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Messier 54 (also known as M54 or NGC 6715) is a globular cluster in the constellation Sagittarius. [ a ] It was discovered by Charles Messier in 1778 and then included in his catalog of comet -like objects.
This is a compilation of initialisms and acronyms commonly used in astronomy. Most are drawn from professional astronomy, and are used quite frequently in scientific publications. A few are frequently used by the general public or by amateur astronomers.
This is a compilation of symbols commonly used in astronomy, particularly professional astronomy. Age (stellar) τ - age; Astrometry parameters. ...
It is a compendium of astronomy that is easier to remember, ... [54] The Surya Siddhanta calculates the solar year to be 365 days 6 hours 12 minutes and 36.56 seconds.
Hencke requested that the symbol for 5 Astraea be an upside-down anchor; [54] however, a weighing scale was sometimes used instead. [16] [55] Gauss named 6 Hebe at Hencke's request, and chose a wineglass as the symbol. [56] [57] As more new asteroids were discovered, astronomers continued to assign symbols to them.
The basic elements of Ptolemaic astronomy, showing a planet on an epicycle (smaller dashed circle), a deferent (larger dashed circle), the eccentric (×) and an equant (•). In both Hipparchian and Ptolemaic systems, the planets are assumed to move in a small circle called an epicycle , which in turn moves along a larger circle called a ...
The Sun is constantly losing mass by radiating away energy, [54] so the orbits of the planets are steadily expanding outward from the Sun. This has led to calls to abandon the astronomical unit as a unit of measurement. [55]
[54] In July 2021 the ... Because the galaxy has a high surface brightness and relatively large angular size, it is an ideal target for amateur astronomy observations.