Enlarge / A starburst galaxy, which produces stars at a high rate. (credit: NASA)

The size of a star determines its ultimate fate. The smallest stars will burn lighter elements for tens of billions of years; stars like the Sun will make some heavier elements before shrinking into white dwarfs; and massive stars will create the heavier elements and scatter them into the Universe as they explode. So knowing how many we have of each type of star form tells us a lot about what the Universe should look like.

Estimating the frequency at which different mass stars form is relatively easy—we can simply survey the Milky Way, counting how many of each type of star we see. That, however, assumes the Milky Way is typical of other galaxies out there. Earlier this year, we got a hint that it wasn’t. Observations of one of the dwarf galaxies orbiting the Milky Way suggested a star-forming region within it had an excess of massive stars.

But a dwarf galaxy is even more likely to have an atypical star-formation process than the Milky Way. So we really needed more general measures of the sizes of stars being formed in the larger Universe. We now have one, and big stars are still showing up at much higher rates than previous estimates would suggest.