Possible Venus twin discovered around dim star

Astronomers, using NASA's Kepler space telescope, have discovered a Venus-like planet orbitting a dim star that is one-fifth the diameter of our Sun and is located 219 light-years away from Earth. This newly found world is only slightly larger than Earth, and it tightly embraces its low-temperature star called Kepler-1649, encircling it every nine days. The tight orbit causes the flux of sunlight reaching the planet to be 2.3 times as great as the solar flux on Earth.

For comparison, the solar flux on Venus is 1.9 times the terrestrial value. The discovery will provide insight into the nature of planets around M dwarf stars, by far the most common type in the universe.

While such stars are redder and dimmer than the Sun, recent exoplanet discoveries have revealed instances in which Earth-sized worlds circle an M dwarf in orbits that would place them in their star's habitable zone.

However, such worlds may not inevitably resemble Earth, with its salubrious climate. They could just as well be analogues of Venus, with thick atmospheres and scalding temperatures.
The study of planets similar to the Venus analogue Kepler 1649b is "becoming increasingly important in order to understand the habitable zone boundaries of M dwarfs," said Isabel Angelo, a scientist at SETI Institute, research organisation in the US.

"There are several factors, like star variability and tidal effects, that make these planets different from Earth-sized planets around Sun-like stars," said Angelo. It is said that Venus is Earth's sister planet, but in many ways it is not a close sibling.

Despite being the same size as Earth, and only 40 per cent closer to the Sun, its atmosphere and surface temperature are wildly different from our own. If we wish to find life on other Earth-sized worlds, we should get to know the territory.

"Many people are hung up on finding other Earths. But Venus analogues are just as important," said Elisa Quintana, from the SETI Institute and NASA Goddard Space Flight Centre.

"Since new telescopes coming down the pike will allow us to probe atmospheres, focusing on both Earth and Venus analogs may help decipher why, in our Solar System, one planet allows life to thrive, and one does not, despite having similar masses, comparable densities, etc," said Quintana, a member of the Kepler 1649b discovery team.