Robotic telescope discovers three super-earth planetary neighbors | Hacker News Reader

Robotic telescope discovers three super-earth planetary neighbors

newscenter.berkeley.edu

52 pointsanigbrowl8 comments

Is super-earth some term with meaning here, or are they purely using it as a headline? I don't imagine with orbits closer to their host start than mercury and mass 7-8 times that of the earth that they are actually all that earth-like.

A super Earth is a planet that's larger than Earth, but not large enough to be a gas giant.

Compared to something like Jupiter that has 300 Earth mass, they are quite Earth-like. Though Uranus is 15 Earth masses but it's quite far from the sun and is significantly composed of gas and ice.

It's a term used to describe a planet more massive than the Earth, but less massive than Neptune. These planets are thought to be typically rocky. From the introduction of the paper:

> The archetypical planets of our Solar System --- Jupiter the gas giant, Neptune the "ice" giant, and Earth the terrestrial planet --- represent an incomplete inventory of the planet types in our galaxy. We are locally impoverished in "super-Earths," the broad category of planets intermediate in size and mass between Earth and Neptune.

Solar inner planets are mostly metal-silicate worlds. The seven major satellites are mostly hydric.

Under different circumstances, particularly if there were no Jupiter, we might expect a metal-poor, water-rich rocky planet in the system, larger in volume and more massive than Earth.

Jupiter has had a huge influence on the solar system, and if that mass were not concentrated there, it would have to be somewhere. The H and He would probably have blown away, but the silicaceous, carbonaceous, hydric, and metallic materials might have contributed to terrestrial planets.

If you squashed all the moons of Jupiter together along with the entire asteroid belt, you almost get a wetter, less dense Mars. Add the 5% of Jupiter that isn't light gases, and you get about 1*10^26 kg, which is about 16 times the mass of Earth.

So if the light gases blew away instead of forming Jupiter, and the remaining mass formed asteroids that combined via capture and collision, the solar system could have had a super-Earth. But instead, Jupiter sucked down most of that mass and put the rest into stable orbits around itself.

Apparently it doesn't mean "much better than the real Earth", sadly.

Duh. THAT term is 'super duper earth'.

calling them sub-neptunes doesn't get as many clicks :-) Generally though it translates loosely to 'rocky' plant (vs gas/ice)

Reply on news.ycombinator.com