(Space.com) Astronomers have pinned down some details of an exotic nearby alien planet that’s almost as dense as lead. The exoplanet, called 55 Cancri e, is 60 percent larger in diameter than Earth but eight times as massive, researchers revealed Friday (April 29). That makes the alien world the densest solid planet known — It’s twice as dense as Earth.
Astronomers previously thought 55 Cancri e took about 2.8 days to orbit its parent star. But the new study reveals that the exoplanet is so close to its host star that it completes a stellar lap in less than 18 hours.
The super-dense alien world is part of a multiplanet solar system about 40 light-years from Earth, in the constellation Cancer (The Crab). Its sunlike parent star, 55 Cancri, is bright enough to be seen from Earth by the unaided eye, researchers said.
Since 1997, astronomers have discovered five planets circling 55 Cancri (including 55 Canrci e in 2004). All five alien worlds were detected using the so-called radial velocity — or Doppler — method, which looks for tiny wobbles in a star’s movement caused by the gravitational tugs of orbiting planets.
Initially, astronomers thought 55 Cancri e had an orbital period of about 2.8 days. But last year, two researchers — Harvard grad student Rebekah Dawson and Daniel Fabrycky of the University of California, Santa Cruz — re-analyzed the data. They suggested that the alien planet might actually zip around its host star much faster than that.