16 Psyche

16 Psyche

A three-dimensional model of 16 Psyche based on its light curve.
Discovery
Discovered by Annibale de Gasparis
Discovery date 17 March 1852
Designations
MPC designation (16) Psyche
Pronunciation /ˈsaɪkiː/ SY-kee
Named after
 Psychē
none
Main belt
Orbital characteristics[1]
Epoch JD 2453300.5 (22 October 2004)
Aphelion 3.328 AU (497.884 Gm)
Perihelion 2.513 AU (375.958 Gm)
2.921 AU (436.921 Gm)
Eccentricity 0.140
4.99 yr (1823.115 d)
17.34 km/s
323.379°
Inclination 3.095°
150.352°
228.047°
Physical characteristics
Dimensions 186 km (Geometric mean)
253.2 ± 4 km (IRAS)[1]
Mass 2.27×1019 kg[2]
Mean density
 3.3 ± 0.7 g/cm³[3]
~0.11 m/s²
~159 m/s
0.1748 d (4.196 h)[1][4]
Albedo 0.120 (geometric)[1]
0.29±0.11 (radar)
Temperature ~160 K
max: ~280 K (+7 °C)
Spectral type
 M[1]
9.22 to 12.19
5.90[1]

    16 Psyche is one of the ten most massive asteroids in the asteroid belt. It is over 200 km (120 mi) in diameter and contains a little less than 1% of the mass of the entire asteroid belt. It is thought to be the exposed iron core of a protoplanet.[5] It is the most massive metallic M-type asteroid. Psyche was discovered by the Italian astronomer Annibale de Gasparis on 17 March 1852 from Naples and named after the Greek mythological figure Psyche.[6]

    Symbol

    The first fifteen asteroids to be discovered were given symbols by astronomers as a type of shorthand notation. Psyche was given an iconic symbol, as were several other asteroids discovered over the next few years. This symbol , a semicircle topped by a star, represents a butterfly's wing, symbol of the soul (psyche is the Greek word for 'soul'), and a star.[7] In 1851, German astronomer J. F. Encke suggested using a circled number, and 16 Psyche was the first new asteroid to be discovered that was designated using this scheme when American astronomer James Ferguson published his observations in 1852.[8]

    Characteristics

    Composition, dimension and genesis

    Radar observations indicate that Psyche has a fairly pure iron–nickel composition,[9][10] consistent with it having the highest radar albedo of any asteroid in the asteroid belt (0.29±0.11).[11] Psyche seems to have a surface that is 90% metallic (iron),[12] with small amounts of pyroxene.[13]

    Therefore, Psyche appears to be an exposed metallic core from a larger differentiated parent body some 500 kilometers in diameter. If Psyche is indeed one, there could be other asteroids on similar orbits. However, Psyche is not part of any identified asteroid family.[14] One hypothesis is that the collision that formed Psyche 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. However, this scenario is considered to have a probability of just 1%. An alternative is that Psyche was broken by impacts, but not catastrophically torn apart. In this case, it may be a candidate for the parent body of the mesosiderites, a class of stony–iron meteorites.[14]

    Psyche is massive enough that its gravitational perturbations on other asteroids can be observed, which enables a mass measurement. IRAS data shows it to have a diameter of 253 km,[1] whereas observations of an occultation in 2004 that provided five cross-sectional chords suggest an outline of 214×181 km.[15] Further estimates in 2006 and 2011 that also suggested a smaller size have resulted in an increase in its estimated density to one that is more appropriate for a metallic asteroid.[2][3] Psyche appears to have a fairly regular surface and is approximately ellipsoidal in shape. Light-curve analysis has indicated that Psyche's pole points towards either ecliptic coordinates (β, λ) = (−9°, 35°) or (β, λ) = (−2°, 215°) with a 10° uncertainty.[16] This gives an axial tilt of 95°.

    It is possible that at least some examples of enstatite chondrite meteorites originated from this asteroid, based on similar spectral analysis results.

    Presence of water

    The NASA Infrared Telescope Facility at the Mauna Kea Observatories released evidence of the presence of water or hydroxyl ions on the asteroid in October 2016. The water is believed to have reached Psyche via past impacts from smaller asteroids containing volatile substances such as carbon, hydrogen and water.[17][18][19]

    Value

    Lindy Elkins-Tanton, the lead scientist on the NASA Psyche mission, estimated that if the 200-kilometre-wide body could somehow be transported back to our planet the iron alone would be worth US $10,000 quadrillion.[20]

    Exploration

    Artist's concept of the Psyche spacecraft

    No spacecraft has visited Psyche, but in 2014 a mission to Psyche was proposed to NASA.[21][22] A team led by Lindy Elkins-Tanton,[5] the director of the School for Earth and Space Exploration at Arizona State University, presented a concept for a robotic Psyche orbiter. This team argued that 16 Psyche would be a valuable object for study because it is the only metallic core-like body discovered so far.[22]

    The spacecraft would orbit Psyche for six months, studying its topography, surface features, gravity, magnetism, and other characteristics and would be based on current technology, avoiding high cost and the necessity to develop new technologies. On September 30, 2015, the Psyche orbiter mission was one of five Discovery Program semifinalist proposals.[23]

    The mission was approved by NASA on January 4, 2017 and was originally targeted to launch in October 2023, arriving at the asteroid in 2030, following an Earth gravity assist spacecraft maneuver in 2024 and a Mars flyby in 2025.[24] In May 2017 the launch date was moved up to target a more efficient trajectory, launching in 2022 and arriving in 2026 with a Mars gravity assist in 2023.[25]

