January 11 – Oberon and Titania

January 11th 1787 was a good day for William Herschel.  Not many of us get to discover even one major moon in a lifetime, but on this particular day in history Herschel was fortunate enough to find both the largest moon of Uranus, Titania, and the second largest, Oberon.

Both moons were named after characters from Shakespeare’s A Midsummer Nights Dream; they were king and queen of the faeries.  They joined the sprites, Ariel (from The Tempest), and Umbriel (from Alexander Pope’s The Rape of the Lock) which had been discovered in October 1851.

Oberon is the outermost major Uranian moon, and the ninth most massive moon in the solar system.  It is about 50/50 rock and ice, with the rock probably forming the core.  It’s quite “moonish” in appearance, being fairly dark and rather cratered by impacts, much like our own companion.  However, unlike our dry Moon, as well as being partly icy, Oberon may well have a layer of liquid water between the core and the mantle.

Oberon from Voyager 2 (image: NASA)
Oberon from Voyager 2 (image: NASA)

Titania is similar in appearance and composition to Oberon, but is less heavily cratered, possibly as a result of internal processes that removed some of the older cratering.  Both moons were probably formed in situ from an accretion disc.

Titania from Voyager 2 (image: NASA)
Titania from Voyager 2 (image: NASA)

Only Voyager 2 has ever been close enough to Uranus to capture good shots of Oberon and Titania.  It made its closest approach to the planet on January 26th 1986, but had already got to about 300,000 miles of Titania and 400,000 miles from Oberon two days earlier, at which time it took these photographs.

1865   –   German astronomer Johannes Franz Hartmann born.


January 10 – Discovery of Asteroid 170 Maria (1877)

Asteroid 170 Maria was discovered on January 10th 1877 by Henri Joseph Perrotin (1845-1904).  It is an S-type asteroid in the main belt, is 44.3 km in diameter, and rotates every 13.14 hours.

Maria was named after the sister of Antonio Abetti (1846-1928), the Italian astronomer and director of the Arcetri Observatory, who worked out its orbit.

Antonio Abetti (I can't find a photograph of his sister).
Antonio Abetti (I can’t find a photograph of his sister).

Maria is the head of a small family of similarly inclined asteroids orbiting between 2.5 and 2.7 AU from the Sun.

1894   –   Asteroid 381 Myrrha discovered by Auguste Charlois, and named after the mother of Adonis.

1936   –   American astronomer and co-discoverer of the cosmic microwave background radiation, Robert Woodrow Wilson born in Houston, Texas.  Wilson was awarded (jointly with Pyotr Kapitsa and Arno Penzias) the Nobel Prize in Physics, 1978, for the discovery.

1969   –   Launch of the Venera 6 spacecraft by the USSR, five days after Verera 5.  The mission to Venus was a success, with 51 minutes of data regarding the Venusian atmosphere being returned while the craft descended to the surface by parachute, before being destroyed by that same atmosphere.

2002   –   Discovery of classical Kuiper Belt object 2002 AW197 by six astronomers using observations from Mauna Kea and Palomar (deciding where and by whom these things were discovered was a lot easier in the 19th century when they were usually discovered by one man in Austria or France).  2002 AW197 might be a dwarf planet, but this has yet to be confirmed.


January 08 – Asteroid 379 Huenna

Asteroid 379 Huenna was discovered on the 8th of January 1894 by August Charlois, and is a carbonaceous C-type asteroid, a member of the Themis or Themistian family in the outer reaches of the asteroid belt. In August 2003 it was discovered that Huenna has a small (7 km wide) satellite. It remains unnamed at present, except for its official designation S 2003 (379) 1.

Huenna was named after the island of Ven (or Hven in older Danish), the site of two observatories, Uraniborg and Stjerneborg, built by Tycho Brahe, and now a popular tourist destination. Uraniborg was built around 1580 and named after Urania, the muse of astronomy. It was, apparently, the last observatory to be built without a telescope as its main observing instrument. Stjerneborg was built partly underground (I’m sure there was a good reason) and means “star castle”.

