March 28 – Discovery of Asteroid 2 Pallas (1802)

Asteroid 2 Pallas was discovered on March 28th, 1802, by Heinrich Wilhelm Olbers, physician by day, astronomer by night, and the man after whom the Olbers Paradox (the one about why the sky is dark if the universe is infinite) is named.  He discovered Pallas while trying to locate Ceres, which had been discovered by Giuseppe Piazzi the previous year.

Pallas (from the Hubble Space Telescope). Image: NSAS
Pallas (from the Hubble Space Telescope). Image: NASA

Pallas is at the larger end of the minor planet scale,  being about 550 km wide on average (it isn’t round). It is a B-type body, one of the less common asteroid types. B’s are similar to the much more populous C-types, but with a greater albedo, and different a absorption lines in their spectra.

Statue of Pallas Athene above the Austrian Parliament Building in Vienna (image credit: Max Novara)
Statue of Pallas Athene above the Austrian Parliament Building in Vienna (image credit: Max Novara)

Pallas is named after the Greek goddess Athena (she was often referred to as Pallas Athena/Athene), goddess of wisdom, daughter of Zeus and Metis, owner of the Aegis, and friend of owls. Her Roman equivalent was Minerva.

On March 28, 1900, asteroid 454 Mathesis was discovered from Heidelberg by Friedrich Karl Arnold Schwassmann. Mathesis is a main belt asteroid of about 81.6 km diameter, having, apparently, a rather pleasing year of 1555.5 days, and an equally pleasing albedo of 0.0555. I wonder if that’s why it was named after mathematics?

Schwassmann was discoverer of 22 asteroids, but this was his first without the assistance of the even more prolific discoverer, Max Wolf .

 2009  –  Start of ISS expedition 19.

March 01 – A Flurry of Asteroids

Asteroid 28 Bellona was discovered by Robert Luther on March 1st 1854, three weeks before the start of the Crimean War, so the name was chosen to be topical (Bellona was a Roman goddess of war).   Bellona is a large S-type asteroid of somewhere between 110 and 120km across.

An even larger S-type asteroid, at over 200km wide, is 29 Amphitrite, discovered on the same day, several hundred miles from Luther in Regent’s Park, London, by another German astronomer, Albert Marth.  Marth was working at the time for George Bishop, the owner of a private observatory in the park.  Bishop chose the name.  Amphitrite was Marth’s only asteroid, but John Russell Hind, who we meet in these pages every so often, used Bishop’s 7″ refractor to greater effect to discover ten asteroids between 1847 and 1854.  Unfortunately the observatory is no longer in Regent’s Park; the telescope was moved to his son’s residence in Twickenham after Bishop’s death, and then donated to an Italian Observatory.

In ancient Greek mythology, Amphitrite was a Nereid, and wife of Poseidon.

185 Eunike is a dark, large, carbonaceous main-belt asteroid, approximately 157 kilometres in diameter. It was discovered on March 1st, 1878 by Christian Heinrich Friedrich Peters, and named, in a politically motivated fashion after yet another Nereid, Eunike, whose name means ‘happy victory’.  This is a reference to the Treaty of San Stefano, signed on March 3rd 1878 between the Russian Empire and the Ottoman Empire at the end of the Russo-Turkish War. The treaty led to the creation of an autonomous Bulgaria, became the central point of Bulgarian foreign policy, lasting until 1944, and led to the Second Balkan War and Bulgaria’s entry into World War I.

306 Unitas is another main belt asteroid, discovered by Elia Millosevich on March 1st, 1891. in Rome, and named by the director of the Modena Observatory in honor of the Italian astronomer Angelo Secchi.  It is classified as an S-type asteroid.  Unitas has a similar orbit to the Vesta family, but has been found to be unrelated to them.

1894  –  385 Ilmatar and 386 Siegena

385 Ilmatar is a large main belt asteroid discovered by Max Wolf on this day in 1894.  Ilmatar is the virgin spirit of the air in Finnish mythology.

