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How Well is the Distance to Gl-581 Known?

-- David | October 13, 2020

Question:

Do we have the exact distance from the center of our sun to the center of the Gliese 581 Solar system. I was told it was 20 light years away. Is is possible to get a more accurate distance. I assume this distance is rounded. I’m not sure if our instruments have that capability or not. I’m kind of new to astronomy.

-- David

Answer:

Gl-581 is an M3 dwarf star whose distance is derived from its apparent parallactic motion of p = 159.52+-2.27 milli-arcsec. Since the distance to a star is related to its parallax as d = 1/p, where the distance is in parsecs and the parallax in arcsec, we can calculate the distance to Gl-581 as: d = 1/0.15952 = 6.27 parsec = 20.45 light years. The uncertainty on this distance is determined by how well the star’s parallax is known, which is 2.27/159.52, or about 1.4%, which would be about 0.29 light years.

-- Jeff Mangum

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