In the last few decades, we've gone from knowing of exactly zero exoplanets to several thousand. That's largely thanks to the Kepler Space Telescope, but that mission is nearing its end. Luckily, NASA launched a successor several months ago. The Transiting Exoplanet Survey Satellite (TESS) only started operating over the summer, but NASA reports it has already spotted two potential exoplanets.
Like Kepler, TESS uses the transit method to detect distant exoplanets. It has a quartet of 16.8-megapixel cameras, each once covering a square of the sky 24 degrees across. Together, the cameras let TESS scan a narrow strip of the sky stretching from the polar region to the equator. It watches all the stars in the observational area for small dips in brightness. If the drops occur at predictable intervals, it can indicate there's an exoplanet passing in front of the star.
The crucial difference between Kepler and TESS is the regions of space they observe. Kepler could scan stars up to 3,000 light years away, but it covered very small parts of the sky. TESS will focus on stars 300 light years away or less, but it will eventually scan 85 percent of the sky over its two-year mission. It's starting with the southern hemisphere before moving on to the northern half next year.
The newly detected exoplanets orbit stars in the southern hemisphere and both are vaguely Earth-like. Don't go booking passage yet, though. They don't seem like pleasant vacation spots. There's Pi Mensae c, which orbits a yellow dwarf star (like the sun) about 60 light years away. It's roughly twice the size of Earth, and it orbits very close to the star. A year on Pi Mensae c is 6.27 Earth days. Researchers believe the planet has a rocky iron core with lighter materials like water, methane, and hydrogen. There's also a massive gas giant called Pi Mensae b in that system, which was discovered in 2001.
A bit closer to home, LHS 3844 b orbits a red dwarf star 49 light years away. It's only 1.3 times the size of Earth, but it orbits even closer to the star. A year on LHS 3844 b is just 11 Earth hours. Even though this is a cooler red dwarf, LHS 3844 b is probably too close to have liquid water or an atmosphere.
Technically, we don't know for sure either of these planets exists yet. They're just candidate exoplanets for now. More observations will have to confirm their existence before they're entered into the history books as the first exoplanets spotted by TESS.