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Encyclopedia > 2003 EL61
2003 EL61|-
Artist's conception of 2003 EL61 
Artist's conception of 2003 EL61
 
Discovery A
Discoverer Mike Brown et al.
Discovery date 2004 December 28
Alternate
designations
B
no official name; 'Santa'
is an internal code name
Category Trans-Neptunian object
Orbital elements C
Epoch 2005-08-18 (JD 2453600.5)
Eccentricity (e) 0.18874
Semi-major axis (a) 6484 Gm (43.335 AU)
Perihelion (q) 5260 Gm (35.164 AU)
Aphelion (Q) 7708 Gm (51.526 AU)
Orbital period (P) 104,234 d (285.4 a)
Mean orbital speed 4.484 km/s
Inclination (i) 28.19°
Longitude of the
ascending node
(Ω)
121.90°
Argument of
perihelion
(ω)
239.51°
Mean anomaly (M) 198.07°
Physical characteristics D
Dimensions ~ 1960×1520×1000 km
(~ 1500 km)
Mass (4.2±0.1) × 1021 kg
Density 2.6–3.3 g/cm³
Surface gravity 0.44 m/s²
Escape velocity 0.84 km/s
Rotation period 0.16314 ± 0.00001 d
(3.9154 ± 0.0002 h)
Spectral class  ?
Absolute magnitude 0.1
Albedo 0.7 ± 0.1
Mean surface
temperature
 ? K

2003 EL61 (also written 2003 EL61), nicknamed "Santa" (non-official designation), is a large and very unusual Kuiper belt object discovered by Mike Brown et al. at Caltech in the United States. Its two moons, rapid rotation, and high albedo due to crystalline water ice on the surface, make it exceptional among the known cubewanos. Image File history File links 2003EL61art. ... Dr. Michael (Mike) E. Brown has been an associate professor of planetary astronomy at the California Institute of Technology (Caltech) since 2002. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... December 28 is the 362nd day of the year (363rd in leap years) in the Gregorian Calendar, with 3 days remaining. ... The provisional designation of comets and asteroids are similar to each other: they both follow a pattern set in 1925 by the Minor Planet Center of the IAU. Historical designations At first, astronomers strove to assign symbols to the minor planets: 1 Ceres a stylized sickle 2 Pallas a lozenge... Minor planets, or planetoids are minor bodies of the Solar system orbiting the Sun (or of other planetary systems orbiting other stars) that are larger than meteoroids (the largest of which might be taken to be around 10 meters or so across) but smaller than major planets (Mercury having a... A trans-Neptunian object (TNO) is any object in the solar system which orbits the sun at a greater distance on average than Neptune. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... August 18 is the 230th day of the year (231st in leap years) in the Gregorian calendar. ... JD is the name of a GunBound mobile JD is the IATA code for Japan Airlines domestic service JD or jd may also stand for: Johnny Depp James Dean Jermaine Dupri John Deere John Doe Johnny Damon Jon Dorian, the fictional lead character of the sitcom Scrubs Julian date, the... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... In geometry, the semi-major axis (also semimajor axis) a applies to ellipses and hyperbolas. ... giga- (symbol: G) is a prefix in the SI system of units denoting 109, or 1 000 000 000. ... The metre, or meter, is a measure of length. ... The astronomical unit (AU or au or a. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... A day (symbol: d) is a unit of time equal to 24 hours. ... In astronomy, a Julian year is a unit of time defined as exactly 365. ... The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body. ... Look up second in Wiktionary, the free dictionary. ... Inclination in general is the angle between a reference plane and another plane or axis of direction. ... A degree (in full, a degree of arc, arc degree, or arcdegree), usually symbolized °, is a measurement of plane angle, representing 1/360 of a full rotation. ... The Longitude of the ascending node () is one of the orbital elements used to specify the orbit of an object in space. ... The argument of the perihelion is one of the orbital elements describing the orbit of a planet. ... In the study of orbital dynamics the mean anomaly is a measure of time, specific to the orbiting body p, which is a multiple of 2π radians at and only at periapsis. ... For the majority of numbered asteroids, almost nothing is known apart from a few physical parameters. ... Mass is a property of a physical object that quantifies the amount of matter it contains. ... The international prototype, made of platinum-iridium, which is kept at the BIPM under conditions specified by the 1st CGPM in 1889. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... A cubic centimetre (cm3) is an SI derived unit of volume, equal to the volume of a cube with side length of 1 centi metre. ... Gravity is a force of attraction that acts between bodies that have mass. ... In physics, for a given gravitational field and a given position, the escape velocity is the minimum speed an object without propulsion, at that position, needs to have to move away indefinitely from the source of the field, as opposed to falling back or staying in an orbit within a... In astronomy, a rotation period is the time an astronomical object takes to complete one revolution around its rotation axis. ... Asteroids are assigned a type based on spectral shape, color, and sometimes albedo. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us. ... Albedo is the measure of reflectivity of a surface or body. ... Temperature is also the name of a song by Sean Paul. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... Artists rendering of the Kuiper Belt and hypothetical more distant Oort cloud. ... Dr. Michael (Mike) E. Brown has been an associate professor of planetary astronomy at the California Institute of Technology (Caltech) since 2002. ... California Institute of Technology The California Institute of Technology (commonly known as Caltech) is a private, coeducational university located in Pasadena, California, in the United States. ... A cubewano is any substantial Kuiper belt object, orbiting beyond about 41 AU and not controlled by resonances with the outer planets. ...


