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A parsec is the distance from the Sun to an astronomical object that has a parallax angle of one arcsecond (not to scale). The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,265 astronomical units (AU), i.e. 30.9 trillion kilometres (19.2 trillion miles).
Hubble Space Telescope precision stellar distance measurement has been extended 10 times further into the Milky Way. [10] The motion of the Sun through space provides a longer baseline of the parallax triangle that will increase the accuracy of parallax measurements, known as secular parallax.
The motion of the Sun through space provides a longer baseline of the parallax triangle that will increase the accuracy of parallax measurements, known as secular parallax. For stars in the Milky Way disk, this corresponds to a mean baseline of 4 AU per year, while for halo stars the baseline is 40 AU per year. After several decades, the ...
The discovery of the near-Earth asteroid 433 Eros and its passage near Earth in 1900–1901 allowed a considerable improvement in parallax measurement. [51] Another international project to measure the parallax of 433 Eros was undertaken in 1930–1931.
The catalogue was published in June 1997 and contains 118,218 stars; an updated version with re-processed data was published in 2007. It is particularly notable for its parallax measurements, which are considerably more accurate than those produced by ground-based observations.
The difference in magnitude that was bridged in order to match the two groups is called the distance modulus and is a direct measure for the distance (ignoring extinction). This technique is known as main sequence fitting and is a type of spectroscopic parallax. Not only the turn-off in the main sequence can be used, but also the tip of the red ...
The other, observable, part is an acceleration toward the galactic center of approximately 2.5 × 10 −10 m/s 2, which yields a change of aberration of about 5 μas/yr. [15] Highly precise measurements extending over several years can observe this change in secular aberration, often called the secular aberration drift or the acceleration of ...
The Atlas Coeli covers both hemispheres with 16 charts. The coordinate system is referred to equinox 1950.0 and the scale is 1° = 0.75 cm. There are six charts of the equatorial regions on a rectangular graticule, covering declinations from +25° to -25°; four charts for each hemisphere with straight, converging hour circles and concentric, equally-spaced declination circles covering ...