Worlds upon worlds await us in the cosmos and we’re finding more all the time. Before 1992, we weren’t even completely certain planets existed outside of our solar system. Now, astronomers are finding an average of one new alien world every day. In fact, as of September 2025, the official list of confirmed exoplanets reached 6,000 and counting!
For most of human history, the boundaries of our universe stretched only from horizon to horizon. Later, when early astronomers gazed up at the stars, seemingly fixed in their positions within the heavens, they noticed a few outliers drifting along their own paths. They called those distant points of light planētēs, Greek for “wanderers.” Today, we call them planets.
With the invention of the telescope, we could glimpse those worlds for the first time and our cosmic neighborhood got a little larger. There are island worlds out there in the dark, at least in our own neck of the woods. But, besides the sun, the star that the planets in our solar system orbit around, the other stars are shockingly far away.
What is the closest known star to Earth, after the sun?
The closest one, Proxima centauri, is 4.2 light-years away, roughly 24 trillion miles. For context, the Parker Solar Probe (the fastest spacecraft ever built with a top speed of 430,000 miles per hour) could fly around the Earth in three and a half minutes, but it would take more than 6,000 years to get to the nearest star. Those early primitive telescopes didn’t have a chance of seeing that far.
It wasn’t until the ‘90s that our astronomical powers advanced enough to confirm the existence of worlds around other stars. Since that very first discovery, more than 6,000 exoplanets have been confirmed with another 8,000 candidates awaiting confirmation.
“This milestone represents decades of cosmic exploration driven by NASA space telescopes — exploration that has completely changed the way humanity views the night sky,” said NASA acting director, Astrophysics Division, Shawn Domagal-Goldman. “Step by step, from discovery to characterization, NASA missions have built the foundation to answering a fundamental question: Are we alone?”
What kinds of exoplanets are there?
Among the 6,000 and counting confirmed exoplanets, astronomers have detected worlds like the ones in our solar system, even a few that seem pretty similar to Earth. They’ve also found some truly bizarre worlds we might hardly recognize. There are gas giants larger than Jupiter, orbiting closer than Mercury. There are rogue planets traveling alone through the universe without any parent star. There are planets orbiting multiple stars, planets covered entirely in water, planets in the process of being consumed, and planets where it rains glass at 5,000 miles per hour.
How exoplanets are found and confirmed
Most exoplanets are too far away for astronomers to observe directly with a telescope. Instead, exoplanets are usually discovered by looking for the signs they leave behind. Fewer than 100 exoplanets have been discovered through direct observation, but that number is expected to grow as new observatories (both on the ground and in space) are constructed.
Usually, astronomers look for ways that a planet interacts with its more visible parent star to infer its presence. One way is the transit method, which looks for planets passing between us and the parent star. If the planet’s orbit takes it between us and the star, then astronomers can measure the dip in light caused by the planet’s transit.
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In other cases, astronomers can find a planet by watching the star wobble. While stars exert a gravitational pull on nearby planets, those planets also pull on the star. By closely watching the way the star wobbles, astronomers can tell if there are planets nearby, even if they can’t see them. In either case, astronomers have to confirm the dimming or wobbling isn’t caused by something else, which is part of the reason so many candidate planets are waiting to be confirmed.
The study of exoplanets is relatively new but it’s proceeding quickly. The exoplanet database hit 5,000 confirmed exoplanets just three years ago in 2022. Today, we’re discovering approximately one new exoplanet every day and as observation methods and techniques improve, as new telescopes are built or launched, as candidates are confirmed, the rate of discovery will only get faster.
Travel to an exoplanet with the crew of the Ark One in SYFY’s The Ark.