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When I use the Gaia star catalogue, the parallax values often have large uncertainties which, therefore, leads to a large uncertainty for the distances to the stars.

If you were interested in the distance to one particular star and money was no object (i.e. you could buy time on any instrument) - what would be the optimum thing that could be done to improve the precision in the star's distance?

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You would have to pay a lot more than buying time on existing instruments. You would have to pay for the construction of new and very expensive instruments

You could pay to have copies of the Gaia spacecraft built and sent into orbit around the giant planets in our solar system and/or at their L4 and L5 positions. Thus two or more such observatories could study the same star at the same time with a baseline between them tens of times greater than the baseline resulting from the orbit of the Earth around the Sun. Thus the parallaxes and distances should be tens of times as precise.

And if you pay for the development of more precise instruments than Gaia has, you can increase the accuracy and precision of the parallaxes and distances even more.

And you could pay to have several such observatories sent out of the solar system in various directions so that they will eventually be separated by even greater distances than the outer planets are, thus making their parallax and distance measurements even more accurate.

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  • $\begingroup$ Thank you. And is using parallax for distance measurements always the best we can do? Are there other methods that are more precise than using Gaia parallax? $\endgroup$ – user1551817 Dec 2 '20 at 19:49
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    $\begingroup$ @user1551817. Generally no. For some types of object, where the intrinsic brightness of the object is known, you can infer a distance from its apparent brightness, but for most objects withing 10000 ly or so, parallax is the best we have. $\endgroup$ – Steve Linton Dec 3 '20 at 11:13
  • $\begingroup$ Why doesn't ESA launch another Gaia somewhere else? $\endgroup$ – fasterthanlight Dec 3 '20 at 13:46

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