9 Metis

9 Metis is one of the larger main-belt asteroids. It is composed of silicates and metallic nickel-iron.

Metis was discovered by Andrew Graham on 25 April 1848, at Markree Observatory in Ireland. Its name comes from the mythological Metis, daughter of Tethys and Oceanus.

“Metis was discovered by Andrew Graham on 25 April 1848, at Markree Observatory in Ireland; it was his only asteroid discovery.[11] It also has been the only asteroid to have been discovered as a result of observations from Ireland until 7 October 2008, when, 160 years later, Dave McDonald from observatory J65 discovered (281507) 2008 TM9.[12]

“Graham discovered the asteroid 9 Metis from Markree on 25 April 1848 while observing with a 3-inch aperture wide-field telescope manufactured for comet searching by the German instrument maker Ertel.[7][8]

“Only eight minor planets were known before then, with the first four having been found in the period 1801–1807, and Graham’s discovery consequently attracted considerable attention. His mathematical abilities allowed him to compute the orbit of the minor planet and to predict its apparent position into the future, including the gravitational effects of planets on its orbit around the Sun.[3]

“Graham worked as First Assistant at the Cambridge Observatory, England, from 1864 to 1903.[3]

“There he worked on the Cambridge Zone Catalogue, the Observatory’s contribution to the catalogue of stars brighter than magnitude 9.5 organised by the Astronomische Gesellschaft in Germany.

“Graham collaborated with Ms Anne Walker in the observing, who, although employed as a `lady computer’ to perform routine mathematical calculations, regularly shared the observing tasks with Graham in a successful professional partnership.[6]

“Graham retired from his post at the Cambridge Observatory in 1903 at the age of 88 years. He was granted a pension by the University of Cambridge. He died in Cambridge in 1908 aged 93 years.[3]Wikipedia

At Andrew Graham’s retirement, Ms Anne Walker resigned as well, bringing her astronomical career at the Cambridge Observatory to an end after 21 years. She was 36. There is no record of her receiving a pension.

Ms Walker was much more than a routine computer. She took part in observations with Graham. This makes her the second woman of the “modern era” after Caroline Herschel to have been formally engaging in night-time astronomical observations.

(Sorry for the ‘divergence’ here. I find the personal and professional histories and lives of the astronomers and scientists of some interest.)

Metis has dimensions of 222x182x130 km. Hubble space telescope images and lightcurve analyses are in agreement that Metis has an irregular elongated shape with one pointed and one broad end. Metis appears to be more dense than most other asteroids with a diameter close to 200 km. This may support the theory that Metis is the core remnant of a large evolved asteroid for which 90% of the original mass has been lost.

The surface of Metis has been estimated as 30-40% metal-bearing olivine and 60-70% Ni-Fe metal. Searches with the Hubble Space Telescope in 1993 found no satellites.

A spectroscopic analysis found strong spectral similarities between 9 Metis and 113 Amalthea, and it is suggested that these asteroids may be remnants of a very old dynamical family whose smaller members have been pulverised by collisions or perturbed away from the vicinity. The putative parent body is estimated to have been 300 to 600 km in diameter (Vesta-sized) and differentiated. Metis would be the relatively intact core remnant, and Amalthea a fragment of the mantle.

Coincidentally, both Metis and Amalthea have namesakes among Jupiter’s inner moons.

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