230 relations: Achernar, Alkali metal, Alnilam, Alpha Centauri, Alpha Leporis, Altair, Ammonia, Angelo Secchi, Annie Jump Cannon, Annual Review of Astronomy and Astrophysics, Antares, Antonia Maury, Ap and Bp stars, Apparent magnitude, Arabic numerals, Arcturus, Astrograph, Astronomical Society of the Pacific, Astronomical spectroscopy, Astronomy, Asymptotic giant branch, Atmosphere, B(e) star, B-type main-sequence star, Balmer series, Bellatrix, Beta Andromedae, Beta Aquarii, Beta Aquilae, Beta Canum Venaticorum, Beta Leporis, Beta Lyrae, Betelgeuse, Biology, Black hole, Brady Haran, Bright giant, Brown dwarf, Calcium, Cambridge University Press, Capella, Carbon, Carbon star, Carbon-12, Carbon-13, Cecilia Payne-Gaposchkin, Centre de données astronomiques de Strasbourg, Chemical element, Chemically peculiar star, Chi Cygni, ..., Chi Pegasi, Chi2 Orionis, Chromaticity, Chromium, Color index, Continuous spectrum, Cyanide, Cygnus OB2-12, Degenerate matter, Deneb, Deuterium, Diatomic carbon, Diffraction grating, Dwarf star, Edith Kellman, Edward Charles Pickering, Effective temperature, Electromagnetic radiation, Epsilon Cygni, Epsilon Eridani, Epsilon Geminorum, Epsilon Virginis, Eta Aurigae, Eta Boötis, Eta Canis Majoris, Eta Leonis, Eta Ursae Majoris, European Southern Observatory, Fomalhaut, Forbidden mechanism, Galaxy, Gamma Cassiopeiae, Gamma Cygni, Gamma Draconis, Gamma Ursae Majoris, Geologic record, Giant star, Gravity, Guest star (astronomy), Harvard College Observatory, HD 149382, HD 21389, HD 93129, Helium, Hertzsprung–Russell diagram, Hydride, Hydrogen, Hydrogen line, Hydrogen spectral series, Hypergiant, Illuminant D65, Infrared, International Astronomical Union, Ionization, Iron, Jupiter, K-type main-sequence star, Kappa Ceti, Kappa Geminorum, Kappa Ophiuchi, Kelvin, Kelvin–Helmholtz mechanism, Lacaille 8760, List of most massive stars, Luminosity, Luminous red nova, Magnesium, Magnitude (astronomy), Main sequence, Manganese, Meghnad Saha, Metallicity, Methane, Methylidyne radical, Micrometre, Milky Way, Mnemonic, Molecular cloud, Molecule, Mu Cephei, Mu Herculis, Mu Normae, Nebula, Neutron star, Nitrogen, Nuclear fusion, OB star, Omicron2 Canis Majoris, Order of magnitude, Orion (constellation), Oxide, Oxygen, P Cygni, Parallax, Philip Childs Keenan, Photometric system, Photosphere, Planetary nebula, Pollux (star), Prism, Protoplanetary disk, Protostar, Publications of the Astronomical Society of the Pacific, Quantum mechanics, Red dwarf, Rho Boötis, Rigel, Roman numerals, RW Cephei, S Monocerotis, S-process, Shell star, Sigma Draconis, Silicon, SIMBAD, Sirius, Sodium, Solar mass, Solar radius, Spectral bands, Spectral line, Spectral signature, Spectroscopic notation, Spectrum, Spiral galaxy, Star, Star count, Stellar classification, Stellar evolution, Stellar kinematics, Stellar mass, Stellar population, Stellar rotation, Stellar wind, Subdwarf, Subgiant, Substellar object, Sun, Supergiant star, Surface gravity, Taxonomy (biology), Temperature, The Astronomical Journal, The Astrophysical Journal, Titanium, Titanium(II) oxide, Triple-alpha process, Type (biology), UBV photometric system, Ultraviolet, University College London, University of Nottingham, Upsilon Orionis, V838 Monocerotis, Van Maanen 2, Vanadium(II) oxide, Vega, Visible spectrum, VY Canis Majoris, Water, Wavelength, White dwarf, Wide-field Infrared Survey Explorer, William Wilson Morgan, Williamina Fleming, WISE 0855−0714, WISE 1828+2650, Wolf–Rayet star, Yellow supergiant star, Yerkes Observatory, Zeta Leonis, Zeta Persei, Zirconium, 10 Lacertae, 59 Cygni, 61 Cygni, 61 Ursae Majoris, 78 Ursae Majoris, 9 Cephei, 9 Pegasi. Expand index (180 more) » « Shrink index
Achernar is the name of the primary (or 'A') component of the binary system designated Alpha Eridani (α Eridani, abbreviated Alf Eri, α Eri), which is the brightest 'star' or point of light in, and lying at the southern tip of, the constellation of Eridanus, and the tenth-brightest in the night sky.
