Astronomers discovering Earth-like planets with conditions ripe for the potential of carrying life is nothing new, but none have been quite as old as one identified recently orbiting a relatively close star.
An international team of astronomers, found two planets around the star Kapteyn, which is one-third the mass of our Sun and is only 13 light years away. Other planets that could be habitable found by NASA's Kepler mission were hundreds of light years away.
"We were surprised to find planets orbiting Kapteyn's star," lead author Dr. Guillem Anglada-Escude, a former Carnegie postdoc now with Queen Mary University of London, said. "Previous data showed some irregular motion so we were looking for very short period planets when the new signals showed up loud and clear."
Kapteyn's star and its planets likely come from a dwarf galaxy now merged with the Milky Way. The bottom right panel shows characteristic streams of stars resulting from such a galactic merging event. (Image source: Victor Robles, James Bullock, and Miguel Rocha at University of California Irvine and Joel Primack at University of California Santa Cruz)
One of these two planets, called Kapteyn b, could support water, the researchers said. It is at least five times the mass of Earth and orbits the star every 48 days, which would make it warm enough to support water. The second planet is not thought to hold water because it is likely too cold, taking more than 100 days to complete an orbit.
Further measurements of the planets' atmospheres in the future could officially verify the presence of water.
"Finding a stable planetary system with a potentially habitable planet orbiting one of the very nearest stars in the sky is mind blowing," Pamela Arriagada, another author on the study and a Carnegie postdoctoral researcher, said. "This is one more piece of evidence that nearly all stars have planets, and that potentially habitable planets in our Galaxy are as common as grains of sand on a beach."
The age of Kapteyn and its planets is thought to be around 11.5 billion years old -- 2.5 times older than Earth and only 2 billion years younger than how old scientists think the universe itself is.
"It does make you wonder what kind of life could have evolved on those planets over such a long time," Anglada-Escude said.
These findings were published in Monthly Notices of the Royal Astronomical Society.