Found: A Blue Planet That Rains Glass
One of the strangest and loveliest exoplanets yet gives the galaxy another pale blue dot
Back in the early 90’s, the Voyager 2 space probe, already out beyond Neptune and on its way toward the edge of the Solar System, swiveled its camera around to look back at its home world. It was difficult to see, but there, nearly three billion miles (4.8 billion km) away, lay Earth. Our entire planet, with all its flora and fauna and history and civilizations was nothing more than a blip of blue against the background of stars—an object so tiny and frail that the phrase “pale blue dot” inspired the great astronomer-communicator Carl Sagan to write a book about humanity’s future in space.
Now astronomers are abuzz with news of a second pale blue dot—a planet orbiting the star HD 189733, about 60 light-years from Earth. It’s a tiny bit less hospitable than Earth: known as HD 189733b, the planet is a giant, gaseous world resembling Jupiter, but much hotter. With a surface temperature of 1800°F (980°C), rainstorms of glass (yes, glass) and winds that reach 4,000 m.p.h. (6,400 k/h), it’s not even remotely likely to be home to flora and fauna.
Measuring the color of this so-called exoplanet is a major scientific milestone nonetheless: it provides important clues to what the atmosphere is made of, which can in turn tell scientists something about the origins and composition of the planet itself. And while it’s not possible with current technology, observations like this one are a warmup for studies of true Mirror Earths—smaller, more temperate worlds like ours, where life could plausibly exist.
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