A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

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Questions related to the phenomenon whereby electromagnetic radiation (such as visible light) generated by an object moving away from an observer will have increased in wavelength (i.e. shifted toward…
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Questions involving the property of astronomical objects that determines their inertial resistance and gravitational interaction with other bodies.
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Questions regarding the phenomenon in the early universe characterized by an extreme expansion of space.
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Questions about the dynamical processes leading to the assembling of a celestial object.
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Questions about the source or effects of the matter that makes up 85% of the matter in the universe but appears to only interact gravitationally.
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Questions about solar system planets/moons and exoplanets that exhibit similar features to the Earth.
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Questions on objects passing through the atmosphere which leave visible wakes of incandescent material.
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Questions regarding the planet Venus, the second planet from Earth's sun.
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Questions related to the physical processes involved in or to the observations of the process of forming a star.
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Questions involving life in the universe, especially the possibility of life outside our planet, or the influence of astronomical forces on life on Earth.
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Questions regarding the universe shortly after it's formation
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Questions on systems to uniquely determine position of a point or other geometric element on a manifold such as Euclidean space.
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gravitationally linked and orbiting around their common center of mass.
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Questions regarding the as-yet-unknown energy permeating the universe that is responsible for its expansion.
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Questions related to the evolution of stars.
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mainly composed of neutrons.
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Questions on astronomical objects orbiting a star massive enough to be rounded, not massive enough to cause fusion, and which have cleared its orbit of planetesimals.
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Questions about photography of celestrial objects by amateur astronomers.
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Questions regarding celestial objects which emit regular pulses of electromagnetic energy.
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Questions on celestial bodies that orbit planets.
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Questions regarding the cosmic microwave background, or CMB, the leftover radiation that is taken by many as proof of the Big Bang.
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Questions regarding Electro-Magnetic fields, which are generated by charged sub-atomic particles (ions).
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Questions regarding two objects colliding into each other with considerable force.
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Questions regarding Albert Einstein's theory that posits, among other things, the equivalence of mass and energy.
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Questions involving a star along with all celestial material in its sphere of influence.
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Questions about the water molecule (composed of two atoms of hydrodgen and one atom of oxygen) and its detection in celestial objects.
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Questions about the outermost layer of a body.