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Philosophaie
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Are the stars fixed according to RA and Dec? If not is there equations using Julian Date for their movement?
The concept of fixed or moving stars depends on the perspective of the observer. From the Earth's point of view, stars appear to be fixed in the night sky, as they maintain the same relative positions to each other. However, from a larger perspective, stars are constantly moving relative to each other due to the rotation and revolution of the Earth, as well as their own motion through space.
RA (Right Ascension) and Dec (Declination) are coordinates used to locate stars in the sky. RA is measured in hours, minutes, and seconds and represents the position of a star east or west of the celestial equator. Dec is measured in degrees and represents the position of a star north or south of the celestial equator.
The Julian date is a continuous count of days starting from January 1, 4713 BC. To calculate the Julian date for a star, you will need to know its RA and Dec coordinates, as well as the current date and time. Using mathematical formulas and astronomical tables, you can convert the RA and Dec coordinates into a Julian date.
Yes, stars can be used to determine the Earth's position in space. By measuring the position of stars in the night sky, astronomers can calculate the Earth's orientation and movement in space. This information is crucial for navigation and understanding the Earth's place in the universe.
Scientists can observe and measure the changes in a star's position over time to determine its motion. This can be done through astrometry, which is the precise measurement of the positions and motions of stars. Additionally, the Doppler effect can be used to measure a star's radial velocity, or its speed towards or away from the observer, providing evidence of its motion.