Ilmatar (R W Ekman)
Ilmatar (R W Ekman)

386 Siegena is another large, C-type asteroid.  It, too, was discovered by Max Wolf in 1894.  It is named after the city of Siegen in Germany.


February 26 – Defining Minor Planets: A Major Headache

1842  –  Birth of Nicolas Camille Flammarion, astronomer and science fiction author, in  Montigny-le-Roi, France.

1880  –  Birth of Kenneth Edgeworth, the first person to propose the existence of what would eventually become known as the Kuiper Belt.

1965  –  Launch of the experimental meteorological satellite Cosmos 58 by the USSR.

Today, as we have no “asteroid” discoveries to discuss, we’re going to have a crash course in a couple of groups of large flying things that used to be called asteroids, but are now commonly known as minor planets.  The term refers to all sorts of things, and can be broadly defined as anything orbiting the Sun that isn’t a planet or a comet.   The terminology, however, is confused and confusing, and unlikely to become any clearer as more bodies are discovered beyond the traditional confines of the Solar System.  So nowadays you have to decide whether you’re talking about a dwarf planet, an asteroid, a trojan, a centaur, a comet, a small Solar System body,  a Kuiper Belt object or a trans-Neptunian object.

The IAU prefer the term small Solar System body for comets and anything too small to use gravity to maintain an ellipsoidal shape, and have done so since their General Assembly of 2006 (IAU 2006), the same one that decided the fate of Pluto.  According to this classification, anything that is not a planet, but which is able to become roughly planet-shaped is a dwarf planet.

So now we have to briefly ask “What is a planet?”  well, according to Resolution 5A of IAU 2006 a planet has to (a) be orbiting the Sun, (b) be able to use its own gravity to keep a nearly round shape, and (c) be sufficiently well-developed to have “cleared the neighbourhood“.  This might be a new phrase to you, but all it means is that the object under consideration has become the dominant one in its orbit, so that there is nothing left nearby of comparable size (except possibly its own satellites).  A dwarf planet meets conditions (a) and (b), but not (c).

So, let’s have a quick look at a couple of the various types of non-planets (I don’t want to drive you away by tackling them all at once).

There are presently known to be five DWARF PLANETS in the Solar System.  These are Pluto, Ceres, Eris, Haumea and Makemake.  Several further trans-Neptunian objects (including Sedna and Quaoar) may well swell their ranks shortly, but their size and distance makes pinning them down difficult.  However, as the outer reaches of the Solar System are explored it is thought that hundreds, possibly thousands, more will turn up.  It is probably only our inability to see beyond the Kuiper Belt that is keeping the numbers down.

Ceres from the DAWN spacecraft (image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)
Ceres from the DAWN spacecraft (image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

I’m not fond of the term dwarf planet, as it suggests that these are small planets, whereas the idea was, I believe, that they aren’t planets at all.  For this reason I would maybe prefer the older term planetoid.  The Japanese have got the right idea: their name for dwarf planets, junwakusei, can be translated as “almost a planet”, which I like almost as much as the suggestion of Alan Stern and Harold Levison from their paper to the IAU in 2000.  They adopted the words überplanet for the big eight, and unterplanet for the rest.
TROJANS are interesting characters. I don’t want to get bogged down explaining Lagrangian points and barycentres (yet) so I’ll just say that a trojan shares an orbit with another (larger) body at the Lagrangian points, approximately 60° ahead of or behind it. We have more interchangeable terminology here: a trojan can also be called a Lagrangian object, and the Lagrangian points are sometimes called trojan points. Saturn has a great collection of trojan moons: they are (i) Telesto and Calypso (trojans of Tethys), and (ii) Helene and Polydeuces (trojans of Dione).

