Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Across the world, children fall asleep under the faint light from glow-in-the-dark astronomy stickers. Though undeniably adorable, these ceiling planetariums are too jam-packed to be realistic. You’d never see stars, dozens of spiral galaxies, and comets all at the same time, all shining together from the same patch of sky. Unless, of course, you had Hubble.
On April 30, NASA’s Hubble Space Telescope observed Comet ISON. Compared to the stars and galaxies twinkling behind it, ISON is just a stone’s throw from Earth. Here, though, we see the comet splashed out over deep space, in a collage with colorful, distant neighbors.
This Hubble Heritage image combines two Hubble filters. One filter lets in red light, which is represented here as red, and the other a greenish-yellow color, which is represented as blue. In general, redder things are older, more evolved, than blue things – this is true both for the crosshair-spiked stars and the smudges of distant galaxies. If you’re wondering what color the Sun would appear in this image, look no further than ISON itself. Unlike the objects in the frame, ISON isn’t bright on its own – it just reflects sunlight back to Earth.
In other ISON observations, Hubble has slewed to point at the comet as it moves across the stars. This is great for getting an image of ISON, but not so great if you want to see the fainter galaxies and stars that comprise ISON’s celestial neighborhood. So for these images, we settled on a tradeoff: as Hubble orbited the Earth, snapping pictures of ISON, we kept the telescope trained on the stars instead of following the comet.