September 12 – Gemini XI

Gemini XI, launched on September 12th 1966, was the 17th manned US spaceflight, and the 9th manned flight of the Gemini programme. It was crewed by Charles “Pete” Conrad and Richard “Dick” Gordon. The main aim of the mission was to rendezvous with an Agena Target Vehicle, to simulate the return of a Lunar Module to the Command/Service Module following a landing. Several such rendezvous were performed successfully, as well as two periods of extra-vehicular activity (that’s space walks to you and me).

The Crew of Gemini XI

The Crew of Gemini XI (image credit: NASA)

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Asteroid 59 Elpis  is a rather large, dark (albedo 0.04) C-type asteroid in the main belt. It has a diameter of 165 km.  Elpis was discovered by Jean Chacornac on September 12th 1860 (it was his last find). The name Elpis was chosen by Karl L Lithow, director of the Vienna Observatory. Elpis is the personification of ‘hope’ in Greek mythology, and was supposedly the only item left in Pandora’s pithos (jar, not box) after she had emptied it.

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Firstly, asteroid 117 Lomia was discovered by Alphonse Borrelly on September 12th 1871 from Marseilles. It has a nearly circular orbit, and in composition is somewhere between a C-type and an X-type. The origin of the name is unknown.

And secondly, asteroid 241 Germania (C-type, main belt) was discovered today in 1884 by Robert Luther in Düsseldorf. He named it, obviously, after his homeland.  I was tempted here to insert a photograph of a moustachioed general in a uniform and spiky helmet, but I resisted. No racial stereotypes here.

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September 05 – Voyager 1

Launched September 5th 1977, Voyager 1 is now, 40 years later, 20 billion km (132 AU) from the Sun, and still working.  I say from the Sun because it sometimes gets closer to the earth due to the speed of this planet around our star.  It has recently been announced that Voyager 1 has finally reached interstellar space, although as it is still some years from the inner edge of the Oort Cloud, I’m not so sure.

Voyager 1 (image credit: NASA)

Voyager 1 (image credit: NASA)

I won’t say too much here about what Voyager 1 achieved, because there will be other opportunities for that on the anniversaries of its encounters with Jupiter (April 13) and Saturn (December 14).

All we need to mention here is the launch, via a Titan launch vehicle (that’s a rocket to you and me) from Cape Canaveral, two weeks after Voyager 2. Voyager 1, following a shorter trajectory, reached Jupiter and Saturn first though, so the numbering system makes sense.

Launch of Voyager 1 (image credit: NASA)

Launch of Voyager 1 (image credit: NASA)

The timing of the Voyager missions was spookily convenient. Jupiter, Saturn, Uranus and Neptune line up in such a way as to optimise a “gravity assist” flyby of all four every 175 years. This alignment coincided nicely with the technology necessary for the flight becoming available in the late 1970s. Even so, the cost of building a spacecraft capable of definitely making it as far as Neptune was so great that most of the effort went into ensuring a successful mission as far as Saturn, with finger-crossing and prayer being employed for the remainder of the trip.

As it happened, of course, they both turned out to be even more reliable than a Lexus, and they, with their golden discs, continue to carry greetings from Earth, and the music of Chuck Berry, to the edge of the Solar System and beyond. (Did anybody ever stop to consider whether Johnny B. Goode might be a declaration of war on some planets?)

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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 – Johannes Kepler

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.

Also today, globular cluster Messier 92 was discovered in 1777 by Johann Elert Bode.

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 located in the constellation of Hercules. It is one of the oldest and brightest globular clusters, and is about 27,000 light years from Earth.

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 19 – Asteroid 397 Vienna

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 publically, 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 18 – Epimetheus

Saturn’s moon Epimetheus, discovered today in 1966 by Richard Walker, is a non-identical twin.  It, and its larger brother, Janus, which had been discovered three days previously by Audouin Dollfus, fly round Saturn in almost identical orbits (their mean orbital radii differ by a mere 50km or so).  Obviously, at the time of discovery, with only  the evidence of Earth-based telescopes to go by, this caused a certain amount of confusion among astronomers trying to work out where the supposed new single moon was.  At the time it was thought, also fairly obviously,  highly unlikely that two moons would share the same orbit without hitting each other.

