September 30 – 81 Terpsichore

Asteroid 81 Terpsichore, discovered on September 30th 1864 by Ernst Wilhelm Tempel, is a large (about 120 km diameter), dark, “C” type (carbonaceous) main-belt asteroid.  Terpsichore is named after my least favourite muse, the one in charge of dancing.  Her name means “delight in dancing“, an alien concept to myself.  According to the epic poem the Dionysica of Nonnus, she was the mother of the Sirens.

Terpsichore by Antonio Canova (Cleveland Museum of Art)
Terpsichore by Antonio Canova (Cleveland Museum of Art)

The Jovian moon Themisto, discovered on September 30th 1975 by Charles Kowal and Elizabeth Roemer, is a rather small, irregular moon, orbiting about halfway between Jupiter’s large, well known Galilean moons and the rather less famous Himalia Group of prograde irregular companions. The best photographs currently available on the Internet show Themisto as a white pinhead on a black background, so I haven’t bothered “borrowing” one.

Themisto was named after a character from Greek mythology, the subject of a tragedy by Euripides which has unfortunately been lost. In the play, Themisto accidentally kills her own children, believing them to be the offspring of her husband’s first wife. When she realises what has happened, Themisto does what the star of any tragedy would be expected to do, and kills herself as well. The Greek stage at an average drama festival was littered with more bodies than an entire season of Murder She Wrote.

Co-discoverer Elizabeth Roemer also has two asteroids to her name, the magnificently named 1930 Lucifer and 1983 Bok. Charles T Kowal does even better, with 19 minor planets discovered between 1970 and 1981, including 2060 Chiron, the first of the centaurs. His collection of astronomical trophies also boasts a few comets, and Leda, another Jovian satellite.


ALSO TODAY . . .

Asteroid 191 Kolga was discovered today in 1878 by C H F Peters, and named in honour of the daughter of a Norse sea God. The name means “chilling wave”.

Chilling Wave
Chilling Wave

Two years later to the day, Johann Palisa added asteroid 219 Thusnelda to his collection. Thusnelda is an S-type main belt asteroid of approximately 38 km diameter. The name comes from a Germanic princess captured in AD 15 by the Roman general Germanicus Julius Caesar , adoptive son of the Emperor Tiberius, and father of Caligula.


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September 29 – OSO-7

The Orbiting Solar Observatory 7 (OSO-7 ) was the seventh of eight similar satellites, and was launched on September 29th 1971, straight into a drama, when a problem with the second-stage guidance system left it in an unplanned orbit, and pointing in unexpected directions. Fortunately, John Thole at NASA (who we might well come across again in connection with Echo 2) managed to get the mission back on course with a mix of skill and luck, saving the day. I can’t imagine how he must have felt, slewing this huge craft around from so far away he couldn’t even see it. It’s bad enough when your spaceship is made by Nintendo and you get to start again if you crash.

OSO-& (image credit: NASA)
OSO-& (image credit: NASA)

OSO-7, like its brethren, came in two main parts, known as the “sail” and the “wheel”. The sail faced the Sun (during its day) and measured solar x-rays and coronal activity. The wheel, as the name suggests, rotated continuously, measuring solar x-rays and cosmic x- and gamma-rays. The spinning of the wheel, combined with the axial movements that kept the sail pointing at the Sun, allowed two of the wheel-based experiments to cover the whole sky every six months.

OSO-7 re-entered the Earth’s atmosphere on July 9th 1974.


ALSO TODAY . . . .

1884  —  Discovery of asteroid 243 Ida by Johann Palisa.  Ida has been visited by the Galileo spacecraft.  Thanks to Galileo, we have pretty good photographs of Ida, and we now know it has a small companion, Dactyl.

Ida and Dactyl, courtesy of Galileo (image: NASA/JPL)
Ida and Dactyl, courtesy of Galileo (image: NASA/JPL)

Dactyl is pretty teeny, measuring just over a kilometre across in most directions. The name comes from a race of mythical beings who inhabited Mount Ida in Crete.  They are credited with discovering how to use fire to work metal.


1962  —  Launch of satellite Alouette 1.


1988  —  Launch of shuttle mission STS-26 (“Discovery“).


September 28 – Ananke

Ananke is one of Jupiter’s many smaller moons.  It was discovered on September 28th 1951 by Seth Barnes Nicholson at Mount Wilson Observatory.  It takes its name from the mythological personification of “Necessity” (the word means something similar in Greek).  Ananke was the mother of the Fates (also kmown as the Moirai), their father being Zeus (surprise, surprise).

Ananke
Ananke

Ananke is an irregular retrograde satellite, and lends its name to the Ananke group  of similarly inclined moons, as at 14km in diameter it is the largest of the type (the other members being Praxidike, Iocaste, Harpalyke, ThyoneEuanthe, and Europie).  The retrograde motion and eccentric orbits of the group lend credence to the theory that they may all be the remains of asteroids captured by Jupiter.

As far as I am aware there are no photographs of Ananke that show it as anything more than a faint grey spot.


 ALSO TODAY . . . .

1852  —  Birth of Elizabeth Isis Pogson, the first woman to attempt to gain membership of the Royal Astronomical Society (it took five years for her to succeed).


1876  —  Discovery of asteroids 168 Sibylla (by J C Watson) and 169 Zelia by Paul and Prosper Henry (a rarity, classified as “O-type” in the SMASS-based system devised by Bus and Binzel).