The alkali metals are a group (column) in the periodic table consisting of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, natrium and kalium; these are still the names for the elements in some languages, such as German and Russian.
Alnilam, designated Epsilon Orionis (ε Orionis, abbreviated Epsilon Ori, ε Ori) and 46 Orionis (46 Ori), is a large blue supergiant star some 2,000 light-years distant in the constellation of Orion.
Alpha Centauri (α Centauri, abbreviated Alf Cen or α Cen) is the star system closest to the Solar System, being from the Sun.
Alpha Leporis (α Leporis, abbreviated Alpha Lep, α Lep), also named Arneb, is the brightest star in the constellation of Lepus.
Altair, also designated Alpha Aquilae (α Aquilae, abbreviated Alpha Aql, α Aql), is the brightest star in the constellation of Aquila and the twelfth brightest star in the night sky.
Ammonia is a compound of nitrogen and hydrogen with the formula NH3.
Annie Jump Cannon (December 11, 1863 – April 13, 1941) was an American astronomer whose cataloging work was instrumental in the development of contemporary stellar classification.
The Annual Review of Astronomy and Astrophysics is an annual peer reviewed scientific journal published by Annual Reviews.
Antares, also designated Alpha Scorpii (α Scorpii, abbreviated Alpha Sco, α Sco), is on average the fifteenth-brightest star in the night sky, and the brightest star in the constellation of Scorpius.
Antonia Maury (March 21, 1866 – January 8, 1952) was an American astronomer who published an important early catalog of stellar spectra.
Ap and Bp stars are chemically peculiar stars (hence the "p") of types A and B which show overabundances of some metals, such as strontium, chromium and europium.
The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth.
Arabic numerals, also called Hindu–Arabic numerals, are the ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, based on the Hindu–Arabic numeral system, the most common system for the symbolic representation of numbers in the world today.
An astrograph (astrographic camera) is a telescope designed for the sole purpose of astrophotography.
The Astronomical Society of the Pacific (ASP) is an American scientific and educational organization, founded in San Francisco on February 7, 1889.
Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light and radio, which radiates from stars and other celestial objects.
Astronomy (from ἀστρονομία) is a natural science that studies celestial objects and phenomena.
The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars.
An atmosphere is a layer or a set of layers of gases surrounding a planet or other material body, that is held in place by the gravity of that body.
A B star, frequently called a B-type star, is a B-type star with distinctive forbidden neutral or low ionisation emission lines in its spectrum.
A B-type main-sequence star (B V) is a main-sequence (hydrogen-burning) star of spectral type B and luminosity class V. These stars have from 2 to 16 times the mass of the Sun and surface temperatures between 10,000 and 30,000 K. B-type stars are extremely luminous and blue.
The Balmer series or Balmer lines in atomic physics, is the designation of one of a set of six named series describing the spectral line emissions of the hydrogen atom.
Bellatrix, also designated Gamma Orionis (γ Orionis, abbreviated Gamma Ori, γ Ori), is the third-brightest star in the constellation of Orion, 5° west of the red giant Alpha Orionis (Betelgeuse).
Beta Andromedae (β Andromedae, abbreviated Beta And, β And), also named Mirach, is a prominent star in the northern constellation of Andromeda.
