NASA has so far verified 6,000 exoplanets – a vast collection of alien worlds, from fiery giants and oceans of lava to stars with “gemstone” clouds or a density similar to Styrofoam.
NASA has so far verified 6,000 exoplanets – a vast collection of alien worlds, from fiery giants and oceans of lava to stars with “gemstone” clouds or a density similar to Styrofoam.
This milestone is not only a testament to the vast diversity of worlds beyond our solar system, but also to humanity's evolving capabilities to locate and explore them.
Another 8,000 signals destined for detection as planets
NASA’s official count of exoplanets—those orbiting stars beyond our sun—currently stands at 6,000. There is no single “planet 6,000,” as discoveries are gradually being added by researchers around the world. The count is managed by NASA’s Exoplanet Science Institute (NExScI) at Caltech’s IPAC Center in Pasadena, California. More than 8,000 additional candidates await verification, and NASA continues to lead the global effort to search for signs of life beyond Earth.
“This is the result of decades of cosmic exploration led by NASA space telescopes—exploration that has completely changed the way we look at the night sky,” said Sean Dumagell-Goldman, acting administrator of the Astrophysics Division at NASA Headquarters. “Step by step, from discovery to characterization, the missions have built the foundation for the fundamental question: Are we alone? Now, with the Nancy Grace Roman Space Telescope and the Habitable Worlds Observatory, the United States will lead the next leap—in studying worlds like our own around sun-like stars. It’s American ingenuity, and the promise of discovery, that unites us all.”
From the first three decades to the present day
This milestone comes thirty years after the first planet was confirmed around a sun-like star (1995). Planets had been discovered around “dead stars” (stars that have run out of nuclear fuel and collapsed) even before that. Estimates suggest billions of planets in the Milky Way, but discoveries remain challenging. As the catalog grows, researchers are not only discovering intriguing individual worlds, but also understanding the similarities and differences between our solar system and other planetary systems.
Our solar system has a numerical balance between rocky planets and gas giants; outside of it, rocky planets seem to be more common. Types that have no parallel in our own have also been discovered: Jupiter-sized worlds in orbits closer to the sun than a hot star, planets orbiting two suns—or none (free-roaming), companions of stars that have undergone cosmic death, “lava worlds,” bodies as low as Styrofoam, and even planets whose skies may be filled with clouds of gems.
“Each new type of planet teaches us about the conditions under which worlds form, and ultimately how common Earth-like worlds might be and where to look for them,” said Dawn Gallino, head of NASA’s Exoplanet Exploration Program (ExEP) at JPL.
How do you find other worlds?
Fewer than a hundred planets have been directly imaged to date; most are extremely faint and are engulfed in the glow of their host star. The remaining detection methods are indirect. The transit method, for example, looks for a tiny dip in the star's light when a planet passes in front of it.
To make sure the signal isn’t due to something else, most candidates require follow-up measurements—sometimes with another telescope—and that takes time. That’s why NASA’s planetary archive at NExScI has a long queue of candidates waiting to be confirmed.
Graphic credit: NASA/JPL-Caltech – NASA space and ground missions, European Space Agency (ESA), The Canadian Agency (THAT'S IT) and-NSF Contribute to searches.
Collaborations and acceleration of discoveries
“We need the entire community to leverage the investments in missions that are ruling out candidates at an increasing rate,” said Ora Kesseli, deputy science director for NASA’s Planetary Archive at IPAC. “A key part of our work is building tools that help the community verify or rule out planets.”
The pace of discoveries is accelerating (the 5,000 mark was crossed only three years ago), and this trend is expected to continue. Kessel and her colleagues anticipate thousands more candidates from ESA’s Gaia mission using astrometry, and from NASA’s Nancy Grace Roman Space Telescope, which will discover thousands of new planets mainly using gravitational microlensing.
The Future: Detecting Earth-like Worlds
Looking ahead, science will focus on finding rocky, Earth-like planets and studying their atmospheres for biosignatures—characteristics or molecules that could indicate past or present life. The James Webb Space Telescope has already analyzed the chemical compositions of more than 100 atmospheres.
But studying the atmospheres of worlds the size and temperature of Earth requires new technology, especially blocking the glare of the parent star. In the case of an Earth-like world, the challenge is enormous: the Sun is 10 billion times brighter than Earth – a glow that “drowns” the planet’s light to a distant observer.
A novel telescope and the pursuit of habitable worlds
NASA has two main steps to overcome the challenge. The Nancy Grace Roman Space Telescope will be equipped with a technological device called the Roman Coronagraph – a tool that will block starlight and reveal faint planets. At its peak, the coronagraph is expected to directly image a planet the size and temperature of Jupiter around a sun-like star, at an orbital distance similar to Jupiter. Combined with the microlensing survey, Roman will reveal new details about the diversity of planetary systems and help estimate how common our own sun-like systems are.
To detect an Earth-like world, an even more advanced coronagraph is needed. NASA is developing an instrument for such a mission called the Habitable Worlds Observatory.
NASA's Exoplanet Exploration Program (ExEP) leads the agency's efforts to discover and understand planetary systems around neighboring stars: formulating unified strategies, leading current and future missions, and emphasizing the detection of worlds with possible life.
The center of scientific and analytical activity is NexScI – NASA’s Exoplanet Science Institute at IPAC (Caltech Astrophysical Data Center) in Pasadena. The institute provides the global community with tools, data, and coordination, and, together with ExEP, is managed by Caltech’s JPL for NASA, maintaining rigorous research and technological innovation at the forefront of world exploration.
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