TRAPPIST-1 is the name of a system of seven Earth-size planets orbiting a dwarf star "just" 40 light-years away. Three of the planets sit in the habitable zone of their star, making it possible they could support liquid water on the surface and sustain life.
"People remember it very well because (the name) is very peculiar and that it is linked to a Belgian project," said astronomer Emmanuel Jehin.
Trappist beer bottles and exoplanet posters are proudly displayed inside team members' modest offices at the University of Liège. A small "control room" with four computers is used to monitor their telescopes thousands of miles away in Chile and Morocco.
Jehin and fellow teammate and astronomer Michaël Gillon speak passionately about the secrets the newly discovered TRAPPIST system may hold.
"Even back in the time of Isaac Newton, they had some belief about the existence of aliens around other stars, but it was just speculation," Gillon said. "We've been speculating for centuries. Now, we are going to enter the realm of scientific answers for these specific questions. That is what makes this so exciting."
Finding the TRAPPIST exoplanets
Theoretical studies suggested that ultracool dwarf stars were simply too small for Earth-size planets to orbit. Most astronomers were focused instead on stars roughly the size of the sun. Previously, exoplanets had been found orbiting massive stars, rendering them impossible to study in great detail using current technology.
Gillon questioned these theories and trained his telescopes on ultracool dwarf stars. He believed the key to finding planets that scientists could study would involve these types of stars because they are smaller, closer and easier to search for life.
It's 80 times easier to study these planets because they cast a shadow on their star, similar to how Jupiter would look against our sun.
"I don't believe in theory," Gillon said. "When they are not constrained by observations, they are worth nothing. They are just theoretical speculations, with nice equations."
The next step was to secure funding. For astronomers, "telescope time" is precious. They need lots of it to observe the stars, scanning for the dips in light that indicate the presence of an exoplanet. One of the best places to search the heavens is the Atacama Desert in Chile, home to world-renowned observatories because of high altitudes, clear skies and little light pollution.
"It is very difficult to get time in Chile because there are many hundreds of astronomers fighting for that zone," Jehin said. "We had a crazy idea at that time to build our own telescope. ... You just have to have to guts to do it."
Gillon and Jehin secured $635,000 from the National Science Foundation in Belgium and the University of Liège for two TRAPPIST telescopes, one in Morocco and one in Chile. Each took a year to build.
TRAPPIST was a prototype project meant to search for exoplanets while Gillon and Jehin secured funding for more powerful robotic telescopes. They said they hoped, but never really expected, to find something of significance using the prototype. Nevertheless, they diligently manipulated the telescopes from thousands of miles away in Belgium.
"This is how science works in the 21st century," Gillon said. "You don't have to be on location looking into your telescope. It's robotic; you can even control it by iPhone and look at the result on your iPad. You can really have access to the data from anywhere in the world."
For five years, the search turned up nothing but false positives. But one day, incredibly, Gillon discovered the first TRAPPIST exoplanet -- while sitting on his couch at home.
"I saw this drop in brightness, which was a clear indication that something had passed in front of the star," Gillon said. "My wife was already sleeping, my daughter was going to bed, and I said, 'hey, look! This is an Earth-sized planet.' She was not impressed at all because it was just a graphic."
Gillon frantically called Jehin, excited but also wary of yet another false lead. Not only was the team able to confirm Gillon's find, over the next year, they discovered a staggering six more exoplanets closely orbiting the same star.
"I was dreaming of one planet, so when we saw two, it was becoming crazy, three totally crazy and then in 2016 four, five ... wow. ... It was like some fantasy, some kind of dream," Gillon said. "It's like a cosmic joke."
On the horizon
Although the team was excited, they knew they needed to keep the discovery under wraps. If word got out, other astronomers could start sniffing around their star before their research was complete.
"For many weeks, it stayed between us and maybe two other people," Jehin said. "It is very hard to keep a secret, because you want to talk. ... We were more worried about leaks in our team."
"But (Jehin) is a very paranoid guy. ... I'm not that anxious," Gillon joked.
Once the discovery was published in February
, it quickly stirred popular imagination. The tiny solar system, no bigger than Jupiter and its moons, has inspired a Google Doodle
, a NASA travel poster
and VR experience
, science fiction
, cartoons, songs and paintings. There's even a video game
"For a sci-fi geek, it's a wonderful system," Jehin said. "You can imagine life on different planets, traveling from one planet to the other, speaking to each other."
"It's frustrating to not see the planet, but we can use imagination to go there," Gillon added.
The new and larger telescopes called SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars), named after a famous type of Belgian cookie, will explore 1,000 of the nearest ultracool dwarf stars, looking for more TRAPPIST-like systems.
In the coming months, the four new telescopes, at a cost of about $1 million each, will come online in Chile.
Jehin and Gillon will also focus on the system they already found. Using newer and more sophisticated technology, they'll try to determine whether any of the planets have Earth-like atmospheres and try to detect life-signifying molecules such as water, carbon and methane.
"We still don't know if these are habitable," Gillon said. "We don't know what to expect, but we have plenty of theories. But as I say, theories are often wrong. We will have plenty of surprises in the coming years."