Achievement Locked

NASA Discovers Fourth Moon Around Pluto:

Astronomers have discovered a fourth moon orbiting Pluto. The tiny new satellite, temporarily designated “P4″, has an estimated diameter of 8 to 21 miles.

P4 was first seen in a photo taken with Hubble’s Wide Field Camera 3 on June 28…



  1. Did Earth already cash in or just enter a cheat-code?

  2. Very funny. Poor Pluto

  3. Nerd-rock musician Jonathan Coulton wrote a song called “I’m Your Moon” which was written as a love song from Charon to Pluto after Pluto had been downgraded…it’s surprisingly sweet!

  4. What is that “upgrade” panel from? :D

  5. […] Not even the discovery of a fourth moon around Pluto can get it back in the big kids’ club. (Defective Yeti) […]

  6. I thought the shape of the orbit also determined whether it was a planet or dwarf-planet. I think Pluto’s orbit was not in the same plane as the orbit of the eight planets. I don’t remember number of moons, or even possession of moons, qualified as a quality of a planet. According to Wikipedia, Haumea, a dwarf-planet, has a couple of moons.

  7. It was solely based on size, from what I heard. It makes sense, too. There are much bigger astronomical objects that we don’t call planets, so it was either upgrade those or downgrade Pluto.

  8. Didn’t we kick Pluto out from our club?

  9. I was under the impression that the main reason Pluto was downgraded was because a planet has to sweep up sufficient debris in its orbit, and because Pluto passes through the Kuiper belt, it clearly hasn’t done that.

  10. A planet is determined by where the axis of rotation between it and its moon is located. If the axis is located inside the planet, then it is indeed a planet. The axis of rotation between Pluto and Charon is located in space, which means the two bodies rotate around each other.

  11. A planet has nothing to do with its moon.

    A planet in our solar system must orbit the Sun (not some other body), have sufficient mass to achieve hydrostatic equilibrium (be roughly spherical), and have cleared the neighborhood around its orbit. By that, they mean that any debris in the objects orbit must be either accreted, pushed out of that orbit, or brought into an orbit around the object or around the Lagrangian points of the objects orbit and the Sun.

  12. so how is Pluto still not a planet

  13. […] Defective Yeti. Share this:TwitterFacebook astronomy ← Previous post @dnghub db at mail dot ubc dot […]

  14. the cool thing is that in only four short years and with a bit more luck, we get pictures from a Pluto flyby

    Also, Pluto Today, for all your on-the-spot Plutonian reporting, And more!

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