Epimetheus from the Cassini Orbiter (image: NASA/JPL/SSI)

Epimetheus from the Cassini Orbiter (image: NASA/JPL/SSI)

It is possible that at some time in the past Epimetheus and Janus were part of a single larger body, but if that is the case it is likely to have been a very long time ago.  Both are heavily cratered, and their surface features display softening of their edges by the accumulation of dust, suggesting nothing much has changed there for some time.

Epimetheus was, in Greek mythology, a Titan (nowadays the name of a rather larger Saturnian moon), brother of Prometheus (also a moon of Saturn).  The pair were sons of Iapetus (another Saturnian satellite).  Epimethius was, according to some myths, married to Pandora (and guess what she gave her name to?).

Epithemius was given the job, shortly after the creation of the Earth, of finding a positive trait to give to each of the newly designed animals.  Unfortunately he ran out of good characteristics with one animal remaining, which you’ve probably already guessed was man.  That’s when Prometheus came along and gave  man the gift of fire, after which it all went downhill.

Epimetheus (3rd left) meets Pandora for the first time.

Epimetheus (3rd left) meets Pandora for the first time.

As it happens, though, they do share the orbit, and they don’t hit each other.  One moon does catch the other up every four years, but interactions between their gravities causes the inner moon to move faster (which causes it to move to a higher orbit) and the outer moon to slow down, causing its own orbit to drop a little.  So they actually exchange places, which is why I’m not going to call them the fifth and sixth moons, because they are each neither and both.

Launch, in 1958, of SCORE, the world’s first communications satellite (Signal Communications by Orbiting Relay Equipment).  The launch, from Cape Canaveral, was via an Atlas-B 10B rocket.

December 14 – Tycho Brahe

Tycho Brahe was born today in 1546 in Denmark. As the child of a wealthy family (he was born in a castle) he was well placed to receive a good education, and took up astronomy while studying law.

Tycho Brahe wearing the Order of the Elephant (and the Moustache of the Walrus)

Tycho Brahe wearing the Order of the Elephant (and the Moustache of the Walrus)

Tycho made several leaps of the imagination, including the development of his own model of the solar system, which he nearly got right. He correctly deduced that the Moon orbits the Earth, and that the planets orbit the Sun. unfortunately he also decided that the Sun must orbit the earth; an easy mistake to make I suppose at that time, if you spend your entire life seeing it cross the sky thousands of times in front of your very eyes.

Tycho was also the first person to decide that novae (they weren’t called that at the time) originated further away than the Moon. The popular view was that the stars were fixed and unchanging, and anything that appeared in the sky had  to be closer than them. But Tycho noticed that a bright new star in Cassiopeia (now called SN1572) did not move against the background stars, and so must be farther away than all the objects that did. It sounds fairly reasonable to us, but in the 16th century the night sky was anything but obvious.

2009 – Launch of the Wide-field Infrared Survey Explorer (WISE) by NASA, on a mission  to map 99% of the sky. So far, it has found more than 33,000 asteroids and comets, over 200 Near-Earth Asteroids (including 43 potentially hazardous ones), the most luminous galaxy in the known universe, and numerous brown dwarfs.

2013  –  the Chinese Chang’E 3 mission lands on the Moon.

The Chang'E Lunar Lander, imaged by the Yutu rover (image: China National Space Administration)

The Chang’E Lunar Lander, imaged by the Yutu rover (image: China National Space Administration)



December 10 – Asteroid 211 Isolda

Asteroid 211 Isolda, discovered on December 10th 1879 by Johann Palisa, is about as average as asteroids get.  It’s dark, in the main belt, C-type, 150-ish km across, and has an orbital period of 5.3 years.

So today, as well as mentioning those orbital characteristics of Isolda with which we all should now be familiar from previous posts (aphelion – 3.53 AU; perihelion – 2.54 AU; semi-major axis – 3.04 AU, and longitude of ascending node – 263.8°) I’m going to say that Isolda has an eccentricity of about 0.16.

