“We don’t know,” says Ed Churchwell, professor of astronomy. “We know it’s a very large number.”
It’s in the hundreds of billions, Churchwell says. In contrast, there are but 4 billion stars in our own galaxy, the Milky Way — and the number will keep growing for some time before we run out of galaxies to [...]

In astronomy, it helps to get above it all. Three cool orbiting telescopes are collecting visible, infrared and X-ray light. We ogle their greatest hits.