Jupiter also has a large collection of trojans, traditionally named after the two camps of the Trojan Wars. Greek trojans are located at one Lagrangian point, and Trojan trojans are at the other. There are two exceptions to this rule (because their discovery pre-dates it): they are 617 Patroclus ( a Greek, but with the Trojans), and 624 Hektor (a Trojan with the Greeks). I never liked Hektor much when I read the Iliad, so this doesn’t surprise me in the slightest.

Next time I get a quiet day I’ll move onto centaurs and Kuiper Belt objects (if I remember).


February 18 – Discovery of the “Planet” Pluto (1930)

I feel sorry for Pluto. When I was younger it was the ninth biggest planet in the solar system, but unfortunately is now (probably) only the second biggest “dwarf planet” following the discovery of minor-planet 136199 Eris by the Palomar Observatory on January 5th 2005. This discovery encouraged an acceleration of the debate over whether or not Pluto should ever have been called a planet, the result being that the IAU published their Definition of a Planet in the Solar System on August 24th 2006. So I suppose that’s the day on which Pluto stopped being a planet, and became a Kuiper Belt Object. And as if that weren’t damage enough for Pluto’s image, there is still a debate going on as to whether Pluto and Charon should be re-classified as a binary system. At the moment Charon is a moon of Pluto; but the centre of their combined mass doesn’t lie within either body, so strictly speaking it should get higher billing.

On the upside, Pluto does get its own Disney character, and lends its name to both plutoids (anything beyond the orbit of Neptune that has managed to attain a roughly spherical shape) and plutinos (anything in the above group that orbits the Sun twice in the same time it takes Neptune to make it round three times).

Pluto was discovered on February 18th 1930 by Clyde Tombaugh from Illinois. Tombaugh was a prolific discoverer of variable stars, and also of asteroids, many of which he found while searching for Pluto. But Pluto will always be his claim to fame, and following his death in 1997 a small quantity of his ashes were sent on their way out there aboard the New Horizons probe, which arrived at the ex-planet on July 14th 2015 to a blaze of publicity, and began sending back fabulous snapshots.

Pluto from the New Horizons probe (image credit: NASA/APL/SwRI)
Pluto from the New Horizons probe (image credit: NASA/APL/SwRI)

And not before time, as you can see from the second photograph (below); because close-ups of Pluto from the enormous distance of the Earth don’t reveal a great deal of detail.

Pluto and Charon (image: NASA)
Pluto and Charon, pre-New Horizons (image: NASA)

As well as the aforementioned Charon, Pluto has four other moons: Nix, Hydra, Kerberos and Styx. All moons of Pluto are named in accordance with the convention that they are mythological, and have some association with their parent (Hydra, for example, was the nine-headed guardian of an entrance to the underworld).

Surface detail of Pluto from New Horizons (image credit: NASA)
Surface detail of Pluto from New Horizons (image credit: NASA)

As I just mentioned, Pluto is a Kuiper Belt object (KBO). The Kuiper belt, (rhymes with sniper, not kipper, although I have to admit that I do find the concept of a kipper belt rather appealing) or, to give it its full name the Edgeworth-Kuiper Belt, stretches from about 30 to 50 AU from the Sun, and contains an enormous number of mostly smallish bodies (trans-Neptunian Objects, or TNOs) left over from the formation of the Solar System.

A Selection of KBOs (image: NASA)
A Selection of KBOs (image: NASA)

Why Edgeworth gets edged out in popular literature while Kuiper gets the kudos is something I might know more about by the time his birthday comes around (Feb 26th, 1880). Neither of them correctly predicted what the belt was like anyway, so it’s anybody’s guess.

Anyhoo, there are thought to be as many as 100,000 TNOs within the belt with a diameter of over 100km (which is why I say “smallish” not “small”) and, because Pluto is now a member, everybody knows the name of at least one.

Results from New Horizons are changing our view of Pluto for ever. It now see that a crust of water ice might be acting in place of a bedrock, supporting mountains made of frozen nitrogen and methane. It also seems that Pluto might, somehow, be still geologically active. We need to visit again!