The nickname stems from its discovery just after Christmas, on December 28, 2004, although the Caltech team had acquired images of it starting May 6, 2004. Following IAU guidelines, the object should be named after a deity related to a creation myth. Christmas (literally, the Mass of Christ) is a traditional holiday celebrating the birth of Jesus with both religious and secular aspects, commonly observed on 25 December. ... December 28 is the 362nd day of the year (363rd in leap years) in the Gregorian Calendar, with 3 days remaining. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... May 6 is the 126th day of the year in the Gregorian Calendar (127th in leap years). ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Logo of the IAU The International Astronomical Union (French: Union astronomique internationale) unites national astronomical societies from around the world. ...

Contents


Discovery controversy

José Luis Ortiz Moreno, an astronomer at the Sierra Nevada Observatory in Spain, and colleagues Francisco José Aceituno Castro and Pablo Santos-Sanz announced the discovery of the object on July 25, 2005, when they re-analysed observations they had made on March 7, 2003. They then scoured older archives (a process known as precovery) and found the object in images dating back to 1955. Ortiz's group announced their discovery on July 27, 2005, and it was published two days later by the MPC. José-Luís Ortiz Moreno is an astronomer at the Instituto de Astrofísica de Andalucía, Spain. ... The Sierra Nevada Observatory (OSN) (37° 03′ 51″ N 03° 23′ 05″ W 2896m) is located at Loma de Dilar in the Sierra Nevada mountain range, in the province of Granada. ... July 25 is the 206th day (207th in leap years) of the year in the Gregorian calendar, with 159 days remaining. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... March 7 is the 66th day of the year in the Gregorian Calendar (67th in Leap years). ... 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... Precovery is a term used in astronomy that describes the process of finding the image of an object (usually a minor planet) in old archived images or photographic plates, for the purpose of calculating a more accurate orbit. ... 1955 (MCMLV) was a common year starting on Saturday of the Gregorian calendar. ... July 27 is the 208th day (209th in leap years) of the year in the Gregorian Calendar, with 157 days remaining. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... The Minor Planet Center operates at the Smithsonian Astrophysical Observatory (SAO), which is part of the Center for Astrophysics (CfA) along with the Harvard College Observatory (HCO). ...


