Y'know, when I'm really old and past my prime, I expect to watch a lot of TV and take naps. But when NASA's missions are old and having trouble, they produce images like this:
Whoa. Click to embiggenate. Spitzer Space Telescope is an infrared observatory that launched in 2003. Infrared light is emitted by warm objects: dust, stars, gas, planets, and so on. That includes the telescope itself: unless cooled, the mirror and the rest of the telescope will glow brightly in the infrared, making it impossible to do any science. It would be like shining a flashlight down the 'scope! So Spitzer uses liquid helium to cool some of its instruments down almost to absolute zero. Or, I should say it "used" liquid helium: over time, the helium warms up, and in May 2009 the last of the liquid helium boiled away. What this means is that some of ...
