In order to know whether a planet could be home to alien life, we have to be able to see it.
Our solar system is but a small part of the galaxy we live in, never mind the entire universe. Astronomers are constantly searching for life on other planets, but distances and light in space make this search complicated.
Over 2,000 exoplanets — planets outside our solar system — have been discovered, but not just any planet can play host to other life forms. What we’re really searching for is a rocky planet that is the right distance from its Sun, in what is known as the “Goldilocks zone,” neither too hot nor too cold.
Finding exoplanets is the relatively easy portion of the task. Researchers can detect their gravitational pull on a star, or spot fluctuations in a star’s light as a planet orbits in front of it. However, getting a good look at them is nearly impossible. The stars that they orbit are much brighter than the planets, so they are obscured by the light. According to How Stuff Works, seeing exoplanets has been compared to “standing in Boston and trying to spot a firefly next to a searchlight in San Francisco.”
SETI (Search for Extraterrestrial Life) is a scientific organization devoted to the search for intelligent alien life. "We've detected thousands of them, but we've only seen a handful," Seth Shostak, senior astronomer and director of the SETI Institute, told How Stuff Works.
NASA’s Jet Propulsion Laboratory at CalTech is working on a way around the problem. They have plans for a massive shade, or space umbrella, that could fly with a space telescope to block out excess sunlight. The screen, which would look like a giant flower, could block out the light surrounding an exoplanet, while letting through the planet’s own light, according to a report published in March. The exact size has yet to be determined, but one proposal calls for it to be at least 328 feet (100 meters) in diameter, about the size of a football field.
Plans are for Aerospace contractor Northrop Grumman to build the starshade. Their engineers tested different shapes and found that the “petals” worked best. "If we can feather the edges, soften those edges so we can control diffraction, well, then we can see a planet," explained Princeton University aerospace engineer Jeremy Kasdin, who is helping to develop the starshade, in a TED Talk.
Plans are underway for the starshade to be deployed in 2024, but there is still much to figure out. The starshade will have to fly in tight formation with a telescope more than 30,000 miles (48,280 kilometers) away.
What kind of information can we expect from the starshade-telescope pair? Although we won’t be getting high-resolution images, the starshade could make it possible for researchers to analyze an exoplanet’s atmosphere — one step in determining its ability to host life.
"You could pass the light through a spectrograph, to see if there are chemicals that are possible biological signs there," said Kasdin. “Another possibility involves spotting chemicals that might be pollution created by a civilization, such as chlorofluorocarbons emitted by air conditioners and refrigerators,” reports How Stuff Works.
If we ever actually find life on a distant planet, the next step will be figuring out how to make contact. But for the moment, we might as well take things one step at a time. Just knowing that alien life is out there would be pretty incredible.