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Moon and Jupiter

May 23, 2015

Until a couple of decades ago, Jupiter was the king of the planets — the biggest, heaviest world yet discovered. Today, it’s still the king of our own solar system — it’s more massive than all the other planets combined. But when you include the planets beyond the solar system, Jupiter doesn’t even rank in the top 500.

Astronomers discovered the first Jupiter-like planet in 1995. It was about half Jupiter’s mass. Since then, planets heavier than Jupiter have been popping up faster than wildflowers after a spring rain. Quite a few of those worlds are more than a dozen times as massive as Jupiter, and the biggest are about twice Jupiter’s diameter.

One reason so many giant planets have turned up is that they’re a lot easier to find than smaller ones.

One technique detects planets through their gravitational pull on their parent stars. This pull produces a slight back-and-forth shift in the star’s light. Heavy planets have stronger gravity, so they produce a larger shift.

Another technique looks for a planet to pass in front of its star. That blocks some of the star’s light. A bigger planet blocks more light, making it easier to detect.

And Jupiter itself is quite easy to detect right now. This evening, it’s close to the upper right of the Moon, and shines like a brilliant star. It’ll be about the same distance to the lower right of the Moon tomorrow night — a giant world that’s still the king of the solar system.


Script by Damond Benningfield, Copyright 2015

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