So this astronomer walks into a bar and says, “It’s the holy grail of exoplanet research…” You can pretty much fill in the rest of the joke yourself.

Holy grails are supposed to be rare and precious things, but hardly a month goes by lately when the science media fail to breathlessly report the discovery of a new planet, in some star’s “habitable zone,” that might hypothetically be capable of supporting life. Not, of course, that there’s any positive evidence of life actually existing there or anywhere but our own planet.

This month the newly discovered exoplanet is the romantically named GJ 667Cc, some four and a half times the mass of Earth — a “super-Earth” — and orbiting one of three stars in a triple solar system only 22 light years from us. A member of the team that found it, Steven Vogt at U.C. Santa Cruz, enthused about his discovery:

It’s the holy grail of exoplanet research to find a planet around a star orbiting at the right distance so it’s not too close where it would lose all its water and boil away, and not too far where it would all freeze. It’s right smack in the habitable zone — there’s no question or discussion about it. It’s not on the edge, it’s right in there.

A co-author on the study, Guillem Anglada-Escudé of the Carnegie Institution for Science, said: “This planet is the new best candidate to support liquid water and, perhaps, life as we know it.”
The “best” yet! Did you hear that? For a sober view, we asked an expert on planet-habitability, astronomer Guillermo Gonzalez. He explained:

Here are a couple important points about this particular system. First, the planets orbit an M dwarf star. M dwarfs provide very poor environments for life. They show erratic brightness fluctuations, and they produce powerful flares with dangerous radiation. Planets in the habitable zone of an M dwarf will spin down fairly quickly, leading to a “tidally-locked” situation that leads to all sorts of problems.

Second, terrestrial planets more massive than Earth are likely less habitable than Earth for several reasons. For instance, they will have less surface relief, which makes it less likely they will have dry land.

Don’t you get the impression that Gonzalez probably spoils every party he shows up at? The excitement about GJ 667Cc seems premature, to say the least. It’s a shame, though not much of a surprise.