Almost two decades ago, Hubble Space Telescope unveiled a new class of galaxies, known as tadpoles. And recent observations from ground-based observatories suggest that tadpoles are well named — they seem to be young galaxies caught in the act of growing larger. A tadpole galaxy has a bright head, where new stars are forming, and a faint tail. Astronomers recently observed seven tadpoles that are within about 600 million light-years of Earth, which is close enough to study them in some detail. The observations revealed that most tadpoles rotate, just like disks of spiral galaxies like our own Milky Way. But there was also a surprise: The tadpoles’ bright heads have less oxygen than their dim tails. That’s opposite the pattern in most large galaxies, where the bright regions near the galactic centers are richest in oxygen because they’re full of oxygen-producing stars. The astronomers suspect that a stream of oxygen-poor gas is falling onto one spot of the tadpole’s disk. That triggers
