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History of observations. The first known globular cluster, now called M 22, was discovered in 1665 by Abraham Ihle, a German amateur astronomer. The cluster Omega Centauri, easily visible in the southern sky with the naked eye, was known to ancient astronomers like Ptolemy as a star, but was reclassified as a nebula by Edmond Halley in 1677, then finally as a globular cluster in the early 19th ...
The Milky Way contains at least one planet per star, resulting in 100–400 billion planets, according to a January 2013 study of the five-planet star system Kepler-32 by the Kepler space observatory. A different January 2013 analysis of Kepler data estimated that at least 17 billion Earth-sized exoplanets reside in the Milky Way.
The galactic coordinate system is a celestial coordinate system in spherical coordinates, with the Sun as its center, the primary direction aligned with the approximate center of the Milky Way Galaxy, and the fundamental plane parallel to an approximation of the galactic plane but offset to its north. It uses the right-handed convention ...
The Milky Way has several smaller galaxies gravitationally bound to it, as part of the Milky Way subgroup, which is part of the local galaxy cluster, the Local Group.. There are 61 small galaxies confirmed to be within 420 kiloparsecs (1.4 million light-years) of the Milky Way, but not all of them are necessarily in orbit, and some may themselves be in orbit of other satellite galaxies.
The galactic plane is the plane on which the majority of a disk-shaped galaxy 's mass lies. The directions perpendicular to the galactic plane point to the galactic poles. In actual usage, the terms galactic plane and galactic poles usually refer specifically to the plane and poles of the Milky Way, in which Planet Earth is located.
Alpha Centauri ( α Centauri, Alpha Cen, or α Cen) is a triple star system in the southern constellation of Centaurus. It consists of three stars: Rigil Kentaurus (Alpha Centauri A), Toliman (B) and Proxima Centauri (C). [13] Proxima Centauri is the closest star to the Sun at 4.2465 light-years (1.3020 pc ). Alpha Centauri A and B are Sun-like ...
Makemake. Makemake [e] ( minor-planet designation: 136472 Makemake) is a dwarf planet and the second-largest of what is known as the classical population of Kuiper belt objects, [b] with a diameter approximately that of Saturn's moon Iapetus, or 60% that of Pluto. [24] [25] It has one known satellite. [26]
Navigation in the Milky Way is also identified with cardinal directions, indicating distance from the Sol System: for example, Ultima Segmentum, the largest segmentum in the Imperium of Man, is located to the galactic east of the Sol System. The 0° "north" in Imperial maps does not correspond to the 0° in the real-world. See also