November 11 – Philae Lands on Comet 67P/C-G

2015Four years years ago today ESA successfully landed (or bounced) their Philae lander on comet 67P/Churyumov–Gerasimenko, having been launched from the Rosetta spacecraft some hours earlier.

The Philae Lander viewed from Rosetta, a few hours into the flight to Comet 67P. (Image credit: ESA)

Rosetta had been launched from French Guiana in 2004, and a soft landing on the target comet was going to be the highlight of the trip. One of Philae’s thrusters was known to be faulty before separation from Rosetta, but there wasn’t much that could be done about it so they went ahead anyway. Earlier I said that Philae “bounced” onto 67P, which I think needs a little more information. There isn’t much gravity on a comet; so if you bounce, you’ll bounce high. Philae bounced just over half a mile (1 km) before coming down again. It was a whisker away from not coming back down and carrying on into space.

Fortunately, despite landing at a jaunty angle and in an unfavourable location, Philae was able to deploy some of the experiments on board, and was capable of several periods of communication with ground controllers via Rosetta.

September 18 – 375 Ursula / 1965 S1 Ikeya-Seki

Comet C 1965 S1 Ikeya-Seki was first spotted on September 18th 1965 by Kaoru Ikeya and Tsutomu Seki, observing independently of one another. At magnitude -10 it was visible in daylight, and has earned the name The Great Comet of 1965.

Ikeya-Seki (photograph by Maynard Pittendreigh)
Ikeya-Seki (photograph by Maynard Pittendreigh)

Ikeya-Seki is one of a group of over-performers known as the Kreutz Sungrazers. The group also contains the Great Comets of 1843 and 1882, and is thought to comprise fragments of a huge parent comet that broke up in 1106.

The photograph above by Carolina astronomer (and Presbytarian minister) Maynard Pittendreigh might look a little dated to the Hubble generation, but to me it’s just fabulous.  It was probably all accidental, and he might have been going for a perfect shot, but I love the star trails, the scratches, the unidentified smear in the centre, and the telegraph wires.   It wouldn’t look out of place in a futuristic film from the early twentieth century, or a Bogus Blimp video.

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ALSO TODAY . . .

“Cool Jovian-mass” extrasolar planet MOA-2007-BLG-400Lb discovered today in 2008 in Sagittarius by Subo Dong and others.

Asteroid 375 Ursula is a fairly bulky main belt asteroid (approx 216 km diameter) discovered by Auguste Charlois on September 18th 1893. Ursula is another one of his finds with no readily apparent reasoning behind the name (you may recall 298 Baptistina from September 9th). If I could only find out on what date the naming happened, and maybe who came up with “Ursula” (it isn’t always the discoverer) I might get somewhere.

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July 23 – Discovery of Asteroid 114 Kassandra (1871)

Asteroid 114 Kassandra was discovered by prolific asteroid hunter Christian Heinrich Friedrich Peters on July 23rd 1871.  It is in the main belt, is about 100km in diameter, and is of spectral type “T”.  We don’t get many T-types in these pages, mainly because you don’t get many T-types anywhere.  They tend to orbit in the inner main belt, and are thought to be related to P-types, but as we don’t have any convenient examples to study, very little is known about them.

Woodcut showing Cassandra predicting the fall of Troy and her own death.
Woodcut showing Cassandra predicting the fall of Troy and her own death.

Kassandra is named after the tragic Greek prophetess of the same name but with a “C”, cursed by her spurned would-be lover Apollo to be able to foretell the future but never be believed.

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ALSO TODAY . . . .

1995  –  Today in 1995 saw the discovery of Comet Hale-Bopp by Alan Hale (New Mexico) and Thomas Bopping (Arizona). “C/1995 01” was one of the brightest comets of the 20th century, visible with the naked eye for over eighteen months around its perihelion at April 1st 1997. It became the most observed comet in history, largely due to the increase in Internet availability happening at the time, and NASA’s Hale-Bopp Web page was their first to receive over a million hits in one day. How much scrutiny Hale-Bopp receives next time around is anyone’s guess. Perihelion is expected in around 4385 AD, by which time I expect Richard Branson’s descendants to be offering cut-price round trips through the tail (with a free night on Mars if you book early).

1999  –  Launch of the CHANDRA spacecraft.

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July 14 – Elst-Pizarro: Asteroid or Comet?

Minor planet 7968 Elst-Pizarro was discovered by Eric W Elst and Guido Pizarro from photographic plates taken by Pizarro while he and his brother Oscar were working as assistants with the ESO Schmidt telescope at La Silla Observatory, on July 25, 1979. The discovery was reported by Elst, of the Royal Observatory, Uccle, Belgium, on August 7th. Comet 133P/Elst-Pizarro was discovered by M R S Hawkins and R H McNaught on July 14, 1996.  They are one and the same.

133P/Elst-Pizarro has characteristics of both an asteroid (for a start, it’s in the asteroid belt, with an orbit varying between 2.6 and 3.6 AU) and a comet (it sometimes has a tail). The tail suggests a non-asteroidal icy composition, although it is also possible that this is a rocky body that occasionally expresses dust due to the gas pressure of evaporating ice.  This is where I go off at a tangent to make sure we’re on the same wavelength with the word “express”.  Your small strong coffee is called an espresso because of the way the water is forced under pressure through the beans,  like so much ice from the surface of comet 133P/Elst-Pizarro (possibly) and has nothing to do with the speed of it’s drinking, or the way it makes you rush around like a lunatic for thirty minutes afterwards.  And while we’re on the subject, look up the origin of the name cappuccino. (End of pointless aside.)

The occasional nature of the tail doesn’t do much for E-P’s comet cred. It only tends to appear close to the perihelion of its 5.62 year journey around the Sun.