Starship Asterisk*

[img3="Artist’s illustration of an M-dwarf star surrounded by three planets. A recent study examines which stars make the best targets when searching for habitable exoplanets.
[Credit: NASA/JPL-Caltech]"]http://aasnova.org/wp-content/uploads/2016/04/fig17.jpg[/img3]

M-dwarf stars are excellent targets for planet searches because the signal of an orbiting planet is relatively larger (and therefore easier to detect!) around small, dim M dwarfs, compared to Sun-like stars. But are there better or worse stars to target within this category when searching for habitable, Earth-like planets?

Radial velocity campaigns search for planets by looking for signatures in a star’s spectra that indicate the star is “wobbling” due to the gravitational pull of an orbiting planet. Unfortunately, stellar activity can mimic the signal of an orbiting planet in a star’s spectrum — something that is particularly problematic for M dwarfs, which can remain magnetically active for billions of years. To successfully detect planets that orbit in their stars’ habitable zones, we have to account for this problem.

In a recent study led by Elisabeth Newton (Harvard-Smithsonian Center for Astrophysics), the authors use literature measurements to examine the rotation periods for main-sequence, M-type stars. They focus on three factors that are important for detecting and characterizing habitable planets around M dwarfs:

1. Whether the habitable-zone orbital periods coincide with the stellar rotation ...
2. How long stellar activity and rapid rotation last in the star ...
3. Whether detailed atmospheric characterization will be possible ...

• Astrophysical Journal Letters 821(1):L19 (10 Apr 2016) DOI: 10.3847/2041-8205/821/1/L19
  arXiv.org > astro-ph > arXiv:1604.03135 > 11 Apr 2016