"Photosphere The photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/""phos, photos"" meaning ""light"" and σφαῖρα/""sphaira"" meaning ""sphere"", in reference to it being a spherical surface that is perceived to emit light. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately 2/3, or equivalently, a depth from which 50% of light will escape without being scattered. In other words, a photosphere is the deepest region of a luminous object, usually a star, that is transparent to photons of"
"electromagnetic radiation emitted from these bodies as black-body radiation. The figure shows a highly schematic cross-section to illustrate the idea. The photosphere of the star, where the emitted light is generated, is idealized as a layer within which the photons of light interact with the material in the photosphere and achieve a common temperature ""T"" that is maintained over a long period of time. Some photons escape and are emitted into space, but the energy they carry away is replaced by energy from within the star, so that the temperature of the photosphere is nearly steady. Changes in the core"
"space as both electromagnetic radiation and particle radiation. The particle radiation emitted by a star is manifested as the stellar wind, which streams from the outer layers as electrically charged protons and alpha and beta particles. Although almost massless, there also exists a steady stream of neutrinos emanating from the star's core. The production of energy at the core is the reason stars shine so brightly: every time two or more atomic nuclei fuse together to form a single atomic nucleus of a new heavier element, gamma ray photons are released from the nuclear fusion product. This energy is converted"
"star consists of a dense ""core"", with its surface defined as the sonic point, and a surrounding optically dense wind. The observed radiation from the star is entirely generated at different layers within the wind. The properties of a Wolf Rayet star are typically reported at an ""inner boundary"" of the wind, arbitrarily set at an optical depth of 20. The radius of this inner boundary in WR 114 is . The sonic point of WR 114 lies at about optical depth 60. At this level the temperature is much hotter. Another common definition for the surface of a star"
"Starlight Starlight is the light emitted by stars. It typically refers to visible electromagnetic radiation from stars other than the Sun observable from Earth during the night time although a component of starlight is observable from the Earth during the daytime. Sunlight is the term used for the Sun's starlight observed during daytime. During nighttime, albedo describes solar reflections from other Solar System objects including moonlight. Observation and measurement of starlight through telescopes is the basis for many fields of astronomy, including photometry and stellar spectroscopy. Hipparchus did not have a telescope or any instrument that could measure apparent brightness"
"rotating shell star that may have recently ejected mass from its outer atmosphere. Alpha Pictoris is larger than the Sun, with twice the mass and a 60% greater radius. It is radiating 13 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of . At this heat, the star glows with the white hue of an A-type star. The space velocity components of this star in the galactic coordinate system are U = -22, V = -20 and W = -9 km/s. Data from the Hipparcos mission indicate this may be an unresolved binary"
"the Universe, including all stars outside our galaxy, the Milky Way, are invisible to the naked eye from Earth. Indeed, most are invisible from Earth even through the most powerful telescopes. For at least a portion of its life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space. Almost all naturally occurring elements heavier than helium are created by stellar nucleosynthesis during the star's lifetime, and for some stars by supernova nucleosynthesis when it explodes. Near the end of its life, a"
"shell He-n, B6p shell, B4III, B3IV:e-shell, and B3 shell by different sources. As is the norm for a shell star, it is spinning very rapidly with a projected rotational velocity of 400 km/s − matching or exceeding 80% of the critical velocity. This is giving the star a pronounced oblate shape with an equatorial bulge that is estimated to be 43% larger than the polar radius. It has six times the mass of the Sun and four times the Sun's radius. The star is radiating 1,100 times the Sun's luminosity from its photosphere at an effective temperature of 7,612 K."