The brass mural quadrant at Uraniborg.
The brass mural quadrant at Uraniborg.

The picture above shows the large brass mural “quadrant” attached to the observatory wall at Uraniborg, a three-man instrument used to measure the positions of celestial objects. And if you were looking for Quadrantid meteors last week you will probably remember that their radiant is in the vicinity of the now defunct constellation of Quadrans Muralis.
380 Fiducia, another C-type asteroid, was also discovered by Charlois on January 8th 1894. It was named after the Latin word for “confidence”.

1642 – Death of Galileo.

1942 – Birth of Stephen Hawking.

2002 – Discovery of exoplanet Iota Draconis b.

January 04 – Discovery of Asteroid 86 Semele (1866)

Making his first and last appearance in the field of asteroid discovery today is German astronomer Friedrich Tietjen.  On January 4th 1866, from the New Berlin Observatory (the place where Neptune was discovered) he found asteroid 86 Semelea large, dark, C-type body of about 120 km wide, in the main belt.

Aphelion 3.761 AU
Perihelion 2.467 AU
Semi-Major Axis 3.114 AU
Orbital Period 5.5 years
Inclination 4.822°
Eccentricity 0.208

Semele is named after the daughter of Cadmus and Harmonia (asteroid 40).  She was the mother of Dionysus.  Zeus was the father, as usual (where did he find the time?).

Jove and Semele (S Ricci)
Jove and Semele (S Ricci)

Today’s picture is of Jove and Semele, by the Italian artist Sebastiano Ricci, a man whose private life would not have shocked the average Greek or Roman god.  He was imprisoned at a young age when, in an attempt to avoid marriage, he tried to poison a young woman he had made pregnant.  He did eventually marry her, but I doubt there was much trust in the relationship.

1797  –  Birth of Wilhelm Beer, moon mapper and accurate predictor of the rotation of Mars (only about a tenth of  a second away from today’s value).

1876  –  158 Koronisa 35.4 km diameter S-type main belt asteroid, discovered by Russian astronomer Viktor Knorre.  Koronis is the head of the Koronidian asteroid family, created from a collision about 15 million years ago.  No known member of the family is particularly large (the biggest, 28 Lacrimosa, is only about 41 km across), but there are a lot of them, with over 300 known members.

1908  –  Discovery of asteroid 654 Zelinda by August Kopff, from the Heidelberg-Königstuhl State Observatory in Germany.  Zelinda is in the main belt, and measures somewhere in the region of 130 km across (opinions vary).  Zelinda was named by the Italian astronomer Elia Millosevich, in honour of the daughter (again, opinions vary, with The Dictionary of Minor Planet Names saying she was his sister, but she was thirty years younger than him, so I’m going with daughter) of mathematician and politician Ulisse Dini (a friend of Millosevich).

2010  –  Exoplanet Kepler-7b, a “hot Jupiter”, discovered by NASA’s Kepler spacecraft.  The planet was recently found to have a surprisingly predictable weather.

December 31 – Death of John Flamsteed (1719)

I normally only do birthdays, not deathdays, but here is a brief post to mark the passing, on December 31st, 1719, of Denby’s most famous son, John Flamsteed, the first Astronomer Royal, and the man who nearly discovered Uranus (he thought it was a star).

Flamsteed is remembered mostly as a star cataloger, and his posthumously-published Historia Coelestis Britannica contained nearly 3,000.

John Flamsteed
John Flamsteed

These days he is commemorated by the obligatory asteroid (4987), a crater on the Moon in the Oceanus Procellarum, and a school and memorial garden in his home village in Derbyshire, England.

Also in the news today, asteroid 583 Klotilde was discovered by Johann Palisa on December 31, 1905 (he must have had a similar view to me regarding going out on New Years Eve). It was named after the daughter of the Austrian astronomer H E Weiss, director of the observatory from where the discovery was made.

George W Ritchey is today’s second birthday boy. The American astronomer and telescope maker (co-inventor of the Ritchey-Chretien reflector) was born today in 1864.


It’s my birthday!

