A Supernova in our backyard

A supernova is the most spectacular way in which a star ends its life cycle; and there is a possibility that we can witnessing this phenomenon, since it is possible that this happens to a nearby star.

If you look up at the sky one of the most notorious constellations we can see in a starry night is Orion, with its distinctive set of three aligned stars forming Orion’s belt in the middle, and four bright stars around these. This constellation is practically above us, visible in the early night during the winter months of the year (in the northern hemisphere); it is definitely hard to miss.

The distinctive stars in Orion’s belt are Alnitak, Alnilam y Mintaka, and the four bright stars are Saiph, Rigel, a blue super giant, Bellatrix and finally Betelgeuse, another giant star, a red giant.


Orion (Astronomytrek.com)


But let’s focus now on Betelgeuse; this star, located in the upper left corner of the Orion constellation is a star at a distance of 640 light years from earth of and a radius that’s around 1,000 times bigger than our Sun. To make a comparison, if we had Betelgeuse instead of our Sun, its surface would be beyond Saturn’s orbit.

This star is particularly interesting as it is predicted that its life will end in a very spectacular way; as a supernova explosion. This is not common for all stars; it is a distinction that’s reserved for super giant stars, as Betelgeuse, or even as the mentioned Rigel. These stars are so massive than once the nuclear furnace that keep them alive start to wind up, after exhausting all the light elements it fusions; suddenly due the lack of “fuel material” start to loss the battle versus gravity which start to crush it, until the it reaches a point where internal pressure becomes so intense that it suddenly explodes with a great intensity that practically destroys it.
This is possible due the high mass these stars have, and is an essential process for life, since these explosions are the ones that generates most of the chemical compounds from which it is formed.

But going back to the subject; Betelgeuse, being a massive red giant, through observations and studies has been predicted that it is in its final life stages, given the studies of scientist that monitor its behavior. First it is releasing a huge amount of gaseous matter that’s forming a sort of “halo” around the star. Another phenomenon observed in it is that it is “pulsating” as it periodically, reduces and increases its diameter, with a variation of as much as fifteen percent; as its temperature decreases and again increases. Another deduction made by scientists observing it is the presence of a big protuberance in this star’s surface, noticed first by scientist in Japan and also visible in the best picture taken from this star by the “Atacama Large Millimeter/sub-millimeter Array” (ALMA) radio telescope in the Atacama desert in Chile.

ALMA's Betelgeuse photo

ALMA’s Betelgeuse photo (www.eso.org)

On the odds that we witness Betelgeuse becoming a supernova, well these aren’t that great, but is predicted it will become supernova in the coming hundred thousand years, so… You better be patient on this one; yet still, there’s a small possibility of seeing Betelgeuse becoming a supernova, this can’t be totally discarded.

Given its distance from Earth, it is considered that it doesn’t poses a threat to us, but if this phenomenon happens, we will be up for a cosmic treat, as this star will become so bright that it will be visible even during the day, and will stay like this for several weeks, before its glow changes from bluish-white to reddish, staying like this for three to four years until it finally it fade out … And disappear from our sight forever.

Cosmic neighbors

But this distinction of being a potential supernova is not exclusive to Betelgeuse, there are a few other stars that are in the same situation, some of them even closer to us. Antares, a red super giant, is in a similar situation, and at a distance of 550 light years. Also Alpha Lupi, located at 460 light years; and Spica a binary system, with two stars very close to each other, having the biggest star a radius 7 times that of our Sun, and the minor star with a radius 3 times greater than the Sun; and at a distance of 250 light years.

Finally, IK Pegasi another binary system, considered to be a candidate to become a type I-a supernova, the most intense of these (as the supernovae used to measure cosmic distances), at a distance of 150 light years from us, IK Pegasi-a has a a radius of 1.6 times greater that our Sun, and IK Pegasi-b is a white dwarf is a star that’s very small and it’s very close to its sister star. As a comparison, this dwarf star it’s closer to IK Pegasi-a, than what Mercury is from our Sun.

IK Pegasi, White Dwarf & the Sun compared

IK Pegasi, White Dwarf & the Sun compared (wikipedia.org)

So, as you can see, there are some options to have a supernova in our proximity aside of Betelgeuse.

The distances to these stars are less than the distance from Betelgeuse; so, the question still stand, are we safe? Well the major threat of a close supernova explosion is the exposure to hi energy X and Gamma rays, which can drastically alter life on earth as these can damage the atmosphere’s ozone layer, potentially killing  all the plankton in oceans, and of course damaging live beings, including us humans.

But fear not my friends, It is estimated that a supernova at a distance of 50 to to 100 light years is fairly safe for Earth, so in most cases it seems we will dodge the danger a supernova might pose, at least for those of known candidate stars; so if this happens, just enjoy the show, it definitely will be awesome!

Regards, Alex; Sciencekindle.

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