Exoplanetary Scratchpad

[SysBP Img]

A bright orange dwarf star that lies 42 light years away, which is of spectral type K2.5v and has a temperature of 5000 Kelvin. It has 6 super-Earths in orbit. They each have 4.0, 6.6, 9.5, 3.5, 5.2 and 7.1 times as much mass as Earth and periods of 4.3, 9.6, 20.4, 34.6, 51.8 and 197.8 days, respectively. Dynamic studies suggest that the planets are smaller versions of Neptune, rather than larger versions of Earth. The sixth planet out from the star orbits within the habitable zone.

HD 40307 System Web Pages

HD 40307 System Artwork

Template:HD 40307 Gallery

HD 40307 System In the News

3 Super-Earth system announced with 45 super earths (Jun 2008)

Terrestrials or Ice Giants? (Jan 2009)

Habitable-zone super-Earth candidate in a 6 planet system around the K2.5V star HD 40307 (Nov 2012) (WARNING: Browse This News Site With Care. Occasionally Right-Wing Biased)

HD 40307 System Fun Links

System Factoids

  • Sample Factoid
  • Sample Factoid

HD 40307 Star Factoids

  • Age in billions of years - 1.2
  • Distance in light years - 41.8 ± 0.3 and in parsecs - 12.83 ± 0.09
  • Number of planets (as of November 2012) - 6
  • Temperature in Kelvin - 4977 ± 59, Celsius - 4704 ± 59 and Fahrenheit - 8499 ± 106
  • Spectral Type - K2.5v
  • Luminosity as a percentage of the Sun (sol): Bolometric - 23% and Visual - 19%
  • Metallicity as a percentage of the Sun (sol) - 48.98% ± 3.5
  • Diameter and radius as a percentage of the Sun (sol) - 71.6% ± 1
  • Mass as a percentage of the Sun (sol) - 75% ± 4

Planet g Factoids

  • 7.1 times the mass of Earth
  • Sixth planet out from the star
  • Orbits within the habitable zone, at a semi-major axis of 0.6 au, with an eccentricity of 0.29. Perihelion is at 0.426 au and aphelion at 0.774 au
  • Orbits every 197.8 days or 7 months and 2 days (month=28 days), with the seasons approximately lasting for the summer 2 months, spring 1 month, autumn 1 month and winter 3 months.
  • Probably not tidally locked as orbit is sufficiently distant considering the star's young age of 1.2 billion years and its high orbital eccentricity
  • Average visual luminosity (visible light) reaching the planet is 53% of that reaching Earth, ranging from 105% at perihelion to 32% at aphelion. Though, that would be slightly higher on the surface of the planet, assuming it has an Earth like atmosphere, because the star produces less blue light as a proportion of its emitted light to be scattered in the upper atmosphere and more red light which more easily penetrates right down to the planet's surface.
  • Average bolometric luminosity (ultraviolet, visible and infrared light) reaching the planet is 64% of that reaching Earth ranging from 127% at perihelion to 38% at aphelion.
  • The ultraviolet light levels reaching the planet at perihelion would be similar to the amount reaching Earth. The star is quite young and so produces more UV light than a mature star would but, to balance that, it is of a spectral type that produces less UV light anyway and so the amount emitted as a proportion of its total emitted radiation is reasonably similar to that of our Sun.

Map of HD 40307 System

0.00 AU - HD 40307
x.xx AU - <periapsis/semi-major-axis/apapsis of sample planet>
x.xx AU - <habitability zone/stability zone/disk feature positions>

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