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Messier 60
Messier 60 or M60, also known as NGC 4649, is an elliptical galaxy approximately 57 million light-years away in the equatorial constellation of Virgo. Together with NGC 4647, it forms a pair known as Arp 116. Messier 60 and nearby elliptical galaxy Messier 59 were discovered by Johann Gottfried Koehler in April 1779, observing a comet in the same part of the sky. Charles Messier added both to his catalogue about three days after this. Characteristics This is an elliptical galaxy of type E (E1.5), although some sources class it as S0 – a lenticular galaxy. An E2 class indicates a flattening of 20%, which has a nearly round appearance. The isophotes of the galaxy are boxy in shape, rather than simple ellipses. The mass-to-light ratio is a near constant 9.5 in the V (visual) band of the UBV system. The galaxy has an effective radius of (translating, at its distance, to about 10 kpc), with an estimated mass of ~1012 within a threefold volume, of which near ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Messier Object
The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ''Catalogue des Nébuleuses et des Amas d'Étoiles'' (''Catalogue of Nebulae and Star Clusters''). Because Messier was only interested in finding comets, he created a list of those non-comet objects that frustrated his hunt for them. The compilation of this list, in collaboration with his assistant Pierre Méchain, is known as ''the Messier catalogue''. This catalogue of objects is one of the most famous lists of astronomical objects, and many Messier objects are still referenced by their Messier numbers. The catalogue includes most of the astronomical deep-sky objects that can easily be observed from Earth's Northern Hemisphere; many Messier objects are popular targets for amateur astronomers. A preliminary version first appeared in 1774 in the ''Memoirs'' of the French Academy of Sciences for the year 1771. The first version of Messier's catalogue contain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Messier
Charles Messier (; 26 June 1730 – 12 April 1817) was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the ''Messier objects''. Messier's purpose for the catalogue was to help astronomical observers distinguish between permanent and transient visually diffuse objects in the sky. Biography Messier was born in Badonviller in the Lorraine region of France, the tenth of twelve children of Françoise B. Grandblaise and Nicolas Messier, a Court usher. Six of his brothers and sisters died while young, and his father died in 1741. Charles' interest in astronomy was stimulated by the appearance of the great six-tailed comet in 1744 and by an annular solar eclipse visible from his hometown on 25 July 1748. In 1751, Messier entered the employ of Joseph Nicolas Delisle, the astronomer of the French Navy, who instructed him to keep careful records of his observations. Messier's first doc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophysical Jet
An astrophysical jet is an astronomical phenomenon where outflows of ionised matter are emitted as an extended beam along the axis of rotation. When this greatly accelerated matter in the beam approaches the speed of light, astrophysical jets become relativistic jets as they show effects from special relativity. The formation and powering of astrophysical jets are highly complex phenomena that are associated with many types of high-energy astronomical sources. They likely arise from dynamic interactions within accretion disks, whose active processes are commonly connected with compact central objects such as black holes, neutron stars or pulsars. One explanation is that tangled magnetic fields are organised to aim two diametrically opposing beams away from the central source by angles only several degrees wide Jets may also be influenced by a general relativity effect known as frame-dragging. Most of the largest and most active jets are created by supermassive black holes (S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Galactic Nucleus
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not produced by stars. Such excess non-stellar emission has been observed in the radio, microwave, infrared, optical, ultra-violet, X-ray and gamma ray wavebands. A galaxy hosting an AGN is called an "active galaxy". The non-stellar radiation from an AGN is theorized to result from the accretion of matter by a supermassive black hole at the center of its host galaxy. Active galactic nuclei are the most luminous persistent sources of electromagnetic radiation in the universe, and as such can be used as a means of discovering distant objects; their evolution as a function of cosmic time also puts constraints on models of the cosmos. The observed characteristics of an AGN depend on several properties such as the mass of the central black hole, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Most Massive Black Holes
This is an ordered list of the most massive black holes so far discovered (and probable candidates), measured in units of solar masses (), approximately . Introduction A supermassive black hole (SMBH) is an extremely large black hole, on the order of hundreds of thousands to billions of solar masses (), and is theorized to exist in the center of almost all massive galaxies. In some galaxies, there are even binary systems of supermassive black holes, see the OJ 287 system. Unambiguous dynamical evidence for SMBHs exists only in a handful of galaxies; these include the Milky Way, the Local Group galaxies M31 and M32, and a few galaxies beyond the Local Group, e.g. NGC 4395. In these galaxies, the mean square (or root mean square) velocities of the stars or gas rises as ~1/r near the center, indicating a central point mass. In all other galaxies observed to date, the rms velocities are flat, or even falling, toward the center, making it impossible to state with certainty that a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supermassive Black Hole
