Updated: Jan 13
Aquarius constellation hosts the ultracool star TRAPPIST-1, which is only 40 light-years from Earth (about 10 times the distance from our planet to the nearest star system, Alpha Centauri.) In 2017, astronomers announced that the star hosts at least seven exoplanets, all Earth-sized worlds that are likely also rocky. Many of these planets orbit in the habitable region of the star, which is defined as the zone in which water could exist in the planets' surfaces (depending on parameters such as the planet's atmosphere).
Because TRAPPIST-1 is about 8 percent the size of the sun, this means that its habitable zone is much closer to the star; in other words, the planets need to huddle close for liquid water to flow on their surfaces. The seven worlds discovered so far all orbit closer to their parent star than Mercury orbits the sun in our own solar system.
Planets were first discovered around this star using Chile's Transiting Planets and Planetesimals Small Telescope (TRAPPIST), in 2010. Follow-up observations have been performed with observatories such as the Very Large Telescope (VLT) in Chile and NASA's Spitzer Space Telescope, but astronomers say a more detailed look may need to wait until NASA's James Webb Space Telescope (scheduled to launch in 2019) can examine the system.
Astronomers are using TRAPPIST-1 as a springboard to better understand the proliferation of Earth-sized, rocky planets across the universe, coupled with observations from other telescopes such as Kepler — a prolific planet-hunting telescope that has found thousands of exoplanets since its launch in 2009.