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Astronomy and Cosmology
Astronomy and Astrophysics
Orientation of the Earth, Sun and Solar System in the Milky Way
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[QUOTE="fizixfan, post: 5589830, member: 506800"] I've been tinkering with a few diagrams in an attempt to illustrate the motion of the solar system in its journey around the Milky Way. I also wanted portray how the celestial, ecliptic and galactic coordinate systems are related to each other in a single picture. Note: in the Celestial, or Equatorial system, the Celestial North Pole (an extension of the Earth's axis of rotation), uses the default setting of North as "up." The Ecliptic and Galactic also use North as "up" with reference to the Celestial North Pole. Some people say that in space there is no such thing as "up" or "down," but in determining the position of a celestial object (e.g., declination and right ascension of a star or deep-sky object) is DOES matter. [B]Please have a look at these diagrams and feel free to comment on any errors, or make suggestions as to how I could make them better. I drew these images, but anyone is free to re-use them without restriction.[/B] Figure 1 shows the motion of the Earth and Sun around the Milky Way. The solar system is actually well within the galactic disk, which is about 1,000 light years thick. The sun and the planets that circle it is roughly 50 light years above the galactic plane, and passed northward through it about 3 million years ago in its undulating path around the galactic center. Note: this diagram is not to scale. The northernmost excursion of the solar system takes it about 250 light years above the galactic plane. This means it would only subtend an angle of about 0.55° relative to the galactic center. Figure 1. Motion of Earth and Sun around the Milky Way [ATTACH=full]107278[/ATTACH] Figures 2. and 3. show the orientation of the Earth, Sun & Solar System in the Milky Way - similar diagrams, just presented in different ways. Figure 2. Orientation of Celestial, Ecliptic and Galactic Poles and Planes [ATTACH=full]107279[/ATTACH] Figure 3. Orientation of astronomical coordinates projected on the Celestial Sphere. [ATTACH=full]107280[/ATTACH]The angle between Celestial Equator (an imaginary plane passing through the Earth's equator) and the Ecliptic Plane (an imaginary plane extended through the Sun's equator) is 23.4°. The angle between the North Celestial Pole (an imaginary line extending through Earth's axis of rotation) and the North Ecliptic Pole (an imaginary line extending through the Sun's axis of rotation) is the same - 23.4°. This is the familiar value for the "tilt" of the Earth in its path around the Sun. The angle between the Ecliptic Plane and the Galactic Equator (an imaginary plane passing through, and parallel to, the disk of the Milky Way) is 60.2°. The angle between the North Ecliptic Pole and the North Galactic Pole (an imaginary line extending through the Milky Way's axis of rotation) is also 60.2°. The angle between the Celestial Equator and the Galactic Equator is 62.9°, as is the angle between the North Celestial Pole and the North Galactic Pole. These three angles = 23.4°, 60.2° and 62.9° cannot be shown or calculated in two dimensions, because they represent separate planes which do not intersect at a common point. If you look at Figure 3, you can see that this is so. References: [URL]https://en.wikipedia.org/wiki/Celestial_coordinate_system#Galactic_system[/URL] [URL]https://www.eso.org/public/news/eso0932/[/URL] [URL]http://www.engineeringanddesign.com/1/054.htm[/URL] [/QUOTE]
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Astronomy and Astrophysics
Orientation of the Earth, Sun and Solar System in the Milky Way
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