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Space Facts

HD 40307g
Super Earth?

Earthdate: 2012:1107

 Artist concept of planet HD 40307g
Artist's impression of HD 40307g and two of its sibling planets closer in. Illustration courtesy J. Pinfield, for the RoPACS network at the University of Hertfordshire

HD 40307 is a Solar-like star, but somewhat dimmer, known to have 5 other planets. This, its sixth planet, is still undergoing confirmation tests, but seems at this point a virtual shoe-in for the catalog of extrasolar worlds.

With a mass of at least 7 times that of Earth, if its density is similar to that of Earth, then its surface gravity will be significantly higher.

What is significant about this discovery is that the planet is securely embedded in the system's habitable zone. This is where liquid water is possible, if the planet has a modest atmosphere, like that of Earth.

System Parameters:
Name: HD 40307
Apparent Magnitude: 7.17
Distance: 41.73 light years (12.8 parsecs)
RA: 5h 54m 4.0s
DE: -60° 1' 24"
Spectral Type: K2.5 V
Mass: 0.77 ☉
Radius: ? ☉
Fe/H: -0.31
Temperature: 4,977 °K

Planet: HD 40307g
Discovered: 2012
Mass: 0.0223 MJ (7.085 MEarth)
Radii: ? RJ (? REarth)
Semi-major Axis: 0.6 AU
Orbital Period: 197.8 days
Eccentricity: 0.29
Inclination: ?°
Effective Temperature: ?

References:, retrieved 2012:1119., retrieved 2012:1109, retrieved 2012:1109

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