Tuesday, August 18, 2009

A Sky Without Betelgeuse?

Betelgeuse
Orion's premier red supergiant was the first star ever to have its diameter measured by interferometry, and the first to be directly imaged as a disk, by the Hubble in 1996. Only a handful of extrasolar stars can be thus observed, Betelgeuse and Antares among them. This image of Betelgeuse is a new one, reported in Sky & Telescope a couple of weeks ago. (Yes, I'm playing catch-up here.)

Betelgeuse's stellar stats are widely available but always worth repeating. At 640 light years away it is one of the nearer supergiants, with a total luminosity (mostly in the IR) about 100,000 times brighter than the Sun. The measured diameter depends on the wavelength you use - the star probably has no sharply defined surface - but comes to about 900 solar diameters, comparable to the size of the asteroid belt.

And astronomically speaking, it is not long for our sky. An artist's conception shows it boiling ominously, with bubbles the size of the orbit of Mars. Betelgeuse is blowing off an Earth mass or so every year, and - also rather ominous - its diameter seems to have decreased about 15 percent in the last 15 years.

In fact, Betelgeuse is in a pre-supernova state ... but just how pre-? I initially misread one of the researchers' linked press releases, saying that it expected to blow 'in the next few thousand to hundred thousand years' as 'in the next thousand years.' It sort of jolted me. But even the correct statement amounts, in astrophysical terms, to any time now.

Whenever Betelgeuse goes off, it will be hard to miss. No supernova has been observed in the Milky Way since 1604, and the brightest recorded one, in the year 1004, was of a star 7100 light years away - more then 10 times the distance to Betelgeuse. The supernova of 1054, that formed the Crab Nebula, was 4000 light years away. The Geminga supernova was only some 550 light years away, but it went off 300,000 years ago.

So the Betelgeuse supernova will be at least dozens of times brighter than any observed in the historical era, perhaps a hundred times brighter, nearly as bright as a full moon. Wow!

Yet afterwards, as the first commenter on the Sky & Telescope article noted, it will be rather strange not to have the familiar figure of noble Orion in the sky anymore. It is the first constellation I ever recognized, and because at the start of each season I see it rising in the southeast, on its side, I think of its figure as representing not a giant but an exotic stringed instrument, its strings running from Betelgeuse to Rigel, with the Belt stars as pegs on the soundboard. Without Betelgeuse the instrument's symmetry will be broken, the music of the spheres altered.

But if you gotta go, what a spectacular exit!


Related links: I previously wrote about the pleasures of both sky observing and, more recently, armchair astronomy.

10 comments:

Jean Remy said...

Back when I lived in France my family had an estate in the alps. It is rather too grand term a for a two story stone house impossible to heat in winter and whose most advanced amenity was a black-and-white TV, but to me it was an estate.

Most valuable to me as an amateur astronomer was its remoteness, a sky unblemished by the lights of civilization. Armed with a small refraction telescope and star charts I would spend hours trying to catch a glimpse at some fuzzy images, or, more often, I would just lie in the grass and learn to recognize constellations and individual stars. Of those, Orion was always my favorite, as was Betelgeuse.

I can't quite picture a sky without its Betelgeuse anchor. Is it odd to feel melancholy for something that will not go missing in my lifetime? Is it odd to feel sorry for those future generations of amateur astronomers and star gazers, looking up at the sky, and them not seeing her?

Although, there might be a fairly spectacular nebula left behind, and the supernova itself will be impressive, so I am now caught between melancholy and jealousy for those who will see it.

Kedamono said...

I grew up in the town of Lake Orion Michigan. (Pronounced or-REE-on, not or-RYE-on). I took special pride as a kid that there was a constellation in the heavens with the same name as my home town.

I never knew how to pronounce Betelgeuse, and used to call it "Bet-el-geese". It wasn't until later that did I learn how to pronounce it correctly. (No, not That movie. Uncle Ike Asimov)

I even worked up a story where a scientist tries to ignite Betelgeuse into a nova, just prove a theory of his. Still might make a good movie.

For all we know, it's gone nova now and we won't see the results for another 640 years.

Rick said...

Jean - I have precisely the same mixed feelings, as did the commenter at S&T. We haven't had a real supernova show in 400 years, but there's something about losing a familiar celestial landmark and friend.

The best candidate for a supernova spectacle in our lifetimes is probably Eta Carinae, which is already in a very violent state, and underwent a 'supernova imposter' event in 1843.


Kedamono - Now I'm curious about how Lake Orion got its pronunciation. And for that matter its name. There must be a lot of star names we don't pronounce 'correctly,' since we're so much more likely to know them from reading, not hearing the name said.

Carla said...

Mixed feelings indeed. But I think you sum it up neatly: if you have to go, what a spectacular way to do it!

Kedamono said...

@Rick

There's a story behind that and you're not too far off as to the origin of how Lake Orion got it's pronunciation:

"Char-LOTT": Charlotte, a Michigan village close to Lansing. Related: Durand, MI, pronounced "DUrand", Saline, pronounced "SuhLEEN", its neighbor "MYlun" (spelled Milan), and of course, Lake Orion, pronounced "OReeyun." This phenomenon is what happens when townsfolk in the 1800's weren't quite sure how to pronounce "all them fancy French" town names, and is actually much more prevalent throughout Ohio (e.g., Delhi, OH, pronounced "Dell-High"; Lancaster, OH, pronounced "LANKster"; Marseilles, OH, pronounced "MarSAYLES", and my favorite, Bellefontaine, amazingly pronounced... "Bell Fountain"! Ohio Public Schools is all I'm sayin'...)

From the Michigan Accent "pronounceation" page.

Anonymous said...

Worchester.

Don't think of Betelgeuse the nebula as a consolation prize. Think of Betelgeuse the star as a prelude.

Ian_M

Anonymous said...

I'm just wondering what kind of effects the Supernova of Betelgeuse would cause on Earth? Would it screw up our communications/power production/other tech or would it 'merely' be the most spectacular sight in the sky in Human history?

Ferrell

Rick said...

Carla - the Anglo-Saxons would appreciate that perspective!

Kedamono - thanks for the link! Apparently greater communication and travel are not causing the blurring of local accents, as commonly assumed. Alas I have no handy link, but I've heard/read this repeatedly in linguistics circles.

Ian - Think of Betelgeuse the star as a prelude. Nice one!

No conspicuous star seems to have blown in the historical era, since none seem to be 'lost.' There is a tradition of a 'lost Pleiad,' probably Plione, not now readily visible to most people, but nothing in the Pleiades has blown up.

Ferrell - Good question! I've read some fairly lurid descriptions of how nearby supernovae could wipe out most of the world's integrated circuits, but I don't know whether Betelgeuse is close enough for that. I'll make a sheer guess that the disruption might be comparable to a major solar storm.

A.J. Stoner said...

I have mixed feelings about this. One the one hand, it would be a spectacular show and a great thing to see in one’s meager little time on earth. On the other, I have used Betelgeuse going supernova in a story I’ve just sold, set a thousand years in the future, and if it were to go off while I’m still alive I would feel more than a little foolish.

Rick said...

AJ - On the other hand, a missed prediction in a short story is a small price to pay for the sky show of the millennium!

By the way, I've been meaning to email you to note that your link for the original Tough Guide should be updated. It is now:

http://rocketpunk-observatory.com/spaceguide.htm