Astronomy may be hard science, but there’s always been a whiff of Disney about it too. What else beyond enchantment could explain the ice volcanoes on Neptune’s moon Triton, the helium rain in the atmosphere of Jupiter, the beads of colored glass scattered across the surface of the moon? Now you can add one more through-the-looking-glass feature to the fantasyland that is the cosmos: the green crystal rain falling on a young star in the constellation Orion.
When most people think of what makes up a star, little more than gas and fire come to mind — and that’s not a bad start. It’s hard for much else to survive in so superhot a mass. But a star’s reach is a lot bigger than we think, blasting flares and plumes high into space — and out there, things get a lot colder.
Since 2003, the Spitzer Space Telescope has been studying the universe in the infrared spectrum — looking, essentially, at how different phenomena play out at different temperatures — and the upper reaches of stars has been one of its areas of investigation. Several years ago, the telescope turned its giant eye toward a star called HOPS-68, which is located in Orion about 1,350 light years from Earth. The data it gathered, like much of the information all space telescopes collect, was initially recorded and banked, awaiting the time astronomers could break it down and analyze it. That analysis was just completed and the findings were published in the newest edition of Astrophysical Journal Letters. The conclusions the scientists reached were clearly worth the wait.
What Spitzer observed was a sort of perpetual crystalline rainstorm made of a bright green mineral of a class called olivine, pouring down on the infant star. Olivine is a magnesium iron silicate that exists throughout the universe — in distant galaxies and local comets — as well as in earthly jewelry stores, in a pristine, gem-quality form called peridot. Various kinds of olivine were also collected on the moon throughout the Apollo program. Lunar olivine was created by great volcanoes called fire fountains, which sprayed superheated lava into the sky. As the aerosolized material settled back down to the surface and cooled, it formed glass beads. It was the crew of Apollo 15 who first found green olivine — specifically, a magnesium-rich variety that goes by the name forsterite, which is also the kind that was spotted by Spitzer.
