New stars form all the time in most galaxies, but some galaxies spawn new stars at such an amazing rate that astronomers call them “starburst galaxies.”
In M94, the action is happening in the ring of bright blue stars out in the galaxy’s spiral arms. A pressure wave radiating from the galaxy’s centre is compressing the clouds of gas and dust in this “starburst ring,” which causes then to collapse under their own gravity to form denser clouds. The material at the centre of a collapsing cloud of gas is under tremendous pressure, and that compression generates heat energy. Eventually, hydrogen atoms at the core of the cloud are forced together with enough energy to fuse them together into helium atoms. When that happens, a new star ignites with a massive fusion reactor at its core.
M94 isn’t the only starburst galaxy in the universe. Another well-known starburst galaxy is the Cigar Galaxy, M82, about 12 million light years away.
And as the Antennae Galaxies merge, their clouds of gas and dust are colliding, setting off waves of star formation.
Antennae Galaxies. NASA/ESA.
You can recognise areas of star formation easily in these images; look for groups of bright blue and white stars. These hot, bright stars are newly formed.