100 billion planets populate the Milky Way

American astronomers predict that the Milky Way is home to at least 100 billion stars and 100 billion planets.

The number of planets in the Milky Way could be up to 200 billion. Photo: Space.

Jonathan Swift, a researcher at the California Institute of Technology in the US, and colleagues studied five planets orbiting a star about 915 light years from Earth. Kepler-32, the name of this five-planet system, was discovered by the Kepler space telescope, The Astrophysical Journal reported.

The star in the Kepler-32 system is an M-dwarf, meaning it is smaller and cooler than the sun. M-dwarfs are the most common type of star, making up about 75 percent of the more than 100 billion stars in the Milky Way.

What's more, five of the planets in the Kepler-32 system are Earth-sized and quite close to their stars. The Kepler space telescope has also found similar planets orbiting other M-class dwarf stars.

"We therefore conclude that Kepler-32 is representative of the majority of planets in our galaxy," the team argues.

Based on a series of factors in the Kepler-32 system (such as the brightness of the star, the temperature of the planets' surfaces, the observational ability of the Kepler telescope), Swift and his colleagues believe that at least one planet orbits a star in the Milky Way. Since the Milky Way contains at least 100 billion stars, it also contains at least 100 billion planets. The research team even believes that the number of planets could be as high as 200 billion.

According to VnExpress - VT