A planet that goes around a star other than our Sun is called an exoplanet. As of October 2026, NASA has confirmed more than 6,000 exoplanets, out of billions believed to exist. Some are rogue planets that orbit no star. Telescopes, some of them out in space, are used to look for planets around other stars. One way is to watch a star for tiny dips in its light. A dip means a planet passed in front of it. The Kepler space telescope launched on March 6, 2009, and found planets by watching for transits. It left a legacy of more than 2,600 planet finds before NASA retired it in October 2018.

TESS, the Transiting Exoplanet Survey Satellite, launched on April 18, 2018. It watches patches of sky for transits. As of November 2026, TESS has finished a two-year primary mission and is now in an extended mission. Another way, called radial velocity, looks for shifts in a star's spectrum. The gravity of an orbiting planet tugs a star back and forth. That makes the star wobble. Repeated shifts from red to blue can be caused by one or more orbiting planets. A third method is microlensing. A foreground star's gravity magnifies a background star, and a planet shows up as a smaller second spike. Direct imaging is hard. The star's light overwhelms the planet.

Once a planet is found, a new question comes up: could it hold life? The habitable zone is the area around a star where a planet could have liquid water on its surface, not too hot and not too cold. It is also called the Goldilocks zone, because liquid water is essential for life as we know it. Astrobiology is the study of how life began, how it evolved on Earth, and where it might exist elsewhere; NASA has funded it since its first exobiology grant in 1959. As of November 2026, scientists have not found life anywhere beyond Earth, and the search goes on.

Mars is one place where the search is under way. Long ago it had rivers and lakes: it has ancient river valleys, deltas and lakebeds, so water most likely once flowed there. Rovers are robots with wheels that drive around Mars, taking pictures and measurements. As of November 2026, some of them look for signs that tiny living things could have lived there long ago. Perseverance landed on Feb. 18, 2021, in Jezero Crater, and its goals include seeking signs of ancient life. The Ingenuity helicopter that traveled with Perseverance to Mars became the first aircraft to achieve powered, controlled flight on another planet.

Others search in another way. The SETI Institute is a nonprofit that searches for life beyond Earth. Its work is one part of the wider search for life. Radio telescopes are one tool for that search. Its Allen Telescope Array is the first radio telescope designed from the ground up to be used for SETI searches. The Drake equation was formulated largely by astrophysicist Frank Drake, and it carries his name. It was first discussed in 1961 at a SETI conference in Green Bank, West Virginia. It estimates the number of technically advanced civilizations in the Milky Way from a chain of factors.

People also report strange things in the sky. UFO means unidentified flying object: something the person who saw it could not identify at that moment. Bright planets such as Venus and Jupiter, and meteors, are sometimes reported as strange lights because they can look like they are hovering or moving. From 1947 to 1969, the Air Force investigated reports under Project Blue Book. Each report was classed as identified with an astronomical, atmospheric or human-made cause, or unidentified. Of 12,618 sightings, 701 stayed unidentified. Some of those had too little information to match a known cause. Blue Book found no sign that any case was a vehicle from another world.

The Pentagon's All-domain Anomaly Resolution Office, called AARO, says many reports are listed as unidentified simply because sensors could not collect enough information to name what was seen. It lists common causes. They are windborne debris like plastic bags and mylar balloons, birds, balloons, planes, drones, rocket launches, and sunlight glinting off satellites. NASA's own study of unidentified anomalous phenomena (UAP) found no sign that UAPs come from other worlds, and says there are too few high-quality observations to draw scientific conclusions. As of November 2026, asked whether it has found any evidence of extraterrestrial technology, AARO answers "No," adding that examination of UAP sightings is ongoing.

Words to know

• exoplanet: far-off planet
• spectrum: light spread out
• microlensing: gravity magnifying light
• astrobiology: study of life
• unidentified: not yet named