A Blip on a Telescope in a Colorado Parking Lot Bolstered a Space Mission That Has Found Thousands of Planets … and Counting

The Kepler telescope changed how we saw the sky. It’s just one of the devices we’ve sent out beyond the reach of humans to search our solar system

Linda Shiner

Data visualization by Ethan Kruse

Summer 2026

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On September 9, 1999, a 25-year-old Harvard graduate student, David Charbonneau, made one of the closing century’s most consequential astronomical discoveries, using a four-inch telescope set up inside a plywood shed in a Colorado parking lot. Charbonneau and his adviser, Tim Brown, who had built the telescope, had been measuring the light from a sunlike star with the undramatic designation HD 209458. They hoped to use a technique called photometry—measuring a star’s light—to confirm speculations that HD 209458 had an orbiting planet. At the time, NASA was deciding whether to fund the Kepler mission, a space telescope that would use the same technique. Kepler was a long shot, because photometry had never before detected a planet orbiting a star outside our solar system. Brown and Charbonneau were about to change a long shot into a sure bet. 

In 1999, there were very few confirmed exoplanets, or planets outside our own solar system, and these were gas giants on the order of Jupiter, not smaller, rocky planets like Earth. They had been confirmed using a method known as Doppler spectroscopy, which registered shifts in the color spectrum over time as the star was tugged to and fro by orbiting planets. Doppler was useful for finding Jupiter-size planets that were close to their stars, but it couldn’t always deliver clear data on smaller planets that were farther from their stars. Astronomers using Doppler spectroscopy had noticed something unusual happening around HD 209458, about 150 light-years from Earth, but the “wobbles” in the color spectrum could have had another cause, such as the star contracting and expanding. 

In theory, the photometry method that Charbonneau and Brown used would be able to show more decisively whether a planet was orbiting a far-off sun. Many photometric telescopes couldn’t register changes in brightness that were smaller than a few percent. But Brown designed his telescope to continuously monitor a change in a star’s brightness as small as 1 percent—the dip a Jupiter-size planet would cause as it passed in front of its star. 

As Charbonneau and Brown trained their sights on HD 209458, computer software graphed the star’s brightness. Charbonneau saw the predicted 1 percent dip—the first clear photometric evidence of a planet eclipsing, or transiting, a star. At first, he felt anxious. “Here was a phenomenon that no one had ever seen before,” he recently said. “You really do ask yourself, ‘Am I delusional? Have I fooled myself? Is there a problem with the telescope, or a problem with the data?’” There was not. Two months later, another team collected similar photometric data on HD 209458. 

Kepler Orrery V

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Some believe that Charbonneau’s discovery was the moment that led NASA to greenlight the Kepler mission—a multiyear project that has so far confirmed the existence of more than 2,700 planets orbiting other stars. (The data is still being analyzed.) The mission’s principal investigator, William Borucki, had been pushing for the use of photometry for years. He believed that measuring a planet’s transit across its sun was the best way to identify smaller, rocky, potentially habitable worlds outside our solar system—which was one of Kepler’s main goals. “I was sure I could develop the transit technique sufficiently to find Earth-size planets in the habitable zone of stars like our sun,” he said in a recent NASA oral history. By 1999, Borucki’s team had proved in the lab that the Kepler instrument was precise enough to find a planet the size of Earth.

NASA formally approved the mission in 2001, and the Kepler Space Telescope launched aboard a Delta 2 rocket from Cape Canaveral, Florida, just before 11 p.m. local time on March 6, 2009. The 0.95-meter telescope contained a mosaic of photometric cells that allowed it to detect changes in brightness as tiny as 0.002 percent. It zeroed in on an area of the sky in the Cygnus-Lyra constellations, gathering light from the same group of around 200,000 stars for four years. The spacecraft was designed to trail behind the Earth as it orbited the sun, giving it a continuous, unobstructed view of the sky. The mission quickly achieved a thrilling pace of discovery. In 2010, the Kepler team announced that the mission had confirmed five new exoplanets in its first six weeks. In December 2011, the scientists announced the discovery of the first planet in the habitable zone of its star—not too hot or too cold for life to exist. In 2013, NASA engineers were able to extend the original life span of the equipment, and a second phase of the project, called K2, brought the total number of surveyed stars to half a million. In April 2014, scientists announced the first Earth-size planet—the kind of rocky world that might be able to support Earth-like life. 

