#mini-neptune

This Is Why You Must Never Try And Colonize A Super-Earth Planet

“Although it’s fascinating to know that rocky planets — and hence, possibly life — existed so long ago, it would be absolutely foolhardy to go looking for life on the worlds that we call “super-Earths.” Once you get to be about twice as massive as Earth, or just about 25-30% larger in radius than our planet, you’re no longer rocky with only a thin atmosphere, but are overwhelmingly likely to be Neptune-like, with a full fledged large envelope of hydrogen, helium, and other light gases.

Unless you’re close enough to a star to boil your entire atmosphere away, leaving only an exposed planetary core, these worlds that we’ve called “super-Earths” for years are more like mini-Neptunes, or as astronomer Jessie Christiansen poetically calls them, “Neptinis.” If you want to colonize another planet, look for one with a surface you can land on. That means, unless you’ve got your sights set on a boiled-off planetary core, to steer clear of the super-Earths. Even if you make it down to the surface, you won’t last long under those crushing atmospheric conditions!”

Spying on distant Super-Earths

At the summit of Mauna Kea, Hawaii, the National Astronomical Observatory of Japan’s (NAOJ) Subaru Telescope has been turning its attention to distant worlds. Latest reports of blue-light observations from the telescope indicate that a super-Earth called Gilese 1214b (GJ 1214 b) appears to have a water-rich atmosphere. GJ 1214 b sits forty light years away in the constellation Ophiuchus, northwest of the centre of the Milky Way.

As a “super-Earth”, GJ 1214 b is one of a number of planets that are larger than Earth, but smaller than the Solar System’s gas giants, like Uranus and Neptune. The reported results were obtained by looking at the influence of GJ 1214 b’s atmosphere on scattered light as it passed in front of its star. Changes in the spectrum of light received from the star as the planet passed in transit can be explained in terms of light scattering in its atmosphere, which in turn provides clues as to its formation and birthplace within its star system – hydrogen-rich atmospheres are typical of distant planets, beyond the star system’s “snow line”, for example.

Two cameras on the Subaru Telescope were fitted with a blue transmission filter, and found no evidence for strong Rayleigh scattering as GJ 1214 b passed before its star. This implies that it has a water-rich or a hydrogen-dominated atmosphere. Combining the results with earlier data the team concluded that the atmosphere was most likely water-rich, with extensive clouds.

These are the first steps in discovering what sorts of planets these large objects are – are they “super-Earths” or “sub-Neptunes”. Watch out for more news of exo-geology as the results from telescopes like Subaru begin to accumulate.

~SATR

Image: The Subaru telescope sits to the left of the Keck and Infrared observatories, at Mauna Kea’s summit. (Source: Wikimedia Commons)

Une “Mini-Neptune” a été découverte

Une planète gazeuse chaude d’environ trois fois le diamètre de la Terre entoure une étoile naine orange à environ 53 années-lumière de la Terre, ont rapporté le 7 janvier les astronomes lors de la réunion annuelle de l’American Astronomical Society à Seattle, dans l’État de Washington.

Une mini-Neptune

La planète, baptisée HD21749b (représentée ci-dessus dans une représentation artistique), est…