Beta Aquarii (β Aquarii, abbreviated Beta Aqr, β Aqr) is a double star in the constellation of Aquarius.
Beta Aquilae, Latinized from β Aquilae (abbreviated Beta Aql or β Aql) is a binary star in the equatorial constellation of Aquila.
Beta Canum Venaticorum (β Canum Venaticorum, abbreviated Beta CVn, β CVn), also named Chara, is a G-type main-sequence star in the northern constellation of Canes Venatici.
Beta Leporis (β Leporis, abbreviated Beta Lep, β Lep), also named Nihal, is the second brightest star in the constellation of Lepus.
Beta Lyrae (Latinized from β Lyrae, abbreviated Beta Lyr, β Lyr), also named Sheliak, is a binary star system approximately from the Sun in the constellation of Lyra.
Betelgeuse, also designated Alpha Orionis (α Orionis, abbreviated Alpha Ori, α Ori), is the ninth-brightest star in the night sky and second-brightest in the constellation of Orion.
Biology is the natural science that studies life and living organisms, including their physical structure, chemical composition, function, development and evolution.
A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it.
Brady John Haran (born 18 June 1976) is an Australian-born British independent filmmaker and video journalist who is known for his educational videos and documentary films produced for BBC News and his YouTube channels, the most notable being Periodic Videos and Numberphile.
The luminosity class II in the Yerkes spectral classification is given to bright giants.
Brown dwarfs are substellar objects that occupy the mass range between the heaviest gas giant planets and the lightest stars, having masses between approximately 13 to 75–80 times that of Jupiter, or approximately to about.
Calcium is a chemical element with symbol Ca and atomic number 20.
Cambridge University Press (CUP) is the publishing business of the University of Cambridge.
Capella, also designated Alpha Aurigae (α Aurigae, abbreviated Alpha Aur, α Aur), is the brightest star in the constellation of Auriga, the sixth-brightest in the night sky, and the third-brightest in the northern celestial hemisphere after Arcturus and Vega.
Carbon (from carbo "coal") is a chemical element with symbol C and atomic number 6.
A carbon star is typically an asymptotic giant branch star, a luminous red giant, whose atmosphere contains more carbon than oxygen; the two elements combine in the upper layers of the star, forming carbon monoxide, which consumes all the oxygen in the atmosphere, leaving carbon atoms free to form other carbon compounds, giving the star a "sooty" atmosphere and a strikingly ruby red appearance.
Carbon-12 is the more abundant of the two stable isotopes of carbon (Carbon-13 being the other), amounting to 98.93% of the element carbon; its abundance is due to the triple-alpha process by which it is created in stars.
Carbon-13 (13C) is a natural, stable isotope of carbon with a nucleus containing six protons and seven neutrons.
Cecilia Helena Payne-Gaposchkin (May 10, 1900 – December 7, 1979) was a British–American astronomer and astrophysicist who, in 1925, proposed in her Ph.D. thesis an explanation for the composition of stars in terms of the relative abundances of hydrogen and helium.
The Centre de Données astronomiques de Strasbourg (CDS; English translation: Strasbourg Astronomical Data Center) is a data hub which collects and distributes astronomical information.
A chemical element is a species of atoms having the same number of protons in their atomic nuclei (that is, the same atomic number, or Z).
In astrophysics, chemically peculiar stars (CP stars) are stars with distinctly unusual metal abundances, at least in their surface layers.
Chi Cygni (χ Cyg, χ Cygni) is a variable star of the Mira type in the constellation Cygnus, and also an S-type star.
Chi Pegasi (χ Peg) is a class M2+III (red giant) star in the constellation Pegasus.
Chi2 Orionis (Chi2 Ori / χ2 Orionis / χ2 Ori) is a B-type supergiant star in the constellation of Orion.
Christmas is an annual festival commemorating the birth of Jesus Christ,Martindale, Cyril Charles.
The Christmas season, also called the festive season, or the holiday season (mainly in the U.S. and Canada; often simply called the holidays),, is an annually recurring period recognized in many Western and Western-influenced countries that is generally considered to run from late November to early January.
Christmas Eve is the evening or entire day before Christmas Day, the festival commemorating the birth of Jesus.
