September 06 – Discovery of Asteroid 94 Aurora (1867)

At 225 km long by 173 km wide, the extremely sooty (albedo 0.04) 94 Aurora is one of the largest asteroids known (currently occupying 25th place).  It was discovered on September 6th 1867 by James Craig Watson.

Albedo, as I’m sure you know, is a measure of how reflective a surface is.  It goes from ‘zero’ (completely black) to ‘one’ (perfectly white). Aurora’s 0.04, to give you an idea, is the albedo of charcoal (fresh snow is 0.9).

ans “dawn” in Latin, as in Aurora Borealis, the “northern sunrise” (Borealis comes from Boreas, Greek god of the cold North wind).  Aurora’s family history is a little sketchy and inconsistent, but her siblings are Sol (the Sun) and Luna (have a guess).  She may or may not, depending on who you read, been mother of the Anemoi, the gods of the winds (one of whom of course was Boreas).

Aurora and Cephalus (Guérin).
Aurora and Cephalus (Guérin).

Today’s picture is by our old friend Pierre-Narcisse Guérin, the highly-rated French painter (he was a member of the very exclusive Académie des Beaux-Arts) making his second appearance in a week (see also Phaedre on September 02).

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ALSO TODAY . . . .

1891  –  Birth of Finnish astronomer Yrjö Väisälä.

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September 02 – Discovery of Asteroid 147 Phaedra (1877)

Discovered on September 2nd 1877 by James Craig Watson, 147 Phaedra is a bog-standard S-type (stony) asteroid, possibly with an elongated shape, in the main belt.  It takes approximately 4.8 years to get around the Sun, rotating every 5 hours as it does so.  Phaedra has a diameter of less than 70km, so determining the rotation rate by direct observation from Earth is, to say the least, difficult.  This is where light curve observations come in.  If you measure the light coming from an asteroid for long enough you end up with a collection of readings that, when plotted on a graph, repeat every so often.  What you need to do is measure the time between similar maxima or minima to give you a pretty good idea of the length of a day on the asteroid.  By the way, a rotation rate of 5 hours gives Phaedra a year of about 1700 days.  You’re going to need a bigger diary if you’re thinking of moving there.

Watson discovered 22 asteroids, but could have gone on to be one of the great rock-spotters had he not died of peritonitis at the age of 42.

Phaedra and Hippolytus (print by A G L Desnoyers of a painting by Pierre Guérin)
Phaedra and Hippolytus (print by A G L Desnoyers of a painting by Pierre Guérin)

Phaedra (from the Greek for “bright”) was married to Theseus, but fell for his illegitimate son Hippolytus (eponymous hero of a play by Euripides that I was forced to spend far too long studying in 1981) under the influence of Aphrodite, goddess of love, who was annoyed by Hippolytus’ chastity.  Basically, Phaedra makes the mistake of telling her nurse that she fancies her stepson.  The nurse tells Hippolytus; he goes ballistic; Phaedra knows things are going to get complicated, hangs herself and leaves a suicide note saying Hippolytus has raped her.  Theseus finds it, exiles his son and curses him.  Now, Theseus’ father is Poseidon, so it’s not quite the same as me or you cursing a neighbour for parking in front of our house.  In this case, as Hippolytus is fleeing into exile in his chariot, a huge bull appears from the sea, frightens his horses, and causes him to crash and be fatally wounded (he survives just long enough to be carried back on stage to make peace with his father, who has learned the truth).

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May 16 – Discovery of Asteroid 87 Sylvia

Asteroid 87 Sylvia was discovered on May 16th 1866 by N R Pogson, author of the Madras Catalogue of stars, at Madras Observatory.

Sylvia is a large asteroid in the Cybele group of bodies in the outer core of the main belt.  She is an x-type asteroid, with “x” in this case doing its usual job of signifying the uncertainty surrounding their composition.

Sylvia is named after Rhea Silvia, descendant of Aeneas, daughter of Numitor, and, in an unusual career move for a Vestal Virgin, mother of Romulus and Remus, the supposed founders of Rome who as babies were set adrift on the river Tiber by a servant who had been ordered to kill them, later to be found and suckled by a wolf who had lost her cubs.

Rhea Silvia, torso from the amphitheatre at Cartagena, Spain.
Rhea Silvia, torso from the amphitheatre at Cartagena, Spain.

Sylvia has two satellites. They were given the fairly obvious names of Romulus (discovered in 2001) and Remus (2004).


1888  –  Discovery of asteroid 278 Paulina by Johann Palisa. Nobody is quite sure who Paulina, Paul or Paula was.


2011 saw the launch of the Alpha Magnetic Spectrometer 02 (AMS-02) via shuttle Endeavour, to be mounted onboard the International Space Station.  AMS-02′s raison d’etre is to measure cosmic rays as part of the ongoing search for dark matter.  It seems to be working well so far, making 1,000 recordings a second, and passing the 90 billion mark in 2016.

AMS-02 Patch (NASA/JSC).

If particle physics is your thing, the AMS-02 website is probably where you’ll want to go next.


Last updated: May 2019.

May 14 – Discovery of Asteroid196 Philomela

Asteroid 196 Philomela was discovered by Christian Heinrich Friedrich Peters at Hamilton College, Clinton (New York) on May 14th 1879.  It is a large, bright, S-type (stony) main belt asteroid, and studies of light curve data have decided it is smooth and asymmetrically shaped.

Philomela and Procne showing Itys'head to Tereus. Engraving by Bauer for a 1703 edition of Ovid's Metamorphoses
Philomela and Procne showing Itys’ head to Tereus. Engraving by Bauer for a 1703 edition of Ovid’s Metamorphoses

Philomela was the daughter of King Pandium I of Athens, and had a sister called Procne.  Procne’s husband, Tereus, raped Philomela, and according to Ovid, cut out her tongue.  To get her revenge Philomela wove a tapestry (she couldn’t just write it down?) telling her story, and sent it to her sister.  Procne took the news badly, killing her son by Tereus, boiling him, and serving him to her husband.

Tereus failed to see the funny side, and pursued the sisters with the aim of killing them.  But they prayed to the gods for assistance, and were transformed into birds (Procne a swallow, and Philomela a nightingale).


1917 –  Discovery of main belt asteroid 871 Amneris (a character in the opera Aida) by Max Wolf at the Heidelberg Observatory.  Amneris is now known to have its own small family of 20 or so asteroids.


1973   –   Unmanned launch of Skylab, the first orbiting space station of the United States.  Although the final manned mission left the station in 1974, Skylab remained potentially operational, and the plan was to move it into a higher orbit using the space shuttle.  Unfortunately the development of the shuttle took longer than planned, so NASA were forced to allow Skylab to re-enter Earth’s atmosphere.


2009   –   Launch of PLANCK by ESA and the Herschel Space Observatory (a joint mission by NASA and ESA). PLANCK was equipped with instruments to detect at infrared and microwave, while Herschel was the largest infrared telescope ever launched, with a primary mirror measuring 11 feet in diameter. Herschel’s mission ended on 29th April 2013, when the liquid helium needed to cool it’s instruments ran out. PLANCK lasted a little longer, being told to shut down on 23rd October the same year.

At time of writing (May 2019, the ESA/PLANCK website was still up and running.


Last updated: May, 2019.