An exoplanet three 23 times heavier than Earth has been discovered close to our solar system.
The small new planet, named HD 21749b, orbits a bright, nearby dwarf star around 53 light years away in the constellation Reticulum, researchers said.
It is the third planet to be discovered by NASA's new planet-hunting Transiting Exoplanet Survey Satellite (TESS) in the first three months of observations, scientists announced at the annual American Astronomical Society meeting in Seattle.
HD 21749b journeys around its star in a relatively leisurely 36 days, compared to the two other planets - Pi Mensae b, a "super-Earth" with a 6.3-day orbit, and LHS 3844b, a rocky world that orbits its star in just 11 hours.
Despite its proximity to its star, which is almost as bright as the sun, the planet's surface is relatively cool at around 148C.
As such it could offer scientists new information on relatively small, temperate planets.
"It's the coolest small planet that we know of around a star this bright," says Diana Dragomir of MIT's Kavli Institute for Astrophysics and Space Research, who led the new discovery.
"We know a lot about atmospheres of hot planets, but because it's very hard to find small planets that orbit farther from their stars, and are therefore cooler, we haven't been able to learn much about these smaller, cooler planets.
"But here we were lucky, and caught this one, and can now study it in more detail."
The planet is around three times the size of Earth - putting it in the category of a "sub-Neptune" - and 23 times as massive.
But researchers said it is unlikely that the planet is rocky and therefore habitable.
It is more likely that HD 21749b is made of gas - of a kind that is much more dense than the atmospheres of either Neptune or Uranus.
Researchers have also detected evidence of a second planet in the same planetary system, with a shorter, 7.8 day orbit.
If it is confirmed as a planet, it could be the first Earth-sized planet discovered by TESS.
NASA's TESS mission launched in April 2018 aboard a SpaceX Falcon 9 rocket.
The planet-hunting satellite will survey 200,000 of the brightest stars near the sun over the course of two years to search for transiting exoplanets - planets outside of our solar system.
It is expected to vastly increase the number of known exoplanets.