February 18th, 1977 was the day on which the space shuttle Enterprise made her first “attached” flight. Strictly speaking, I suppose, this wasn’t the maiden flight of a shuttle, as Enterprise was securely strapped to the back of a specially adapted Boeing 747 for the duration. I now know that she didn’t have any engines or a heat shield, and was therefore incapable of actually flying in space, but at the time I was young(er), and mightily impressed (and it was the first time a shuttle’s wheels had been higher than the hangar roof, so it counts). I was even more impressed when Enterprise was flown, again attached to the 747, over the family home at Brown Edge, Staffordshire, six years later as part of a promotional tour of Europe, drumming up satellite launching business for NASA.

February 10 – Discovery of Asteroid 624 Hektor (1907)

Asteroid 624 Hektor was discovered on February 10th 1907 by August Kopff, a German astronomer working out of the Humboldt University of Berlin, who eventually discovered 68 asteroids.

Being numbered 624 would normally put it below the radar, but this one gets a mention because it is the largest of the Jupiter trojans.  It’s a reddish D-type asteroid (as are the majority of Jupiter trojans) and lies at the L4 Lagrangian point (in other words it precedes Jupiter in its orbit).

L4 Jupiter trojans are supposed to be named after characters from the Greek side of the Trojan Wars.  Hektor is therefore misnamed, as he was on the Trojan side (617 Patroclus is also in a similar predicament, being a Greek hero in the Trojan camp at the L5 Lagrangian point).

Hector Reproaches Paris, by Pierre Delorme (1783-1859).
Hector Reproaches Paris, by Pierre Delorme (1783-1859).

Hektor measures 370 km long by 200 km wide, an unusual shape for an asteroid, leading astronomers to conclude that it might be a “binary”, two conventionally shaped asteroids drawn together by their mutual gravitational pull.  Observations indicate this may well be the case, but with an object of that size at such a great distance, it’s hard to be absolutely sure.

Hektor has also been shown to have a moon, about 12 km in diameter, going by the name S/2006 (624) 1.  Around 6,000 Jupiter trojans are known at present (although there are thought to be around a million up there of over 1 km diameter).  At present, Hektor is the only one at L4 thought to be a binary, and the only one known to have a satellite.

Hektor (you can call him Hector if you like, but there is no “C” in the Greek alphabet), as you may know, was the son of King Priam and Queen Hekabe, and the greatest Trojan hero of the wars, making it all the more unusual that he should be named as one of the Greek asteroids.



February 06 – Asteroid 212 Medea

Asteroid 212 Medea was discovered from Pula (or Pola) in Croatia by Johann Palisa on February 6th 1880.  It’s another big main-belter, about 144 km (90 miles) across, with, in the absence of much else to say about it, the following orbital characteristics, plucked from the JPL Small Body Database:

Epoch 27 April 2019
Aphelion 3.464 AU
Perihelion 2.804 AU
Semi-Major Axis 3.124 AU
Eccentricity 0.103
Orbital Period 5.49 years
Average Orbital Speed 16.88 km/s
Inclination 4.265°
Longitude of Ascending Node 313.059°
Argument of Perihelion 102.928°
Mean Anomaly 205.318°

Medea is our second Greek tragedy in two days.  This one is by Euripides (c. 484 to 406 BC), the most modern of the “big three” Athenian dramatists.  He was about fifty when he wrote it, and it was perhaps a little too much for his audience, who placed it last in the City Dionysia of 431 BC, behind Sophocles in second, and Euphorion (son of the more famous Aeschylus) who won.

Jason & Medea (Carle van Loo, 1705-65)
Jason & Medea (Carle van Loo, 1705-65)

Medea was the wife of Jason (of “and the Argonauts” fame).  She obviously had a sharp temper, shown most vividly by her killing her own children to spite Jason after he’d had a fling with the daughter of the King of Corinth.

