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Know Thy Star, Know Thy Planet: How Gaia is Helping Nail Down Planet Sizes

18 May 2018, 02:14 UTC
Know Thy Star, Know Thy Planet: How Gaia is Helping Nail Down Planet Sizes
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Gaia’s all-sky view of our Milky Way and neighboring galaxies. (ESA/Gaia/DPAC)


(This column was written by my colleague Elizabeth Tasker, now at the Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Sciences (ISAS). Trained as an astrophysicist, she researches planet and galaxy formation and also writes on space science topics. Her book, “The Planet Factory,” came out last year.)


Last month, the European Space Agency’s Gaia mission released the most accurate catalogue to date of positions and motions for a staggering 1.3 billion stars.
Let’s do a few comparisons so we can be suitably amazed. The total number of stars you can see without a telescope is less than 10,000. This includes visible stars in both the northern and southern hemispheres, so looking up on a very dark night will allow you to count only about half this number.
The data just released from Gaia is accurate to 0.004 milli-arcseconds. This is a measurement of the angle on the sky, and corresponds to the width of a human hair at a distance of over 500km. These results are from 22 months of observations and Gaia will ultimately whittle down the stellar positions ...

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