"to other forms of electromagnetic energy of lower frequency, such as visible light, by the time it reaches the star's outer layers. The color of a star, as determined by the most intense frequency of the visible light, depends on the temperature of the star's outer layers, including its photosphere. Besides visible light, stars also emit forms of electromagnetic radiation that are invisible to the human eye. In fact, stellar electromagnetic radiation spans the entire electromagnetic spectrum, from the longest wavelengths of radio waves through infrared, visible light, ultraviolet, to the shortest of X-rays, and gamma rays. From the standpoint"
"shell containing a fast burning tailed or charcoal star that is burst very hard so that the stars travel in a straight and flat trajectory before slightly falling and burning out. This appears in the sky as a series of radial lines much like the legs of a spider. An effect created by large, slow-burning stars within a shell that leave a trail of large glittering sparks behind and make a sizzling noise. The ""time"" refers to the fact that these stars burn away gradually, as opposed to the standard brocade ""rain"" effect where a large amount of glitter material"
"cases starlight photography may also overlap with a need to understand the impact of moonlight. Starlight Starlight is the light emitted by stars. It typically refers to visible electromagnetic radiation from stars other than the Sun observable from Earth during the night time although a component of starlight is observable from the Earth during the daytime. Sunlight is the term used for the Sun's starlight observed during daytime. During nighttime, albedo describes solar reflections from other Solar System objects including moonlight. Observation and measurement of starlight through telescopes is the basis for many fields of astronomy, including photometry and stellar"
"Radiation zone A radiation zone, or radiative region is a layer of a star's interior where energy is primarily transported toward the exterior by means of radiative diffusion and thermal conduction, rather than by convection. Energy travels through the radiation zone in the form of electromagnetic radiation as photons. Matter in a radiation zone is so dense that photons can travel only a short distance before they are absorbed or scattered by another particle, gradually shifting to longer wavelength as they do so. For this reason, it takes an average of 171,000 years for gamma rays from the core of"
"helium core. For most stars the convective zones will also vary over time as the star ages and the constitution of the interior is modified. The photosphere is that portion of a star that is visible to an observer. This is the layer at which the plasma of the star becomes transparent to photons of light. From here, the energy generated at the core becomes free to propagate into space. It is within the photosphere that sun spots, regions of lower than average temperature, appear. Above the level of the photosphere is the stellar atmosphere. In a main sequence star"
"be detected as opaque clouds blocking light from luminous objects behind them; they are called ""dark nebulae"". Although these nebulae have different visibility at optical wavelengths, they are all bright sources of infrared emission, chiefly from dust within the nebulae. Planetary nebulae are the remnants of the final stages of stellar evolution for lower-mass stars. Evolved asymptotic giant branch stars expel their outer layers outwards due to strong stellar winds, thus forming gaseous shells, while leaving behind the star's core in the form of a white dwarf. The hot white dwarf illuminates the expelled gases producing emission nebulae with spectra"
"a radiation zone, with the amount of mass within the convective zone increasing with the mass of the star. In the Sun, the region between the solar core at 0.2 of the Sun's radius and the outer convection zone at 0.71 of the Sun's radius is referred to as the radiation zone, although the core is also a radiative region. The convection zone and the radiation zone are divided by the tachocline, another part of the Sun. Radiation zone A radiation zone, or radiative region is a layer of a star's interior where energy is primarily transported toward the exterior"
"is over forty parsecs wide and contains about of hydrogen. It is unclear which of the two stars is primarily responsible for creating the shell. WR 134 WR 134 is a variable Wolf-Rayet star located around 6,000 light years away from Earth in the constellation of Cygnus, surrounded by a faint bubble nebula blown by the intense radiation and fast wind from the star. It is five times the radius of the sun, but due to a temperature over 63,000 K it is 400,000 times as luminous as the sun. WR 134 was one of three stars in Cygnus observed"
"Corona A corona (Latin, 'crown') is an aura of plasma that surrounds the Sun and other stars. The Sun's corona extends millions of kilometres into outer space and is most easily seen during a total solar eclipse, but it is also observable with a coronagraph. The word ""corona"" is a Latin word meaning ""crown"", from the Ancient Greek κορώνη (korōnè, “garland, wreath”). Spectroscopy measurements indicate strong ionization and plasma temperature in excess of 1,000,000 kelvins, much hotter than the surface of the Sun. Light from the corona comes from three primary sources, from the same volume of space. The K-corona"
"both reflection and emission components such as the Trifid Nebula. Emission nebula An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy 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. Usually, a young star will"
"star is in the process of evolving into a giant star as the supply of hydrogen at its core becomes exhausted. Compared to the Sun it has 240% of the mass and 230% of the Sun's radius, but is radiating 37 times as much luminosity. This energy is being emitted from the star's outer atmosphere at an effective temperature of 9,280 K, giving it the characteristic white-hot glow of an A-type star. ""λ Ursae Majoris"" (Latinised to ""Lambda Ursae Majoris"") is the star's Bayer designation. It bore the traditional names ""Tania"" (shared with Mu Ursae Majoris) and ""Tania Borealis"". ""Tania"""
"its nuclear fuel. As an O-class main sequence star, it would be 8 times the solar radius and 62,000 times the Sun's luminosity. Star A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, the brightest of which gained"
