“I want to find another Earth. That’s what I’m living for.”
MIT astrophysicist Sara Seager has been looking at planets beyond our solar system, known as exoplanets, for almost 20 years.
When the first ones were discovered in the 1990s, many questioned the finding and didn’t think it was real. But since then, with better technology, we have observed more than 6,000 of them, most of which are giant balls of gas.
Today, the list grows every week.
With so many planets now coming out of hiding, the race is on to identify one that resembles Earth: a rocky world with liquid water just like ours, and suitable to host life.
Seager believes she knows how to make that discovery.
‘These aren’t planets!’
It’s not easy to see exoplanets as you can’t just look at them through a telescope. This is due to the blinding light coming from their host stars, which can be very different in size and features compared to our sun. The process is often described as trying to spot a firefly circling a lighthouse, from thousands of miles away.
The first ones were discovered indirectly, in 1995, by just looking at stars to see if they would wobble slightly, responding to the pull of another object’s gravity
At this time, Seager was a graduate student at Harvard searching for a topic for her Ph.D. and she was intrigued by the newborn field of faraway planets.
“Since the planets were discovered indirectly, most people didn’t believe that the discoveries were real. They’d say to me ‘Why are you doing this? These aren’t planets!’,” says Seager.
The contrarians weren’t entirely wrong: the wobble can be caused by other factors such as another star and several planet discoveries have been retracted over time for this reason.
But then a different technique was found to make their hunt easier, called transit. This is when a planet moves in front of its host star and causes the star’s light to dim slightly.
“One of the planets from the wobble technique showed transit: it went in front of the star at exactly the time it was predicted to and that was basically incontrovertible,” says Seager.
Exoplanets were real.