It's official: NASA confirms that we have found 5,000 worlds outside the Solar System

It's official: NASA confirms that we have found 5,000 worlds outside the Solar System

The confirmed exoplanet count just surpassed the 5,000 mark, representing a 30-year journey of discovery led by NASA's space telescopes.

Not long ago, we lived in a universe with only a small number of known planets, all of them orbiting our Sun. But a new series of discoveries marks a scientific high point: More than 5,000 planets are now confirmed to exist beyond of our solar system.

The planetary odometer spun on March 21, with the latest batch of 65 exoplanets—planets outside our immediate solar family—added to NASA's Exoplanet Archive. The archive records exoplanet discoveries that appear in peer-reviewed scientific articles and that have been confirmed using multiple detection methods or by analytical techniques.

The more than 5,000 planets found so far include small, rocky worlds like Earth, gas giants many times larger than Jupiter, and “hot Jupiters” in scorchingly close orbits around their stars. There are “super-Earths,” which are possible rocky worlds larger than our own, and “mini-Neptunes,” smaller versions of our system's Neptune. Add to the mix planets orbiting two stars at once and planets stubbornly orbiting the collapsed remains of dead stars.

“It's not just a number,” said Jessie Christiansen, the archive's scientific director and a research scientist at NASA's Exoplanet Science Institute at Caltech in Pasadena. “Each one of them is a new world, a new planet. “I get excited about everyone because we don't know anything about them.”

We know this: our galaxy probably contains hundreds of billions of such planets. The steady pace of discovery began in 1992 with strange new worlds orbiting an even stranger star. It was a type of neutron star known as a pulsar, a rapidly spinning stellar corpse that pulses with millisecond bursts of searing radiation. Measuring slight changes in the timing of the pulses allowed scientists to reveal planets orbiting the pulsar.

Finding just three planets around this rotating star essentially opened the floodgates, said Alexander Wolszczan, lead author of the paper that, 30 years ago, revealed the first confirmed planets outside our solar system.

“If you can find planets around a neutron star, planets have to be basically everywhere,” Wolszczan said. “The planet production process has to be very robust.”

Wolszczan, who still searches for exoplanets as a professor at Penn State, says we are ushering in an era of discovery that will go beyond simply adding new planets to the list. The Transiting Exoplanet Survey Satellite (TESS), launched in 2018, continues to discover new exoplanets. But soon, powerful next-generation telescopes and their highly sensitive instruments, starting with the recently launched James Webb Space Telescope, will capture light from exoplanets' atmospheres, reading what gases are present to potentially identify telltale signs of habitable conditions.

Wolszczan, who still searches for exoplanets as a professor at Penn State, says we are ushering in an era of discovery that will go beyond simply adding new planets to the list. The Transiting Exoplanet Survey Satellite (TESS), launched in 2018, continues to discover new exoplanets. But soon, powerful next-generation telescopes and their highly sensitive instruments, starting with the recently launched James Webb Space Telescope, will capture light from exoplanets' atmospheres, reading what gases are present to potentially The Nancy Grace Roman Space Telescope, which Expected to launch in 2027, it will make new exoplanet discoveries using a variety of methods. ESA's (European Space Agency) ARIEL mission, launching in 2029, will observe exoplanet atmospheres; A piece of NASA technology on board, called CASE, will help zero in on exoplanet clouds and hazes.

“In my opinion, it is inevitable that we will find some kind of life somewhere, most likely of some primitive kind,” Wolszczan said. The close connection between the chemistry of life on Earth and the chemistry found throughout the universe, as well as the detection of widespread organic molecules, suggests that the detection of life itself is only a matter of time, he added.

How to find other worlds

The image didn't always look so bright. The first planet detected around a Sun-like star, in 1995, turned out to be a hot Jupiter: a gas giant about half the mass of our own Jupiter in an extremely close four-day orbit around its star. A year on this planet, in other words, lasts only four days. Identify telltale signs of habitable conditions.

More such planets appeared in data from ground-based telescopes once astronomers learned to recognize them: first dozens, then hundreds. They were found using the “wobble” method: tracking slight back and forth movements of a star, caused by gravitational pulls from orbiting planets. But still, nothing seemed likely to be habitable.

Finding small, rocky worlds more like our own required the next big leap in exoplanet search technology: the “transit” method. Astronomer William Borucki came up with the idea of attaching extremely sensitive light detectors to a telescope and then launching it into space. The telescope would observe a field of more than 170,000 stars for years, looking for small dips in starlight when a planet crossed the face of a star.

That idea was realized on the Kepler Space Telescope.

Borucki, principal investigator of the now-retired Kepler mission, says its 2009 launch opened a new window on the universe.

“I have a real sense of satisfaction and really awe at what is out there,” he said. “None of us expected this enormous variety of planetary systems and stars. It's just amazing.”