The radii of planets found in the Kepler dataset by Dressing & Charbonneau (2015) as a function of the amount of star light (insolation) they receive. The pink and green lines show ranges of insolation we think might allow the planets to be habitable.
In journal club today, we discussed a recent study by Dressing & Charbonneau (2015) that used the Kepler dataset to search for possibly habitable planets around small (M-dwarf) stars.
Dressing and Charbonneau applied a sophisticated and comprehensive search scheme to look for habitable planets and estimate how effective their search was in finding such planets. Based on their analysis, they estimated that about 1 in 4 M-dwarf stars have planets about the size of Earth in their habitable zones and that the nearest such planet is about 8.5 light years away.
This is far enough that we’d probably still need a generation ship to reach it but a lot closer than one case, 20 light years to the nearest habitable planet, considered by Hein et al. (2012) in their analysis of interstellar colonization. This reduction in travel time could reduce the minimum population required to make the trip from maybe 7,000 to 4,000 people.
Of course, the habitable planet sought in such a trip would orbit a much cooler, redder star than the Sun, so the colonists should be prepared to plant very different crops than we have on Earth.
Attendees of today’s journal club included Simon Pintar, Nathan Grigsby, Jacob Sabin, Tyler Wade, Liz Kandziolka, Jennifer Briggs, and Emily Jensen.
Mechanical failures interrupted Kepler’s original mission, but the telescope is still hunting exoplanets. From http://www.nature.com/news/three-super-earth-exoplanets-seen-orbiting-nearby-star-1.16740.
Discussed a brilliant paper today in journal club from Ian Crossfield and collaborators, in which they announce the discovery of a three-planet system around a nearby M-dwarf star.
The team found the new system in data from the re-incarnated Kepler mission called K2. This system is only the second discovered by the mission (the first was announced a few months ago).
This new system is especially exciting because, as the authors point out, it is observable by other available facilities, allowing astronomers to characterize the planets and star in detail.
The outermost planet in the system, with an orbital period of 45 days, is very near the inner edge of the system’s habitable zone and has a temperature of about 310 K (100 F), making it plausibly habitable. Combined with the fact that we can probably characterize the planet in detail, there’ll probably be a flurry of exciting studies of the system very soon.
Journal club was attended by Jennifer Briggs, Trent Garrett, Nathan Grigsby, Emily Jensen, Liz Kandziolka, and Brenton Peck.