Trappist-1 is an ultracool dwarf star nearly 40 light years from Earth. For astronomers, a star is an "ultracool dwarf" when it has low mass and a temperature under 2,700 kelvins (2,430 degrees Celsius). But Trappist-1 is "ultracool" even for nonscientists because it is home to seven Earth-size planets that scientists believe have conditions that could support liquid water and perhaps even life itself.

The discovery of those features means Trappist-1 now sets the record for having both the most Earth-size and potentially habitable planets around a single star. While scientists caution that the circumstances on those planets are very different from those that we know can sustain life, they are temperate and the right size to do just that. Excitement is building among the scientific community.

Located in the constellation Aquarius, Trappist-1 — the name comes from the Transiting Planets and Planetesimals Small Telescope, and the scientists who run the project are Belgian — is a little larger than Jupiter and whose mass is about 8 percent of our sun. In 2010, researchers identified it as a likely candidate for having planets since they observed that its brightness changes regularly, an indication that something is coming between it and Earth — something like a planet. In 2016, scientists concluded that the star had three planets in orbit round it. That announcement generated more attention and that scrutiny yielded four more planets.