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posted by martyb on Friday December 08 2017, @03:25AM   Printer-friendly
from the amazing-resolution dept.

When astronomers were trying to determine the mass of a "super-Earth" exoplanet orbiting the red dwarf K2-18, they found a second one:

When K2-18b was first discovered in 2015, it was found to be orbiting within the star's habitable zone (aka. "Goldilocks Zone"). The team responsible for the discovery also determined that given its distance from its star, K2-18b's surface received similar amounts of radiation as Earth. However, the initial estimates of the planet's size left astronomers uncertain as to whether the planet was a Super-Earth or a mini-Neptune.

For this reason, Cloutier and his team sought to characterize the planet's mass, a necessary step towards determining it's atmospheric properties and bulk composition. To this end, they obtained radial velocity measurements of K2-18 using the HARPS spectrograph. These measurements allowed them to place mass constraints on previously-discovered exoplanet, but also revealed something extra.

[...] Essentially, their radial velocity measurements revealed that K2-18b has a mass of about 8.0 ± 1.9 Earth masses and a bulk density of 3.3 ± 1.2 g/cm³. This is consistent with a terrestrial (aka. rocky) planet with a significant gaseous [envelope] and a water mass fraction that is equal to or less than 50%. In other words, it is either a Super-Earth with a small gaseous atmosphere (like Earths) or "water world" with a thick layer of ice on top.

They also found evidence for a second "warm" Super Earth named K2-18c, which has a mass of 7.5 ± 1.3 Earth masses, an orbital period of 9 days, and a semi-major axis roughly 2.4 times smaller than K2-18b. After re-examining the original light curves obtained from K2-18, they concluded that K2-18c was not detected because it has an orbit that does not lie on the same plane.

K2-18b was discovered by the Kepler Space Observatory in 2015.

Also at the University of Toronto Scarborough.

Characterization of the K2-18 multi-planetary system with HARPS: A habitable zone super-Earth and discovery of a second, warm super-Earth on a non-coplanar orbit


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  • (Score: 0) by Anonymous Coward on Friday December 08 2017, @07:34AM (1 child)

    by Anonymous Coward on Friday December 08 2017, @07:34AM (#607122)

    Planets on a different orbital planes ... stuff like that doesn't happen by accident, you know? Or to be precise: as far as we know it happens _only_ because of a big f***ing accident!

    Methinks additional research is warranted.

  • (Score: 2) by takyon on Friday December 08 2017, @04:59PM

    by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Friday December 08 2017, @04:59PM (#607267) Journal

    I want Planet Nine. [wikipedia.org]

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