Comparison of TRAPPIST-1 to the Solar System (IMAGE)
Caption
This graph presents measured properties of the seven TRAPPIST-1 exoplanets (labeled b through h), showing how they stack up to each other as well as to Earth and the other inner rocky worlds in our own solar system. The relative sizes of the planets are indicated by the circles. All of the known TRAPPIST-1 planets are larger than Mars, with 5 of them within 15% of the diameter of the Earth. The corresponding "habitable zones" of the two planetary systems, regions where an Earth-like planet could potentially support liquid water on its surface, are indicated near the top of the plot. The offset between the two zones is due to the cooler TRAPPIST-1 star emitting more of its light in the form of infrared radiation that is more efficiently absorbed by an Earth-like atmosphere. Since it takes less illumination to reach the same temperatures, the habitable zone shifts further away from the star. The masses and densities of the TRAPPIST-1 planets were determined by careful measurements of slight variations in the timings of their orbits using extensive observations made by NASAs Spitzer and Kepler space telescopes, in combination with data from Hubble and a number of ground-based telescopes. The latest analysis, which includes Spitzer's complete record of over 1,000 hours of TRAPPIST-1 observations, has reduced the uncertainties of the mass measurements to a mere 2-3%. These are by far the most accurate measurements of planetary masses anywhere outside of our solar system.
Credit
NASA/JPL-Caltech
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