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.
An alien world that orbits a distant star in the constellation of Lyra may be the most Earth-like planet ever found outside the solar system. The planet, named Kepler 438b, is slightly larger than Earth and circles an orange dwarf star that bathes it in 40% more heat than our home planet receives from the sun.