NASA's Hubble Finds Water Vapor on Habitable-Zone Exoplanet for the First Time

To date, approximately 4,000 planets have been found orbiting other stars. The majority are extremely hostile to any chances for life: with exotic atmospheres, wide temperature extremes, and oddball orbits. Astronomers have now made an important step toward the ultimate goal of finding an exoplanet with an atmosphere more like Earth's, and having moderate temperatures. Water vapor has been identified in the atmosphere of a planet called K2-18b, located 110 light-years away. And, where there's water there could be clouds and rain. The planet is also at the right distance from its star to have a temperate climate where the water doesn't evaporate or freeze. But don't go looking for real estate yet. The planet is in a category not found in our solar system. It is larger than Earth but smaller than Neptune. It might have a rocky surface, but it is more likely a giant ball of liquid and gas, like Neptune. Hundreds of known exoplanets fall into this mass range. So, it's important for astronomers to characterize the worlds and assess the chances for supporting life as we know it.