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Sunday, 15 April 2012

33th Largest Asteroid, 16 Psyche

16 Psyche is a large main-belt asteroids and the largest member of the Themistian asteroid family. Psyche is the 33th largest asteroid and is the most massive metallic M-type asteroid currently known.


16 Psyche was discovered on 17 March 1852 by Annibale de Gasparis at Naples.


Psyche the asteroid was named after the Greek mythological figure Psyche.

In Greek mythology, Psyche was the deification of the human soul. She was portrayed in ancient mosaics as a goddess with butterfly wings (because psyche is also the Greek word for 'butterfly').

Psyche was originally the youngest daughter of the king and queen of Sicily, and the most beautiful person on the island. Suitors flocked to ask for her hand.

She eventually boasted that she was more beautiful than Aphrodite (Venus) herself, and Aphrodite sent Eros to transfix her with an arrow of desire, to make her fall in love with the nearest person or thing available. But even Eros (Cupid) fell in love with her, and took her to a secret place, eventually marrying her and having her made a goddess by Zeus (Jupiter).


Diameter (mean): 186 km
Aphelion: 3.328 AU
Perihelion: 2.521 AU
Semi-major axis: 2.922 AU
Orbital Period: 4.99 years
Rotation period: 4.20 hrs
Date discovered: 1852.3.17
Class: M
Type: Main-belt Asteroid

Physical Characteristics

Radar observations indicate Pysche has a fairly pure iron–nickel composition. Psyche appears to be a genuine case of an exposed metallic core from a larger differentiated parent body. Psyche is the most massive metallic M-type asteroid currently known.

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. Small amounts of pyroxene appear to be present.

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

Asteroid family ?

If Psyche is the core remnant of a larger parent body, we might expect other asteroids on similar orbits. However, we do not find any asteroid family belonging to Psyche.

One hypothesis 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.

Star occultation

16 Psyche on August 21, 2010 occulted the star HIP 22112 in Taurus over a long path that passed from the central Baja peninsula to the central Atlantic coast. Maximum duration was predicted to be 10.3 seconds. For this event, 12 observers at 17 sites recorded 14 chords across the profile of the asteroid. Fifteen sites used video to record the event while one station used visual techniques and one station used drift scan.

The resulting chords and least squares ellipse produce a smooth ellipse with dimensions of 235.4 ± 3.9 x 230.4 ± 2.4 km. The maximum occultation duration of 10.12 seconds occurred at station nine and is just 2% shorter than predicted. The observed path was just 32 km north of the prediction.

Only two other occultations by Psyche have been observed: a single-chord event on 2002 March 22 and a five-chord occultation on 2004 May 16 (TYC 5783-01228-1). The four useable chords for the 2004 event were spaced well across the asteroid, being fit by an ellipse with axes of 214 ± 6 km by 181 ± 7 km.

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