Monday 12 July 2021


It's been a while, I know. Unfortunately, other priorities keep me from being more active with my blog and especially from making more sketches. Don't worry, though, because I'm still out under the stars regularly with my bino. Actually, I'm even playing with the idea of founding a public observatory some day... when Covid will be behind us (let's stay optimistic).

Anyway, there's one object for which I wanted to make an exception, and that's Pluto. Long thought to be a planet, it was eventually declassified to dwarf planet status in 2007. Not really surprising if you consider that Pluto's a piece of rock and ice much smaller than our own Moon (diameter 2,373km vs. 3,474km) which is only half as wide as the U.S.! It still is the biggest of the dwarf planets known to date, beating Eris by about 50km, but it is far smaller than any real planet. Even Mercury measures 4,874km and weighs in at 0.055 Earth Masses whereas Pluto only weighs a scant 0.0022 Earth Masses. Or in other words, tiny Mercury weighs 25 times as much as Pluto! What's more, Pluto is so far away from us that even light, with its formidable speed, needs more than six hours to travel to it! Sorry, dear astrology-frauds, but you're making yourself ridiculous if you still want anyone to believe that this little piece of rock has a bearing on our lives or personalities. 

And yet, how insignificant as it may seem, Pluto turned out to be a most fascinating world when NASA's New Horizons space probe zoomed past it in 2015. It features mountains as high as the Alps covered in snow (something not seen on any other celestial body in our Solar System so far), gigantic glaciers and a very thin but blue atmosphere. Actually, most of the snow on Pluto is... red, due to its unique chemical composition. Methane and Nitrogen combined into so-called Tholins, organic micromolecules that may be essential building blocks for life! Now it is very improbable that Pluto harbours any lifeforms because it simply is far too cold (up to -240°C), but the abundant presence of these complex molecules is astonishing in itself. Observations also reveal the likely presence of geysers and volcanoes. In any case, the surface of Pluto contains only very few impact craters, suggesting that it is very young and geologically active.

Another oddity about Pluto is its biggest of five moons, Charon, which is half as big as Pluto itself. No other moon in our Solar System is so big compared to its (dwarf) planet. Also Charon exhibits likely geysers and the same reddish deposits as Pluto on its polar caps which were blown off the dwarf planet's atmosphere, traveled 19,000km through space and settled on Charon.

As much as Pluto may stir the imagination of every astornomy enthusiast, observing it will always be disappointing since it merely shows itself as a tiny, 14th magnitude star in our skies. This means that you need a sizeable telescope to see it, and... you need to know exactly which of the hundreds of tiny little stars in the field of view is Pluto. Last Friday, however, I got lucky. The infamous dwarf planet was close to an asterism in an otherwise poor star field, which would allow me to identify it easily, and so it turned out. Actualy, it was the first time in my life that I've observed it with absolute certainty! Sky conditions were not bad, but not exceptional either. 

Deep down I hoped to also be able to make out Charon, which would theoretically be possible with mag. 16 and 0.8" distance from Pluto, but unfortunately I wasn't able to. Perhaps under a perfect sky... one day?