The spacecraft finally ran out of fuel in 2018, but Kepler had time to detect many wondrous things: one planet orbiting two stars, like the planet Tatooine in Star Wars; planetary systems with three, four or five planets; a giant gas planet with the density of a marshmallow. These discoveries vastly broadened the field of exoplanet research, which NASA’s TESS spacecraft has continued and which the Nancy Grace Roman Telescope will carry on when it goes into orbit within the next year. This new telescope will add to Kepler’s findings by detecting the gravitational fields of planets even smaller than Earth and capturing direct images of Jupiter-size planets outside our solar system for the first time.

By some measures, the Kepler mission was a modest one. Since 1958, NASA has dispatched spacecraft to every planet in the solar system and measured the faint hum left behind by the Big Bang. The twin Voyager spacecraft, launched in 1977, are still speaking to their operators by radio from billions of miles away. Yet the Kepler mission changed the way astronomers understand the whole galaxy. It revealed that planets orbiting around other stars are not rare but commonplace, and that some of them might have the right conditions to support life. Before Kepler, we looked at the sky and saw stars; after Kepler, we see solar systems. 

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The Past, Present and Future of Space Exploration

Mariner 2 and Mariner 4: The first functioning spacecraft to reach another planet, Mariner 2, the width of about five refrigerators, launched in 1962 on a mission to Venus, where it found that the planet had a dense CO2 atmosphere and a hellishly hot surface, above 800 degrees. In 1965, Mariner 4 transmitted the first close images of Mars using a TV camera with a magnetic-tape recorder. 

The Pioneers and Voyagers: Pioneer 10 launched in 1972, crossing the asteroid belt to measure Jupiter’s radiation and magnetic fields. In 1973, Pioneer 11 headed toward Saturn, where it discovered a new ring and two moons. Voyager 1 later found volcanism on Jupiter’s moon Io, and Voyager 2 found rings and several moons around both Uranus and Neptune. 

Galileo, Cassini and Juno: Galileo spent 1995 to 2003 gathering data from Jupiter and its moons, discovering evidence of an underground ocean on Europa with more water than all the oceans on Earth. In 2004, Cassini began orbiting Saturn and released the Huygens probe on its moon Titan, where gasoline-like liquid rains from the sky. In 2016, Juno discovered that Jupiter’s colorful bands extend to a depth of 1,900 miles. 

The Mars Rovers: In 1997, Pathfinder deployed a rover named Sojourner, the first wheeled vehicle on the Red Planet, which used an alpha proton X‑ray spectrometer to analyze rocks and soil. In 2004, larger rovers Spirit and Opportunity arrived, confirming that Mars once had water. Car-size Curiosity landed in 2012, followed in 2021 by Perseverance, which deployed the helicopter Ingenuity. Collectively, these rovers have traveled more than 80 miles, analyzing clues left by ancient lakes and rivers. 

Europa Clipper and Dragonfly: The Europa Clipper will arrive at Jupiter’s icy moon in 2030 to search for environments that could support life, using tools such as an ice‑penetrating radar, an ultraviolet spectrograph and high‑resolution cameras. Dragonfly, scheduled to launch in 2028, will send a large rotorcraft to Saturn’s moon Titan. Equipped with spectrometers, a sample drill and a camera suite, the craft will fly through the thick atmosphere and alight on frozen dunes and other lunar terrain.

Linda Shiner | Read More

Linda Shiner is the former editor of Air & Space.

Ethan Kruse | | Read More

Ethan Kruse is a postdoctoral fellow at NASA who researches exoplanets.