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 – Discovery of Messier 92 (1777)

The small, densely packed globular cluster Messier 92 was discovered on this day in 1777, not by Charles Messier, but by Johann Elert Bode.  Messier didn’t spot it until 1781.

M92 (Photo courtesy of the Isaac Newton Group of Telescopes, La Palma)
M92 (Photo credit: the Isaac Newton Group of Telescopes, La Palma)

M92 is a barely-naked eye object of magnitude 6.4, located in the constellation of Hercules. It is one of the oldest and brightest globular clusters, though not as bright as its neighbour in Hercules, M13, and is about 27,000 light years from Earth.

Some of the stars in M92 are about 14 billion years old, making them roughly the same age as the Universe.  This established age probably led to lively debate among astronomers when the Hubble Constant was first used to put the age of the Universe at 12 billion years.

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 24 – Discovery of Saturn’s Moon, Rhea (1672)

Saturn’s second-largest moon, Rhea, was discovered on this day in 1672 by Giovanni Domenico Cassini, who had presumably finished his Christmas shopping early.

Rhea from the Cassini probe (image: NASA / JPL / SSI)
Rhea from the Cassini probe (image: NASA / JPL / SSI)

Like our own Moon, Rhea always keeps one side, the one you can’t see in this photo, facing towards the parent planet, and from the above view of Rhea’s cratered anti-Saturnian surface, this does look to be a place very much like the Moon we are familiar with down here.  But appearances can be deceptive.  For a start, it’s a lot smaller than the moon, and if it soft-landed on the Earth it would fit quite comfortably inside the borders of Zaïre (in this country people usually use Wales as the benchmark for large areas, but I felt like a change).  Secondly, although it looks nice and rocky, Rhea is thought to be comprised of as much as three-quarters ice, and only one quarter rock (studies of Rhea’s inertia suggest that it doesn’t even posses a rocky core).

Rhea is named after a Titaness of some standing, the daughter of Uranus and Gaia.  As mother of Zeus and Hera, she was grandmother or great-grandmother to almost all the Olympian gods and goddesses worth mentioning.


There are several suggestions doing the rounds concerning the origin of the name Rhea.  It may derive from the word for “flow”, or it could have a root in a much older word for “powerful”.  But the guy who named the large, flightless, South American bird after her was almost certainly thinking of a derivation of the Greek έρα, meaning “ground”.

Another Rhea
Another Rhea



December 22 – Discovery of Asteroid 323 Brucia (1891)

Thirty-three kilometre wide asteroid 323 Brucia was the first to be discovered by the new fangled process known as astrophotography.

It was discovered by Max Wolf, and named in honour of Mrs Catherine Wolfe Bruce, who had donated the instrument on which it was captured, the 16 inch double astrograph at Heidelberg.

The Bruce Astrograph, Heidelberg

Mrs Bruce was a generous supporter of astronomy (she also provided instruments for Harvard and Yerkes), and now, as well as an asteroid, has a lunar crater named after her. She established an annual award for the Astronomical Society of the Pacific, the “Catherine Wolfe Bruce Gold Medal”, one of the most prestigious awards in astronomy. Over the years the Bruce Medal has been awarded to the likes of Poincaré, Hubble, Hoyle and Chandrasekhar, and also to a certain Max Wolf, who received the honour in 1930.

I’ve included a picture of the Bruce Medal because photographs of Catherine are hard to come by.  There’s one doing the rounds online, but I’m fairly sure it isn’t her, so I’m not using it.

December 22 – Discovery of Asteroid 264 Libussa (1886)

Discovered on December 22nd 1886 by C H F Peters, asteroid 264 Libussa is an asymmetrical S-type main belt asteroid of somewhere between 50 and 60 km diameter.

It was named after Libussa (Lubossa or Libuše), a half-elf daughter of the mythical Czech king Krok. She eventually became the founder of the city of Prague, and ancestor of the whole Czech nation.

Libuse (photo credit: Palic Kap)
Libuse (photo credit: Palic Kap)

Today’s photo shows a detail from the Octárna Hotel, Kroměříž, Czech Republic. This is alunette (a half moon shaped space) by local artist Max Švabinský. It shows Princess Libuse prophesying the glory of Prague.

There’s not a great deal more to say about Libussa, so it’s back to orbital characteristics. To date we have come across aphelion (3.18 AU for this particular rock), perihelion (2.42 AU), semi-major axis (2.8 AU), longitude of ascending node (49.8°), and inclination (10.4°). Today we add another important element of an asteroid’s orbit: the argument of perihelion. For Libussa, this is 339.27°, and in orbital calculations it is depicted by the letter ω. It’s not a “w”, by the way, but a lower-case omega (the word means “great o”) the last letter of the Greek alphabet. Remember that, because one of these days I’m going to work out how to put some of these calculations in this blog in the form of a table.

The argument of perihelion is the angle between the perihelion and the ascending node. So if, for example, the value was 90°, that just means that the asteroid would be at perihelion when it reached the northerly point in its orbit.

1891 ⇒ Asteroid 323 Brucia becomes the first asteroid to be discovered by astrophotography, by Max Wolfe.

December 19 – Asteroid 397 Vienna

Firstly, a brief asteroid. 397 Vienna was discovered by Auguste Charlois on December 19th, 1894. It is an S-type main belt asteroid of about 43 km diameter. There are no prizes for guessing the origin of the name.

In the 1960’s, the only way to spy from above on your decadent imperialist western enemies was to send collections of cameras into orbit, shoot a few rolls of film, bring the whole thing back down, and hope you could make it land in a suitable place for retrieval.
Kosmos 24 (also known officially, but less publicly, as Zenit 2, Number 15) was one such Soviet reconnaissance satellite, launched on December 19th, 1963, and recovered by the military nine days later. The launch took place at the Baikonur Cosmodrome via a Vostok 2 rocket, and as far as anyone is aware it was a success.

Kosmos 24

There were over 500 Zenit 2 launches, mostly carrying four cameras, with each camera capable of shooting 1500 frames. And what I didn’t know until very recently was that the Zenit camera I owned in the late 1970’s was made by the same company who manufactured the equipment for the Kosmos satellites. I Wish I’d kept it.

2013 – Launch of the Gaia Space Observatory.


December 19 – Discovery of Tau Ceti ‘e’ and ‘f’ (2012)

Tau Ceti e and Tau Ceti f are exoplanets orbiting, fairly obviously, the star Tau Ceti, a G-type main sequence star in the constellation Cetus (usually referred to as “the whale”, but actually a sea monster from Greek mythology). They are the fourth and fifth planets out from the star, and were discovered on December 19th, 2012, by the “radial velocity” method, the oldest known means of detecting planets outside our system.

Location of Tau Ceti
Location of Tau Ceti

Both planets are likely to be a fair bit bigger than the Earth (“f” could be up to seven times larger), and they had initially excited astronomers by possibly being in the habitable zone of Tau Ceti. It was thought they could have temperatures of up to 50 or 60°C, which is plenty warm enough for the existence of life. Unfortunately though, later refinements have suggested this might not be the case, and also unfortunately for any potential Tau Cetians, the parent star is known to have an extensive “debris disk”, meaning that any planets nearby would face a regular pounding by rocks of varying shapes and sizes, almost certainly including some big enough to cause serious problems for any fledgling species trying to evolve.