Christmas traditions vary from country to country.
Chromaticity is an objective specification of the quality of a color regardless of its luminance.
Chromium is a chemical element with symbol Cr and atomic number 24.
In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature.
In physics, a continuous spectrum usually means a set of attainable values for some physical quantity (such as energy or wavelength) that is best described as an interval of real numbers, as opposed to a discrete spectrum, a set of attainable values that is discrete in the mathematical sense, where there is a positive gap between each value and the next one.
A cyanide is a chemical compound that contains the group C≡N.
Cygnus OB2 #12 is an extremely bright blue hypergiant with an absolute bolometric magnitude (all electromagnetic radiation) of −10.9, among the most luminous stars known in the galaxy.
Degenerate matter is a highly dense state of matter in which particles must occupy high states of kinetic energy in order to satisfy the Pauli exclusion principle.
Deneb, also designated α Cygni (Latinised alpha Cygni, abbreviated Alpha Cyg, α Cyg), is the brightest star in the constellation of Cygnus.
Deuterium (or hydrogen-2, symbol or, also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1).
Diatomic carbon (systematically named ethenediylidene and dicarbon(C—C)), also called dicarbon, is an inorganic chemical with the chemical formula C.
In optics, a diffraction grating is an optical component with a periodic structure that splits and diffracts light into several beams travelling in different directions.
A dwarf star is a star of relatively small size and low luminosity.
Edith Kellman (April 4, 1911, Walworth, Wisconsin – May 11, 2007, Walworth, Wisconsin) was a noted American astronomer who is known for her work on the Yerkes system of stellar classification, also called the MKK system.
Prof Edward Charles Pickering FRS(For) HFRSE (July 19, 1846 – February 3, 1919) was an American astronomer and physicist and the older brother to William Henry Pickering.
The 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.
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space-time, carrying electromagnetic radiant energy.
Epsilon Cygni (ε Cygni, abbreviated Eps Cyg, ε Cyg) is multiple star system in the constellation of Cygnus.
Epsilon Eridani (ε Eridani, abbreviated Epsilon Eri, ε Eri), also named Ran, is a star in the southern constellation of Eridanus, at a declination of 9.46° south of the celestial equator.
Epsilon Geminorum (ε Geminorum, abbreviated Epsilon Gem, ε Gem), also named Mebsuta, is a star in the constellation of Gemini and is located on the outstretched right 'leg' of the twin Castor.
Epsilon Virginis (ε Virginis, abbreviated Epsilon Vir, ε Vir), also named Vindemiatrix, is a star in the zodiac constellation of Virgo.
Eta Aurigae (η Aurigae, abbreviated Eta Aur, η Aur), also named Haedus, is a star in the northern constellation of Auriga.
Eta Boötis (η Boötis, abbreviated Eta Boo, η Boo) is a binary star in the constellation of Boötes.
Eta Canis Majoris (η Canis Majoris, abbreviated Eta CMa, η CMa), also named Aludra, is a star in the constellation of Canis Major.
Eta Leonis (η Leo, η Leonis) is a fourth-magnitude star in the constellation Leo.
Eta Ursae Majoris (η Ursae Majoris, abbreviated Eta UMa, η UMa), also named Alkaid, is a star in the constellation of Ursa Major.
The European Southern Observatory (ESO) is a 15-nation intergovernmental research organization for ground-based astronomy.
Fomalhaut, also designated Alpha Piscis Austrini (α Piscis Austrini, abbreviated Alpha PsA, α PsA) is the brightest star in the constellation of Piscis Austrinus and one of the brightest stars in the sky.
In spectroscopy, a forbidden mechanism (forbidden transition or forbidden line) is a spectral line associated with absorption or emission of light by atomic nuclei, atoms, or molecules which undergo a transition that is not allowed by a particular selection rule but is allowed if the approximation associated with that rule is not made.
A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.
Gamma Cassiopeiae, Latinized from γ Cassiopeiae, is a star at the center of the distinctive "W" asterism in the northern circumpolar constellation of Cassiopeia.
