But if GJ 357 d is rocky and has just the right kind of atmosphere, liquid water and maybe even life could exist on its surface.
GJ 357 is a small M-type dwarf star, which is 40 percent cooler than the sun.
Just 31 light-years away, one of the closest worlds ever detected could harbour liquid water on its surface.
Follow-up observations and data collected by Earth-based telescopes dating back two decades led to the discovery of the planet's siblings, GJ 357 c and GJ 357 d. The more distant of the two additional planets discovered by astronomers, GJ 357 d, would be much more comfortable, and if it has a suitable atmosphere it may be a lot like Earth.
It's also "quiet", meaning it has few flares and allows scientists to observe it and its orbiting planets more easily."We've found very few planets like this in the habitable zone, and many fewer around a quiet star, so this is rare", said Kane. It orbits 11 times closer to its star than Mercury does our Sun.
However, scientists admit further research is needed to work out whether GJ 357 d's atmosphere is dense and warm enough to host liquid water.
"We describe GJ 357 b as a 'hot Earth, '" explains co-author Enric Pallé, an astrophysicist at the IAC and Luque's doctoral supervisor.
The new star system, called TESS Object of Interest, or TOI-270, is exactly what the Transiting Exoplanet Survey Satellite, or TESS, was created to find, said researchers from the University of California, Riverside in the US.
The team hope to determine whether rocky planets like Earth and massive icy worlds develop along the same formation path, or through different processes.
This illustration shows one interpretation of what GJ 357 d may be like.
Temperatures given for TOI 270's planets are equilibrium temperatures, calculated without the warming effects of any possible atmospheres. The former is estimated to weigh about seven times the mass of the earth, while the second is approximately five times the mass of the earth.
The planet, named GJ 357 d, is about six times larger than Earth and orbits a dwarf sun GJ 357, much smaller than our own, every 55.7 days.
"This technique is precisely what TESS was created to search out - small, temperate planets that go, or transit, in front of an inactive host star, one missing excessive stellar exercise, akin to flares", mentioned the research's lead author, Maximilian Günther, in a statement on NASA's website. On the other hand, the observable cosmos is over 14 billion light-years across.
TESS kept tabs on the star for about a month and produced ground-based date from the European Southern Observatory and the Las Campanas Observatory in Chile among others.
The world was noticed by astronomer Jennifer Winters of the Harvard-Smithsonian Heart for Astrophysics and colleagues by in search of the periodic dimming of sunshine from the primary star because the planet repeatedly passes - or transits - in entrance of it.