    References

    1. 1 2 3 4 5 6 7 "JPL Small-Body Database Browser: 16 Psyche" (2008-09-19 last obs). Retrieved 2008-12-04.
    2. 1 2 Baer, Jim (2011). "Recent Asteroid Mass Determinations". Personal Website. Retrieved 2012-04-14.
    3. 1 2 Lupishko, Dmitrij F. (2006). "On the bulk density and porosity of M-type asteroid 16 Psyche". Solar System Research. 40 (3): 214–218. Bibcode:2006SoSyR..40..214L. doi:10.1134/S0038094606030051.
    4. ↑ PDS lightcurve data Archived January 17, 2010, at WebCite
    5. 1 2 Elkins-Tanton, L. T.; et al. (March 2014). "Journey to a Metal World: Concept for a Discovery Mission to Psyche" (PDF). LPI Contribution No. 1777. 45th Lunar and Planetary Science Conference. p. 1253. Bibcode:2014LPI....45.1253E. Retrieved 2015-10-05.
    6. ↑ Schmadel, Lutz D. (2012). Dictionary of Minor Planet Names (6th ed.). Springer Science & Business Media. pp. 14−15. ISBN 3642297188.
    7. ↑ Sonntag, A. (1852). "Elemente und Ephemeride der Psyche". Astronomische Nachrichten. 34 (20): 283. Bibcode:1852AN.....34..283.. doi:10.1002/asna.18520342010. (in a footnote) Herr Professor de Gasparis schreibt mir, in Bezug auf den von ihm März 17 entdeckten neuen Planeten: "J'ai proposé, avec l'approbation de Mr. Hind, le nom de Psyché pour la nouvelle planète, ayant pour symbole une aile de papillon surmontée d'une étoile."
    8. ↑ Hilton, James (2001-09-17). "When Did the Asteroids Become Minor Planets?". U.S. Naval Observatory. Archived from the original on 2010-01-18. Retrieved 2007-04-03.
    9. ↑ Ostro, S. J. (1985). "Radar observations of asteroids and comets". Publications of the Astronomical Society of the Pacific. 97: 877. Bibcode:1985PASP...97..877O. doi:10.1086/131619.
    10. ↑ Magri, C.; et al. (1999). "Mainbelt Asteroids: Results of Arecibo and Goldstone Radar Observations of 37 Objects during 1980–1995". Icarus. 140 (2): 379. Bibcode:1999Icar..140..379M. doi:10.1006/icar.1999.6130.
    11. ↑ Ostro, S. J. (October 1985). Radar observations of asteroids and comets. Astronomical Society of the Pacific, Symposium on New Directions in Asteroids and Comet Research, Northern Arizona University. 97. Astronomical Society of the Pacific. pp. 877−884. Bibcode:1985PASP...97..877O. doi:10.1086/131619.
    12. ↑ Callahan, Jason (March 30, 2015). "Discovery lives". The Space Review. Retrieved 30 March 2015.
    13. ↑ Hardersen, Paul S.; Gaffey, Michael J. & Abell, Paul A. (2005). "Near-IR spectral evidence for the presence of iron-poor orthopyroxenes on the surfaces of six M-type asteroids". Icarus. 175 (1): 141. Bibcode:2005Icar..175..141H. doi:10.1016/j.icarus.2004.10.017.
    14. 1 2 Davis, D. R.; Farinella, Paolo & Francesco, M. (1999). "The Missing Psyche Family: Collisionally Eroded or Never Formed?". Icarus. 137 (1): 140. Bibcode:1999Icar..137..140D. doi:10.1006/icar.1998.6037.
    15. ↑ "Occultation of TYC 5783-01228-1 by (16) Psyche 2004 May 16". Royal Astronomical Society of New Zealand, Occultation Section. Retrieved 2015-10-05.
    16. ↑ Kaasalainen, M.; et al. (2002). "Models of Twenty Asteroids from Photometric Data" (PDF). Icarus. 159 (2): 369. Bibcode:2002Icar..159..369K. doi:10.1006/icar.2002.6907. Archived from the original (PDF) on 2008-02-16. Retrieved 16 May 2006.
    17. ↑ Atkinson, Nancy. "Pure Metal Asteroid Has Mysterious Water Deposits". Universe Today. Retrieved 11 November 2016.
    18. ↑ Simpson, Julia. "Giant Metallic Asteroid Psyche May Have Water". Politicallore. Retrieved 12 November 2016.
    19. ↑ http://www.space.com/34525-giant-metallic-asteroid-psyche-water.html
    20. ↑ http://globalnews.ca/news/3175097/nasa-plans-mission-to-a-metal-rich-asteroid-worth-quadrillions/ NASA plans mission to a metal-rich asteroid worth quadrillions
    21. ↑ Chang, Kenneth (6 January 2017). "A Metal Ball the Size of Massachusetts That NASA Wants to Explore". The New York Times. Retrieved 7 January 2017.
    22. 1 2 Wall, Mike (15 January 2014). "Strange Metal Asteroid Targeted in Far-Out NASA Mission Concept". Space.com. TechMedia Network. Retrieved 16 January 2014.
    23. ↑ Brown, Dwayne C.; Cantillo, Laurie (September 30, 2015). "NASA Selects Investigations for Future Key Planetary Mission". NASA TV. NASA. Retrieved 2015-10-05.
    24. ↑ Northon, Karen (2017-01-04). "NASA Selects Two Missions to Explore the Early Solar System". NASA. Retrieved 2017-01-04.
    25. ↑ "NASA Moves Up Launch of Psyche Mission to a Metal Asteroid". NASA. 2017-05-24. Retrieved 2017-05-24.
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