December 30 – Launch of RXTE

December 30th seems to be a thin day astronomically, but I did manage to find, in 1995, the launch of the Rossi X-Ray Timing Explorer from Cape Canaveral. Bruno Rossi, after whom the satellite was named, was the discoverer of the first source of x-rays beyond the Sun.

Artist's Impression of RXTE
Artist’s Impression of RXTE

Over a sixteen year lifespan, RXTE did exactly what its name suggests: it timed variations in emissions from x-ray sources using three experiments (a proportional counter array, theHigh Energy X-ray Timing Experiment, and an all-sky monitor).

Also today, in 1924, Edwin Hubble announced to the world that the Milky Way is not the only galaxy. Using the 100-inch Hooker Telescope at Mount Wilson, Hubble was able to calculate the distance to Cepheid variable stars in the Andromeda Galaxy using a technique devised by Harvard astronomer Henrietta Swan Leavitt. At the time, “spiral nebulae” were assumed to be patches of dust or gas within the Milky Way, but calculating a distance to Andromeda of approximately 860,000 light years changed the scale of the Universe for ever.

December 27 – Birth of Johannes Kepler (1571)

Today is Johannes Kepler’s birthday.

Kepler was born in Weil der Stadt, a small town near Stuttgart, on December 27th 1571, and was introduced to astronomy from an early age, whether he liked it or not, by being taken outside to witness the Great Comet of 1577, C/1577 V1, at age 6. The comet was also seen, incidentally, by Tycho Brahe, with whom Kepler would later spend some time studying at the site of Brahe’s new observatory near Prague.

Johannes Kepler
Johannes Kepler

Kepler’s works included many revolutionary (and I mean that in several ways) publications on the behaviour of planets. His Astronomia Nova, published in 1609, contained arguments in favour of a heliocentric ‘universe’, and Harmonia Mundi (“The Harmony of the World”, 1619) was the setting for his third law of planetary motion.

As well as being an influential astronomer, Kepler was also a major influence in the field of optics (possibly because his own eyesight wasn’t the best). He was the first person to explain how a telescope works; worked out how our eyes perceive depth; investigated how a pin hole camera might be used to produce pictures, and discovered total internal reflection.

1968 – Splashdown, south of Hawaii, of Apollo 8, following a 6 day flight that included the first Earthrise seen by humans, and the first Christmas broadcast from a craft orbiting the Moon.


December 25 – Birth of Sir Isaac Newton (1642)

Where do you start?

As Christmas presents to the human race go, this one has to be up there in the top three. Isaac Newton is widely considered to be one of the most important scientific brains of all time. His three laws of motion would have been enough on their own for him to be celebrated everywhere, but add universal gravitation to the mix and you’ve got a genius on your hands. Then throw in calculus and it starts looking like God was seeing how much he could fit into one head.

Newton was born on December 25th 1642, and then again on January 4th 1643 (not really – we need to remember that there were two calendars in use at the time: the old Julian calendar was still around, running ten days behind the new Gregorian calendar we use now).

Newton was born in the village of Woolsthorpe-by-Colsterworth in Lincolnshire, England. The house of his birth, to where he returned in 1666 while Cambridge University was closed following an unfortunate outbreak of the plague, still stands, and is in the hands of the National Trust. The house still contains the apple tree which it is alleged gave Sir Isaac the idea for a force of gravity.

Today’s photo is of the memorial to Newton in Westminster Abbey. It is not where he is buried, but it’s pretty close.

Various lists of the most influencial and important scientists of all time have given the top spot to either Newton or Einstein. I suppose it depends on your point of view. Newton himself was modest regarding his achievements, but that could be because he was too clever to boast, just in case.

December 16 – Discovery of Asteroid 351 Yrsa (1892)

Asteroid 351 Yrsa was discovered today in 1892 by Max Wolf.  There isn’t a great deal to say about it:  it’s in the main belt, and is about 40 km across.  It is thought to have been named after the wife of King Eadgils of Swedish legend.  her father, Helghe, who had only had a brief fling with her mother, visited the region where she lived years later and, not knowing she was his daughter, got her in the family way, as they say.   Unlike the average Greek or Roman god, who would have thought nothing of it, he did the decent thing and killed himself upon discovering the truth.