February 05 – Discovery of Asteroid 129 Antigone (1873)

Asteroid 129 Antigone was discovered on February 5th, 1873 by C H F Peters. It’s a fairly regularly shaped body of about 120 km across, and is composed of a nickel-iron mix, putting it firmly in the metallic M class, and leading scientific types to conclude that it is probably the remains of the core of a planetesimal, destroyed at some point in the dim and distant past.

Antigone, as you know, was the daughter of Oedipus, the king of Thebes, and Jocasta, his queen (and mother). Basically, after Oedipus’ death, Antigone upsets King Creon, Oedipus’ predecessor,  who had taken the opportunity to rule Thebes again after Oedipus’ sons had fallen out with one another in a big way.  The upset comes about as a result of Antigone trying to arrange a decent burial for her brother Polynices, who was regarded as a traitor.  Long story short: she hangs herself, and her beau (Creon’s son Hæmon) kills himself in his grief.

Oedipus and Antigone (Aleksander Kokular)
Oedipus and Antigone (Aleksander Kokular)

The depiction of Oedipus and Antigone above is by the amazingly-named Aleksander Kokular (1793 – 1846) a Polish painter and educator, and co-founder of the Warsaw School of Fine Arts.  He was well-known for his mythological (as you can see) and religious works.

The story of Antigone with which most of us are familiar comes from Sophocles’ three Theban Plays (there are three of them, but they’re not a trilogy).  I can`t recommend the Theban Plays highly enough.  I consider Sophocles to be way above Aeschylus and Euripides when it comes to tales of misery and woe.  Euripides did actually write an Antigone himself; the text is lost, but it’s known that tragedy is averted in this version by divine intervention.  That’s not what I want!  It’s supposed to be a tragedy!  Make it tragic!
And I’m going to get really nerdy now, and say try to get the E F Watling translation.  Robert Fagles is fine, but Watling is my preference.

A Classic.
A Classic.

Today’s second photograph is the front cover of my latest copy of the Theban Plays (Penguin Classics).  It shows Oedipus dressed as a traveller (in other words wearing a hat and carrying a staff) pondering the riddle of the Sphinx.

1877  –  S-type asteroid 172 Baucis discovered by Alphonse Borrelly, and named after a character in Ovid’s Metamorphoses.

1987  –  Japanese X-Ray satellite Ginga (otherwise known as Astro-C) was launched.  It sounds like an acronym, but it isn’t.  It’s Japanese for “galaxy”.


2002  –  The Reuvan Ramaty High Energy Solar Spectroscopic Imager (HESSI, or RHESSI) was launched to study solar flares, with a view to working out why they occur, and how so much energy can be released in such a short time.  Reuvan Ramaty, by the way, was an expert in cosmic rays, and one of the original members of the HESSI team.  Unfortunately he died on April 8th, 2001, less than a year before launch.


February 04 – Discovery of Asteroid 52 Europa (1858)

February 4th 1858  marks the discovery, by Hermann Goldschmidt, of asteroid 52 Europa.  Europa is approximately 315km in diameter, making it the sixth largest asteroid, and is named after a mythical Phoenician woman with whom Zeus had a fling (for some reason he had decided that taking the form of a white bull was a good idea for this particular wooing, and it worked).  Europa, believe it or not, gave her name to Europe.

"The Abduction of Europa" (Rembrandt)
“The Abduction of Europa” (Rembrandt)

The asteroid Europa is the second largest of the C-type asteroids.  C-types are the most common asteroids, accounting for about three quarters of all those known.  They are carbonaceous, and difficult to spot because of their dark colour.  Spectrographic studies of this particular one in the 1990s by the University of Texas have found evidence of the presence of olivines and pyroxenes.

1960   ⇒   Launch of Discoverer 9.  There isn’t much to say about this one, as it failed to reach orbit following a premature 1st stage cut-off.  It had been intended as a low resolution photo surveillance satellite, and was launched from Vandeburg Air Force Base by the USAF.  The aim was to replace the U2 spyplanes and gather photographic evidence of how quickly the Soviet Union was producing ballistic missiles and long-range bombers.

