The number of exoplanet candidates detected by NASA's Transiting Exoplanet Survey Satellite (TESS) recently surpassed 5,000, and Newsweek has collected some of the weird and exciting worlds that have been discovered over the years.
The TESS mission, launched in 2018 and led by the Massachusetts Institute of Technology (MIT), helps scientists to discover distant worlds outside of our solar system.
These worlds, called exoplanets, can be discovered whenever they pass in front of their stars along the telescope's line of sight. When this happens, the star's brightness appears to dip repeatedly.
The process is called transit photometry, and scientists use it to learn all sorts of characteristics about exoplanets including size, shape of orbit, and how long it takes to orbit the star in question.
Ground-based follow-up missions can help further confirm these exoplanets and determine their mass and what they're made of.
Exoplanets discovered by TESS are usually known as TOIs, or TESS Objects of Interest. As of January 26, the number of planet candidates listed in the TOI catalog on the MIT website was 5,210.
Michelle Kunimoto, a postdoctoral researcher at MIT who has helped boost the catalog's numbers, said in an MIT press release on January 20: "This time last year, TESS had found just over 2,400 TOIs. Today, TESS has reached more than twice that number—a huge testament to the mission and all the teams scouring the data for new planets. I'm excited to see thousands more in the years to come!"
Many exoplanets identified by TESS have stood out either due to their likeness to Earth or their general weirdness.
One such planet, TOI-2109b, orbits its parent star in just 16 hours at a distance of just 1.5 million miles. For perspective, Earth's average distance to the sun is about 93 million miles and orbits the sun once a year. The day-time temperature of TOI-2109b, located around 855 million light-years from Earth, is a searing 6,000 F.
Likewise, there is the much nearer exoplanet GJ 367b which TESS helped to detect. One of the smallest planets detected at the time of its discovery, it is located 31 light-years away but has an extra-fast orbit of just eight hours. Its daytime side is thought to experience temperatures of 2,700 F.
Similarly speedy planets have been dubbed "super-Earths," meaning that while they are rocky like our own planet, they are also considerably larger. One, TOI-1634b, was the most massive super-Earth with an ultrashort orbit found at the time, with a radius almost twice that of our own planet.
On the other end of the scale are exoplanets that may be similar to Earth in some respects. About 100 light-years away is the planet TOI 700 d, described by NASA in January 2020 as the first Earth-sized planet within the habitable zone of its star discovered by TESS at the time. It is a potentially rocky world only slightly larger than Earth.
It isn't just exciting planets that have been discovered using TESS data. The satellite also spotted the tear-shaped star HD74423 that is stretched out by the gravity of another star that it orbits.
It is hoped that the recently launched James Webb Space Telescope will help study the atmospheres of exoplanets when it starts operating later in 2022.
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