One More Planet, One More Moon

By Christopher Moore

As if we didn’t already have enough planets …

The Associated Press reports that the same astronomers who claim to have discovered a 10th planet now claim that the new rock has its very own moon.

Read the AP report here:

While observing the new, so-called planet from Hawaii last month, a team of astronomers led by Michael Brown of the California Institute of Technology spotted a faint object trailing next to it. Because it was moving, astronomers ruled it was a moon and not a background star, which is stationary.

The so-called 10th planet (named Xena) was discovered in July. The existence of an observable moon is good news for astronomers, since it will allow them to ascertain the mass and size of the planet.

Cosmic Log comments on the discovery and the name.

3 Comments »

1. You can obtain the mass of the planet by observing its moon’s period, but how can you determine the size of the planet by observing its moon?

   Comment by M@Man — Wednesday -- October 5th, 2005 @ 8:25 am

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2. Good question. I would assume you could get a rough estimate by making assumptions about the composition of the planet.

   Also, some info about the planets size might be obtained by watching the lunar “shadow” as it passes infront of the planet. But again, a lot of assumptions would need to be made.

   Comment by Chris Moore — Tuesday -- October 18th, 2005 @ 8:02 pm

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3. I was wondering about this, thanks for the information.

   Comment by stationery — Wednesday -- June 14th, 2006 @ 12:26 pm

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