Star Factories

aIn 1978, two Yale astronomers, Richard Larson and Beatrice Tinsley, discovered that some
ainteracting galaxies are oddly blue. Blue hues usually emit from newly formed stars, so aLarson and Tinsley called these galaxies starbursts. Soon astronomers had found hundreds aof starbursts, some of which were churning out a thousand new stars a year.

aNow, computer simulations have shown how a collision can spark a star factory. As two agalaxies of unequal size meet, the gravitational tides induce a bar-shaped feature across the acenter of the bigger galaxy. The bar forms shock waves which knock the interstellar gas adown to a lower orbit, compressing it. Squeezed tightly together, the gas molecules fuse aand explode like hydrogen bombs all across the galactic core. The starburst lasts for ahundreds of millions of years.