Phoebe

Saturn IX

Phoebe Facts

• Phoebe is the outermost of Saturn's known satellites:
  • distance from Saturn: 12,952,000 km
  • diameter: 220 km
  • mass: 4.0e18 kg
  Phoebe is almost 4 times more distant from Saturn than its nearest neighbor (Iapetus).

• Pronounced "FEE bee"

• Phoebe (Artemis) was the virgin goddess of the hunt and the Moon; twin sister of Apollo.

• Discovered by Pickering in 1898.

• Most of Saturn's moons are bright but Phoebe's albedo is very low (.05), as dark as lampblack.

• All of Saturn's moons except for Phoebe and Iapetus orbit very nearly in the plane of Saturn's equator. Phoebe's orbit is inclined almost 175° (its north pole is in the opposite direction to Saturn's).

• Phoebe's eccentric, retrograde orbit and unusual albedo indicates that it may be a captured asteroid or Kuiper Belt object.

• Phoebe is also unusual in that it does not rotate synchronously as do all the other moons of Saturn except Hyperion.

• Material knocked off of Phoebe's surface by microscopic meteor impacts may be responsible for the dark surfaces of Hyperion and the leading hemisphere of Iapetus.

Pictures

1. (above) Phoebe 8k gif

More about Phoebe

• from LANL

Open Issues

• Why is Phoebe in such an odd orbit?
• Is it really the source of the dark material on Hyperion and the leading hemisphere of Iapetus?
• Phoebe's density is only 0.7 which is anomalously low. What is its composition?