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Finding these “just right” planets in the habitable zone is one of the keys to finding signs of life. De La Torreįor larger, hotter stars, the zone is farther away for smaller, cooler stars, it can be very close indeed. Image credit: NASA/JPL-Caltech/Lizbeth B. Broiling planet Venus is within the inner edge, while refrigerated Mars is near the outer boundary.ĭetermine the distance of an exoplanet from the star itself, as well as the star’s size and energy output, and you can estimate whether the planet falls within the habitable zone. In our solar system, Earth sits comfortably inside the Sun’s habitable zone. In both cases, “just right” is more likely to be somewhere in between.įor a planet, the habitable zone is the distance from a star that allows liquid water to persist on its surface – as long as that planet has a suitable atmosphere. Too far away, and its surface remains cold and unappetizing. Too close, and your marshmallow – or your planet – might end up as nothing more than a charred cinder. Instead, they use a narrower yardstick: the habitable zone.Įvery star, like every campfire, has a definable zone of radiated warmth. But these days, scientists don’t spend a great deal of time discussing it, Domagal-Goldman said. But other moons and planets show signs of potential habitability.ĭrake’s list can be a good conversation starter, and a useful way to frame the complex questions around the possibility of other life. If we develop and launch a powerful enough space telescope, “we could figure out if we have advanced life or biological life,” he said.Īmong the stunning variety of worlds in our solar system, only Earth is known to host life. He studies the habitability and potential for life on exoplanets. Some of the first few items are now known, including the potential presence of habitable worlds, said researcher Ravi Kopparapu from Goddard, also a co-leader of Domagal-Goldman’s team. When Drake introduced this roadmap to life beyond Earth, all the terms – the signposts along the way – were blank. It begins with the rate of star formation in the galaxy and the fraction of stars that have planets, leading step-by-step through the portion of planets that support life and – most speculatively – to the existence and durability of detectable, technological civilizations. Put forward in 1961 by astronomer Frank Drake, the list remains mostly blank. A well-known list of the data needed to determine the likely abundance of life-bearing worlds, though highly conjectural, is known as the “Drake equation.” While the chances of finding life elsewhere remain unknown, the odds can be said to be improving. The goal: unambiguous evidence of another living, breathing world. Working with scientists across NASA, as well as academic and international partners, his team and others are helping to design and build the next generation of instruments to sift through light from other worlds, and other suns. I’ll be planning a party if we find it.”ĭomagal-Goldman co-leads a team of exoplanet hunters who, in the years and decades ahead, are planning to do just that. “I hope it’s there,” said Shawn Domagal-Goldman, a research astronomer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Is there life beyond Earth? So far, the silence is deafening. What's Out There? The Exoplanet Sky So FarĪnd finding non-intelligent life is far more likely Earth existed for most of its history, 4.25 billion years, without a whisper of technological life, and human civilization is a very late-breaking development. No convincing evidence of advanced technology – artificial signals by radio or other means, or the telltale sign of, say, massive extraterrestrial engineering projects – has yet crossed our formidable arrays of telescopes in space or on the ground. Observing signs of possible microbial life in exoplanet atmospheres is currently just out of reach. We have yet to find another “Earth” with life, intelligent or not. The ingredients in the recipe for earthly life – water, elements associated with life, available sources of energy – appear to be almost everywhere we’ve looked. A healthy percentage of them are small, rocky worlds, of a similar size and likely similar composition to our home planet. Our galaxy is crowded with exoplanets – planets around other stars. The good news: We know vastly more than any previous generation. As humanity casts an ever-wider net across the cosmos, capturing evidence of thousands of worlds, an ancient question haunts us: Is anybody out there?