Gamma Cygni (γ Cygni, abbreviated Gamma Cyg, γ Cyg), also named Sadr, is a star in the northern constellation of Cygnus, forming the intersection of an asterism of five stars called the Northern Cross.
Gamma Draconis (γ Draconis, abbreviated Gamma Dra, γ Dra), also named Eltanin, is a star in the northern constellation of Draco.
Gamma Ursae Majoris (γ Ursae Majoris, abbreviated Gamma UMa, γ UMa), also named Phecda, is a star in the constellation of Ursa Major.
The geologic record in stratigraphy, paleontology and other natural sciences refers to the entirety of the layers of rock strata — deposits laid down by volcanism or by deposition of sediment derived from weathering detritus (clays, sands etc.) including all its fossil content and the information it yields about the history of the Earth: its past climate, geography, geology and the evolution of life on its surface.
A giant star is a star with substantially larger radius and luminosity than a main-sequence (or dwarf) star of the same surface temperature.
Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are brought toward (or gravitate toward) one another.
In Chinese astronomy, a guest star is a star which has suddenly appeared in a place where no star had previously been observed and becomes invisible again after some time.
The Harvard College Observatory (HCO) is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy.
HD 149382 is a star in the constellation of Ophiuchus with an apparent visual magnitude of 8.943.
HD 21389 is a supergiant variable star in reflection nebula VdB 15, in the constellation Camelopardalis.
HD 93129 is a triple star system in the Carina Nebula, with all three components being hot O class stars amongst the most luminous stars in the Milky Way.
Helium (from lit) is a chemical element with symbol He and atomic number 2.
The Hertzsprung–Russell diagram, abbreviated H–R diagram, HR diagram or HRD, is a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their stellar classifications or effective temperatures.
In chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, it is a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties.
Hydrogen is a chemical element with symbol H and atomic number 1.
The hydrogen line, 21-centimeter line or H I line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms.
The emission spectrum of atomic hydrogen is divided into a number of spectral series, with wavelengths given by the Rydberg formula.
A hypergiant (luminosity class 0 or Ia+) is among the very rare kinds of stars that typically show tremendous luminosities and very high rates of mass loss by stellar winds.
CIE Standard Illuminant D65 (sometimes written D65) is a commonly used standard illuminant defined by the International Commission on Illumination (CIE).
Infrared radiation (IR) is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is therefore generally invisible to the human eye (although IR at wavelengths up to 1050 nm from specially pulsed lasers can be seen by humans under certain conditions). It is sometimes called infrared light.
The International Astronomical Union (IAU; Union astronomique internationale, UAI) is an international association of professional astronomers, at the PhD level and beyond, active in professional research and education in astronomy.
Ionization or ionisation, is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions, often in conjunction with other chemical changes.
Iron is a chemical element with symbol Fe (from ferrum) and atomic number 26.
Jupiter is the fifth planet from the Sun and the largest in the Solar System.
A K-type main-sequence star (K V), also referred to as an orange dwarf or K dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars ("red dwarfs") and yellow G-type main-sequence stars.
The Bayer designation κ Ceti (Kappa Ceti) is shared by two stars in the constellation of Cetus.
Kappa Geminorum (κ Gem, κ Geminorum) is a binary star system in the northern zodiac constellation of Gemini.
Kappa Ophiuchi (κ Oph, κ Ophiuchi) is a star in the equatorial constellation Ophiuchus.
The Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics.
The Kelvin–Helmholtz mechanism is an astronomical process that occurs when the surface of a star or a planet cools.
Lacaille 8760 (AX Microscopii) is a red dwarf star in the constellation Microscopium.
This is a list of the most massive stars so far discovered, in solar masses.
In astronomy, luminosity is the total amount of energy emitted per unit of time by a star, galaxy, or other astronomical object.
A luminous red nova (abbr. LRN, pl. luminous red novae, pl.abbr. LRNe) is a stellar explosion thought to be caused by the merging of two stars.
Magnesium is a chemical element with symbol Mg and atomic number 12.
In astronomy, magnitude is a logarithmic measure of the brightness of an object in a defined passband, often in the visible or infrared spectrum, but sometimes across all wavelengths.
