A Matter of Time

By | September 27, 2004
1 Comment

Via GeekPress, it’s only a matter of time before we discover an earth-like planet somewhere out in space. So far, fewer than 150 planets have been located outside the solar system, but that’s about to change:

COROT, a French satellite scheduled to be launched in 2006, is designed to discover planets photometrically. Kepler, a similar American mission, is scheduled for launch in October 2007. And another American satellite, the Space Interferometry Mission (SIM), which will use astrometry, is planned for 2009. The SIM will measure the positions of between 10,000 and 30,000 stars, and to do so a hundred times more precisely than they are now known.

If neither of these missions come up with Class M paydirt, there are two others on the drawing boards that probably will:

America’s Terrestrial Planet Finder (TPF) and Europe’s Darwin are friendly rivals. The TPF and Darwin will both look at relatively nearby stars—within 50-75 light years of Earth. But there are so many stars within that sphere that it is reasonable to expect plenty of planets to turn up. The reason for that expectation is that enough exoplanets have been discovered already for statistically meaningful inferences to be made about what other planets are out there, and where they are. Two facts stand out. Of sun-like stars that have been closely investigated for any length of time, 15% have planets. And within the range of detectable planets, lower-mass bodies are exponentially more common than higher-mass ones. Put these facts together and it seems likely that small, rocky planets might be very common indeed.

Whether alternative Earths, complete with oceans and life, are common is a different question—but it is one that spectroscopy should be able to answer. When the data from the TPF and Darwin start rolling in, they may provide a definitive answer to that old, nagging question: “is there anybody out there?” How long that answer would take to become commonplace, though, is anybody’s guess.

I’m guessing sooner rather than later.

Question: Let’s say we discover an earth-like planet within 75 light-years of Earth. Once we know it’s there, we point everything we have at it. We quickly determine that it is not sending out any radio signals (thus chances are that there is no resident civilization) but we do confirm that the atmosphere is rich in oxygen. So there is almost certainly life on that planet. Would we start trying to figure out how to get there?

I think we would.

Read the entire article, which is fascinating not just because it provides an excellent run-down on the methods currently being employed to discover extrasolar planets, but also because it was published in (of all places) The Economist.

  • Karl Hallowell

    The Economist neatly sidesteps the issue, but in general “Earth-like” just means within a zone of a star (or multiple stars/brown dwarf/gas giant system) where the planet receives enough heat/light that liquid water can exist and where the planet has a mass within a certain range of one Earth mass. As I understand it, Venus, Earth, and Mars are all “Earth-like” though Venus may be too close to the Sun to be considered “Earth-like”.

    Europa may be considered “Earth-like”, despite lying well outside the “habitable” zone of the Sun. I don’t know if they consider tidal heating and radiative heating from the brown dwarf or gas giant.