Eccentricity is another fairly simple concept: it’s got very little to do with the behaviour of the English upper classes (you shouldn’t confuse eccentricity with lunacy) but a lot to do with the orbit of almost everything in the solar system being non-circular.  Eccentricity, if we’re talking about planets, moons, asteroids and most known comets, will be measured on a scale somewhere between zero (completely circular) and one (an “escape” orbit).  Planets have a fairly low eccentricities (Earth = about 0.017); asteroids are a bit more wayward (their average is ten times greater, at 0.17), and comets can be anything, with values near to, or even in excess of, 1.0 (eccentricities of more than 1 are reserved for comets that are being flung out of the solar system following their solar fly-by).  Neptune’s moon Triton has the lowest known eccentricity, at 0.000016.  This is about as circular as can be accurately measured.

Isolda, of course, is named after Isolde, (or Iseult of Ireland) the lover of Sir Tristan of Arthurian legend and Wagnerian opera.

Tristan and Isolde

Tristan and Isolde

Today’s photograph shows husband and wife team Ludwig and Malvina Schnorr von Carolsfeld, Wagner’s original 1865 Tristan and Isolde.  Ludwig was a heldentonor, the dramatic tenor typical of Wagnerian  protagonists. Soprano Malvina was the daughter of the Portuguese consul in Copenhagen, and was a great-grand-neice of David Garrick, giant of the English theatre.

1999  ⇒  Launch of ESA’s XMM-Newton (it stands for X-ray Multi Mirror Mission), the largest satellite to date to be launched by the European Space Agency (4 tonnes in weight and 10 meters long).

December 04 – Gemini VII

We have slightly odd numbering here. Gemini 7 (VII) was launched on December 4th, 1965, after Gemini 5, but before Gemini 6A. Gemini 6 was obviously originally planned to go between 5 and 7, but had to be cancelled and rescheduled with an “A”.

The crew of gemini VII (Lovell, left, and Borman)

The crew of Gemini VII (Lovell, left, and Borman)

The plan for Gemini 7 was to observe the effects of prolonged spaceflight on astronauts. The two-man crew, Frank Borman and James Lovell, circled the globe 206 times during their two week confinement. After 11 days they were joined briefly by Walter Schirra aboard Gemini 6A, and practised rendezvousing (at closest approach they were just one foot apart).

Gemini, of course, is the constellation that lies between Cancer and Taurus in the sky (and therefore in the zodiac) and is historically associated with the twin brothers Castor and Polydeuces (or Pollux if you prefer the later Roman name).  I prefer Polydeuces myself, because the translation is “much sweet wine”, which you just don’t get with “Pollux”.  Castor, as any rodentologist will tell you, is Greek for “beaver”.

The Diskouri, in the Museum of Modern Art (image credit: Marie-Lan Nguyen)

The Diskouri, in the Museum of Modern Art (image credit: Marie-Lan Nguyen)

The twins now immortalized in the heavens were collectively known to the Greeks as the Diskouri, or “sons of Zeus” (the noun Gemini is from Roman mythology).  They also had twin half-sisters, even more famous than themselves: Helen (of Troy) and Clytemnestra.


December 02 – SOHO / BBXRT

Built in Europe, the Solar and Heliospheric Observatory (SOHO) was launched on December 2nd, 1995 (and is still going, despite being planned as a two year mission).  It is a joint project between ESA and NASA, designed to provide data to help predict solar weather, and answer questions about the solar interior and corona.  The mission has been a great success, providing significant insights into such areas as the structure of sunspots, the flow of gases inside the Sun, and the dynamics of the solar wind.

Prominence spotted by SOHO (image: ESA / NASA)

Prominence spotted by SOHO (image: ESA / NASA)

In addition to all this, SOHO has still found time to become history’s greatest ever discoverer of comets, with the total ticking over to an astonishing 3000 on September 13th 2015.  Comet number 3000 was spotted by Thai astronomer Worachate Boonplod, part of an amateur army of spotters who betwen them have been responsible for the majority of SOHO discoveries.

The Broad Band X-ray Telescope (BBXRT) was launched today (1990) on board shuttle Columbia flight STS-35. It formed part of the partly-successful “ASTRO-1” payload of four instruments.


In-flight view of BBXRT (image: NASA)

In-flight view of BBXRT (image: NASA)

The mission was somewhat shorter than the previously-mentioned SOHO, as the telescope was attached to the shuttle, and had to go wherever it went (back to Earth).