|That dot? Beta Pictoris b.|
How was this bit of astronomical legerdemain accomplished? With adaptive optics, a serendipitous spinoff from research into antimissile lasers. Adaptive optics is a wondrous technology.
Next up: different cleverness. The Kepler observatory identified, sans direct imaging, many an exoplanet. The method: spotting the slight dips in brightness as distant planets transited distant stars. With the failure of two reaction wheels, the orbiting telescope, alas, can no longer point steadily enough to continue making such precise observations.
Or so it was believed ...
(February 6th update: A mere two days after this post, the proof is in: Kepler can go back to work. See, from New Scientist: "NASA's revived exoplanet-hunter sees its first world.")
|HD 106906 b|
The anomalous exoplanet, HD 106906 b, weighs in at 11 times the mass of Jupiter and orbits its hosting star at ~20 times Pluto's orbit.
By the same theory of planetary formation, of course, Neptune could never have formed where it's observed. So, it is believed, Neptune didn't form where it now orbits, but migrated outward in the complex dance of solar-system formation and maturation. The "hot Jupiter" exoplanets that are often detected (perhaps because they're the easiest to detect) also could not have formed where they are detected. They, it would seem, migrated inward after forming. Yet other planetary mass objects (not technically planets because they don't orbit a star) as large as gas giants have been detected (by gravitational micro-lensing) free-floating in interstellar space. In theory, a star could capture such a planetary mass object into orbit -- making it a planet.
Do any of these scenarios explain HD 106906 b? The jury is out.
We'll end today's survey of exoplanet news with "Weight of the World: New Technique Could Weigh Alien Planets." ("Weigh" is an inexact term, though I concede the value of brevity in a headline. The point is to determine the mass of exoplanets.)
The usual method for estimating an exoplanet's mass is via the wobble that mass induces in the position of its star. Alas, many an exoplanet isn't massive enough, and/or doesn't orbit close enough to its sun, to produce a measurable-from-Earth stellar wobble. The new method relies upon the gravitational effects of a planet's mass on its own atmosphere. The more massive a planet, the more quickly its atmosphere thins with altitude -- and that effect can (in theory) be exploited by observing stars shining through an exo-planetary atmosphere.
Next time ... observations closer to home.