A Caltech team consisting of Michael E. Brown, Chad Trujillo, and David Rabinowitz had been observing the object for half a year with the 1.3m SMARTS Telescope, but had not yet made the data public. Brown et al. initially supported giving Ortiz and his group credit for the discovery, but withdrew support when they found reason to suspect that Ortiz may have used discovery data from Brown's team, which was publicly available on the web through the SMARTS consortium. California Institute of Technology The California Institute of Technology (commonly known as Caltech) is a private, coeducational university located in Pasadena, California, in the United States. ... Dr. Michael (Mike) E. Brown has been an associate professor of planetary astronomy at the California Institute of Technology (Caltech) since 2002. ... Chadwick A. Chad Trujillo (born November 22, 1973) is a postdoctoral scholar at Caltech researching the Kuiper belt and the outer solar system. ... David L. Rabinowitz (born 1960) is a professor at Yale University researching the Kuiper belt and the outer solar system. ...


A week before Ortiz's discovery, on July 20, Brown et al. had published an abstract of a report they intended to use to announce the discovery, in which the object was referred to by the internal code name K40506A. Typing this code into internet search engines allowed anyone to find the observation logs of Brown's group, including the observed positions of the object. Third-party web server logs indicated that the page in question had been accessed by an IP address used by computers at the Instituto de Astrofísica de Andalucía where Ortiz's group worked. Brown's group accused Ortiz's group of a serious breach of scientific ethics and asked the Minor Planet Center to strip them of discovery status. [1] July 20 is the 201st day (202nd in leap years) of the year in the Gregorian Calendar, with 164 days remaining. ... The Minor Planet Center operates at the Smithsonian Astrophysical Observatory (SAO), which is part of the Center for Astrophysics (CfA) along with the Harvard College Observatory (HCO). ...


Ortiz later admitted he accessed the internet telescope logs, downloading the relevant information a day before making his announcement, but denied any wrongdoing. He concedes that it was Brown's team that had discovered the object.


On July 29, 2005, shortly after the Ortiz discovery announcement, Brown's group announced the discovery of another Kuiper belt object, 2003 UB313, which is more distant and is thought to be larger than the planet Pluto. The announcement was made earlier than planned, at the urging of Brian Marsden of the Minor Planet Center, to forestall the possibility of that discovery leaking out as well. July 29 is the 210th day (211th in leap years) of the year in the Gregorian Calendar, with 155 days remaining. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... 2003 UB313 is a trans-Neptunian object (TNO) believed to be larger than the planet Pluto. ... A planet is generally considered to be a relatively large mass of accreted matter in orbit around a star that is not a star itself. ... Atmospheric characteristics Atmospheric pressure 0. ... Brian G. Marsden is an astronomer, the longtime director of the Minor Planet Center. ... The Minor Planet Center operates at the Smithsonian Astrophysical Observatory (SAO), which is part of the Center for Astrophysics (CfA) along with the Harvard College Observatory (HCO). ...


Size and composition

2003 EL61 is circled in red
2003 EL61 is circled in red

Too often, the only element to estimate the size of a trans-Neptunian object is its magnitude assuming the albedo. For larger objects, thermal emissions can be measured providing an independent measure for the albedo. 2003 EL61 is exceptional as its two moons provide the means to determine directly the mass of the system from Kepler's third law. The estimated mass is 4.2×1021 kg, 28% the mass of the Plutonian system.[1] Moreover, as the object rotates extremely rapidly, faster than any known body larger than 100 km in diameter, this rotation should distort its shape into an oblate spheroid. Indeed, 2003 EL61 displays large fluctuations in brightness. Although these fluctuations could be due to a mottled surface1, it is thought that this fluctuation is due to an elongated shape. Rapid rotation and elongated shape result in constraints on the density (denser object would be less elongated), estimated at 2.6-3.3 g/cm³, suggesting substantial non-ice content (compare with Pluto's density of 2.0 g/cm³ and Moon's density of 3.3 g/cm³). These limits on the density, together with the known mass make then possible to estimate the dimensions.[2] If these assumptions are correct, 2003 EL61 has approximately the diameter of Pluto along its longest dimension, and half that along its shortest. This would make it one of the largest trans-Neptunian objects discovered so far; possibly fourth after 2003 UB313, Pluto and arguably 2005 FY9, larger than 90377 Sedna, 90482 Orcus, and 50000 Quaoar. Image File history File links 41354795_object_203. ... Image File history File links 41354795_object_203. ... Johannes Keplers primary contributions to astronomy/astrophysics were his three laws of planetary motion. ... A trans-Neptunian object (TNO) is any object in the solar system which orbits the sun at a greater distance on average than Neptune. ... 2005 FY9 (also written 2005 FY9), codenamed Easterbunny by its discoverers, is a very large Kuiper belt object discovered on March 31, 2005 by the team led by Michael Brown. ... 90377 Sedna is a trans-Neptunian object, discovered by Michael Brown (Caltech), Chad Trujillo (Gemini Observatory) and David Rabinowitz (Yale University) on November 14, 2003. ... 90482 Orcus (originally known by the provisional designation 2004 DW) is a Kuiper Belt object (KBO) that was discovered by Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory, and David Rabinowitz of Yale University. ... Artists impression by G. Bacon of STScI / NASA 50000 Quaoar (pronounced kwah·war, kwah·wor, or kwow·ur, Tongva ) [1] is a Trans-Neptunian object orbiting the Sun in the Edgeworth-Kuiper belt. ...


