The parent star is Tau Ceti, a sun-like star located less than 12 light-years from Earth, in the constellation Cetus.
The planet of interest is estimated to be about 4.3 times more massive than Earth. If confirmed, the planet would be the smallest yet discovered in a star's habitable zone, say scientists who will be publishing their research in an upcoming issue of Astronomy & Astrophysics.
"This discovery is in keeping with our emerging view that virtually every star has planets, and that the galaxy must have many such potentially habitable Earth-sized planets. They are everywhere, even right next door," astronomer Steve Vogt, with the University of California Santa Cruz, said in a statement.
"We are now beginning to understand that nature seems to overwhelmingly prefer systems that have multiple planets with orbits of less than 100 days. This is quite unlike our own solar system where there is nothing with an orbit inside that of Mercury. So our solar system is, in some sense, a bit of a freak and not the most typical kind of system that nature cooks up," Vogt added.
Astronomers used instruments on three telescopes to look for tiny wobbles in starlight coming from Tau Ceti caused by the slight gravitational tugging of its orbiting brood.
The observations have not yet been confirmed.
"They're pulling data out of very noisy signals, so this is still brand new and is being evaluated, but it's very exciting," said John Grunsfeld, NASA's associate administrator for space science.
Image: Artist rendering of newly discovered Tau Ceti planetary system. Credit: University of Hertfordshire