|
Hubble Space Telescope discovery images of S/2011 P 1.
|
|
|
Discovery[1]
|
|
|---|---|
| Discovered by | Showalter, M. R. et al. |
| Discovery date | June 28, 2011 (verified July 20, 2011) |
| Mean orbit radius | (59 ± 2)×103 km |
| Eccentricity | ≈ 0 |
| Orbital period | 32.1 ± 0.3 days |
| Inclination | ≈ 0 |
| Satellite of | Pluto |
|
Physical characteristics
|
|
| Apparent magnitude | 26.1 ± 0.3[1] |
S/2011 P 1 (also known as S/2011 (134340) 1[lower-alpha 1] or P4) is a small natural satellite of Pluto whose existence was announced on July 20, 2011.[1] Its discovery, following the discoveries of Charon in 1978 and Nix and Hydra in 2005, made it Pluto's fourth known moon.
Contents |
S/2011 P 1 was discovered by the Hubble Space Telescope's Pluto Companion Search Team on June 28, 2011, using the Wide Field Camera 3, during an attempt to find any rings that Pluto might possess.[lower-alpha 2][4] Further observations were made on July 3 and July 18, 2011 and it was verified as a new moon on July 20, 2011.[1][5] It was later identified in archival Hubble images from February 15, 2006 and June 25, 2010.[1] S/2011 P 1's brightness is only about 10% of that of Nix, and it was found because the discovery team took 8-minute exposures; earlier observations had used shorter exposures.[6]
With an estimated diameter of 13–34 km (8–21 mi), S/2011 P 1 is the smallest known moon of Pluto.[7][8] This diameter range is derived from an assumed possible geometric albedo range of 0.06 to 0.35.[1][6]
Current observations suggest a circular, equatorial orbit with a radius of approximately 59,000 km (about 37,000 miles).[1][6] The moon orbits in the region between Nix and Hydra and makes a complete orbit of Pluto roughly every 32.1 Earth days.[1][6] This period is close to a 1:5 orbital resonance with Charon, with the timing discrepancy being apparently less than 0.6%. As with the near resonances between Nix or Hydra and Charon (1:4 and 1:6, respectively), determining how close this relationship is to a true resonance will require more accurate knowledge of S/2011 P 1's orbit, in particular its rate of precession.
Like Pluto's other satellites,[9] it is suspected that S/2011 P 1 coalesced from the debris of a massive collision between Pluto and another Kuiper belt object, similar to the "big whack" believed to have created the Earth's Moon.[4]
A formal name for S/2011 P 1 will probably be proposed to the International Astronomical Union by the discovery team. According to team leader Mark Showalter, a name associated with Hades and the underworld will be chosen from Greek mythology.[10]
|
||||||||||||||||||||||
|
|
|||||
|
|||||||||||||||||