Thursday, April 24, 2008

seeing in the dark

I don’t think I’ve ever experienced total darkness. The nearest would have been behind sealed doors in a film-processing darkroom; even then there was an ultra-soft light coming from a large analogue timer. I suppose I could have turned my back on it, but I always knew it was there. And the oddest thing about working in a black darkroom is that it always seemed much better when you closed your eyes.

There’s no chance of real darkness outside in a town, and there’s too much light pollution for it ever truly dark in England, even in the loneliest of places. Cloudy nights disperse light over huge distances, while on clear nights the moon and stars are light in themselves.

Asteroid 253 Mathilde is one of the darker objects wandering around out there in our solar system – the darkest are light-sucking black holes. She dwells in perpetual motion in the asteroid belt between Mars and Jupiter, never closer to Earth than 140 million km, never further away than 630 million km. I prefer to call her a she - I really would have called him a he if his name was John or Trevor - as her two ugly alternative names "1949 OL1" and "A915 TN" reduce her to an it. Even with the best will in the world she has a rather lumpy pock-marked mass with one enormous crater giving her the impression of being squeezed in the middle. Her vital statistics are 66 by 48 by 44 km. And saddest of all, it is likely that she is composed of rubble, leading her too close to cartoon abuse for comfort. One imagines that if she knew she was the subject of ridicule she would set a course to Earth to prove the point that rubble-or-no, I'm still a very big asteroid and you're about to become history! Mathilde is 6 times larger than the probable size of the asteroid that created the Chicxulub Crater in the Yucatán Peninsula in southern Mexico, and is associated with the K-T Extinction - the demise of the dinosaurs - about 65 million years ago.

So why am I going on about a black heap which keeps herself to herself and is all-but invisible? Well her invisibility is the point, she’s very dark – darker than charcoal. Though she was discovered in 1885, she’s only recently visually entered the public domain when this composite image was produced by a spacecraft in 1997. What fascinates me is that NASA has the multi-spectral cameras to create such a full tonal image of an object that is so light-absorbing. Whatever...

Poor Mathilde may also be tetchy about her craters - the 23 largest are all named after coal-fields... The largest of her craters is in this image and is called Ishikari, after Japan's largest coal-field. It's 6km deep and 30km across - a tad smaller than London. I mean, would you tell someone their nose was the size of Detroit? It's really like poking a tiger in the eye! Astronomers really should get out more, or in this case, at least check the real story behind why Mathilde is "Mathilde"!

So the image of Mathilde really was seeing in the dark...

No comments: