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Astronomers See the Glow of a Boiling Planet
The Bad Astronomer writes "For the first time, astronomers have detected the light from a 'super-Earth' exoplanet. The planet 55 Cancri e (with twice the radius and 8 times the mass of Earth) circles its host star every 18 hours, and is so hot it glows in the infrared. By observing in that wavelength, the astronomers measured the dip in light as the planet's glow was blocked by the star itself. This is the reverse of the usual method of detecting a planet as it blocks the light of its host star."
It's not the peak - TFA states the planet's temperature is about 2700C. Which I would call "infernal".
That does, however, explain how the IR emissions are high enough for us to detect here on Earth, light-years away - it's really, really, *really* hot.
According to the article (yes I know it's not cool to RTFA) it's "so close to the star that the surface temperature is probably around 2700C — or 4900F!"
The only planets larger than Earth in the Solar system are the gas giants, so a super Earth is just a designation for a planet more massive than Earth, but not a gas giant.
What exactly justified it to be called super-Earth?
Earth-like but significantly bigger than earth. The planet in question is 8 times the mass of Earth with twice the radius so roughly the same density. It might only be a factor of 8 in mass but if you saw a person with 8 times the average mass, say ~600kg, you'd certainly call them super-sized! As for temperature Venus is hotter than Earth but with a surface temperature of 460C it's decidedly nippy compared to the planet in question which is just over 1700C.
2700ÂC is not just infernal I'd think. That temperature is nearly half the temperature of the sun's photosphere (5500ÂC). Iron melts at 1538ÂC, and boils at 2862ÂC. There could be clouds of iron vapor and rains of molten iron there. If it had any kind of atmosphere it would likely be made up of iron and silicon vapor.
Qu'on me donne six lignes écrites de la main du plus honnête homme, j'y trouverai de quoi le faire pendre.
The problem here is one of nomenclature and trying to define different terms for planets. In our Solar System there are no "super-Earth" sized planets, so until exo-solar planets were discovered there was no need for any classification for planets that sized. Basically there is a need to define planets smaller than the "small gas giants" like Neptune and Uranus and something larger than the size of the Earth or Venus.
Currently that is being called "Super Earth" because it shares many more characteristics with the Earth than it does with the gas giants.
A similar scaling problem exists for planets that are a couple times the size of Jupiter, and larger, but aren't really large enough to ignite nuclear fusion. Sometimes those are called "brown dwarfs", but "super gas giants" is sometimes used too.... odd where a dwarf is more massive than a giant.