The team used the Hubble Space Telescope and other telescopes to study a galaxy called NGC 2903, which lies 25 million light-years away and is similar to our own galaxy. The HST picture shows that known 'hot spots' near the centre of the galaxy are clusters of stars born 5 to 10 million years ago. Other spots in the galaxy are clouds of ionised hydrogen gas where young stars are forming today. The two kinds of spots are far apart, meaning that star-forming activity is shifting from place to place.
Stars form when a giant cloud of cold hydrogen gas collapses in on itself.
The astronomers also found that a dense region of stars in the galaxy, called a bar, seems to funnel gas into the galaxy's centre, fuelling the birth of young stars. Most of the stars are old. But we see a bit more action in places - a couple of discos starting up. That means there are some younger inhabitants as well. The research results are described in Alonso-Herrero et al.