Daily Image
20-03-2007
U Herculis, it still moves (at a distance of 266pc)!
| Submitter: | Wouter Vlemmings and Huib van Langevelde |
| Description: | We have been able to track the motion of the OH maser of the Mira variable U Her for almost 12 years. As expected for an amplified image of the star it shows consistent motion and parallax for the entire period. The parallax is the projection of the earth motion around the sun and allows us to make the most fundamental measurement of the distance to this star. The improved ionospheric conditions and in-beam phase referencing have improved the parallax accuracy in the last 2 years: 3.76 +/- 0.27 mas, consistent with the old result: 3.61 +/- 1.04 mas and much more accurate than the Hipparcos result: 1.88 +/- 1.31. The figures shows the displacement of the stars in Right Ascension and Declination with the inset highlighting the most recent results.
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