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.
Related Stories
Stories submitted via Arthur T Knackerbracket and by NotSanguine about the exoplanet K2-18 b:
James Webb Telescope Detects Further Proof That Distant Exoplanet May Host Life
Arthur T Knackerbracket has processed the following story:
Scientists have discovered methane and carbon dioxide in the atmosphere of K2-18 b, a distant exoplanet that has long piqued the curiosity of astronomers for having the potential to sustain life.
Using data from the James Webb Space Telescope, scientists based at NASA, the Canadian Space Agency and the European Space Agency (ESA) were able to detect the presence of carbon-bearing molecules including methane and carbon dioxide in the atmosphere of the planet that is about 8.6 times the Earth’s mass.
The discovery adds to recent studies that suggested the K2-18 b could be what is known as a Hycean exoplanet – one that has the potential to have a hydrogen-rich atmosphere and a water ocean-covered surface.
[...] “Our findings underscore the importance of considering diverse habitable environments in the search for life elsewhere,” explained Prof Nikku Madhusudhan, an astronomer at the University of Cambridge and lead author of the paper announcing these results, which will be published in The Astrophysical Journal Letters.
“Traditionally, the search for life on exoplanets has focused primarily on smaller rocky planets, but the larger Hycean worlds are significantly more conducive to atmospheric observations.”
These initial Webb observations also provided a possible detection of a molecule called dimethyl sulphide, which on Earth is only produced by life – largely emitted by the vast swathes of phytoplankton that inhabit our oceans.
“Upcoming Webb observations should be able to confirm if [dimethyl sulphide] is indeed present in the atmosphere of K2-18 b at significant levels,” added Madhusudhan.
Even though K2-18 b hosts carbon-bearing molecules and lies in the habitable zone based on the distance from its star, this does not mean it can necessarily support life. Scientists said that the planet’s large size means that its interior likely contains a large mantle of high-pressure ice.
And while Hycean worlds are predicted to have oceans of water, it is possible that the ocean is too hot to be habitable or be liquid.
Paper preprint [PDF]
(Score: 0) by Anonymous Coward on Friday December 08 2017, @07:34AM (1 child)
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
I want Planet Nine. [wikipedia.org]
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