The rotation period of 2003 EL61 is less than four hours, possibly caused by the impact which created its satellites. 2003 EL61 is possibly not the only elongated, rapidly rotating large object. As early as in 2002, Jewitt & Sheppard suggested a shape of elongated spheroid for 20000 Varuna to explain its rapid rotation (see the references there). 20000 Varuna (VAR oo na) is a Kuiper Belt object about 1060 km in diameter, estimated from a combination of thermal and optical measurements. ... 20000 Varuna (VAR oo na) is a Kuiper Belt object about 1060 km in diameter, estimated from a combination of thermal and optical measurements. ...


1Pluto shows such albedo variation, fluctuating in brightness by 35% during its six-day rotation period


Surface

Gemini telescope was able to obtain the spectra of 2003 EL61, which show strong water ice features similar to what is seen on the surface of Pluto's moon Charon. Brown, Truillo et al. report strong presence of crystalline water ice, known so far only on Quaoar.[3] Water ice signature has been reported on many trans-Neptunian objects but typically in the form of amorphous ice. The crystalline ice is unstable within the timescale of 10 million years under the low temperatures and (lack of) pressure conditions encountered in the Kuiper Belt. This discovery hints on the resurfacing processes producing fresh ice, similar to the one observed on icy satellites in the solar system. As surprising as the crystalline form is the inferred amount of ice. Following the report, the surface of 2003 EL61 appears to be covered with 2/3 to 4/5 of pure ice, the remaining component apppearing blue in near infrared could be hydrogen cyanide or kaolinite. However, their presence is conjectural as other components could fit the observed spectra. The Gemini Observatory is an astronomical observatory consisting of 8-metre telescopes at two different sites. ... In most modern usages of the word spectrum, there is a unifying theme of a variety of possible cases between extremes at either end. ... A girl in a swimming pool Water (from the Old English waeter; c. ... Frozen Waterfall in the Rhön mountains A natural, 4 tonne, block of ice on a beach in Iceland Ice can refer any of the 14 known solid phases of water. ... Charon (shair-ən or kair-ən, IPA , Greek Χάρων), or Pluto I, is the largest satellite of Pluto. ... Michael Brown (born circa 1920 in Mexia, Texas) is a producer and writer of songs and books whose most-widely-known work might be several childrens books about Santa Mouse. ... This article is about the trans-Neptunian object. ... Flash point −17. ... Kaolin Kaolinite (Aluminium Silicate Hydroxide) Kaolinite is a clay mineral with the chemical composition Al2Si2O5(OH)4. ...


These findings concur with the high albedo, giving 2003 EL61 the reflectivity of almost that of pure snow. This very high albedo does not appear to be unique among TNOs. The recent measurements of 2003 UB313 imply an even higher (inferred) albedo (0.86) for that object. 2003 UB313 is a trans-Neptunian object (TNO) believed to be larger than the planet Pluto. ...


Orbit

Orbits of 2003EL61 (yellow) and Pluto (red).
Orbits of 2003EL61 (yellow) and Pluto (red).

