A century of astronomy revealed Earth’s place in the universe
Clusters of stars like this one helped show that the Milky Way is enormous and just one of many galaxies. The glittering young stars in this Hubble Space Telescope image are about 20,000 light-years away in the constellation Carina.
A century ago, the Milky Way galaxy was the entirety of the known universe. We had no idea what made the stars shine, and only one star — our own sun — was known to harbor any planets. Of those planets, humans had explored only one: Earth.
“The stellar universe, as we know it … is a flattened, watch-shaped organization of stars and nebulae,” astronomer Harlow Shapley wrote in Science News Bulletin, the earliest version of Science News, in August 1921 (SN: 8/8/1921, p. 3). That sparkling pocket watch was the Milky Way, and at the time Shapley wrote this, astronomers were just beginning to conceive that anything at all might lie beyond it.
Today, spacecraft have flown by every one of the solar system’s planets, taking close-ups of their wildly alien faces. The solar system, it turns out, contains a cornucopia of small rocky and icy bodies that have challenged the very definition of a planet. Thousands of planets have been spotted orbiting other stars, some of which may have the right conditions for life to thrive. And the Milky Way, we now know, is just one of billions of galaxies.
