28978 Ixion
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| Discovered by | Deep Ecliptic Survey Cerro Tololo (807) |
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| 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(s) | 2001 KX76 |
| Minor planet category |
TNO (plutino)[3] |
| Adjective | Ixionian |
| 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) |
| 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[4] < 822 km diameter[5] |
| Surface area | < 2.24 × 106 km² |
| Volume | < 3.15 × 108 km³ |
| Mass | ≈3 × 1020? kg[6] |
| 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[5] 12+14−6[4] |
| Temperature | ≈44 K |
| Spectral type | (moderately red) B-V=1.03; V-R=0.61[7] |
| Apparent magnitude | 19.6 (opposition) [8] |
| Absolute magnitude (H) | 3.2[1] 3.84[4] |
| Angular diameter | 0.022″ |
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 dwarf planet candidate; its diameter of 650 km estimated by Spitzer makes it about the fifth largest plutino. It is named after Ixion, a figure from Greek mythology. Ixion was discovered by the Cerro Tololo Inter-American Observatory (807).[2]
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Physical characteristics
Other than Pluto, Ixion was the first TNO discovered that was originally estimated to be larger than asteroid Ceres.[9] Even in 2002, a year after its discovery, Ixion was still believed to be more than 1000km in diameter.[10] Though the 2002 estimate was a result of a spurious detection at 250GHz that was not confirmed by later observations.[11] More recent estimates suggest that Ixion has a high albedo[5] and is smaller than Ceres.
Ixion is moderately red (slightly redder than 50000 Quaoar) in visible and it has a higher albedo (>0.15) than the mid-sized red cubewanos. The may be an absorption band at the wavelength of 0.8 μm.[12]
The visible and infrared 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.
The Very Large Telescope (VLT) has checked Ixion for cometary activity, but did not detect a coma.[13] Ixion is currently about 41 AU from the Sun,[8] and it is possible that Ixion could develop a coma or temporary atmosphere when it is closer to perihelion.
Occultation
Ixion may occult a relatively bright apparent magnitude 11.5 star in the constellation of Ophiuchus on July 19, 2010.[14] This event may be visible from North America.[14] The RA and DE for this event is in a star-rich region at 16 54 25.8620 −24 24 22.856.[14] The occultation could last up to 45 seconds,[14] but the predicted occultation path will likely miss the Earth. An occultation detection could help refine the diameter of this dwarf planet candidate.
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
- ↑ 1.0 1.1 1.2 "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.
- ↑ 2.0 2.1 Marsden, Brian G. (2001-07-01). "MPEC 2001-N01: 2001 FT185, 2001 KW76, 2001 KX76, 2001 KY76, 2001 KZ76, 2001 KA77". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. http://131.142.24.68/mpec/K01/K01N01.html. Retrieved 2010-01-06.
- ↑ 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.
- ↑ 4.0 4.1 4.2 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.
- ↑ 5.0 5.1 5.2 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
- ↑ Doressoundiram (2004). "The Meudon Multicolor Survey (2MS) of Centraurs and Trans-Neptunian objects". http://www.iop.org/EJ/article/1538-3881/134/6/2186/205733.web.pdf. Retrieved 2006-11-06.
- ↑ 8.0 8.1 8.2 "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.
- ↑ Altenhoff, Bertoldi, Junkes (October 7, 2002). "Beyond Pluto: Max-Planck radioastronomers measure the sizes of distant minor planets". Spaceref.com. http://www.spaceref.com/news/viewpr.html?pid=9446. Retrieved 2010-01-06.
- ↑ Altenhoff, W.J.; Bertoldi, F.; Menten, K.M. (2004). "Size estimates of some optically bright KBOs". Astronomy and Astrophysics 415 (2): 771–775. doi:10.1051/0004-6361:20035603. http://adsabs.harvard.edu/abs/2004A%26A...415..771A.
- ↑ Marchi, S.; Lazzarin, M.; Magrin, S. and C. Barbieri (2003). "Visible spectroscopy of the two largest known trans–Neptunian objects: Ixion and Quaoar". Astronomy and Astrophysics 408: L17–L19. doi:10.1051/0004-6361:20031142. http://adsabs.harvard.edu/abs/2003A%26A...408L..17M.
- ↑ 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:10.1111/j.1365-2966.2007.11487.x. http://www3.interscience.wiley.com/journal/117974948/abstract. Retrieved 2008-10-04.
- ↑ 14.0 14.1 14.2 14.3 Steve Preston (2010 May 26). "(28978) Ixion / UCAC2 22032118 event on 2010 Jul 19, 01:48 UT". http://www.asteroidoccultation.com/2010_07/0719_28978_21077_Summary.txt. Retrieved 2010-07-05.
Further reading
- 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:10.1051/0004-6361:20020533. 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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