A world of molten rock
Kepler-10b, located about 608 light-years away in the constellation Draco, was the first confirmed rocky planet discovered outside our solar system. The announcement came on January 10, 2011, revealing an alien and strangely familiar world. The planet has a radius about 1.47 times that of Earth and a mass of approximately 3.72 times our home world. These figures result in a density of around 6.46 grams per cubic centimeter, suggesting a composition of silicates and iron.
Kepler-10b is an object of intense study because of its extreme environment. It orbits its star, Kepler-10, at a distance less than one-twentieth that of Mercury from our Sun, completing a full year in only 20 hours. This proximity creates blistering surface temperatures. The "dayside" of the planet, which is tidally locked to perpetually face its star, reaches an estimated 1,833 Kelvin (about 2,840°F or 1,560°C). This is hot enough to melt iron, leading scientists to theorize that the entire star-facing hemisphere is a vast, churning ocean of magma.
A terrestrial analog in Hawaii
Directly observing the surface of an exoplanet hundreds of light-years away is beyond current technological capabilities. To understand what a lava world might look like, scientists turn to analog sites on Earth. The lava lakes within the Halemaʻumaʻu crater of Kīlauea volcano in Hawaiʻi Volcanoes National Park are a valuable site for study. These pools of molten basalt show processes that may be occurring on Kepler-10b.
Researchers, including teams from NASA, use instruments like airborne imaging spectrometers to study the Kīlauea lava lake from the air and on the ground. They analyze the spectral signatures of the molten rock and volcanic gases. This data helps them understand how materials differentiate as they cool and how to interpret the light signatures of high-temperature surfaces. By building models based on the behavior of Hawaiian lava, scientists can better interpret the faint data received from distant exoplanets. These studies help distinguish between solid and molten planetary surfaces, helping identify other lava worlds across the galaxy. The confirmation of Kepler-10b's existence heavily relied on data from the W.M. Keck Observatory, also located in Hawaii.