The seven TRAPPIST-1 planets, on the other hand, all share a similar density, which makes the system quite different from our own. Earth, Venus and Mars have similar densities, but Mercury contains a much higher percentage of iron, so although it is the solar system’s smallest planet in diameter, Mercury has the second highest density of all eight planets. The gas giants - Jupiter, Saturn, Uranus and Neptune - are larger, but much less dense than the four rocky planets. In our own solar system, the densities of the eight planets vary widely.
Width and weight together reveal each object’s density, and from there it is possible to infer that the baseball is made of lighter materials, like string and leather, while the paperweight has a heavier composition, like glass or metal. A baseball and a paperweight may be the same size, but the baseball is much lighter. With more precise measurements of an object’s density, we can know more about its composition. Agol and UW co-authors Zachary Langford and Victoria Meadows, a professor of astronomy, analyzed data and performed computer simulations that constrained the orbits of the TRAPPIST-1 planets and calculated their densities. The team - which includes scientists based in the United States, Switzerland, France, the United Kingdom and Morocco - used observations of the starlight dips and precise measurements of the timing of the planets’ orbits to make detailed measurements of each planet’s mass and diameter, and from there to determine its density. And we can actually learn more about a planet by studying its neighbors as well, so this system is perfect for that.” “The TRAPPIST-1 system is fascinating because around this one star we can learn about the diversity of rocky planets within a single system.
#DENSITY OF EXOPLANETS DISCOVERED AT RA 290 FULL#
“The night sky is full of planets, and it’s only been within the last 30 years that we’ve been able to start unraveling their mysteries,” said co-author Caroline Dorn of the University of Zurich. Uncompressed density adjusts for the effect of gravity, and can reveal how the composition of various planets compare. This new study offers the most precise density measurements to date for any group of exoplanets.Ī planet’s density is determined not just by its composition, but also by its size: Gravity compresses the material a planet is made of, increasing the planet’s density. Previous calculations had shown that the planets are roughly the size and mass of Earth and thus must also be rocky, or terrestrial - as opposed to gas-dominated worlds like Jupiter and Saturn. Since they’re too small and faint to view directly, all seven exoplanets were found via the so-called transit method: looking for dips in the star’s brightness created when the planets cross in front of it. Spitzer alone provided over 1,000 hours of targeted observations of the system before being decommissioned in January 2020. Since the initial detection in 2016 of the TRAPPIST-1 worlds, scientists have studied this planetary family with multiple space- and ground-based telescopes, including NASA’s now-retired Kepler Space Telescope and Spitzer Space Telescope. “This is the information we needed to make hypotheses about their composition and understand how these planets differ from the rocky planets in our solar system.” “This is one of the most precise characterizations of a set of rocky exoplanets, which gave us high-confidence measurements of their diameters, densities and masses,” said Agol.
These findings give astronomers new data that they’re using to try to pin down the precise composition of these planets, and compare them not just to Earth, but to all the rocky planets in our solar system, according to lead author Eric Agol, a University of Washington professor of astronomy. If so, then while the TRAPPIST-1 planets might be similar to each other, they appear to differ notably from Earth: They’re about 8% less dense than they would be if they had the same chemical composition as our planet. That could mean they all contain roughly the same ratio of materials thought to be common to rocky planets, such as iron, oxygen, magnesium and silicon. Discovered in 2016 some 40 light-years away, these seven rocky siblings offer a glimpse at the tremendous variety of planetary systems that likely fill the universe.Ī study accepted by the Planetary Science Journal shows that the planets share similar densities. The TRAPPIST-1 star system is home to the largest batch of roughly Earth-size planets ever found outside our solar system. Artist’s depiction of the TRAPPIST-1 star and its seven worlds.
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