Feb 2018

Supernova Betelgeuse?


Keep an Eye on Betelgeuse
by John Hlynialuk

Next to the Big Bang that started the whole shebang, the most energetic event in the universe is a stellar explosion called a supernova. The most colossal of the several types of supernovas involve giant stars, so the explosion (a Type II supernova) is even more awesome than it might be otherwise. The amount of energy released is totally unimaginable, -in a month or so the equivalent of all the energy released during the entire lifetime of our Sun! It is just another way that the Universe can kill us. (Spoiler alert: we are far enough away from any star that could go boom and our Sun is a pretty ordinary star not prone to explode.)


betelgeuse_star
Betelgeuse is one of a few stars big enough to show a disk to Earth-based telescopes
(the big ones anyway)
Betelgeuse imaged in ultraviolet light by the Hubble Space Telescope and subsequently enhanced by NASA.
The bright white spot is likely one of this star’s poles. Image via NASA/ESA.


When a really massive star goes supernova, for a time it can outshine its entire home galaxy of several billion stars and be seen from billions of light years away. Astronomers detect over a hundred supernova per year on average from the billions of galaxies that exist outside our own Milky Way. Within our home galaxy, we see only one or two per century but there would be some hidden on the other side of the dusty central area, so there is no way to give an accurate estimate, -one every 50 years is a lower limit.

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This a composite color image of the Herschel PACS 70, 100, 160 micron-wavelength images of Betelgeuse.
Credit: ESA/Herschel/PACS/L. Decin et a


Planets orbiting these exploding stars and even objects within about 50 light years of the supernova can be “affected” (meaning destroyed) by the explosion. The intense shock wave and extremely energetic pulse of X-rays can disrupt neighbouring stars and strip off the atmospheres of planets around them or just plainly vaporize them if they are too close. Luckily for us there are no supernova candidate stars close enough to our solar system, so death by supernova is less likely than death by comet or asteroid and even those odds are smaller than death by car accident. There is very good evidence that dinosaurs and many other species on Earth were snuffed out by a comet about 65 million years ago, so these are the time scales we are talking about, long by human lifetime standards, but pretty short in the 13.5 billion year lifetime of our universe.

Thankfully, there are no pre-supernova stars within the 50 light-year distance from Earth, but go farther afield, about 10 times farther and we find one very likely candidate for a spectacular explosion, the star Betelgeuse in the constellation Orion. It may happen a million years from now or perhaps tomorrow, astronomers have statistics, but no specific dates. But they are pretty certain that it will go off before a million years go by.

The star Betelgeuse (pronounced “beetle juice” ) is easy to find in the evening sky in February and later in the spring as well. Orion, the Hunter, as a constellation is recognizable by his Belt, a line of three evenly spaced, equally bright stars in the centre of a rectangle of similarly bright stars. Betelgeuse is the one in the upper left corner and has a slightly reddish tinge associated with its red giant status. Compare it to the star Rigel at the lower right corner which is a little whiter, even a bit blue. The diagrams below from Sky Safari 5 show Orion as it would appear above the southeastern horizon at 7 pm EST presently and then at some point in the future with SN Betelgeuse.

Orion Feb pm

Sky Safari 5 Orion as it appears now (above) and with SN Betelgeuse (below)

SN-Betelgeuse-simSS5


Should Betelgeuse explode “tomorrow” keep in mind that the event actually happened over 400 years ago (the current best guess for distance to Betelgeuse is 430 light years) since the light from the supernova would have had to travel from the star to us. Rest assured that we are at a safe distance regardless.

Still, it would be a pretty spectacular sight! Betelgeuse the supernova, shining at its peak would, for several weeks or even months, be the brightest object in the night sky, -perhaps as bright as the full Moon, and visible even in the daytime. Astronomers, both professional and amateur are especially excited about a Betelgeuse supernova since we would have a ring-side seat at the most spectacular phenomenon in the universe! Thank goodness we are far enough away to safely watch the show!