Nix (moon)

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Nothing
Nix best view.jpg
Nothing, captured by the New Horizons spacecraft
Provisional or systematic name S / 2005 P 2
Pluto II
Central body Pluto
Properties of the orbit
Major semi-axis (48,675 ± 21) km
Periapsis 48,563 km
Apoapsis 48,786 km
eccentricity 0.0023 ± 0.0021
Orbit inclination 0.10 ° ± 0.33 (equatorial plane) °
Orbital time 24.8562 ± 0.0013 d
Mean orbital velocity 0.1424 km / s
Physical Properties
Albedo 0.04-0.35
Apparent brightness 23.41 ± 0.15 mag
Medium diameter approx. 42 km × 36 km
Dimensions 5 · 10 16 - 2 · 10 18 kg
Acceleration of gravity on the surface ≈ 0 m / s 2
Escape speed ≈ 0 m / s
Surface temperature −240–−218 ° C / 33–55 K
discovery
Explorer

Research team at the
Lowell Observatory

Date of discovery June 15, 2005

Nix is the third closest and third largest of the five known moons of the dwarf planet Pluto .

Discovery and naming

Nix was found on June 15, 2005 together with Hydra from the Pluto Companion Search Team - 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 on images taken by the Hubble Space Telescope on May 15-18, 2005.

Discovery photos of Nix and Hydra

The two moons were discovered independently on June 15 by Max J. Mutchler and on August 15, 2005 by Andrew J. Steffl. Nix was 2.09 "away from Pluto. When both moons were subsequently localized on images from November 2002, their discovery was announced on October 31, 2005. Nix initially received the provisional designation S / 2005 P 2 . The existence of the two celestial bodies was confirmed by further observations of the Pluto system on February 22, 2006.

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

In addition, the initials of Nix and Hydra correspond to those of the New Horizons space probe , which explored the system in July 2015.

Track properties

Orbits of Pluto, Charon, Nix and Hydra around the barycenter of the system

Nix orbits the common center of gravity of the Pluto-Charon system in a prograde , almost circular orbit at an average distance of 46,640 km (48,675 km distance from Pluto's center, approx. 42.21 Pluto radii). The orbital eccentricity is 0.0023, the orbit is inclined 0.1 ° to the equator of Pluto . The radius of the orbit of the next inner moon Charon is on average 29,103 km smaller, the radius of the orbit of the next outermost known Pluto moon Kerberos is about 10,000 km larger.

Nothing orbits Pluto in 24 days, 20 hours 32 minutes and 55.7 seconds, which corresponds to around 3645.5 orbits in a Pluto year (around 248.09 earth years).

The orbital period is close to a 1: 4 orbital resonance with Charon, with a deviation of 2.7 percent, which indicates that it is not a real resonance. One hypothesis to clarify this question states that such a near-resonance comes from Charon before the outward migration. It is therefore maintained by the periodic local fluctuation of 5 percent in the gravitational field strength due to the orbit of Pluto and Charon around each other.

The rotation of Nix cannot be calculated in advance over long periods of time and its orbital plane is not identical to that of Pluto's largest moon Charon.

Physical Properties

Pluto and its moons Charon, Nix and Hydra

The exact value of the diameter has not yet been determined. When the New Horizons space probe flew past Pluto, however, photographs were taken that allow the diameter to be narrowed in two of the three spatial directions. Accordingly, Nix is ​​approx. 42 km × 36 km in size.

Nix is ​​25 percent fainter than Hydra, which, assuming the same albedo, indicates a size 10 to 15 percent smaller. In the discovery photo, Nix is ​​6300 times fainter than Pluto. Initial studies of the moon indicated a similar red color to Pluto, but more recent studies report a similar neutral gray color to Charon and Hydra, but with an area of ​​the moon, possibly a large impact crater, appearing red.

Analogous to the theory of the formation of the Earth's moon , Nix is ​​presumably the product of the great collision of a predecessor of Pluto with another Pluto-sized body of the Kuiper belt , which formed the moon Charon and in the process debris got into outer orbits around Pluto, which formed the moon Nix .

exploration

After being discovered in the summer of 2005 by images from the Hubble Space Telescope , the two newly discovered moons were observed in September 2005 by the Keck and Gemini observatories in Hawaii and by the ESO-VLT telescope in Chile to confirm the discovery however, it failed because the conditions for an observation of the Pluto system at that time were not favorable. On October 24th, Marc W. Buie and Eliot F. Young were able to make out the moons in the 2002 images.

The New Horizons spacecraft, launched on January 19, 2006, flew on July 14, 2015 at a distance of 27,000 km from Charon and 9,600 km from Pluto. Since the discovery of Nix and Hydra was not yet confirmed when the probe was launched and Kerberos was only discovered afterwards, they were not included in the mission. However, Nix and Hydra were subsequently included in the observation program. They could be located about 90 days before the passage and their trajectories were recorded more precisely in order to ensure their position during the flyby. Nothing could be captured with a resolution of less than 1 km.

See also

Individual evidence

  1. a b "New Horizons captures two of Pluto's smaller moons" , accessed on July 22, 2015 at 12:40 am
  2. http://www.raumfahrer.net/news/astronomie/04062015210943.shtml Ralph-Mirko Richter: At least two of Pluto's smaller moons are tumbling , in Raumfahrer.net, Date: June 4, 2015, Accessed: June 7, 2015.

media

Commons : Nix  - collection of images, videos and audio files

Web links