16 Psyche

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16 Psyche
Discovered by Annibale de Gasparis
Discovery time March 17, 1852
Other names none
Group Main belt
Reference date October 22, 2004 (JD 2453300.5)
Longest distance from the Sun 497.884 Gm (3.328 AU)
Shortest distance from the Sun 375.958 Gm (2.513 AU)
Longest distance from the center of its orbital path
("semi-major axis")
436.921 Gm (2.921 AU)
How egg-shaped its orbit is
How long it takes to complete an orbit 1823.115 d (4.99 a)
Average speed 17.34 km/s
Mean anomaly 323.379°
Angle above the reference plane
Longitude of where it comes up through the reference plane 150.352°
Angle between its shortest distance from what it orbits around and where it comes up through the reference plane
("argument of periapsis")
Size and Other Qualities
Measures ~280×230×190 km[1][2][3][4][5]
Mass ~1.7×1019 kg [6]
Average density 3.3 ± 0.7 g/cm³[7]
Gravity at its surface ~0.06 m/s²
Slowest speed able to escape into space
("escape velocity")
~0.13 km/s
How long it takes to turn around one time 0.1748 d (4.196 h) [8]
How much light it reflects 0.120 (geometric)[1]
Avg. surface temp. ~160 K
max: ~280 K (+7 °C)
Light-band group
("spectral type")
Seeming brightness
("apparent magnitude")
9.27 (brightest?)
True brightness
("absolute magnitude")

16 Psyche is a very big Main belt asteroid, well over 200 kilometers in diameter, and likely the biggest of the metallic M-type asteroids. It is estimated to have 0.6 percent of the mass of the entire asteroid belt.[6]

This asteroid was found by Annibale de Gasparis on March 17, 1852 from Naples and named after the Greek nymph Psyche. The first fifteen asteroids to be found were given symbols by astronomers as a type of short-hand notation. In 1851, however, J. F. Encke suggested using a circled number. 16 Psyche was the first new asteroid to be found that was designated with this scheme (in 1852 by J. Ferguson).[9]

Characteristics[change | edit source]

Radar[10][11] observations indicate that it is made of iron-nickel. Psyche appears to be a case of an exposed metallic core from a bigger differentiated parent body. Unlike some other M-type asteroids, Psyche shows no sign of the presence of water or water-bearing minerals on its surface, consistent with its interpretation as a metallic body.[12] Small amounts of pyroxene appear to be present.[13]

If Psyche is the core remnant of a bigger parent body, we might expect other asteroids on similar orbits. Psyche does not belong to any asteroid family.[14] One theory is that the collision occurred very early in the solar system's history, and all the other remnants have since been ground into fragments by subsequent collisions or had their orbits perturbed beyond recognition.

Psyche is massive enough that its perturbations on other asteroids can be measured, which enables a mass measurement. Its density is fairly low for metal (although fairly common for asteroids as such), indicating a fairly high porosity of 30–40%.[7]

Psyche appears to have a fairly round surface and is approximately ellipsoidal in shape. Recent lightcurve analysis indicates that its pole points towards either ecliptic coordinates (β, λ) = (-9°, 35°) or (β, λ) = (-2°, 215°) with a 10° uncertainty.[3] This gives an axial tilt of 95°.

Two stellar occultations by Psyche have been seen (from Mexico on March 22, 2002, and another on May 16, 2002). Lightcurve changes indicate a non-spherical body, consistent with the lightcurve and radar results.

References[change | edit source]

  1. 1.0 1.1 Supplemental IRAS Minor Planet Survey Archived 17 January 2010 at WebCite
  2. Dunham, D. W. and Herald, D. (2006). "Asteroid Occultations". EAR-A-3-RDR-OCCULTATIONS-V4.1. NASA Planetary Data System. http://www.psi.edu/pds/resource/occ.html. Retrieved 2007-04-03.
  3. 3.0 3.1 M. Kaasalainen et al. (2002). "Models of Twenty Asteroids from Photometric Data". Icarus 159: 369. http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf.
  4. Magnusson, P. and Neese, C., ed. (1996). "Asteroid Spin Vectors". EAR-A-5-DDR-ASTEROID-SPIN-VECTORS-V4.2. NASA Planetary Data System. Archived from the original on 2010-01-17. http://www.psi.edu/pds/resource/spin.html. Retrieved 2007-04-03.
  5. A. Cellino et al. (2002). "Speckle interferometry observations of main belt asteroids at TNG". Proceedings of Asteroids, Comets, Meteors - ACM 2002. International Conference: 497. http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?2002acm..conf..497C&data_type=PDF_HIGH&type=PRINTER&filetype=.pdf.[dead link]
  6. 6.0 6.1 B. Vitaeau (2000). "Mass and density of asteroids (16) Psyche and (121) Hermione". Astronomy & Astrophysics 354: 725. http://aa.springer.de/papers/0354002/2300725.pdf.
  7. 7.0 7.1 Lupishko, D. F. (2006). "On the bulk density and porosity of M-type asteroid 16 Psyche". Solar System Research 40 (3): 214-218. http://adsabs.harvard.edu/abs/2006SoSyR..40..214L. Retrieved 2007-02-04.
  8. PDS lightcurve data Archived 17 January 2010 at WebCite
  9. Hilton, J. (September 17, 2001). "When Did the Asteroids Become Minor Planets?". U.S. Naval Observatory. Archived from the original on 2007-06-23. http://www.webcitation.org/5Pp65T7lT. Retrieved 2007-04-03.
  10. S.J. Ostro (1985). "Radar observations of asteroids and comets". Astronomical Society of the Pacific, Publications 97: 877. http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1985PASP...97..877O&data_type=PDF_HIGH&type=PRINTER&filetype=.pdf.
  11. C. Magri et al. (1999). "Mainbelt Asteroids: Results of Arecibo and Goldstone Radar Observations of 37 Objects during 1980-1995". Icarus 140: 379.
  12. E. Merényi et al. (1997). "Prediction of Water in Asteroids from Spectral Data Shortward of 3 µm". Icarus 129: 421.
  13. P.S. Hardersen, M.J. Gaffey, and P.A. Abell (2005). "Near-IR spectral evidence for the presence of iron-poor orthopyroxenes on the surfaces of six M-type asteroids". Icarus 175: 141. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005Icar..175..141H&db_key=AST&data_type=HTML&format=&high=444b66a47d07948.
  14. D.R. Davis, P. Farinella, & M. Francesco (1999). "The Missing Psyche Family: Collisionally Eroded or Never Formed?". Icarus 137: 140.

Other websites[change | edit source]