2003 EL61 is classified as a classical trans-Neptunian object with an orbit common for large cubewanos: the perihelion close to 35AU and a significant inclinaton. The diagram shows a view of its orbit in yellow (Pluto in red, Neptune in grey) and position (as of April 2006). The perihelion (q) of 2003 EL61 is below the ecliptic. The object passed its aphelion (Q, in 1991) and is currently more than 50AU from the Sun but remains very bright (m =17.4, H =0.2) due to its size and albedo. Image File history File links TheKuiperBelt_Orbits_2003EL61. ... Image File history File links TheKuiperBelt_Orbits_2003EL61. ... A cubewano is any substantial Kuiper belt object, orbiting beyond about 41 AU and not controlled by resonances with the outer planets. ... A trans-Neptunian object (TNO) is any object in the solar system which orbits the sun at a greater distance on average than Neptune. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... Inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit and is the angular distance of the orbital plane from the plane of the reference (usually planets equator or the ecliptic), stated in degrees. ... Adjective Plutonian Atmospheric characteristics Atmospheric pressure 0. ... Adjective Neptunian Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... // Headline text HEY!! HOW ARE YOU ALL?? Its nice of you to come read this page. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us. ... Albedo is the measure of reflectivity of a surface or body. ...


The inclination of its orbit (~28° to compare with 17° for Pluto) and its current position, far from the ecliptic where most of the early surveys took place, combined with a slow mean motion (due to the distance) explain why 2003 EL61 was only discovered recently, in spite of its magnitude. Mean Motion, , is a measure of how far a satellite has progressed around its orbit, from perigee. ...


Moons

S/2005 (2003 EL61) 1

S/2005 (2003 EL61) 1 (provisional designation; nicknamed Rudolph by the Caltech team) is the first satellite discovered around 2003 EL61. It orbits 2003 EL61 once every 49.12 ±0.03 days at a distance of 49,500 ±400 km, with an eccentricity of 0.050 ±0.003 and an inclination of 234.8 ±0.3° [1]. Mutual occultations occurred in 1999 and will not occur again until 2138. The provisional designation of comets and asteroids are similar to each other: they both follow a pattern set in 1925 by the Minor Planet Center of the IAU. Historical designations At first, astronomers strove to assign symbols to the minor planets: 1 Ceres a stylized sickle 2 Pallas a lozenge...


Measured brightness is 5.9 ±0.5% translating into the diameter about 22% of its primary, or in the range of 350 km, assuming similar albedo. To put this in perspective, this moon would be the fifth largest asteroid after 1 Ceres, 2 Pallas, 4 Vesta, and 10 Hygiea if it were in the asteroid belt. 1 Ceres (, Latin CerÄ“s) was the first asteroid to be discovered. ... 2 Pallas (pal-us, Greek Παλλάς) was the first asteroid discovered after 1 Ceres. ... 4 Vesta (ves-ta) is the second most massive asteroid in the asteroid belt, with a mean diameter of about 530 km and an estimated mass 12% the mass of the entire asteroid belt. ... 10 Hygiea (hye-jee-a or hi-jee-a) is the fourth largest Main belt asteroid with a diameter of 407 km. ... Image of the main asteroid belt between the orbits of Mars and Jupiter. ...


Only the total mass of the system is known, but assuming the moon has the same density and albedo as the primary, their magnitude difference (3.3) can be used to estimate the mass of the satellite as 1% of the mass of 2003 EL61.


S/2005 (2003 EL61) 2

S/2005 (2003 EL61) 2 is a smaller second, inner satellite announced on November 29, 2005. It was found 39,300 km away and, with the assumption of a circular orbit, it orbits the primary in 34.1 ±0.1 days, and is inclined 39 ±6° from the larger moon. Measured brightness is 1.5 ±0.5% of the primary what could translate, with the arguably unsafe assumption of an albedo similar to that of the primary, to perhaps 12% of the size of 2003 EL61, maybe 170 km. [4] November 29 is the 333rd (in leap years the 334th) day of the year in the Gregorian Calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ...


External links

Sky & Telescope is a monthly magazine providing articles and information on all aspects of astronomy, space exploration, telescope equipment, and amateur telescope making and use. ... September 13 is the 256th day of the year (257th in leap years). ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ...

