NASA recently announced that it had detected more than 5,000 exoplanets, so we asked astronomers, actors and an astronaut to share their favorite worlds orbiting distant stars.
In January 1992, a pair of astronomers reported a discovery that changed the course of scientific history: They found planets outside our solar system.
The detection of the first confirmed exoplanets — the term for worlds that orbit other stars — validated dreamers who for centuries believed that “innumerable celestial bodies, stars, globes, suns and earths may be sensibly perceived therein by us,” in the words of the Renaissance polymath Giordano Bruno. One such detection — the world 51 Pegasi b in 1995 — led to the award of the 2019 Nobel Prize in Physics to Michel Mayor and Didier Queloz.
Now, 30 years later, the list of known exoplanets has just topped 5,000, according to NASA. This dazzling abundance and variety of worlds has come into view with the aid of ever-more sophisticated space telescopes. There are “hot Jupiters” that orbit scorchingly close to their stars and beefed-up versions of our planet known as “super-Earths.” Rogue planets, unmoored from their stars, wander interstellar space. And some worlds show signs of habitability, meaning they could host alien life.
To celebrate the milestone, experts and enthusiasts shared their favorite exoplanets or exoplanetary systems among the thousands of worlds to choose from.
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Poltergeist and Phobetor were the first confirmed exoplanets ever spotted. Alexander Wolszczan and Dale Frail detected the planets orbiting a neutron star, a type of dead star, using the Arecibo telescope in Puerto Rico.
“Not only did this discovery precede further confirmed exoplanet discoveries by three years, Poltergeist and Phobetor were the first exoplanets with Earth-like masses and the first multiplanet system,” said Dr. Frail, an astronomer at the National Radio Astronomy Observatory.
“This discovery suggested that, if you can make planets around a neutron star, they should be common around all kinds of stars,” said Dr. Wolszczan, a professor at Pennsylvania State University.
No Doubt About It
Though Poltergeist and Phobetor were the first confirmed exoplanets in history, an absolutely humongous gas giant nicknamed Tadmor was spotted in 1988 by scientists based in British Columbia. The existence of Tadmor was disputed for years, even by its own discoverers, but was eventually confirmed in 2002.
Chris Hadfield, a Canadian astronaut, said that “firsts” are always important to him, which is just one of the reasons that Tadmor is his favorite exoplanet.
“Part of the reason I like it is that it was detected by three Canadians,” said Mr. Hadfield, referring to Bruce Campbell, Gordon Walker and Stephenson Yang, “and they just couldn’t believe it.”
“To me, since it’s the first one, it’s the one I think ends up being the most historic and at this point, the most interesting,” he added.
Seven-in-One
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With seven rocky planets and a location just 40 light-years from Earth, the TRAPPIST-1 system is a fan favorite.
Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell University, noted that the system had four planets in the habitable zone — the region around a star where liquid water could potentially exist.
“Wouldn’t it be incredible to find more than one habitable world around one star?” Dr. Kaltenegger said.
Tim Pyle, a multimedia producer who helped create some of the well-known visualizations of TRAPPIST-1 for NASA, noted that the view from these planets would be surreal.
“Having seven roughly Earth-sized planets around a single star excites my imagination,” Mr. Pyle said. “And they’re so close together that they would be looming fixtures in each other’s sky in a breathtaking way. Imagine lying on the deck of a boat on a TRAPPIST-1e ocean, looking above you, and seeing other planets as large as we see the full moon from Earth!”
Precocious Planets
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TOI-1233, a sunlike star more than 200 light-years from Earth, contains five known exoplanets. Four of these worlds were spotted in 2020.
“TOI-1233 is an outstanding planetary system with its high number of transiting planets, sunlike host star and its proximity to the solar system,” said Tansu Daylan, a researcher at the Massachusetts Institute of Technology.
Dr. Daylan detected the system with Jasmine Wright and Ka
