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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 ...
For the small outer irregular moons of Uranus, such as Sycorax, which were not discovered by the Voyager 2 flyby, even different NASA web pages, such as the National Space Science Data Center [6] and JPL Solar System Dynamics, [5] give somewhat contradictory size and albedo estimates depending on which research paper is being cited.
A class of extrasolar planets whose characteristics are similar to Jupiter, but that have high surface temperatures because they orbit very close—between approximately 0.015 and 0.5 AU (2.2 × 10 ^ 6 and 74.8 × 10 ^ 6 km)—to their parent stars, whereas Jupiter orbits its parent star (the Sun) at 5.2 AU (780 × 10 ^ 6 km), causing low ...
Thus, the Sun occupies 0.00001% (1 part in 10 7) of the volume of a sphere with a radius the size of Earth's orbit, whereas Earth's volume is roughly 1 millionth (10 −6) that of the Sun. Jupiter, the largest planet, is 5.2 AU from the Sun and has a radius of 71,000 km (0.00047 AU; 44,000 mi), whereas the most distant planet, Neptune, is 30 AU ...
+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
Many of these planets are of considerable size, approaching the mass of small stars, while many newly discovered brown dwarfs are, conversely, small enough to be considered planets. [81] The material difference between a low-mass star and a large gas giant is not clear-cut; apart from size and relative temperature, there is little to separate a ...
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 ...
Examples of astronomical objects include planetary systems, star clusters, nebulae, and galaxies, while asteroids, moons, planets, and stars are astronomical bodies. A comet may be identified as both a body and an object: It is a body when referring to the frozen nucleus of ice and dust, and an object when describing the entire comet with its ...