"second up to a few minutes at most. Once it disappears, it leaves behind a counterpart at longer wavelengths (X-ray, UV, optical, infrared, and radio) known as the afterglow that generally remains detectable for days or longer. In contrast to the GRB emission, the afterglow emission is not believed to be dominated by internal shocks. In general, all the ejected matter has by this time coalesced into a single shell traveling outward into the interstellar medium (or possibly the stellar wind) around the star. At the front of this shell of matter is a shock wave referred to as the"
"provide essential information about the evolution of galaxies. The ultraviolet universe looks quite different from the familiar stars and galaxies seen in visible light. Most stars are actually relatively cool objects emitting much of their electromagnetic radiation in the visible or near-infrared part of the spectrum. Ultraviolet radiation is the signature of hotter objects, typically in the early and late stages of their evolution. In the Earth's sky seen in ultraviolet light, most stars would fade in prominence. Some very young massive stars and some very old stars and galaxies, growing hotter and producing higher-energy radiation near their birth or"
"Stellar halo The stellar halo of a galaxy refers to the component of its galactic halo containing stars. The halo extends far outside a galaxy's brightest regions and typically contains its oldest and most metal poor stars. Early studies, investigating the shape of the stellar halo of the Milky Way, found some evidence that it may vary with increasing distance from the galaxy. These studies found halos with spherically shaped outer regions and flatter inner regions. Large surveys in the 21st century such as the Sloan Digital Sky Survey have allowed the shape and distribution of the stellar halo to"
"for which the path in excited hydrogen is maximal, that is, tangential to the sphere. In Strömgren's explanations, the shell absorbs only the resonant lines of hydrogen, so that the available energy is low. Assuming that the star is a supernova, the radiance of the light it emits corresponds (by Planck's law) to a temperature of several hundreds of kelvins, so that several frequencies may combine to produce the resonance frequencies of hydrogen atoms. Thus, almost all light emitted by the star is absorbed, and almost all energy radiated by the star amplifies the tangent, super-radiant rays. The Necklace Nebula"
"System beyond the orbit of Neptune. Based on these findings, researchers have concluded that the majority of galactic radiation is emitted in the form of infrared radiation that is generated when light from young stars is absorbed by interstellar dust and then radiated from the dust in the form of heat. In 1984, IRAS found that the galaxy Arp 220, located 300 million light years from Earth, is the closest Ultraluminous Infrared Galaxy, emitting 100 times more energy than the Milky Way galaxy, primarily in the infrared spectrum, even though it is faintly visible by telescope using visible light. Low"
"are the main constituents of the outer layers of the star. Months after the explosion, when the outer layers have expanded to the point of transparency, the spectrum is dominated by light emitted by material near the core of the star, heavy elements synthesized during the explosion; most prominently isotopes close to the mass of iron (iron-peak elements). The radioactive decay of nickel-56 through cobalt-56 to iron-56 produces high-energy photons, which dominate the energy output of the ejecta at intermediate to late times. The use of Type Ia supernovae to measure precise distances was pioneered by a collaboration of Chilean"
"stars. A dense clump of gas near the centre of mass of the system, and co-rotating with the stars, produces the bulk of the emission lines. A more diffuse region of gas surrounds both stars and produces some absorption components in the spectrum. The entire system is surrounded by a shell of material about 0.8 parsecs across, assuming that MWC 314 is 3,000 parsecs away. This appears in infrared images as a circular ring 25 arc-seconds from the central star. There is a much larger bipolar nebula detected by its H radiation. It is 13 parsecs from end to end."
"Gamma Arae Gamma Arae (γ Ara, γ Arae) is a star in the southern constellation of Ara. With an apparent visual magnitude of 3.3, it is the fourth-brightest star in the constellation and is readily visible to the naked eye. From parallax measurements made during the Hipparcos mission, the distance to this star can be estimated as from Earth. This is an enormous star with 23 times the radius of the Sun. It is radiating 120,000 as much energy as the Sun from its outer envelope at an effective temperature of 21,500 K. This heat gives the star the blue-white"
"the exterior. The outgoing flux of energy leaving any layer within the star will exactly match the incoming flux from below. The radiation zone is the region of the stellar interior where the flux of energy outward is dependent on radiative heat transfer, since convective heat transfer is inefficient in that zone. In this region the plasma will not be perturbed, and any mass motions will die out. If this is not the case, however, then the plasma becomes unstable and convection will occur, forming a convection zone. This can occur, for example, in regions where very high energy fluxes"
"Emission nebula An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy 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. Usually, a young star will ionize part of the same cloud from which it was"
"This causes the outer layers to expand even further and generates a strong convective zone that brings heavy elements to the surface in a process called the first dredge-up. This strong convection also increases the transport of energy to the surface, the luminosity increases dramatically, and the star moves onto the red-giant branch where it will stably burn hydrogen in a shell for a substantial fraction of its entire life (roughly 10% for a Sun-like star). The core continues to gain mass, contract, and increase in temperature, whereas there is some mass loss in the outer layers. If the star's"
"Star A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, the brightest of which gained proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. However, most of the stars in"
"the star's surface with a lower temperature and luminosity than average are known as starspots. Small, ""dwarf"" stars such as our Sun generally have essentially featureless disks with only small starspots. ""Giant"" stars have much larger, more obvious starspots, and they also exhibit strong stellar limb darkening. That is, the brightness decreases towards the edge of the stellar disk. Red dwarf flare stars such as UV Ceti may also possess prominent starspot features. The apparent brightness of a star is expressed in terms of its apparent magnitude. It is a function of the star's luminosity, its distance from Earth, the"