Friday, February 3, 2012

Life, the Universe and Everything

Used to be that the discovery of a new planet orbiting another star, an exoplanet, was cause for a large press event announcing it and excitement among the scientific community and the public alike.

Now it’s more like the Apollo 13 mission before the accident, hardly anyone watches or cares, it is so common.  As of February 1, 2012, there are 755 confirmed exoplanets and many hundreds more potential candidates that await confirmation.  As one astronomer put it, “The more we look, the more we find.”  In fact, we now estimate that there are, on average, 1.6 planets for every star in the Milky Way galaxy.  That comes out to more than 200,000,000,000 planets, just in our galaxy alone, not to mention all those other galaxies far, far away.

Now, astronomers have discovered the exoplanet most likely to be able to support life.  It’s a bit bigger than our Earth, at 4.5 times our planet’s mass, what astronomers term a “super-Earth.”  But it is located in the habitable zone of its star, the narrow range of orbits where temperatures support liquid water, an essential requirement for life as we know.  One interesting aspect about this planet designated, GJ 667Cc – aside from the possibility that it can support life – is that its parent star is actually part of a triple-star system.  The other two are so far away that they add little energy to this planet, but would make for pretty interesting sunrises, sunsets and eclipses.

The parent star, GJ 667C, located in the constellation Scorpius, sits a mere 22 light years from Earth and can be seen in a modest telescope.  Not quite our next door neighbor, but on the same block as us.  GJ 667C is an M-class dwarf star, about a third the mass of the sun and therefore quite a bit fainter.  But the planet is in a 28-day orbit, meaning it is close enough to this dim star to be in its habitable zone.

Astronomers believed that planets can only form around stars that have a chemical makeup not too dissimilar to our sun.  About 98% of our sun is hydrogen and helium but that remaining 2%, comprised of all the other elements, is enough to make dense, rocky planets like Earth. Astronomers believed that stars with a lower metal content couldn’t make dense planets, only gas or ice giants like Jupiter, Saturn Uranus and Neptune.  In stellar astrophysical parlance, “metals” refers to all elements farther up the periodic table than helium.  GJ 667C has a much lower metal content than our sun.

All that means is that, once again, we humans have been too narrowly focused what conditions are necessary for life to flourish.  Life will find a way. 

And now we have a whole lot more places to look for life.  Is that good, or bad?  Who knows, but it is exciting!

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