On 22 February 2017, astronomer Michaël Gillon and his team from the University of Liège discovered seven planets located outside of the solar system. These planets, in orbit around a dwarf star named TRAPPIST-1, can help answer the question: "Are we alone in the universe?"
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This discovery results from the Speculoos project, a project to detect potentially habitable exoplanets, supported by the European Research Council. Thanks to Spitzer, the NASA space telescope, Michaël Gillon’s team was able to observe these planets orbiting around a star that is much smaller and cooler than the Sun. Named TRAPPIST-1, it is 39 light years away from us and is said to be "ultra-cool", because its surface temperature is far lower than that of other stars like the Sun. In 2016, Michaël Gillon’s team had already announced the discovery of three planets around TRAPPIST-1. In the end, through more extensive analysis, they were able to discover four others.
All of these planets, which are Earth-sized and similarly rocky, might possibly have liquid water on their surfaces, and therefore hold a potential for life. However, only three of these planets are located within the habitable zone, at the right distance from the star to be neither too hot nor too cold. In comparison, our solar system only has one planet located within its habitable zone: Earth. These three planets are the most promising because they might be home to oceans similar to those found on Earth.
