Nix (moon)

Research team from the Lowell Observatory

Nix is the third closest and third largest moon of Pluto. Its diameter is estimated to be 46-137 kilometers.

Discovery and designation

Nix was on 15 June 2005 along with Pluto Companion Search Team from Hydra consisting of Hal A. Weaver, S. Alan Stern, Max J. Mutchler, Andrew J. Steffl, Marc W. Buie, William J. Merline, John R. Spencer, Eliot F. Young, and Leslie A. Young discovered by observations with the Hubble space Telescope on 15 and 18 May 2005. The two moons were found independently on June 15 by Max J. Mutchler, and on 15 August 2005 by Andrew J. Steffl. Nix was 2.09 arcseconds found distance to Pluto. As both moons could be located later on recordings in November 2002, then the discovery was announced on 31 October 2005; the moon first received the provisional designation S/2005 P 2 The actual existence of the two celestial bodies was confirmed by subsequent observations of the Pluto system on 22 February 2006.

On 21 June 2006, the Moon of the International Astronomical Union ( IAU) officially by Nyx (Greek for "night" ) was named, the goddess of night in Greek mythology. Nyx is also the mother of Charon, Pluto 's largest moon after the Charon is named. It was originally intended to call the Moon Nyx; since the name was already assigned to the asteroid ( 3908 ) Nyx, a slightly different notation was chosen for the Pluto moon. The USGS Gazetteer of Planetary Nomenclature indicates that Nix the " Egyptian pronunciation ", while Jürgen Blunck speaks of a " Spanish translation " of the Greek name.

In addition, the names Nix and Hydra correspond to the initials of the spacecraft New Horizons, which is to explore the system in July 2015.

Web properties

Nix orbiting the common center of mass of the Pluto -Charon system in a prograde, nearly circular orbit at an average distance of 46,640 km ( 48 675 distance from Pluto's center, about 42.21 Pluto radii ). The orbital eccentricity is 0.0023, the orbit is inclined 0.1 ° relative to the equator of Pluto.

The radius of the orbit of the next inner moon Charon is on average less than 29103 km, the radius of the orbit of the next outermost known Pluto moon Kerberos is about 10,000 km greater.

Nix Pluto rotates in 24 days 20 hours 32 minutes and 55.7 seconds, resulting in a Pluto year equals approximately 3645.5 rounds (about 248.09 Earth years ).

The orbital period is close to a 1:4 orbital resonance with Charon, the deviation is 2.7 %, suggesting that it is not a true resonance. One hypothesis to clarify this issue stating that such a near- resonance originates before the current outward migration of Charon. Maintaining it is therefore by the periodic local fluctuation of 5 % in the gravitational field strength through the circulation of Pluto and Charon around each other.

Physical Properties

The exact value of the diameter could not be determined so far as the albedo (albedo ) of the surface is unknown. If the albedo equal to that of Charon ( 0.372 ) may be, this would amount to 46 km, with an albedo of 0.04, corresponding to the darkest Kuiper Belt objects, 137 km.

Nix is fainter by 25 % as Hydra, indicating a 10 - indicating lower 15 % size, assuming an equal albedo of the two moons. On the discovery of photo Nix is 6,300 times fainter than Pluto. Initial studies of the moon indicated a similar red color as Pluto, but recent studies report a similar neutral gray color as Charon, and Hydra.

Nix is likely analogous to the theory on the origin of the Moon, the product of large collision of a predecessor of Pluto with another pluto large body of the Kuiper Belt, which formed the moon, Charon, while debris fell into outer orbits around Pluto, this follows the moon Nix formed.


After the discovery in the summer of 2005, with images from the Hubble Space Telescope, the two newly discovered moons were observed in September 2005 by the Keck and the Gemini Observatory in Hawaii and by the ESO VLT telescope in Chile to confirm the discovery, but this failed, because the conditions for observation of the Pluto system were unfavorable at this time. On October 24, Marc W. Buie and Eliot F. Young could make out the moons in the pictures of 2002.

It is planned to have the space probe launched on January 19, 2006 New Horizons fly by on July 14, 2015, 27,000 km distance to Charon and 9600 km distance to Pluto. Since the discovery of Nix and Hydra was not confirmed at the start of the probe and Kerberos was not discovered until then, they were not planned in the mission. Nix and Hydra, however, were included in the monitoring program afterwards. You should be localizable 90 days prior to the passage and you will then record their tracks more closely to ensure their position in the flyby. It will then both moons capture with a resolution of better than 200 m / pixel, only slightly worse than Charon (200 m / pixel). Under the current simulations, Hydra is on the same side of Pluto as Charon, Nix, however, on the other side, but closer to the probe.