Using gravitational microlensing, researchers have discovered a cold, rocky planet some 3,000 light years away orbiting one member of a binary system- a duo of stars orbiting a common center of mass. While this planet is too chilly to support life as we recognize it, the discovery opens up new locations for astronomers to scour for potentially habitable planets. The study has been published in Science.
The newly detected planet, called OGLE-2013-BLG-0341LBb, is around twice as massive as Earth and, amazingly, is orbiting its host star at almost exactly the same distance that Earth orbits the Sun. Unfortunately, the host star is much less massive than our Sun and therefore around 400 times less luminous also, meaning that the planet’s temperature is around 60 Kelvin (-213oC [-350oF]).
As mentioned, the planet’s host is part of a binary system. These are actually incredibly common in the universe but no one knew whether planets such as this could exist in these systems, let alone in Earth-like orbits, because it was assumed that planetary formation would be disrupted if the host star is locked in such a tight system.
While the host star is not quite right for supporting life on this planet, a similar planet orbiting a Sun-like star in a binary system would lie within the habitable zone and therefore may have the right conditions to support life, such as liquid water, which is exciting.
The astronomers detected this planet using a technique called gravitational microlensing. This is where light from a distant star is bent and focused by the gravitational field of a smaller star passing directly between Earth and the more distant star. The gravity of the smaller star therefore behaves like a lens and causes the brightness from the distant star to increase. Sometimes, if we’re lucky, the signature of a planet will also appear within this magnified signal, and that’s how astronomers detected this new planet.
The newly discovered planet, which the astronomers are confident is rocky based on its mass, was found to be orbiting its host from a distance of around 90 million miles. Both the host and the companion star, which is about as far from its partner as Saturn is from our Sun, are very dim. However, given that binary systems like this are commonplace in the Milky Way, this raises the possibility that we may find more terrestrial planets, some of which could be warm enough to support life.
“Normally, once we see that we have a binary, we stop observing. The only reason we took such intensive observations of this binary is that we already knew there was a planet,” said lead author Andrew Gould in a news-release. “In the future, we’ll change our strategy.”