They've discovered Earth ... again.
The astronomy blogosphere is abuzz with news of "shrunken versions of our solar system" and "miniature worlds in the making," at least according to the press releases I've been reading. Nobody has called them "Hobbit solar systems" yet, but give them time.
Alexander Scholz of the University of St. Andrews in Scotland, and Ray Jayawardhana from the University of Toronto reported discovery of 18 planet-mass objects (planemos) in a star cluster in Orion. Planemos form by the collapse of gas and dust, but they are not massive enough to initiate nuclear fusion and become suns.
Planemos were discovered about the year 2000. Astronomers thought they were either young planets booted out of their solar systems or small stars that failed to ignite. Astronomy has covered the story for years, of course.
In a paper to be published in Astrophysical Journal Letters, Scholz and Jayawardhana describe some important new observations with the Spitzer Space Telescope. The star cluster with the planemos is only 3 million years old, an appropriate time for making new Earths.
And about a third of the planemos are encircled by dusty disks of the type one would expect to see in a star system capable of forming — you guessed it — planets. And not just any old planets; rocky, terrestrial, Earth-like planets.
Also this week, another team reported strong evidence of a dusty, planet-forming disk around the star HD 23514 in the Pleiades star cluster (M45), also in Orion. Apparently, Orion the Hunter knows a lot about birthin' babies.
We can see these systems only because of powerful instruments like Spitzer, which can detect the heat emitted by dusty disks. The objects are essentially invisible in other wavelengths of light. So, kudos (again and again and again) to the Spitzer Space Telescope.
This is all fascinating stuff, but I can't help grinding an old axe: the tendency of the media to frame any new discovery regarding exoplanets in terms of how much they are like or unlike Earth. As I said in an earlier blog kvetching about the media's Earth-obsessed exoplanet coverage:
Gosh, it's just like home! You can't swing a dead cat around the media coverage of Gliese 581C without hitting the word Earth. Earth-like. Super-Earth. Earth-like life. Earth twin. Sister planet. Earth-like conditions. Earth 2. The climate in exoplanet science is positively Earth-centric.
Take the new planemos. If they develop rocky planets, just how Earth-like are they likely to be, besides being solid? Not much like Earth, I suspect. They would lie forever in near pitch-darkness, frozen, barren. As Elton John's Rocket Man might have said, a Hobbit exoplanet ain't the kind of place to raise your kids.
So, let's skip all the Earth talk. The really amazing point is that it looks more and more likely that the universe is just bursting at the seams with planetary systems. If even a small fraction of those planets are in reasonably stable orbits, then the universe could be bursting at the seams with life, too. When you stop to consider that, who needs this "just like Earth" stuff to sell a story?