References

  1. ^ a b M. E. Brown, A. H. Bouchez, D. L. Rabinowitz, R. Sari, C. A. Trujillo, M. A. van Dam, R. Campbell, J. Chin, S. Hartman, E. Johansson, R. Lafon, D. LeMignant, P. Stomski, D. Summers, P. L. Wizinowich Keck Observatory laser guide star adaptive optics discovery and characterization of a satellite to large Kuiper belt object 2003 EL61, The Astrophysical Journal Letters, 632, L45 (October 2005) Full text from caltech
  2. ^ D. L. Rabinowitz, K. M. Barkume, M. E. Brown, H. G. Roe, M. Schwartz, S. W. Tourtellotte, C. A. Trujillo (2005), Photometric Observations Constraining the Size, Shape, and Albedo of 2003 El61, a Rapidly Rotating, Pluto-Sized Object in the Kuiper Belt, The Astrophysical Journal (2006), 639, Issue 2, pp. 1238-1251 Preprint on arXiv (pdf)
  3. ^ C. A. Trujillo, Brown M.E., Barkume K., Shaller E., Rabinowitz D. The Surface of 2003 EL61 in the Near Infrared. To appear in The Astronomical Journal (2006); Preprint on arXiv (pdf)
  4. ^ M. E. Brown, M. A. van Dam, A. H. Bouchez, D. LeMignant, C. A. Trujillo, R. Campbell, J. Chin, Conrad A, .S. Hartman, E. Johansson, R. Lafon, D. L. Rabinowitz, P. Stomski, D. Summers, P. L. Wizinowich Satellites of the largest Kuiper belt objects, The Astrophysical Journal (2006), 639, Issue 1, pp. L43-L46. Preprint on arXiv.
Large trans-Neptunian objectsedit
Kuiper belt: Pluto (Charon) | Orcus | Ixion | 2002 UX25 | Varuna | 2002 TX300 | 2003 EL61 | Quaoar | 2005 FY9 | 2002 AW197
Scattered disc: 2003 UB313 | 2004 XR190 | Sedna
 See also Triton, astronomical objects and the solar system's list of objects, sorted by radius or mass
For pronunciation, see: Centaur and TNO pronunciation.
† Current MPC classification. Some consider Sedna an Oort cloud object.
The minor planetsedit
Vulcanoids | Near-Earth asteroids | Main belt | Jupiter Trojans | Centaurs | Damocloids | Comets | Trans-Neptunians (Kuiper belt · Scattered disc · Oort cloud)
For other objects and regions, see: asteroid groups and families, binary asteroids, asteroid moons and the Solar system
For a complete listing, see: List of asteroids. See also Pronunciation of asteroid names and Meanings of asteroid names.

  Results from FactBites:
 
2003 EL61 (Kuiper Belt object) (480 words)
The uncertainty in estimates of the size of 2003 EL61 is due to uncertainty in its albedo: it may be a smaller, brighter body or a larger, dimmer one.
2003 EL61 has an average heliocentric distance of 52 AU (never coming closer to the Sun than Neptune and spending most of its time much further out than Pluto) and a visual magnitude of 17.5, giving it an absolute magnitude of about 0.4 (the largest of any known minor planet.
This longer period is a result of both the more distant orbit of the satellite from 2003 EL61 and the lower mass of the primary; the orbit is nearly circular.
2003 UB313 - Wikipedia, the free encyclopedia (3707 words)
Claims that 2003 UB has been officially named 'Xena' or 'Lila' are incorrect; 'Xena' is an informal codename used by its discoverers among themselves, and 'Lila' is a name in the address of the website where the object was announced, after the newly-born daughter of one of the discoverers.
As 2003 UB is larger than Pluto, it might come to be considered as the tenth planet in the Solar system, and was initially described as such by NASA and in media reports of its discovery.
Methane is very volatile and its presence shows either that 2003 UB has always resided in the distant reaches of the solar system where it is cold enough for methane ice to persist, or that it has an internal source of methane to replenish gas that escapes from its atmosphere.
  More results at FactBites »

 
 

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