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Discovery
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| Discovered by | Deep Ecliptic Survey |
| Discovery date | 22 May 2001 |
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Designations
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| MPC designation | 28978 Ixion |
| Pronunciation | /ɪkˈsaɪ.ən/ ik-SYE-ən [note 1] |
| Alternate name | 2001 KX76 |
| Minor planet category |
TNO (plutino)[1] |
| Epoch December 31, 2006 (JD 2 454 100.5) | |
| Aphelion | 7 370.503 Gm (49.269 AU) |
| Perihelion | 4 501.495 Gm (30.091 AU) |
| Semi-major axis | 5 935.999 Gm (39.680 AU) |
| Eccentricity | 0.242 |
| Orbital period | 91 295.847 d (249.95 a) |
| Average orbital speed | 4.66 km/s |
| Mean anomaly | 268.546° |
| Inclination | 19.584° |
| Longitude of ascending node | 71.028° |
| Argument of perihelion | 298.779° |
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Physical characteristics
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| Dimensions | 650+260−220 km[3] < 822 km diameter[4] |
| Surface area | < 2.24 × 106 km² |
| Volume | < 3.15 × 108 km³ |
| Mass | ≈3 × 1020? kg[5] |
| Mean density | 2.0? g/cm³ |
| Equatorial surface gravity | < 0.229 7? m/s² |
| Escape velocity | < 0.434 6? km/s |
| Rotation period | ? d |
| Albedo | 0.15-0.37[4] |
| Temperature | ≈44 K |
| Spectral type | (moderately red; B-V=1.03, V-R=0.61) |
| Apparent magnitude | 19.6 (opposition) [6] |
| Absolute magnitude (H) | 3.2[2] |
28978 Ixion is a Kuiper belt object discovered on May 22, 2001. Ixion is a plutino (an object that has a 2:3 orbital resonance with Neptune) and a potential dwarf planet; its estimated diameter of 800 km makes it the third largest plutino. It is named after Ixion, a figure from Greek mythology.
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Physical characteristics
Ixion is moderately red (slightly redder than 50000 Quaoar) and it has a higher albedo (0.15) than the mid-sized red cubewanos.
The latest spectroscopic results indicate that Ixion's surface is a mixture of dark carbon and tholin, which is a heteropolymer formed by irradiation of clathrates of water and organic compounds (see TNO spectra). Water ice absorption lines (1.5 and 2 μm) were absent (Licandro et al. 2002). Unlike Varuna, Ixion does not show greater reflectivity for longer waves (the so-called red slope) in infrared.
Other than Pluto, Ixion was the first TNO discovered that was originally estimated to be larger than asteroid Ceres.[7] But more recent estimates suggest that Ixion has a high albedo[4] and is smaller than Ceres. It is more likely that 20000 Varuna or 50000 Quaoar may turn out to the first TNO discovered that is larger than Ceres.
The Very Large Telescope (VLT) has checked Ixion for cometary activity, but did not detect a coma.[8] Ixion is currently about 41 AU from the Sun,[6] and it is possible that Ixion could develop a coma or temporary atmosphere when it is closer to perihelion.
Orbit
Ixion and Pluto follow similar but differently oriented orbits: Ixion’s perihelion is below the ecliptic whereas Pluto's is above it. Uncharacteristically for bodies locked in resonance with Neptune (such as Orcus), Ixion approaches Pluto with less than 20 degrees of angular separation. Ixion is currently crossing the ecliptic heading below, and will reach its perihelion in 2070. Pluto has passed its perihelion (1989) and is descending toward the ecliptic. Ixion's orbital period is almost 250 Earth years, about 0.5% larger than Pluto's.
See also
Notes
- ^ Or as in Latin: Ixīōn, Ancient Greek: Ιξίων. Sometimes erroneously pronounced /ˈɪksiən/ IK-see-ən.
References
- ^ Marc W. Buie (2007-07-12). "Orbit Fit and Astrometric record for 28978". SwRI (Space Science Department). http://www.boulder.swri.edu/~buie/kbo/astrom/28978.html. Retrieved 2008-09-29.
- ^ a b "JPL Small-Body Database Browser: 28978 Ixion (2001 KX76)". 2007-07-12 last obs. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Ixion. Retrieved 2008-10-04.
- ^ John Stansberry, Will Grundy, Mike Brown, Dale Cruikshank, John Spencer, David Trilling, Jean-Luc Margot (2007). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope". University of Arizona, Lowell Observatory, California Institute of Technology, NASA Ames Research Center, Southwest Research Institute, Cornell University. http://arxiv.org/abs/astro-ph/0702538v2. Retrieved 2008-11-17.
- ^ a b c Wm. Robert Johnston. "TNO/Centaur diameters and albedos". http://www.johnstonsarchive.net/astro/tnodiam.html.
- ^ Using the 2007 Spitzer spherical radius of 325 km; volume of a sphere * an assumed density of 2 g/cm³ yields a mass (m=d*v) of 2.8E+20 kg
- ^ a b c "AstDys (28978) Ixion Ephemerides". Department of Mathematics, University of Pisa, Italy. http://hamilton.dm.unipi.it/astdys/index.php?pc=1.1.3.0&n=Ixion. Retrieved 2009-08-13.
- ^ Richard Stenger (2001-08-24). "New object deemed largest minor planet". CNN (space). http://edition.cnn.com/2001/TECH/space/08/24/minor.planet/index.html. Retrieved 2008-02-29.
- ^ O. Lorin and P. Rousselot (2007). "Search for cometary activity in three Centaurs (60558) Echeclus, 2000 FZ53 and 2000 GM137 and two trans-Neptunian objects (29981) 1999 TD10 and (28978) Ixion". Royal Astronomical Society 376 (2): 881–889. doi:. http://www3.interscience.wiley.com/journal/117974948/abstract. Retrieved 2008-10-04.
- H. Boehnhardt, S. Bagnulo, K. Muinonen, M. A. Barucci, L. Kolokolova, E. Dotto and G. P. Tozzi (2003). "Surface characterization of 28978 Ixion (2001 KX76)". Astronomy & Astrophysics 415: L17–L19. Pre-print about Ixion's surface from the Planetary Systems Research group of the University of Helsinki
- J. Licandro, F. Ghinassi, L. Testi (2002). "Infrared spectroscopy of the largest known trans-neptunian object 2001 KX76". Astronomy & Astrophysics 388: L9. doi:. Pre-print on arXiv
- W. J. Altenhoff, F. Bertoldi and K. M. Menten (2004). "Size estimates of some optically bright KBOs". Astronomy & Astrophysics 415.
External links
- AstDys orbital elements
- Orbital simulation from JPL (Java) / Ephemeris
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