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.


November 15 – Discovery of Asteroid 21 Lutetia (1852)

M-type asteroid 21 Lutetia was discovered on November 15th 1852 by Hermann Goldschmidt.  It’s about 100 km (60 miles) in diameter, is irregularly shaped,  fairly dense and heavily cratered.

Lutetia, for the second time in a week, is unusual for a low-numbered asteroid, in that you’re going to get an actual photograph of it, courtesy of the Rosetta probe, which paid it a visit in July 2010 on its way to study  comet 67P/Churyumov–Gerasimenko.

Lutetia from the Rosetta probe. (Photo: ESA)
Lutetia from the Rosetta probe. (Photo: ESA)

If you look at the photo of Luteita, it seems to have no sharp edges to any of the craters. This is thought to be the result of a fine regolith (layer of loose material) covering the surface, possibly to a depth of several kilometres.

Today’s asteroid was named after Lutetia, the pre-Roman and Roman city that stood on what is now the site of Paris. Some of it still remains in the Latin Quarter, including the impressive Arènes de Lutèce, which I came across by accident a few years ago at the back of the Rue Monge.  I forget where I was going (probably looking for a coffee)  but it was quite a surprise to suddenly find myself in a Roman amphitheatre.

Arènes de Lutèce, Paris. (Image credit: me!)
Arènes de Lutèce, Paris. (Image credit: me!)

1630  ⇒  Death of Johannes Kepler in Regensberg, Bavaria, aged 58.

1738  ⇒  Birth of Frederick William Herschel in Hanover, Germany.

by Lemuel Francis Abbott,painting,1785
Herschel, by L F Abbott, 1785

The portrait above is by Lemuel Francis Abbott (1760-1802), mostly known for his famous portrait of Nelson.

Herschel is one of the very, very few people who can claim to have discovered a planet in our solar system.  He was the first person to recognise Uranus for what it was, despite firstly speculating that it might be a comet, in March 1781.  he also discovered two Uranian moons (Titania and Oberon) and a moon of Saturn, later named Mimas.


1927  ⇒  Comet 29P/Schwassmann-Wachmann discovered by A Schwassmann and A A Wachmann at the Hamburg Observatory, Germany.