Three Nearby Earths

As the search for planets in the galaxy continues, there are two places to focus on: Distant stars with potential large planets, and nearby stars with potential small planets. If we are able to find Earth-like planets orbiting nearby stars, they will be prime targets for future generations to explore.

Artist’s Impression of a new planetary system discovered recently. Credit: ESO/M. Kornmesser

Astronomers have just announced the discovery of three new planets orbiting a star only 40 light years from Earth.  The star is a very small red dwarf, only slightly larger than Jupiter, and even though it’s close to Earth, it can’t be seen with the naked eye or even with a large amateur telescope.  Yet even with it’s small size, astronomers using the TRAPPIST telescope at ESO’s La Silla Observatory have discovered three planets orbiting it, all of them comparable in size and temperature to the Earth.

The star, named 2MASS J23062928-0502285, now also known simply as TRAPPIST-1, was observed to dim at regular intervals, suggesting that a planet was passing between the star and Earth.  Astronomers took a closer look and ended up finding the three planets, similar in size to Earth and having orbital periods of 1.5, 2.4, and 4.5-73 days respectively.

“With such short orbital periods, the planets are between 20 and 100 times closer to their star than the Earth to the Sun. The structure of this planetary system is much more similar in scale to the system of Jupiter’s moons than to that of the Solar System,” explains Michaël Gillon, lead author of the study from the Institut d’Astrophysique et Géophysique at the University of Liège in Belgium.

Since the planets are so close to their parent star, they receive more than twice the radiation that the Earth does from the Sun, putting them inside the habitable zone of their star.  They won’t be the ideal place to find life, but there may be regions on the planets that are habitable, given their fast orbits.

This discovery opens up a new target for astronomers, since 15% of stars near the Sun are classified as Ultra-Cool Dwarf stars like TRAPPIST-1.

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