1961   ⇒   Launch of Sputnik 7.  Possibly the first Soviet attempt to launch a probe to Venus, or then again possibly just a tester for Sputnik 8.  Either way, Sputnik 7 (14,290 lb) was launched by an A2e launch vehicle (the “A” refers to the core Vostok launch vehicle, with “2″  denoting an extra 2-engined third stage and “e” meaning it carried an escape capsule) and came quickly back down from orbit on Feb 25.

1888   ⇒   Main belt asteroid 272 Antonia discovered by Auguste Charlois.

1906   ⇒   Birth of Clyde Tombaugh, American astronomer, discoverer of Pluto.


January 18 – Asteroid 221 Eos

221 Eos is a K class (more about this in a minute) main belt asteroid discovered by Johann Palisa on January 18th 1882. It’s about 100 km wide, weighs in at a healthy six million trillion tonnes (give or take a few hundred thousand) and is quite dim at magnitude 7.67.

Eos lends its name to an extensive family of asteroids, all sharing roughly similar orbits, and all thought to have originated from an almighty collision some time in the distant past, which the latest best guesses put at around a billion years ago. About 300 members of the family are known, all being similar to S-types, but not identical, so they get their own category, the aforementioned K-type.


Eos was named after the Greek goddess of the dawn, shown above in her winged chariot.  She was the sister of Helios (Sun) and Selene (Moon) and it was her job to open up heaven in the morning so that Helios could do his thing.

Also today, asteroid 468 Lina, a member of the Themis family, was discovered today in 1901 by Max Wolf and named after the family housemaid. It’s probably best if I don’t speculate as to why that might be.


January 07 – Discovery of Asteroid 410 Chloris (1896)

Asteroid 410 Chloris was discovered on January 7th 1896 by Auguste Charlois.  It’s a large, C-type, main-belt asteroid of approximately 115 km diameter, and lends its name to a family of similar bodies.

The Chloris family contains an unknown number of members, obviously, because we can never be sure they’ve all been found.  But even if we only consider those asteroids we know about, there is still some uncertainty surrounding how many asteroids there are in the family, depending on which method you use to determine whether a particular asteroid should be included or not.  For example, using hierarchical clustering, the family has 21 members, but using wavelet analysis, there are 27.  One day in the distant future, when I lose the will to live, I’ll try to explain these methods.  In the meantime, here are the facts and figures.

Aphelion 3.376 AU
Perihelion 2.082 AU
Orbital period 4.51 years
orbital speed 18.03 km/second
Semi-major axis 2.729 AU
Eccentricity 0.237
Inclination 10.921°
Longitude of ascending node 97.251°

The name Chloris comes from a Greek work meaning something along the lines of pale greenish (think “chlorophyll”).  There are several mythological characters with the name, but the one apparently invoked in this case was one of the Niobids, the fourteen children of Niobe and Amphion, most famous for being nearly all killed by Apollo and Artemis.  Chloris had been born with the name Meliboea, but was turned permanently palid by the aforementioned ordeal (which she survived) and changed her name to something suitably pale and interesting.

Artemis and Apollo Killing the Niobids
Artemis and Apollo Killing the Niobids

The photograph (above) shows a detail from a Roman sarcophagus found near the Via Appia in Rome in 1824, and now housed in the Glyptothek in Munich, a museum built specifically to house the Greek and Roman sculptures of King Ludwig I of Bavaria.

Aside:  I can’t let this post go by without directing you to an exceptional recording by Susan Graham and Roger Vignoles of À Chloris, one of my favourite songs by the Venezuelan composer Reynaldo Hahn.  CLICK HERE first to hear it, they buy the album (“La Belle Epoque”, Sony, SK60168).  I apologise in advance for the adverts YouTube will fire your way.