Four astronomers from the Harvard Smithsonian Centre for Astrophysics (Cfa) have taken a giant step in the relatively new science of exobiology. They’ve been successful in probing the atmosphere around the transiting super-Earth known as GJ1214b.
This exoplanet isn’t exactly our size but it’s close enough to set pulses running. It is 6.5 Earth masses and measures 2.7 Earth radii, and it orbits a small M-dwarf star whose diameter is only 21% of the Sun’s.
The Cfa astronomers – Zachory Berta, David Charbonneau, Jean-Michel Desert and Jonathan Irwin – used the Hubble Telescope’s infrared spectrometer to observe the planet as it passed across the face of the star. In doing so, the planet’s atmosphere absorbed light from the star, subtly altering the star’s intrinsic spectrum as we observe it. This spectrum was carefully measured and subtracted after the transit.
So what is a super-Earth? It’s an exoplanet (a planet around another star) whose mass is between about two and ten Earth masses. Planets larger than this are closer to our gas giants in size, and perhaps in other physical properties as well.
The “super-Earth” category at present refers only to the mass of the object – not to its radius, its orbital distance from the star, surface temperature or atmosphere. Of the 576 exoplanets whose approximate parameters are currently known, 36 are in the...
