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Stars that have magnitudes between 1.5 and 2.5 are called second-magnitude; there are some 20 stars brighter than 1.5, which are first-magnitude stars (see the list of brightest stars). For example, Sirius is magnitude −1.46, Arcturus is −0.04, Aldebaran is 0.85, Spica is 1.04, and Procyon is 0.34. Under the ancient magnitude system, all of ...
within 5° used to be the North Star at about 4,420 BC Alpha Draconis: Thuban: 3.65: Draco: within 0.1° used to be the North Star at about 3,000 BC Kappa Draconis: 3.82: Draco: within 6° a near-north star, shares timing with Kochab: Beta Ursae Minoris: Kochab: 2.08: Ursa Minor: within 7° used to be the North Star at about 1,100 BC
These stars, known as neutron stars, are extremely small—on the order of radius 10 km, no bigger than the size of a large city—and are phenomenally dense. Their period of rotation shortens dramatically as the stars shrink (due to conservation of angular momentum ); observed rotational periods of neutron stars range from about 1.5 ...
It was believed that the cutoff for round objects is somewhere between 100 km and 200 km in radius if they have a large amount of ice in their makeup; [1] however, later studies revealed that icy satellites as large as Iapetus (1,470 kilometers in diameter) are not in hydrostatic equilibrium at this time, [2] and a 2019 assessment suggests that ...
+6.5: Approximate limit of stars observed by a mean naked eye observer under very good conditions. There are about 9,500 stars visible to mag 6.5. [5] +6.64: dwarf planet Ceres: seen from Earth maximum brightness +6.75: asteroid Iris: seen from Earth maximum brightness +6.90: spiral galaxy M81: seen from Earth
A study of the Arches Cluster suggests that 150 M ☉ is the upper limit for stars in the current era of the universe. [5] [6] [7] The reason for this limit is not precisely known, but it is partially due to the Eddington luminosity which defines the maximum amount of luminosity that can pass through the atmosphere of a star without ejecting ...
An artist's concept of a planetary system. A planetary system is a set of gravitationally bound non-stellar bodies in or out of orbit around a star or star system.Generally speaking, systems with one or more planets constitute a planetary system, although such systems may also consist of bodies such as dwarf planets, asteroids, natural satellites, meteoroids, comets, planetesimals [1] [2] and ...
Stars slowly lose mass by the emission of a stellar wind from the photosphere. The star's magnetic field exerts a torque on the ejected matter, resulting in a steady transfer of angular momentum away from the star. Stars with a rate of rotation greater than 15 km/s also exhibit more rapid mass loss, and consequently a faster rate of rotation decay.