The impeller made out of cast material in many cases may be called rotor, also. It is cheaper to cast the radial impeller right in the support it is fitted on, which is put in motion by the gearbox from an electric motor, combustion engine or by steam driven turbine.
Earth remains the only known planet to host life, due to a unique combination of factors. However, continued monitoring of alien worlds might one day change that, by finding other planets that share these attributes or by discovering other ways that life has found to blossom in the universe.
Earth, the fifth largest planet in the solar system, is the only one known to support life. It revolves around the sun in about 365 days. Estimated to be 4.5 billion to 5 billion years old, this planet has one natural satellite, the moon.