse declined to V’ ~+1.25 mag. At its average maximum brightness light (V ~ 0.3 - 0.4 mag), Betelgeuse is the 6 - 7th brightest star. But by 2019 mid-December the star has slipped to the ~21st brightest star. The red supergiant is now closer in brightness to Bellatrix (V =+1.64 mag) than to Rigel (V =+0.13 mag). Wing three-band Near-IR and TiO photometry carried out at Wasatonic Observatory shows that Betelgeuse is also cooler with an inferred spectral-type near ~M3.5 Iab (Teff ~ 3,545 K from TiO-photometry). This is about 150 K cooler than measured near maximum light. Analysis of the last 25-yrs of V-band and Wing TiO and Near-IR photometry shows a dominant ~425+/-10 day period as well as a long-term ~5.9+/-0.5 year period. The current faintness of Betelgeuse appears to arise from the coincidence of the star being near the minimum light of the ~5.9-yr light-cycle as well as near, the deeper than usual, minimum of the ~425-d period. We plan to continue to monitor the star. If the star continues to follow above periods, light minimum should occur soon. But this needs to be checked. This continues to be an opportune time to carry out complementary measures of Betelgeuse while it is in its current low state and is unusually cool and faint.


http://www.astronomerstelegram.org/?read=13365

The opportunity to study a red supergiant up close, one that's about to go supernova relatively soon (at least, on astronomical timescales), has never occurred like this before. At only 640 light-years distant, Betelgeuse could have gone supernova at any time since the 14th century and that signal would not yet have arrived here on Earth.

When that supernova does occur, however, we're in for a real treat. The runaway fusion reaction that occurs in the final few instants of the star's life will generate neutrinos that should lead to millions of detectable events here our terrestrial neutrino detectors. The star will brighten to the point where it will rival or possibly even exceed the brightness of the full Moon, casting brilliant shadows at night and being clearly visible during the day for more than a year.

Is Betelgeuse About To Explode?

So even before the star brightens, the first event will be a burst of neutrinos. Neutrinos are so small that they will normally pass through matter, which in this case is the shell of matter encasing an exploding star. This will trigger many astronomers to search for the source. Then several hours later, the supernova will become self-evident.

It will grow and maybe even rival the brightness of the sun. Probably what happens next will depend on the spin axis of Betelgeuse. If Earth lies along the spin axis then we might experience a gamma ray burst (GRB). But if Earth lies perpendicular to the spin axis, then we might experience a surge of very high energy particle (protons, ions) with relativistic speeds. Some scientist have made observations of the spin axis and it is offset. So if that is an accurate assessment, this supernova will be just an interesting visual anomaly for a year or two.

I've decided to take the stance of being as a Betelgeuse denier. It is not going supernova. That's just a lot of fear mongering to boost telescope sales.