A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions of times the mass of the Sun (). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space from which nothing can escape, not even light. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its Central massive object, center. For example, the Milky Way has a Galactic Center#Supermassive black hole, supermassive black hole in its Galactic Center, corresponding to the Astronomical radio source, radio source Sagittarius A*. Accretion (astrophysics), Accretion of Interstellar medium, interstellar gas onto supermassive black holes is the process responsible for powering Active galactic nucleus, active galactic nuclei (AGNs) and quasars. Two supermassive black holes have been directly imaged by the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Matter
Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not absorb, reflect, or emit electromagnetic radiation and is, therefore, difficult to detect. Various astrophysical observationsincluding gravitational effects which cannot be explained by currently accepted theories of gravity unless more matter is present than can be seenimply dark matter's presence. For this reason, most experts think that dark matter is abundant in the universe and has had a strong influence on its structure and evolution. The primary evidence for dark matter comes from calculations showing that many galaxies would behave quite differently if they did not contain a large amount of unseen matter. Some galaxies would not have formed at all and others would not move as they currently do. Other lines of evidence include observa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Effective Radius
Galaxy effective radius or half-light radius (R_e) is the radius at which half of the total light of a galaxy is emitted. This assumes the galaxy has either intrinsic spherical symmetry or is at least circularly symmetric as viewed in the plane of the sky. Alternatively, a half-light contour, or isophote, may be used for spherically and circularly asymmetric objects. R_e is an important length scale in \sqrt R term in de Vaucouleurs law, which characterizes a specific rate at which surface brightness In astronomy, surface brightness (SB) quantifies the apparent brightness or flux density per unit angular area of a spatially extended object such as a galaxy or nebula, or of the night sky background. An object's surface brightness depends on it ... decreases as a function of radius: : I(R) = I_e \cdot e^ where I_e is the surface brightness at R = R_e. At R = 0, : I(R=0) = I_e \cdot e^ \approx 2000 \cdot I_e Thus, the central surface brightness is approximately 2000 \cdot I_ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UBV System
The UBV photometric system (from ''Ultraviolet, Blue, Visual''), also called the Johnson system (or Johnson-Morgan system), is a photometric system usually employed for classifying stars according to their colors. It was the first standardized photometric system. The apparent magnitudes of stars in the system are often used to determine the color indices B-V and U-B, the difference between the B and V magnitudes and the U and B magnitudes respectively. The choice of colors on the blue end of the spectrum was assisted by the bias that photographic film has for those colors. It was introduced in the 1950s by American astronomers Harold Lester Johnson and William Wilson Morgan. A telescope and the telescope at McDonald Observatory were used to define the system. The filters are selected so that the mean wavelengths of response functions (at which magnitudes are measured to mean precision) are 364 nm for U, 442 nm for B, 540 nm for V. Zero points were calibrate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass-to-light Ratio
In astrophysics and physical cosmology the mass-to-light ratio, normally designated with the Greek letter upsilon, , is the quotient between the total mass of a spatial volume (typically on the scales of a galaxy or a galaxy cluster, cluster) and its luminosity. These ratios are often reported using the value calculated for the Sun as a baseline ratio which is a constant = 5133 kilogram, kg/Watt, W: equal to the solar mass divided by the solar luminosity , . The mass-to-light ratios of galaxies and clusters are all much greater than due in part to the fact that most of the matter in these objects does not reside within stars and observations suggest that a large fraction is present in the form of dark matter. Luminosities are obtained from photometry (astronomy), photometric observations, correcting the observed brightness of the object for the cosmic distance ladder, distance dimming and interstellar extinction, extinction effects. In general, unless a complete electrom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isophote
In geometry, an isophote is a curve on an illuminated surface that connects points of equal brightness. One supposes that the illumination is done by parallel light and the brightness is measured by the following scalar product: :b(P)= \vec n(P)\cdot \vec v=\cos\varphi where is the unit normal vector of the surface at point and the unit vector of the light's direction. If , i.e. the light is perpendicular to the surface normal, then point is a point of the surface silhouette observed in direction Brightness 1 means that the light vector is perpendicular to the surface. A plane has no isophotes, because every point has the same brightness. In astronomy, an isophote is a curve on a photo connecting points of equal brightness. J. Binney, M. Merrifield: ''Galactic Astronomy'', Princeton University Press, 1998, , p. 178. Application and example In computer-aided design, isophotes are used for checking optically the smoothness of surface connections. For a surface (implicit or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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