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).

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