The Case for Dwarf K Stars

61 Cygni, a binary K-type star system - via commons

The stellar main-sequence is a strip that cuts diagonally the Hertzsprung-Russell diagram, a star's plot of stellar color versus brightness. The main feature of main-sequence stars is that they burn hydrogen. In this group the K dwarfs, or orange dwarfs, are intermediate stars in size between red M stars (red dwarfs) and yellow G stars. Their mass is between 0.5 and 0.8 times the Sun's mass and surface temperature is bewteen 3900 and 5200 K.
In the last few years these type of stars have become particularly interesting to astronomers, as they appear to have the characteristics to host life-as-we-know:

Updates from outer space: from Earth to K2-18 b

There are some interesting news about the research of exoplanets, but the first step starting from our planet, the Earth. Indeed, Evelyn Macdonald and Nicolas Cowan used the satellite Scicast to detect the transit spectrum of our planet. The idea is to deduce the atmosphere composition, obtaining the Earth's organic signature, and in this way data to confront with exoplanets transit spectrum.

Macdonald, E. J., & Cowan, N. B. (2019). An empirical infrared transit spectrum of Earth: opacity windows and biosignatures. Monthly Notices of the Royal Astronomical Society, 489(1), 196-204. doi:10.1093/mnras/stz2047

About two weeks after the pubblication of the previous paper, an international team of astronomers have discovered water vapor in the atmosphere of K2-18 b, an exoplanet that orbit in the habitable zone of the red dwarf K2-18. While it was initially considered a mini-Neptune on its 2015 discovery, the improved data on K2-18b has classified it as a super-Earth, although its size and density make it unlikely to be composed entirely of rocky iron and silicates.

Tsiaras A., Waldmann I. P., Tinetti G., Tennyson J., Yurchenko S. N. (2019). Water vapour in the atmosphere of the habitable-zone eight-Earth-mass planet K2-18 b. Nature Astronomy. doi:10.1038/s41550-019-0878-9