This artists impression reveals the super-Earth exoplanet 55 Cancri e in front of its moms and dad star. 55 Cancri e is about 40 light-years away and orbits a star somewhat smaller, cooler, and less intense than our Sun. As the world is so near to its moms and dad star, one year lasts just 18 hours, and temperature levels on the surface are believed to reach around 2000 degrees Celsius. Credit: ESA/Hubble, M. Kornmesser
An exoplanet is a planet that lies outside our Solar System.
By convention, exoplanets have adequate mass to keep a roughly spherical shape, but not so much mass that nuclear fusion is activated in them (as is the case for stars). They may orbit one star, a set of stars, or multiple stars– or not orbit a star at all.
While not one of its initial science objectives, the Hubble Space Telescope has actually gone far for itself as an exoplanet explorer– in particular by studying the environments of exoplanets. The chemical makeup of a worlds atmosphere leaves an unique fingerprint on the starlight that goes through it, which Hubble can study.
An exoplanet is a planet that is situated outside our Solar System. Credit: ESA/Hubble, M. Kornmesser
By convention, exoplanets have adequate mass to maintain an approximately spherical shape, but not so much mass that nuclear combination is activated in them (as is the case for stars). They may orbit one star, a pair of stars, or numerous stars– or not orbit a star at all. In 2001, astronomers utilizing Hubble announced the very first direct detection of the atmosphere of a world orbiting a star outside our Solar System. The planet orbits a yellow, Sun-like star called HD 209458, situated 150 light-years away. Methane has actually been detected on most of the worlds in our Solar System, this was the first time any natural particle was detected on a world orbiting another star.
In 2001, astronomers utilizing Hubble announced the first direct detection of the atmosphere of a world orbiting a star outside our Solar System. The planet orbits a yellow, Sun-like star called HD 209458, situated 150 light-years away. The world was not seen directly by Hubble. Rather, the existence of salt, in addition to evaporating hydrogen, carbon, and oxygen, was identified in light infiltrated the planets atmosphere when it passed in front of its star as seen from Earth. These observations demonstrated that with Hubble and other telescopes it is possible to determine the chemical makeup of alien world environments and to look for the chemical markers of life beyond Earth.
Exoplanet. Credit: ESA/Hubble, M. Kornmesser
In 2008 Hubble identified the very first natural molecule on an exoplanet. This breakthrough was an essential action towards one day determining signs of life on a world outside our Solar System. Hubble discovered the telltale signature of the molecule methane in the atmosphere of the Jupiter-sized exoplanet HD 189733b. Although methane has actually been identified on the majority of the worlds in our Solar System, this was the very first time any natural molecule was detected on a world orbiting another star.
In 2019, in an interesting discovery, Hubble information were used to find water vapor in the atmosphere of a super-Earth within the habitable zone of its host star. K2-18b, which is 8 times the mass of Earth, is now the only planet orbiting a star outside the Solar System, or exoplanet, known to have both water and temperature levels that might support life.
You can find out more about how Hubble studies exoplanets in this video.