Lithograph depicting Yrsa
Lithograph depicting Yrsa

Max Wolf was a great friend of today’s birthday boy, Edward Emerson (E.E.Barnard, namesake of Barnard’s Star, one of the most closely observed objects in the Galaxy.  Barnard was mainly a prolific comet finder, discovering 17 in all (15 solo, and 2 co-discoveries), but he’s always going to be associated with the one star in my mind, because it was, and indeed may still be for all I know, the intended target of Project Daedelus, the mind-bogglingly ambitious unmanned interstellar mission proposed by the British Interplanetary Society.  When I was an impressionable teenager in the 1970’s, Daedelus seemed likely to happen “any year now”.  Unfortunately, 30 years later, they still haven’t quite got around to working out how to get the necessary helium-3 fuel back from Jupiter in order to get it to work, and I suspect that the cost in today’s money of a nuclear-powered spaceship bigger than a Saturn 5 and built in orbit would be rather more expensive than gold-plating the Isle of Wight or the UK buying Australia back.

E E Barnard
E E Barnard



December 15 – Discovery of Saturn’s Moon, Janus (1966)

J R Hind discovered today’s main belt asteroid, 23 Thalia, from Hyde Park, London, on December 15th, 1852 (I’d like to see him try that nowadays). Thalia is an S-type asteroid of about 107 km diameter, located between the 3:1 and 5:2 Kirkwood gaps.

In Greek mythology, Thalia, daughter of Zeus and Mnemosyne, with a name derived from the verb “to flourish”, was the muse of comedy and pastoral poetry. She may or may not (depending on which source you believe) have been the mother of the Corybantes, attendants to the Great Mother of the Gods, and associated with particularly orgiastic rites.

We also have a moon today.  The discovery of Janus, one of the inner Saturnian satellites, is attributed to Audouin Dollfus, who first observed it on December 15th 1966. Three days later, Richard Walker also observed an object in the right place but at the wrong time, which caused confusion for a while, but was eventually found to be another moon, Epimetheus, which shares an orbit with Janus.

Janus, photographed by the Cassini probe (image credit: NASA / JPL / SSI)
Janus, photographed by the Cassini probe (image credit: NASA / JPL / SSI)

Janus is the two-faced Roman god of beginnings, entrances, gates, etc. You should thank him the next time an automatic door opens for you. Janus is also one of the select group of deities after whom a month (January) is named, and strangely he has no Greek counterpart.

1965  –  launch of San Marco 1 by Italy. Being their first satellite, the Italians wisely did not fill it with lots of expensive equipment. It did, though, contain a couple of experiments to study the ionosphere, the layer of the atmosphere stretching from about 60 km to 1,000 km, a region you need to know about if you’re planning to become a space-faring nation, needing to send radio messages over great distances.

2000  –  Death of George Alcock, aged 88, hunter of novae and comets. I believe he found five of each (remarkable for south-eastern England), some of them from indoors using binoculars, and even occasionally through double glazing1!  His eyesight must have been unbelievable.

2014  –  Voyager 1 crossed the termination shock.


2015  –  Launch of Expedition 46 to the International Space Station.  This caused considerable press interest in my homeland (in fact I’m going to call it a frenzy) because in addition to Russian cosmonaut Yuri Malenchenko and American astronaut Tim Kopra, the three-man crew contained Tim Peake, the first Briton to float into the ISS (I was going to say “set foot aboard” the ISS, but I’ve seen the footage, and feet don’t feature much).  Because of the  numbering system they use at the ISS when crews overlap, these three also formed part of Expedition 47.

ISS Expedition 46 Patch
ISS Expedition 46 Patch

As a supporter of Port Vale FC, I was distraught to discover that one of Tim Peake’s tasks whilst on this mission was to unveil a flag featuring the name of our local rivals, Stoke City.  I’ve gone off him a little.


1   Journal of the British Astronomical Association, vol.111, no.2, p.64-66