Eris

From CreationWiki, the encyclopedia of creation science

Eris
Date of discovery	October 21, 200321 October 2003 25 Tishrei 5764 H 25 Eitanim 6162 AM[1]
Name of discoverer	Michael E. Brown[1][2][3]
Name origin	Greek goddess of discord[2]
Orbital characteristics
Celestial class	Dwarf planet
Primary	Sun
Order from primary	11
Perihelion	37.93 AU5.67425e+9 km 3.52581e+9 mi[4]
Aphelion	97.53 AU1.45903e+10 km 9.06598e+9 mi[4]
Semi-major axis	67.732 AU1.01326e+10 km 6.29608e+9 mi[4]
Titius-Bode prediction	154 AU[5]
Orbital eccentricity	0.4400[4]
Sidereal year	557.4 a203,590.35 da[4]
Avg. orbital speed	3.436 km/s12,369.6 km/h 2.135 mi/s 7,686.113 mph
Inclination	44.1595°0.771 rad 49.066 grad to the ecliptic[4]
Rotational characteristics
Sidereal day	8 h0.333 da
Physical characteristics
Mass	1.66 * 1022 kg0.00278 M⊕ 0.226 M☾[4][6][7]
Mean density	2,260 kg/m³2.26 g/ml 141.087 lb/ft³[4]
Mean radius	1,300 km807.783 mi[8]
Surface gravity	0.6554 m/s²2.15 ft/s² 0.0668 g
Escape speed	1.305 km/s4,698 km/h 0.811 mi/s 2,919.202 mph[5]
Surface area	21,237,166 km²8,199,715.634 mi² 0.0416 A⊕ 0.56 A☾[5]
Minimum temperature	30 K-243.15 °C -405.67 °F 54 °R
Mean temperature	42.5 K-230.65 °C -383.17 °F 76.5 °R
Maximum temperature	55 K-218.15 °C -360.67 °F 99 °R
Number of moons	1
Color	#FFFFFF
Albedo	0.87[4]

Eris, alias Xena, alias 2003 UB₃₁₃, the largest of all dwarf planets, is named for the Greek goddess of discord and strife. Considering the debate that the discovery of this object provoked, the name is probably quite apt.

Contents 1 Discovery, Naming, and Debate 2 Orbital characteristics 3 Surface and atmosphere 4 Implications for Other Trans-Neptunian Objects 5 Problem for uniformitarian theories 6 Satellites 7 Observation and exploration 8 References 9 Related Link

Discovery, Naming, and Debate

Eris was first photographed on October 21, 2003, but was at first too slow-moving for the Palomar Observatory image-analytic software to detect. Later, Michael E. Brown, Chad Trujillo, and David Rabinowitz ordered re-analysis of the images with greater sensitivity. They soon realized that the images depicted a new object, and announced their findings on January 5, 2005.

The initial name for the new object was Xena, the title character in an American television action-adventure dramatic series,^[9] and also a name beginning with X, in keeping with the suspicion that this object was the long-sought "Planet X." But the announcement of Eris' discovery on July 29, 2005 presented the International Astronomical Union with an embarrassing problem.^[10] Other observations^[11][12] had already suggested that 2003 UB₃₁₃ might be more massive even than Pluto, then considered the ninth planet in the solar system. Because planets and Kuiper-Belt objects have different naming conventions, and because scatter disk objects had no naming convention at the time, the names for these two objects remained unofficial.^[13]

Finally the International Astronomical Union declared^[14] that Pluto and 2003 UB₃₁₃ were not planets, but belonged to a new category called dwarf planets. Then on September 6, 2006, Mike Brown and his team^[15] recognized that the name "Xena" was inappropriate for 2003 UB₃₁₃ and suggested to the IAU that they name it Eris, after the Greek goddess of discord and strife. They also suggested that the IAU name the satellite Dysnomia, for the Greek goddess of lawlessness and daughter of Eris.^[16] Four days later, the IAU oficially named the primary Eris and named its satellite Dysnomia.^[17]

Orbital characteristics

At 67.7 AU from the Sun, it is the most distant object yet discovered that has the Sun for a primary. At aphelion, it is far beyond the Kuiper belt and in what is known as the scatter disk of the solar system. Because Eris is so distant from Earth (currently near aphelion and hence three times more distant than is Pluto as of 2008), it has a very long sidereal year of 557 Julian years. Its synodic year is very nearly the same as an Earth year.

Surface and atmosphere

Infrared spectroscopic scans of Eris reveal an infrared reflectance spectrum remarkably like that of Pluto, which is known to have a layer of methane on its surface. From this, the discovery team concludes that Eris is surfaced with solid frozen methane, with rock and water ice beneath.

Yet Eris is the second most reflective body in the entire solar system, reflecting about 86% of the incident sunlight. Eris is also uniformly white on its surface, whereas Pluto is a mottled brown. The discoverers believe that this is due entirely to Eris' present far-flung position (near aphelion), and point out that Eris' orbit is the most eccentric orbit of any satellite of the Sun, except for comets.

Implications for Other Trans-Neptunian Objects

Brown et al. noted^[3] in 2005 that Eris, Dysnomia's primary, is one of three of the four brightest Kuiper belt objects that have satellites. (The other two are Pluto and 2003 EL₆₁.) The fourth, 2005 FY₉, has no satellite that Earth-based telescopes can presently detect. Most Kuiper belt objects do not have satellites, and that three of the four brightest should have satellites suggests that their origins were significantly different from those of other Kuiper belt objects.

Problem for uniformitarian theories

Brown states^[6] that the near-circular orbit of Dysnomia about Eris actually is consistent with Dysnomia's origin as the result of a collision between Eris and another object. But no astronomer has ever explained how such a collision would leave an object in a nearly circular orbit about its primary.

Satellites

Eris has one known satellite, a tiny moon called Dysnomia. In classical mythology, Dysnomia is the name given to Eris' daughter, who is a symbol of actual lawlessness.

Table of satellites, in order from the innermost to the outermost:

Name	Perieridion	Apoeridion	Eccentricity	Sidereal month	Inclination	Mass	Sidereal day
Dysnomia	3686400036,864 km2.46421e-4 AU 22,906.228 mi	3783600037,836 km2.52918e-4 AU 23,510.2 mi	0.0130.013	15.77415.774 da0.0432 a	2.4836035255879142.3 °2.484 rad 158.111 grad

Observation and exploration

The Hubble Space Telescope and the Keck Observatory are the first two telescopes to observe the Eridian system. No deep-space missions are planned.

References

Browse

Related Link

• Eris by Wikipedia

	The Solar System
Star	Sol
Planets	Vulcan • Mercury • Venus • Earth • Mars • Jupiter • Saturn • Uranus • Neptune
Dwarf Planets	Ceres • Pluto • Eris
Asteroid Belt	Major asteroids • C-type asteroids • S-type asteroids • M-type asteroids
Trans-Neptunian Objects	Kuiper belt • Scatter disk • Oort cloud • Nemesis
Moons	Terrestrial • Martian • Jovian • Saturnine • Uranian • Neptunian • Plutonian • Eridian
Featured moons	Moon • Phobos • Deimos • Io • Europa • Ganymede • Callisto • Mimas • Enceladus • Tethys • Dione • Rhea • Titan • Hyperion • Iapetus • Miranda • Ariel • Umbriel • Titania • Oberon • Triton • Nereid • Charon • Nix • Hydra • Dysnomia

	The Eridian System
Primary	Eris
Moon	Dysnomia