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Saturn-class Exoplanet Is a Win for Astrometry

5 Aug 2020, 19:16 UTC
Saturn-class Exoplanet Is a Win for Astrometry
(200 words excerpt, click title or image to see full post)

Under other circumstances, the red dwarf TVLM 513–46546 would not cause a ripple in news coverage of exoplanets. What astronomers have found there is a planet of Saturn mass in a 221 day orbit, raising eyebrows only in that while planets are common around M-dwarfs, they are usually smaller, rocky worlds. But the TVLM 513–46546 story gains weight when we consider the methods used to find this planet, which have implications for studying system architectures around many stars as we refine our techniques and new instruments come online.
The star in question is 35 light years from Earth, and we’ve found the planet through astrometry, a method that tracks a star’s position in the sky to an extreme precision and detects the minute variation in motion caused by the gravitational effect of the planet. If this sounds a bit like radial velocity methods, the difference is that with astrometry we are measuring tiny changes in the stars position in the sky, as opposed to the Doppler shift of light from a star as it moves towards us and then away from us, influenced by the gravitational tug of a planet.

Image: Illustration shows how the star’s motion around the center ...

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