f = PN/120 where f is frequency of power supply, P is number of poles in the machine and N = speed in rpm. So, Synchronous speed N = 120f/P. Thus for 50 Hz supply, 2 pole machine; synchronous speed = 3000rpm. ETRICAL
Within our solar system quite a bit of exploration has been done by spacecraft including orbiters and landers. Planets outside our solar system will be difficult or impossible to explore with spacecraft in our lifetimes, so astronomers and astrobiologists use other techniques to search for signs of life on these planets. In particular, astronomers are interested in planets within the habitable zone of stars.
To the outside rim of the Oort Cloud it is just under a light year in diameter. The Oort Cloud defines the outermost edge of a solar system, containing comets and the remains of the nebula material that formed the planets. The orbit of Neptune has a semi-major axis of 4,498,252,900 kilometers or 0.00048 lightyear.