In 2009, the Kepler mission took the transit method to space. Kepler, a NASA spacecraft, launched into an orbit around the sun equipped with instruments to detect dips in the brightness of thousands of stars in its field of view. The mission has discovered thousands of confirmed and potential exoplanets since. NASA now announces the verification of new exoplanets so often—about every few months or so—that these discoveries are no longer headline-making news.
Today, the planets in our solar system seem like the weird ones. Kepler has found rocky planets 10 times the mass of Earth, gas giants the size of Jupiter with scorching temperatures, and even rogue planets floating around the galaxy without a star to call home. At least 30 exoplanets are about the size of Earth and orbit in the habitable zone of their star systems, that cosmic sweet spot where water exists as a liquid on the surface.
“I still think that today, without 51 Peg, Kepler would never have flown,” Queloz said. And if Kepler hadn’t flown, TESS probably wouldn’t have, either. Like Kepler, TESS will search for exoplanets using the transit method.
TESS’s timing couldn’t be better. Kepler is expected to run out of fuel and will cease operations sometime in the coming months. Engineers didn’t give Kepler a gas gauge, so they just have to watch for warning signs of low fuel and wait.
TESS will launch from Cape Canaveral in Florida on a SpaceX Falcon 9 rocket. Once in space, the spacecraft will fire its engines several times to position itself for an encounter with the moon’s gravity, which will push it into its final orbit.
From its vantage point in high-Earth orbit, above where satellites normally operate, TESS will have an unobstructed view of the sky. The telescope will spend two years staring into the cosmos, turning back only to beam home data, covering more area than Kepler did. Kepler could stare only at specific patches of sky at a time, but TESS will be able to see about 90 percent of it.
TESS will focus on exoplanets around the brightest, closest stars in the galaxy, the kind of target perfect for follow-up observations by other space observatories and ground-based telescopes. Astronomers predict TESS will discover more than 1,600 new exoplanets, including about 70 Earth-sized exoplanets.
Where Kepler and TESS leave off, powerful telescopes currently under construction pick up. In the next decade, observatories like the Extremely Large Telescope in Chile will take the study of exoplanets a step further. They will examine the atmospheres of other planets, looking for the molecules that we know can, under the right conditions, create a world suitable for life.
They may even tell us something about 51 Pegasi b. Last year, astrophysicists using an instrument on the Very Large Telescope in Chile said they detected traces of water in the atmosphere of the exoplanet. The object that kicked off the parade of planets more than two decades ago may hold more surprises for us still.