Star HD40307 has been checked out before, and in the first investigation, three massive planets were found - but all of them were fiery worlds orbiting too close to their sun to have water or life on their surfaces.

Now, astronomers Mikko Tuomi of the University of Hertfordshire and Guillem Anglada-Escude of the University of Goettingen have found three more planets in the system, one in the habitable zone of the star, where liquid water could exist.

"The longer orbit of the new planet means that its climate and atmosphere may be just right to support life," Hugh Jones, also a researcher at Hertfordshire, said. "Just as Goldilocks liked her porridge to be neither too hot nor too cold but just right, this planet or indeed any moons that it has lie in an orbit comparable to Earth, increasing the probability of it being habitable."

The boffins calculate that HD40307g has about seven times the mass of Earth, and lies at such a distance from HD40307 that it isn't "tidally locked" with one face constantly pointed at its sun - thus it has days and nights, and is potentially much more hospitable to life. The scientists don't know how large it is, or even for sure that it is a rocky world like ours, which makes it hard to say just how strong the gravity on the surface might be. However it seems safe to say that if the planet is indeed rocky it probably has a much stronger surface gravity than Earth does - probably several Gs or more, depending how much larger it is, which would make it hard for un-adapted humans to live there (having got there somehow). Any resident aliens or future human colonists would probably be extremely physically powerful compared to Earth residents, along the lines of the heavy-world people or lifeforms found in science fiction*.

EE 'Doc' Smith was one of many science fiction authors who were fascinated with the idea of habitable planets with heavy gravity; he wrote about dutch colonists from a heavy gravity planet called Valeria in his 1937 classic Galactic Patrol:

Sergeant Peter van Buskirk led the storming party of Valerians-men of human ancestry, but of extraordinary size, strength, and agility because of the enormous gravitation of the planet Valeria-in wiping out those of the pirate crew not killed in the battle between the two vessels.”

Another example is Jinx, one of Larry Niven's creations from his Known Space stories. Jinx is a satellite of a gas giant named Binary in the Sirius A system. Jinx has a surface gravity of about 1.78 times Earth normal.