Last week, NASA announced that it passed 5,000 planets confirmed to exist outside our humble little solar system. And they’re all kinds of planets: rocky, terrestrial planets like Earth; gas giants like Jupiter and Saturn; Neptune-like planets covered in ice; and “super-Earths” that are enormous versions of our planet where human-like creatures as tall as skyscrapers easily pick fruit from equally tall trees — though that entirely made-up idea still needs to be confirmed.
Thanks to current and future space telescopes, the number of these so-called “exoplanets” is climbing fast, though it may take just a wee bit longer to identify all the estimated hundreds of billions of planets that are orbiting stars just here in our Milky Way — itself an average-sized galaxy estimated to contain upwards of 400 billion stars.
To ensure your brain collapses unto itself (like a neutron star!) while pondering this astronomical (see what I did there?) number of planets, consider that there may be as many as 2 trillion galaxies in the observable universe, fully 10 times more than a previous scientific consensus of 200 billion galaxies. Multiply 2 trillion by an average of 100 billion stars per galaxy and then by at least a planet or two per star and, well, this would be a good time to lie down for a moment and take some deep, calming breaths. And some aspirin.
Astronomers identify exoplanets primarily by watching for bodies that pass in front of stars, which briefly changes the amount of light we see from that star. This is called “transiting,” a word I’ve tried to use frequently in my decades-long effort to educate people about cool things happening in astronomy.
GIRLFRIEND: So, what should we do today? Shop for antiques? See a movie? Have some friends over?
ME: How about we transit down to the coffee shop, get some of them fancy lattes, and then transit back here and sit on the porch, gaze into each other’s eyes, and take turns reading aloud from this month’s issue of Astronomy Magazine? (Holds it up.) Then later we can transit to a restaurant for dinner where, oh, I don’t know, we can talk for hours about transiting exoplanets?
GIRLFRIEND (after a long pause): You know what? I think I’ll transit out of here. For good.
For decades, our tax dollars have supported space-science programs that continue to produce new and fascinating discoveries. To expand the search for transiting exoplanets, in 2018 NASA launched the Transiting Exoplanet Survey Satellite (TESS), which helped to map the sky and has identified, so far, an additional 200 confirmed exoplanets. TESS followed the groundbreaking Kepler Space Telescope, launched in 2009 and responsible for identifying 2,709 confirmed exoplanets. And the recently launched James Webb Space Telescope features powerful technologies that will help to not only identify the existence of exoplanets but also study their atmospheres for clues to their habitability.
And, of course, habitability is what you’re looking for if, say — and I’m just spitballin’ here — you’re a species hell-bent on destroying the natural systems of your home planet, and said home planet is populated by at least a few techno-utopians who believe the best solution to that destruction is to send everyone to live on other planets or aboard orbiting space colonies.
Again, this is a purely hypothetical thought experiment about a hypothetical planet and hypothetical techno-utopians.
(Ahem.)
The search for exoplanets is, in the end, a search for both an understanding of the formation of the cosmos and for evidence of other life. Particularly exciting are exoplanets that exist in the so-called “Goldilocks zone,” which means they’re in a temperature range that’s neither too hot nor too cold, where water can be liquid, the planetary core contains at least 72 percent breakfast porridge, and the surface is populated by talking bears. Why? Don’t ask me, man! Ask the scientists who named it the Goldilocks zone!
Taking my own advice, I spoke this week to Jay Pasachoff, the longtime department chair and Field Memorial Professor of Astronomy at Williams College, where he has taught since 1972. He’s also director of the Hopkins Observatory at Williams, which, regrettably, has not yet reopened to the general public due to COVID restrictions.
Pasachoff is known for his decades of research into solar eclipses, work that has sent him all over the world with colleagues and lucky Williams students in tow. He’s witnessed 36 total solar eclipses and 74 solar eclipses of all types.
I asked him about the evolution in the study of exoplanets since he began his career in the 1970s. “Around 40 years ago, there was an occasional report that a planet had been found around a star. And it was always wrong,” he said. One report from an observatory at Swarthmore suggested a jiggling bit of light was a planet, exciting astronomers, but it turned out to be something else. “They had cleaned a telescope lens and hadn’t reinstalled it correctly,” he told me.
The first confirmed exoplanet sighting was in 1992, of two planets orbiting a pulsar — remnants of supernova explosion — in the constellation Virgo. Since then, space telescopes and advancing science have dramatically picked up the pace of discovery. In addition to the new Webb telescope, there are at least two instruments expected to go live this decade: the Nancy Grace Roman Space Telescope that will launch by 2027, and the European Space Agency’s ARIEL Space Mission, both of which will help identify, image, and study exoplanets.
All these exoplanets have to be named, of course. “My favorite exoplanets orbit the star named Cervantes,” Pasachoff, who serves on the International Astronomical Union’s (IAU) Working Group on Star Names, told me. Exoplanets are named in relation to the star they orbit, so the four planets orbiting Cervantes were named, in a contest hosted by the IAU, for characters in Cervantes’ novel “Don Quixote”: Quijote, Dulcinea, Rocinante and Sancho. (It’s unclear what the residents of those planets think of these names.)
On the milestone of 5,000 confirmed planets and progress in exoplanet research, Pasachoff pointed to the Drake equation, developed in the early 1960s by astronomers Frank Drake, Carl Sagan and others, which is a formula to calculate the likelihood of finding life beyond earth that can communicate with us. It relies on an estimate of the number of planets per star — which was entirely unknown at the time. “Nobody thought there would be so many planets,” he said, noting that it’s now understood that the average number of planets per star is “greater than one.”
And the planets found so far are just those that are nearby. “All are in our part of the galaxy,” he said. “Five thousand is just a first installment. Planets are much more common than we thought.”
While exoplanets found in the habitable zone grab headlines, Pasachoff reminded me that there’s a lot more of interest going on in the night sky. “I think there’s too much attention to whether we’ll discover life on these planets,” he said. “There are many things more interesting in astronomy than [just] the search for life.”
With that in mind, Pasachoff will head to the west coast of Chile next month to pursue some of those interesting things: a partial eclipse that he’ll view “from a hotel balcony overlooking the Pacific” — a powerful reminder that it’s never too late to change careers, earn a Ph.D. in astronomy, and get paid to do science while on a hotel balcony overlooking the Pacific.
And he’s making plans to view the total solar eclipse that will cross the United States on April 8, 2024. While the viewable area of that eclipse includes northern New England, because of iffy early spring weather here, and the possibility of cloud cover, he plans to view it from Mazatlán, Mexico, on the Pacific coast.
Yes, Mazatlán. In Mexico. On the Pacific coast.
Once again: Why are we not all professional astronomers?
Bill Shein plans to enroll in an astronomy Ph.D. program as soon as he’s done typing this sentence.
