When it is daytime, you look toward the Sun as the yellow line shows, and you see the Sun superimposed against the celestial sphere.
As you stand on the Earth, the stars of the celestial sphere surround you, but you are restricted in which direction you can look as the Earth turns. At what RA are the stars you can see? During the daytime, when you're turned toward the Sun at what RA has the Sun been superimposed into?Īs the Earth orbits the Sun, the Sun always remains in the center, but the Sun appears to be superimposed on the celestial sphere of the sky.
At nighttime, the Earth turns you away from the Sun. It may help to envision yourself standing on the Earth (which you are) at each location of the Earth around the Sun below. During the day, the sky appears bright, but there are constellations back behind the Sun in the daytime, washed out by the scattering of sunlight by Earth's atmosphere.Įxamine the diagram below to explore how the sky changes throughout the year, as the Earth orbits around the Sun. Additionally, as the Earth orbits the Sun, the Sun is superimposed on the sky at different locations throughout the year (see the animation to the left). Though for the most part the Earth turns below a stationary, unmoving sky, because the Earth orbits the Sun (our source of night and day), what can at night be seen of the stationary sky changes throughout the year. Dec spans from 90° at the north celestial pole down to -90° at the south celestial pole. Declination, often abbreviated Dec, is measured in degrees, minutes, and seconds (°, ', ''). There are 24 hours of RA, with each hour of RA encompassing 15° of the 360° sky. Right Ascension, often abbreviated RA, is measured in hours, minutes, and seconds (h, m, s). Together, Right Ascension and Declination create a grid on the sky on which any celestial object can be located. The lines of Declination (the analogue of latitude) are lines that arc across the sky parallel to the celestial equator. The 24 lines of Right Ascension (the analogue of longitude) are vertical lines that cross the sky from the north celestial pole to the south celestial pole, perpendicular to the celestial equator. We call these numbers Right Ascension and Declination. Just as you can describe your position on Earth with GPS coordinates of latitude and longitude, you can describe the position of any object in the night sky with numbers. Lines of RA and Dec on the celestial sphere Image Analysis with Solar System Objects.Image Analysis II - Animation and Stacking.Image Analysis I - Image Processing and the Ring Nebula.Exploring the Sky II - Star Charts and Stellarium.Hertzsprung-Russell Diagram and Star Clusters.ASTR:1771 - Intro Astronomy I: Basic Astrophysics.ASTR:1080 - Exploration of the Solar System.
ASTR:1070 - Stars, Galaxies, and the Universe.
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