In astronomy, the main sequence is a continuous and distinctive band of stars that appear on plots of stellar color versus brightness.
Manganese is a chemical element with symbol Mn and atomic number 25.
Meghnad Saha FRS (6 October 1893 – 16 February 1956) was an Indian astrophysicist best known for his development of the Saha ionization equation, used to describe chemical and physical conditions in stars.
In astronomy, metallicity is used to describe the abundance of elements present in an object that are heavier than hydrogen or helium.
Methane is a chemical compound with the chemical formula (one atom of carbon and four atoms of hydrogen).
Methylidyne (also systematically named hydridocarbon(•)), also called carbyne, is an organic compound with the chemical formula CH• (also written as). Methylidyne is the simplest carbyne.
The micrometre (International spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is an SI derived unit of length equaling (SI standard prefix "micro-".
The Milky Way is the galaxy that contains our Solar System.
A mnemonic (the first "m" is silent) device, or memory device, is any learning technique that aids information retention or retrieval (remembering) in the human memory.
A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit the formation of molecules, most commonly molecular hydrogen (H2).
A molecule is an electrically neutral group of two or more atoms held together by chemical bonds.
Mu Cephei (μ Cep, μ Cephei), also known as Herschel's Garnet Star, is a red supergiant star in the constellation Cepheus.
Mu Herculis (μ Herculis) is a nearby star system about 27.1 light years from Earth in the constellation Hercules.
μ Normae, Latinised as Mu Normae, is a blue supergiant star of spectral type O9.7 Iab in the constellation Norma.
A nebula (Latin for "cloud" or "fog"; pl. nebulae, nebulæ, or nebulas) is an interstellar cloud of dust, hydrogen, helium and other ionized gases.
A neutron star is the collapsed core of a large star which before collapse had a total of between 10 and 29 solar masses.
New Year is the time or day at which a new calendar year begins and the calendar's year count increments by one.
New Year's Day, also called simply New Year's or New Year, is observed on January 1, the first day of the year on the modern Gregorian calendar as well as the Julian calendar.
In the Gregorian calendar, New Year's Eve (also known as Old Year's Day or Saint Sylvester's Day in many countries), the last day of the year, is on 31 December which is the seventh day of Christmastide.
Nitrogen is a chemical element with symbol N and atomic number 7.
In nuclear physics, nuclear fusion is a reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles (neutrons or protons).
OB stars are hot, massive stars of spectral types O or early-type B that form in loosely organized groups called OB associations.
Omicron2 Canis Majoris (ο² CMa, ο² Canis Majoris) is a star in the constellation Canis Major.
An order of magnitude is an approximate measure of the number of digits that a number has in the commonly-used base-ten number system.
Orion is a prominent constellation located on the celestial equator and visible throughout the world.
An oxide is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula.
Oxygen is a chemical element with symbol O and atomic number 8.
P Cygni (34 Cyg) is a variable star in the constellation Cygnus.
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.
Philip Childs Keenan (March 31, 1908 – April 20, 2000) was an American astronomer.
In astronomy, a photometric system is a set of well-defined passbands (or filters), with a known sensitivity to incident radiation.
The photosphere is a star's outer shell from which light is radiated.
A planetary nebula, abbreviated as PN or plural PNe, is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives.
Pollux, also designated Beta Geminorum (β Geminorum, abbreviated Beta Gem, β Gem), is an orange-hued evolved giant star approximately 34 light-years from the Sun in the northern constellation of Gemini.
In optics, a prism is a transparent optical element with flat, polished surfaces that refract light.
A protoplanetary disk is a rotating circumstellar disk of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star.
A protostar is a very young star that is still gathering mass from its parent molecular cloud.
Publications of the Astronomical Society of the Pacific (often abbreviated as PASP in references and literature) is a monthly peer-reviewed scientific journal managed by the Astronomical Society of the Pacific.
Quantum mechanics (QM; also known as quantum physics, quantum theory, the wave mechanical model, or matrix mechanics), including quantum field theory, is a fundamental theory in physics which describes nature at the smallest scales of energy levels of atoms and subatomic particles.
