PARALLAX METHOD PC

PARALLAX METHOD PC

At 115 pc the new value is about 15% closer than previously thought, meaning that the cluster stars are actually dimmer than thought previously. One other important finding from Hipparcos was a recalibration of the distance to another open cluster, the Pleiades. Having an accurate HR diagram also allows the distance to other clusters to be determined using the main-sequence fitting technique even if they are too distant to have accurate parallax measurements made. These suggest that the Hyades cluster is 625 million years old. This new value allows the stars in the Hyades cluster to be fitted accurately on to an HR diagram and in turn, test models of stellar evolution. Using Hipparcos data, astronomers have now calculated the distance to the centre of mass of the cluster to be 46.34 ± 0.27 pc. The distance to Hyades is a vital rung in what is commonly referred to as the Cosmic Distance ladder. For more information on the ASP, please visit Brown originally appeared in Mercury magazine, a publication of the Astronomical Society of the Pacific, and appears here courtesy of Dr Brown, Mercury and the ASP. Note the extremely small error bars for the Hipparcos determination, the one on the right. The plot below shows how the uncertainty in the distance to Hyades has changed over recent decades. One key result was an accurate distance to the nearest open cluster, the Hyades, using measurements of parallax and proper motion. It has helped astronomers refine their understanding of stars and calibrate the distance scale of the universe. The resultant Hipparcos catalogue gives positions, distances and proper motions for 118,218 stars to an average accuracy of 1 milliarcsecond (mas). As it orbited the Earth above the effects of the atmosphere, it was able to measure parallaxes to an order of magnitude better precision than previous methods. In 1989, the European Space Agency launched the Hipparcos satellite ( HIgh Precision PARallax COllecting Satellite) to measure the parallax and proper motions of stars. Astrometric accuracy has improved over time.

Parallax method