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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 ...
3.5 cm – width of film commonly used in motion pictures and still photography; 3.78 cm – amount of distance the Moon moves away from Earth each year [113] 4.3 cm – minimum diameter of a golf ball [114] 5 cm – usual diameter of a chicken egg; 5 cm – height of a hummingbird, the smallest-known bird; 5.08 cm – 2 inches,
Many TNOs are often just assumed to have Pluto's density of 2.0 g/cm 3, but it is just as likely that they have a comet-like density of only 0.5 g/cm 3. [ 4 ] For example, if a TNO is incorrectly assumed to have a mass of 3.59 × 10 20 kg based on a radius of 350 km with a density of 2 g/cm 3 but is later discovered to have a radius of only 175 ...
+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
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
Some stars visible to the naked eye have such a low absolute magnitude that they would appear bright enough to outshine the planets and cast shadows if they were at 10 parsecs from the Earth. Examples include Rigel (−7.8), Deneb (−8.4), Naos (−6.2), and Betelgeuse (−5.8).
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 ...
Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun 's photosphere where the optical depth equals 2/3: [ 1 ]