The Goldilocks zone, or the habitable area, is the distance from a star at which liquid water can exist on a planet’s surface. The water is not hot enough to vaporize, but neither cold to cold to be frozen.
These conditions are necessary because we take into consideration liquid water as a crucial ingredient for life. However, it is not the only element that can help scientists estimate a planet’s potential habitability, as per new research on decades of information; there are also Goldilocks stars.
Possible Life Conditions in the Solar System
Not all the stars are created similarly. Some are incredibly hot and bright, like the OB stars, but some are low in temperature, such as the red M-type dwarfs. These could have a suitable temperature, but the Goldilocks area would be incredibly close to the star, and red dwarfs are prone to be violent, whipping the surrounding environment with vicious flares.
The Sun is located between these two edges, which is called a yellow dwarf, a G-type main-sequence star. But, even though researchers know that life has appeared in the Solar System, not even the Sun is a Goldilocks object.
As per astronomers at Villanova University, the best candidates for life are the K-type stars, which are orange stars with a lower temperature than the Sun, and a little warmer than a red dwarf.
“K-dwarf stars are in the ‘sweet spot,’ with properties intermediate between the rarer, more luminous, but shorter-lived solar-type stars (G stars) and the more numerous red dwarf stars (M stars),” explained Villanova astronomer and astrophysicist Edward Guinan.
“The K stars, especially the warmer ones, have the best of all worlds. If you are looking for planets with habitability, the abundance of K stars pump up your chances of finding life.”
Astronomer Scott Engle of Villanova University together with Guinan and others have been observing a few F to G-type of stars in ultraviolet and X-rays in the last 30 years in the Sun and Time program, as well as M-type red dwarfs for a decade as part of the Living with a Red dwarf program.
Both these missions have been aiding to analyze the effects of X-ray and ultraviolet radiation of the stars on the probable habitability of their planets. Not long ago, they furthered their study to include similar information collected on K-type stars, a project they called Living with Goldilocks K-dwarfs. These, apparently, seem to be the most likely stars to support life.
Even though the habitable region of L-type stars is smaller, they are much more regular than G-type stars, with approximately 1,000 of them within just 100 light-years of the Solar System. They have also much longer main-sequence lifetimes.
“Kepler-442 is noteworthy in that this star (spectral classification, K5) hosts what is considered one of the best Goldilocks planets, Kepler-442b, a rocky planet that is a little more than twice Earth’s mass,” Guinan said. “So the Kepler-442 system is a Goldilocks planet hosted by a Goldilocks star!” The study has been presented at the 235th meeting of the American Astronomical Society in Hawaii.