"Another Great Day for Exoplanets"

Say, hypothetically, you want to find life in the universe - you want to try to answer that question we've all wondered about. Great, so what are your options? The way I see it, you've got three options, and by "you" I mean you and millions of dollars of funding.

Perhaps the easiest way is to look at stuff that has come directly from space (meteorites), and if they harbor (uncontaminated) life, then it seems pretty likely that there's life out there, shooting around outer space.


Unfortunately, despite thousands of meteorite samples, that hasn't happened yet, so we're on to the next choice: visiting other worlds and checking them out from the surface. So far, we've only done this on Mars, where we have high resolution cameras, spectrometers, drills, and several other fancy gadgets that allow us to study the planet's prospects for life from the comfort of a desk chair.


But perhaps the future lies in option number 3: remote sensing - pointing spectrometers at far away places and determining what's there based on the energies of light that is being emitted. Our telescopes aren't powerful enough to determine exactly what's there, crawling around on the surface, but a planet's bulk surface characteristics have a way of betraying its inhabitants: certain types of molecules found on a global scale can point strongly to the existence of life.

Oxygen, for example. It didn't exist on Earth before organisms started producing it, and now it's a whopping 21% of our entire atmosphere. Water is another key ingredient - without it, life as we know it is impossible. Methane is often produced biologically, though it can be a product of volcanoes as well. Chlorophyll would be particularly convincing - it is a pretty complex molecule produced only by living things.

Ok, finally getting to the inspiration for today's post. Astronomers from JPL have detected an organic molecule in the atmosphere of an exoplanet for the first time ever. The planet, which goes by the catchy name of HD189733b (artistically rendered below), was stalked as it orbited its star until just the right moment, when it was perfectly backlit by the star's light. The spectrographic signature of the star was well-known, so the changes that occurred as the planet got in the way revealed the planet's bulk atmospheric composition. The researchers found traces of methane and water, two simple yet vitally important molecules in the search for life.



There's no need to get overly excited just yet: our friend HD189733b is an enormous, sweltering ball of gas (with the thermometer topping out at 1700F) that almost certainly is lifeless. But the fact that we now have the ability to probe exoplanets' atmospheres (with an assist from favorable geometry) is revolutionary, and very exciting. What's more, this observation was made with Hubble, an aging telescope never intended for this line of work. Just imagine the potential of the next generation of space telescopes devoted to the study of exoplanets. I imagine there will be many more good days for exoplanets in the future.