Monday, December 14, 2015

Warm Super-Earth Circling a Red Dwarf Star

Circling a red dwarf star located 173 ± 26 light years from Earth is a super-Earth with 2.38 ± 0.25 times the size of Earth. This planet is identified as EPIC 206318379b and its discovery was announced by Teruyuki et al. (2015) using data from NASA’s K2 mission together with follow-up observations. EPIC 206318379b is in a close-in orbit around its host star, circling around its host star once every 2.26 days.

Figure 1: Artist’s impression of a super-Earth.

Being a red dwarf star, the host star of EPIC 206318379b has only 29.3 ± 3.0 percent the diameter and 26.4 ± 5.0 percent the mass of the Sun. The host star of EPIC 206318379b also has an effective temperature of 3214 ± 60 K and it is comparatively metal-rich, with approximately twice the Sun’s metallicity. A star’s metallicity indicates the abundance of elements that are heavier than hydrogen and helium.

EPIC 206318379b is relatively warm as it orbits close to its host star. A reflectivity of zero percent gives the planet an equilibrium temperature of 570 ± 36 K and a reflectivity of 40 percent gives the planet an equilibrium temperature of 502 ± 32 K. EPIC 206318379b is similar in size and receives a similar amount of insolation from its host star as the well-studied GJ 1214b. Follow-up observations to compare the atmospheric properties of these two planets can provide new insights to the atmospheres of such worlds.

Figure 2: Transiting planets around red dwarf stars cooler than 3400 K. Teruyuki et al. (2015)

Teruyuki et al. (2015). “The K2-ESPRINT Project III: A Close-in Super-Earth around a Metal-rich Mid-M Dwarf”, arXiv:1511.08508 [astro-ph.EP]