Science: Diminished Planet

Pluto, the outermost planet of the solar system, is so small, dim and far away (3.7 billion miles) that astronomers have seen it only as a point of light like a star, have had to estimate its size by calculating the apparent effect of its gravitation upon the motion of Neptune. Measured in this indirect way, Pluto was thought by some to be almost as big as the earth. Last week Astronomer Gerard P. Kuiper of Yerkes Observatory, having measured Pluto's diameter with the 200-inch telescope on Palomar Mountain, announced that those estimates were probably wrong.

Using the great telescope visually (it...

Want the full story?

Subscribe Now


Get TIME the way you want it

  • One Week Digital Pass — $4.99
  • Monthly Pay-As-You-Go DIGITAL ACCESS$2.99
  • One Year ALL ACCESSJust $30!   Best Deal!
    Print Magazine + Digital Edition + Subscriber-only Content on

Learn more about the benefits of being a TIME subscriber

If you are already a subscriber sign up — registration is free!