We have reached 5,000 strange, new worlds.
The 5,000th alien world has been added to the NASA Exoplanet Archive.
Recent discoveries and the promise of more insights to come, as NASA's $10 billion James Webb Space Telescope readsies for planet-gazing operations in deep space, has led to the milestone.
JPL officials said Monday that the 5,000-plus planets found so far include small, rocky worlds like Earth, gas giants many times larger than Jupiter, and hot Jupiters.
JPL officials said there are "super-Earths" which are larger than our own and "mini-Neptunes" which are smaller than Neptune.
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The California Institute for Technology houses the NASA Exoplanet Archive. To be added to the catalog, planets must be independently confirmed by two different methods, and the work must be published in a peer-reviewed journal.
The first exoplanets were found in the early 1990s. While telescopes on the ground and in space have done well to get the count to 5,000 since then, the worlds found to date are mostly in this little bubble around our solar system.
Christiansen said that 4,900 of the 5,000 exoplanets are located within a few thousand light-years of us. It is mind-blowing.
The first confirmed planetary discovery came in 1992 when Alex and Dale Frail published a paper in the journal Nature. Two worlds were spotted by measuring the timing of the light as it reached Earth.
The first planet around a sun-like star was discovered in 1995 with the help of ground-based telescopes. The world was not hospitable to life as we know it, it was a hot gas giant that whipped around its parent star in only four Earth days.
These worlds were found by spotting wobbles of stars as planets tugged on them. Larger worlds caused bigger wobbles, so it was easier to spot them. Astronomers said at the time that they would need to try the transit method to find more Earth-sized planets. The light of a star would be looked at to see small fluctuations as a planet passed across the face.
Astronomer William Borucki helped realize that vision as the principal investigator of NASA's Kepler space telescope, which launched in 2009 and exceeded its main mission by several years until it finally ran out of fuel in 2018). More than 2,700 planet discoveries have been made by the telescope, many of them Earth-sized or smaller worlds.
Since the launch of the planet hunt, many other instruments have joined it. The European Southern Observatory's La Silla Observatory is home to the HARPSspectrograph, which is a planet-hunter.
After the first light, HARPS discovered more than 150 exoplanets. While access has been restricted in the last few years due to the coronaviruses, HARPS remains operational and continues to seek new worlds with high precision.
The NASA-European Space Agency, the Hubble Space Telescope, and the Characterizing Exoplanet Satellite are some of the telescopes that assist with the planet search. There are several huge telescopes under construction on the ground, including the Giant Magellan Telescope and the Extremely Large Telescope, which are scheduled to come online later this decade.
By studying the atmospheres of several relatively nearby worlds, Webb will be able to enhance the tally of exoplanets. While such work may focus on gas giants, scientists say it will be useful for a future generation of observatories with even more high-powered telescopes ready to see planets closer in size to Earth.
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