ConstellationA constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the earliest constellations likely go back to prehistory. People used them to relate stories of their beliefs, experiences, creation, or mythology. Different cultures and countries invented their own constellations, some of which lasted into the early 20th century before today's constellations were internationally recognized.
Eridanus (constellation)Eridanus (ᵻˈrɪdənəs) is a constellation in the southern celestial hemisphere. It is represented as a river. One of the 48 constellations listed by the 2nd century astronomer Ptolemy, it remains one of the 88 modern constellations. It is the sixth largest of the modern constellations, and the one that extends farthest in the sky from north to south. The same name was later taken as a Latin name for the real Po River and also for the name of a minor river in Athens. List of stars in Eridanus At its southern end is the magnitude 0.
Reflection nebulaIn astronomy, reflection nebulae are clouds of interstellar dust which might reflect the light of a nearby star or stars. The energy from the nearby stars is insufficient to ionize the gas of the nebula to create an emission nebula, but is enough to give sufficient scattering to make the dust visible. Thus, the frequency spectrum shown by reflection nebulae is similar to that of the illuminating stars. Among the microscopic particles responsible for the scattering are carbon compounds (e. g.
Red supergiantRed supergiants (RSGs) are stars with a supergiant luminosity class (Yerkes class I) of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Antares A are the brightest and best known red supergiants (RSGs), indeed the only first magnitude red supergiant stars. Stars are classified as supergiants on the basis of their spectral luminosity class.
Babylonian star cataloguesBabylonian astronomy collated earlier observations and divinations into sets of Babylonian star catalogues, during and after the Kassite rule over Babylonia. These star catalogues, written in cuneiform script, contained lists of constellations, individual stars, and planets. The constellations were probably collected from various other sources. The earliest catalogue, Three Stars Each, mentions stars of Akkad, of Amurru, of Elam and others. Various sources have theorized a Sumerian origin for these Babylonian constellations, but an Elamite origin has also been proposed.
Blue supergiantA blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They have luminosity class I and spectral class B9 or earlier. Blue supergiants are found towards the top left of the Hertzsprung–Russell diagram, above and to the right of the main sequence. They are larger than the Sun but smaller than a red supergiant, with surface temperatures of 10,000–50,000 K and luminosities from about 10,000 to a million times that of the Sun. Supergiants are evolved high-mass stars, larger and more luminous than main-sequence stars.
BellatrixBellatrix is the third-brightest star in the constellation of Orion, positioned 5° west of the red supergiant Betelgeuse (Alpha Orionis). It has the Bayer designation γ Orionis, which is Latinized to Gamma Orionis. With a slightly variable magnitude of around 1.6, it is typically the 25th-brightest star in the night sky. Located at a distance of 250 light-years from the Sun, it is a blue giant star around 7.7 times as massive as the sun with 5.75 times its diameter.
Bayer designationA Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. The brighter stars were assigned their first systematic names by the German astronomer Johann Bayer in 1603, in his star atlas Uranometria. Bayer catalogued only a few stars too far south to be seen from Germany, but later astronomers (including Nicolas-Louis de Lacaille and Benjamin Apthorp Gould) supplemented Bayer's catalog with entries for southern constellations.
MeissaMeissa 'mais@, designated Lambda Orionis (λ Orionis, abbreviated Lambda Ori, λ Ori) is a star in the constellation of Orion. It is a multiple star approximately 1,300ly away with a combined apparent magnitude of 3.33. The main components are an O8 giant star and a B-class main sequence star, separated by about 4′′. Despite Meissa being more luminous and only slightly further away than Rigel, it appears 3 magnitudes dimmer at visual wavelengths, with much of its radiation emitted in the ultraviolet due to its high temperature.
Emission nebulaAn emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star. Among the several different types of emission nebulae are H II regions, in which star formation is taking place and young, massive stars are the source of the ionizing photons; and planetary nebulae, in which a dying star has thrown off its outer layers, with the exposed hot core then ionizing them.
