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In astronomy or planetary science, the frost line, also known as the snow line or ice line, is the minimum distance from the central protostar of a solar nebula where the temperature is low enough for volatile compounds such as water, ammonia, methane, carbon dioxide and carbon monoxide to condense into solid grains, which will allow their accretion into planetesimals.
The snow line is measured using automatic cameras, aerial photographs, or satellite images. Because the snow line can be established without on-the-ground measurements, it can be measured in remote and difficult to access areas. Therefore, the snow line has become an important variable in hydrological models. [2]
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The history of an object's location through time traces out a line or curve on a spacetime diagram, referred to as the object's world line. Each point in a spacetime diagram represents a unique position in space and time and is referred to as an event. The most well-known class of spacetime diagrams are known as Minkowski diagrams, developed by ...
In Muslim astronomy, the first star chart to be drawn accurately was most likely the illustrations produced by the Persian astronomer Abd al-Rahman al-Sufi in his 964 work titled Book of Fixed Stars. This book was an update of parts VII.5 and VIII.1 of the 2nd century Almagest star catalogue by Ptolemy. The work of al-Sufi contained ...
1868 – Jules Janssen observes a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun, during a total solar eclipse in Guntur, India. Later in the same year, Norman Lockyer observed the same line in the solar spectrum, and concluded that it was caused by an element in the Sun unknown on Earth.
The stellar birthline is a predicted line on the Hertzsprung–Russell diagram that relates the effective temperature and luminosity of pre-main-sequence stars at the start of their contraction. [1] Prior to this point, the objects are accreting protostars , and are so deeply embedded in the cloud of dust and gas from which they are forming ...
In stellar evolution, an isochrone is a curve on the Hertzsprung-Russell diagram, representing a population of stars of the same age but with different mass. [1] The Hertzsprung-Russell diagram plots a star's luminosity against its temperature, or equivalently, its color. Stars change their positions on the HR diagram throughout their life.