Researchers from the University of Naples Federico II and INAF Capodimonte Astronomical Observatory in Italy studied levels of light received by 10 potentially habitable exoplanets around different kinds of star, and failed to find a single match for Earth's atmosphere.
Based on what we've observed of the thousands of planets found orbiting other stars, Earth is already a member of a relatively exclusive club. Once you've excluded numerous gas giants, roasted balls of rock, and frozen super-Earths, there aren't many candidates that might have the kind of biochemistry we're familiar with.
"Since red dwarfs are by far the most common type of star in our galaxy, this result indicates that Earth-like conditions on other planets may be much less common than we might hope," says Covone.
"This study puts strong constraints on the parameter space for complex life, so unfortunately it appears that the "sweet spot" for hosting a rich Earth-like biosphere is not so wide," says Covone.
One planet we know of comes fairly close to that sweet spot.
Kepler-442b orbits an orange dwarf with roughly 60 percent the mass of the Sun's, some 1,200 light years away. At around double the mass of Earth, and a rotation that allows it to shed heat, .......Most photosynthesizing reactions on Earth top out at wavelengths of around 700 nanometers. But if some kind of alien moss on Kepler-442b ... wavelengths, of around 800 nanometers, it would gain the benefits of 20 percent more photons.
As we expand our library of known worlds, it's possible we'll uncover better candidates for biospheres like ours......But based on what we're discovering, we can take a moment to appreciate our flavor of life is pretty special." ScienceAlert
