First-magnitude starFirst-magnitude stars are the brightest stars in the night sky, with apparent magnitudes lower (i.e. brighter) than +1.50. Hipparchus, in the 1st century BC, introduced the magnitude scale. He allocated the first magnitude to the 20 brightest stars and the sixth magnitude to the faintest stars visible to the naked eye. In the 19th century, this ancient scale of apparent magnitude was logarithmically defined, so that a star of magnitude 1.00 is exactly 100 times as bright as one of 6.00.
CanopusCanopus is the brightest star in the southern constellation of Carina and the second-brightest star in the night sky. It is also designated α Carinae, which is Latinised to Alpha Carinae. With a visual apparent magnitude of −0.74, it is outshone only by Sirius. Located around 310light-years from the Sun, Canopus is a bright giant of spectral type A9, so it is essentially white when seen with the naked eye. It has a luminosity over 10,000 times the luminosity of the Sun, is eight times as massive, and has expanded to 71 times the Sun's radius.
Star systemA star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a star cluster or galaxy, although, broadly speaking, they are also star systems. Star systems are not to be confused with planetary systems, which include planets and similar bodies (such as comets). A star system of two stars is known as a binary star, binary star system or physical double star.
Arcturus|- bgcolor="#FFFAFA" | Note (category: variability): || H and K emission vary. Arcturus is the brightest star in the northern constellation of Boötes. With an apparent visual magnitude of −0.05, it is the fourth-brightest star in the night sky, and the brightest in the northern celestial hemisphere. The name Arcturus originated from ancient Greece; it was then cataloged as α Boötis by Johann Bayer in 1603, which is Latinized to Alpha Boötis. Arcturus forms one corner of the Spring Triangle asterism.
Big DipperThe Big Dipper (US, Canada) or the Plough (UK, Ireland) is a large asterism consisting of seven bright stars of the constellation Ursa Major; six of them are of second magnitude and one, Megrez (δ), of third magnitude. Four define a "bowl" or "body" and three define a "handle" or "head". It is recognized as a distinct grouping in many cultures. The North Star (Polaris), the current northern pole star and the tip of the handle of the Little Dipper (Little Bear), can be located by extending an imaginary line through the front two stars of the asterism, Merak (β) and Dubhe (α).
Asterism (astronomy)An asterism is an observed pattern or group of stars in the sky. Asterisms can be any identified pattern or group of stars, and therefore are a more general concept than the 88 formally defined constellations. Constellations are based on asterisms, but unlike asterisms, constellations outline and today completely divide the sky and all its celestial objects into regions around their central asterisms. For example, the asterism known as the Big Dipper comprises the seven brightest stars in the constellation Ursa Major.
Auriga (constellation)Auriga is a constellation in the northern celestial hemisphere. It is one of the 88 modern constellations; it was among the 48 constellations listed by the 2nd-century astronomer Ptolemy. Its name is Latin for '(the) charioteer', associating it with various mythological beings, including Erichthonius and Myrtilus. Auriga is most prominent during winter evenings in the northern Hemisphere, as are five other constellations that have stars in the Winter Hexagon asterism.
Effective temperatureThe effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature when the body's emissivity curve (as a function of wavelength) is not known. When the star's or planet's net emissivity in the relevant wavelength band is less than unity (less than that of a black body), the actual temperature of the body will be higher than the effective temperature.
Red giantA red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or lower. The appearance of the red giant is from yellow-white to reddish-orange, including the spectral types K and M, sometimes G, but also class S stars and most carbon stars.
BoötesBoötes (boʊˈoʊtiːz ) is a constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere. The name comes from Boōtēs, which comes from Boṓtēs 'herdsman' or 'plowman' (literally, 'ox-driver'; from βοῦς boûs 'cow'). One of the 48 constellations described by the 2nd-century astronomer Ptolemy, Boötes is now one of the 88 modern constellations. It contains the fourth-brightest star in the night sky, the orange giant Arcturus.
FomalhautFomalhaut (ˈfɒmələʊt, ˈfoʊməlhɔːt) is the brightest star in the southern constellation of Piscis Austrinus, the Southern Fish, and one of the brightest stars in the night sky. It has the Bayer designation Alpha Piscis Austrini, which is Latinized from α Piscis Austrini, and is abbreviated Alpha PsA or α PsA. This is a class A star on the main sequence approximately from the Sun as measured by the Hipparcos astrometry satellite. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.
AldebaranAldebaran (Arabic: “The Follower”, "الدبران") is a star located in the zodiac constellation of Taurus. It has the Bayer designation α Tauri, which is Latinized to Alpha Tauri and abbreviated Alpha Tau or α Tau. Aldebaran varies in brightness from an apparent visual magnitude 0.75 down to 0.95, making it the brightest star in the constellation, as well as (typically) the fourteenth-brightest star in the night sky. It is positioned at a distance of approximately 65 light-years from the Sun.
BetelgeuseBetelgeuse is a red supergiant star of spectral type M1-2 and one of the largest visible to the naked eye. It is usually the tenth-brightest star in the night sky and, after Rigel, the second-brightest in the constellation of Orion. It is a distinctly reddish, semiregular variable star whose apparent magnitude, varying between +0.0 and +1.6, has the widest range displayed by any first-magnitude star. At near-infrared wavelengths, Betelgeuse is the brightest star in the night sky.
ProcyonProcyon (ˈproʊsi.ɒn) is the brightest star in the constellation of Canis Minor and usually the eighth-brightest star in the night sky, with an apparent visual magnitude of 0.34. It has the Bayer designation α Canis Minoris, which is Latinized to Alpha Canis Minoris, and abbreviated α CMi or Alpha CMi, respectively. As determined by the European Space Agency Hipparcos astrometry satellite, this system lies at a distance of just , and is therefore one of Earth's nearest stellar neighbors.
Giant starA giant star is a star with substantially larger radius and luminosity than a main-sequence (or dwarf) star of the same surface temperature. They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsprung–Russell diagram and correspond to luminosity classes II and III. The terms giant and dwarf were coined for stars of quite different luminosity despite similar temperature or spectral type by Ejnar Hertzsprung about 1905.
RigelRigel is a blue supergiant star in the constellation of Orion. It has the Bayer designation β Orionis, which is Latinized to Beta Orionis and abbreviated Beta Ori or β Ori. Rigel is the brightest and most massive component - and the eponym - of a star system of at least four stars that appear as a single blue-white point of light to the naked eye. This system is located at a distance of approximately from the Sun.