A red dwarf (or M dwarf) is a small and relatively cool star on the main sequence, of M spectral type.
Rho Boötis, Latinized from ρ Boötis, is a single, orange-hued star in the northern constellation of Boötes.
Rigel, also designated Beta Orionis (β Orionis, abbreviated Beta Ori, β Ori), is generally the seventh-brightest star in the night sky and the brightest star in the constellation of Orion—though periodically it is outshone within the constellation by the variable Betelgeuse.
The numeric system represented by Roman numerals originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages.
RW Cephei is an orange hypergiant star in the constellation Cepheus, at the edge of the Sharpless 132 HII region and close to the small open cluster Berkeley 94.
S Monocerotis, also known as 15 Monocerotis, is a massive multiple and variable star system located in the constellation Monoceros.
The slow neutron-capture process or s-process is a series of reactions in nuclear astrophysics that occur in stars, particularly AGB stars.
A shell star is a star having a spectrum that exhibits features indicating a circumstellar disc of gas surrounding the star at the equator.
Sigma Draconis (σ Draconis, abbreviated Sig Dra, σ Dra), also named Alsafi, is a 4.7-magnitude star located at a distance of 18.8 light-years from the Sun in the constellation of Draco.
Silicon is a chemical element with symbol Si and atomic number 14.
SIMBAD (the Set of Identifications, Measurements, and Bibliography for Astronomical Data) is an astronomical database of objects beyond the Solar System.
Sirius (a romanization of Greek Σείριος, Seirios,."glowing" or "scorching") is a star system and the brightest star in the Earth's night sky.
Sodium is a chemical element with symbol Na (from Latin natrium) and atomic number 11.
The solar mass is a standard unit of mass in astronomy, equal to approximately.
Solar radius is a unit of distance used to express the size of stars in astronomy.
Spectral bands are part of optical spectra of polyatomic systems, including condensed materials, large molecules, etc.
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies.
Spectral signature is the variation of reflectance or emittance of a material with respect to wavelengths (i.e.,reflectance/emittance as a function of wavelength).
Spectroscopic notation provides a way to specify atomic ionization states, as well as atomic and molecular orbitals.
A spectrum (plural spectra or spectrums) is a condition that is not limited to a specific set of values but can vary, without steps, across a continuum.
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae(pp. 124–151) and, as such, form part of the Hubble sequence.
A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.
Star counts are bookkeeping surveys of stars and the statistical and geometrical methods used to correct the survey data for bias.
In astronomy, stellar classification is the classification of stars based on their spectral characteristics.
Stellar evolution is the process by which a star changes over the course of time.
In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space.
Stellar mass is a phrase that is used by astronomers to describe the mass of a star.
During 1944, Walter Baade categorized groups of stars within the Milky Way into bluer stars associated with the spiral arms and the general position of yellow stars near the central galactic bulge or within globular star clusters.
Stellar rotation is the angular motion of a star about its axis.
A stellar wind is a flow of gas ejected from the upper atmosphere of a star.
A subdwarf, sometimes denoted by "sd", is a star with luminosity class VI under the Yerkes spectral classification system.
A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as true giant stars.
A substellar object, sometimes called a substar, is an astronomical object whose mass is smaller than the smallest mass at which hydrogen fusion can be sustained (approximately 0.08 solar masses).
The Sun is the star at the center of the Solar System.
Supergiants are among the most massive and most luminous stars.
The surface gravity, g, of an astronomical or other object is the gravitational acceleration experienced at its surface.
Taxonomy is the science of defining and naming groups of biological organisms on the basis of shared characteristics.
Temperature is a physical quantity expressing hot and cold.
The Astronomical Journal (often abbreviated AJ in scientific papers and references) is a peer-reviewed monthly scientific journal owned by the American Astronomical Society and currently published by IOP Publishing.
The Astrophysical Journal, often abbreviated ApJ (pronounced "ap jay") in references and speech, is a peer-reviewed scientific journal of astrophysics and astronomy, established in 1895 by American astronomers George Ellery Hale and James Edward Keeler.
Titanium is a chemical element with symbol Ti and atomic number 22.
Titanium(II) oxide (TiO) is an inorganic chemical compound of titanium and oxygen.
The triple-alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei (alpha particles) are transformed into carbon.
In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached.
The UBV photometric system (Ultraviolet, Blue, Visual), also called the Johnson system (or Johnson-Morgan system), is a wide band photometric system for classifying stars according to their colors.
Ultraviolet (UV) is electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays.
University College London (UCL) is a public research university in London, England, and a constituent college of the federal University of London.
The University of Nottingham is a public research university in Nottingham, United Kingdom.
Upsilon Orionis (υ Ori, υ Orionis) is a star in the constellation Orion.
V838 Monocerotis (V838 Mon) is a red star in the constellation Monoceros about 20,000 light years (6 kpc) from the Sun.
Van Maanen 2 (van Maanen's Star) is a white dwarf.
Vanadium(II) oxide, VO, is one of the many oxides of vanadium.
Vega, also designated Alpha Lyrae (α Lyrae, abbreviated Alpha Lyr or α Lyr), is the brightest star in the constellation of Lyra, the fifth-brightest star in the night sky, and the second-brightest star in the northern celestial hemisphere, after Arcturus.
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye.
VY Canis Majoris (VY CMa) is an extreme pulsating red hypergiant (or supergiant) star located in the constellation Canis Major.
Water is a transparent, tasteless, odorless, and nearly colorless chemical substance that is the main constituent of Earth's streams, lakes, and oceans, and the fluids of most living organisms.
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
A white dwarf, also called a degenerate dwarf, is a stellar core remnant composed mostly of electron-degenerate matter.
Wide-field Infrared Survey Explorer (WISE) is a NASA infrared-wavelength astronomical space telescope launched in December 2009, and placed in hibernation in February 2011.
William Wilson Morgan (January 3, 1906 – June 21, 1994) was an American astronomer and astrophysicist.
Williamina Paton Stevens Fleming (May 15, 1857 – May 21, 1911) was a Scottish-American astronomer.
WISE 0855−0714 (full designation WISE J085510.83−071442.5) is a (sub-) brown dwarf from Earth, whose discovery was announced in April 2014 by Kevin Luhman using data from the Wide-field Infrared Survey Explorer (WISE).
WISE 1828+2650 (full designation WISEPA J182831.08+265037.8) is a brown dwarf or rogue planet of spectral class >Y2, located in constellation Lyra at approximately 47 light-years from Earth.
Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of highly ionised helium and nitrogen or carbon.
A yellow supergiant star is a star, generally of spectral type F or G, having a supergiant luminosity class (e.g. Ia or Ib).
Yerkes Observatory is an astronomical observatory in Williams Bay, Wisconsin operated by the University of Chicago Department of Astronomy and Astrophysics.
Zeta Leonis (ζ Leonis, abbreviated Zeta Leo, ζ Leo), also named Adhafera, is a third-magnitude star in the constellation of Leo, the lion.
Zeta Persei (ζ Per, ζ Persei) is a star in the northern constellation of Perseus.
Zirconium is a chemical element with symbol Zr and atomic number 40.
10 Lacertae (10 Lac) is a star in the constellation Lacerta.
2018 has been designated as the third International Year of the Reef by the International Coral Reef Initiative.
2019 (MMXIX) will be a common year starting on Tuesday of the Gregorian calendar, the 2019th year of the Common Era (CE) and Anno Domini (AD) designations, the 19th year of the 3rd millennium, the 19th year of the 21st century, and the 10th and last year of the 2010s decade.
59 Cygni (59 Cyg) is a star in the constellation Cygnus.
61 Cygni Not to be confused with 16 Cygni, a more distant system containing two G-type stars harboring the gas giant planet 16 Cygni Bb.
61 Ursae Majoris (61 UMa) is an orange-yellow G8 main-sequence star in the constellation Ursa Major.
78 Ursae Majoris (78 UMa) is a binary star in the constellation Ursa Major.
9 Cephei (9 Cep), also known as V337 Cephei, is a variable star in the constellation Cepheus.
9 Pegasi (9 Peg) is a star in the constellation Pegasus.
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