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Mansa Musa was the ruler of the Mali Empire in West Africa. Details recorded here should be sourced; unknown information is left blank.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
| 3C 288 | |
|---|---|
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| Observation data (Epoch J2000) | |
| Constellation | Canes Venatici |
| Right ascension | 13h 38m 49.99s[1] |
| Declination | +38° 51′ 09.5″[1] |
| Redshift | 0.246 000[2] |
| Distance | 960 megaparsecs (3.1×109 ly) h−1 0.73[2] |
| Type | rG, Rad, X, QSO, G[1] G, FR I[2] |
| Apparent dimensions (V) | 0.436' x 0.275'[1] |
| Apparent magnitude (V) | 18.3 |
| Other designations | |
| DA 349, LEDA 2138068, 3C 288, 4C 39.39, QSO B1336+391 | |
| See also: Quasar, List of quasars | |
3C 288 is a radio galaxy[1][2] located in the constellation Canes Venatici.
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 | This galaxy-related article is a stub. You can help Wikipedia by adding missing information. |
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
3C 288 is a radio galaxy located in the constellation Canes Venatici.
3C 285 is a radio galaxy located in the constellation Canes Venatici. It is located about 1 billion light years away. It is a Fanaroff-Riley 2 radio galaxy and is hosted in a disturbed spiral galaxy. 3C 285 is the brightest member of a small galaxy group. Its morphology is peculiar, with an S-shaped envelope that points to another galaxy of the group, located to the northwest. A gas filament 26 arcseconds long extends towards that galaxy. In optical and ultraviolet observations the galaxy features dust lanes, two across the galaxy and one perpendicular to them that also obscures part of the nucleus. Along the edges of the dust lanes knots of elevated ultraviolet emission indicate locations of where new stars are formed. In the centre of 3C 285 lies a supermassive black hole whose mass is estimated to be 107.70±0.10 (40-63 million) M☉ based on stellar velocity dispersion. When observed in radiowaves, 3C 285 has two lobes with filamentary structures in them, and a jet is visible in the eastern lobe. A blue star forming region, named 3C 285/09.6, has been detected within the eastern radio lobe, and it has been suggested that the star formation was induced by the compression of a region of dense intergalactic gas by the radio jet. The gas mass of the region is estimated to be less than 6.2×108 M☉ based on CO imaging and so it is estimated to be depleted if star formation continues at the current rate in less than a billion years.
3C 20 is a radio galaxy located in the constellation Cassiopeia. It features a prominent double hotspot in its eastern lobe. An unusually low fraction of the flux lies within the radio core, which is suggested to be caused by a combination of factors, including jet orientation, synchrotron self-absorption and aging, as well as interactions with surrounding gas and dust.
3C 286, also known by its position as 1328+307 (B1950 coordinates) or 1331+305 (J2000 coordinates), is a quasar at redshift 0.8493 with a radial velocity of 164,137 km/s.It is part of the Third Cambridge Catalogue of Radio Sources (3C Survey). The 3C Survey was conducted at the relatively low radio frequencies of 159 and 178 MHz. The total power measurements were made with an instrument that produced a 4.6 degree by 13.6 arc minute fan-beam, and interferometric measurements were made with a synthesized beam width of about 7.5 arc minutes. Those beams were too broad to produce coordinates precise enough to allow the radio source to be matched with a corresponding faint optical counterpart. In 1962, 3C 286 was observed with the higher frequency two-element interferometer at Owens Valley Radio Observatory, which produced improved source coordinates with a precision of ~10 arc seconds. With the new coordinates, observations at the Palomar Observatory allowed the optical counterpart to be unambiguously identified: a magnitude 17.25 object with a star-like appearance. Because of this early identification of an optical counterpart, 3C 286 was one of the objects described in the paper where the term quaser was first used. 3C 286 is a Compact Steep Spectrum (CSS) source, which means that its size is less than 15 kiloparsecs (13.7 in the case of 3C 286), and the observed spectral flux density is proportional to να, where ν is the frequency and α ≤ -0.5 (in the case of 3C 286 α ≈ -0.61). CSS sources may be relatively young, with jets that are still expanding. While CSS sources represent a large fraction of the radio galaxies found in flux limited surveys, 3C 286 is one of only two CSS sources whose γ-rays were detected by Fermi-LAT. High resolution images made at 8.4 GHz with the Very Large Array show that 3C 286 has a jet about 2.6 arc seconds long extending west-south-west from the core, and a counter jet extending 0.8 arc seconds east from the core. Emission from the jet to the west-south-west is highly polarized, with E-vectors parallel to the jet axis. 3C 286 is one of four primary calibrators used by the Very Large Array (along with 3C 48, 3C 138, and 3C 147). Visibilities of all other sources are calibrated using observed visibilities of one of these four calibrators. It is an important calibrator for polarization measurements made by radio interferometers, because it has a relatively high degree of linear polarization (~10% at a wavelength of 20 cm, increasing to ~17% at 1.3 mm), and the angle of polarization does not change with time (although it is not independent of the wavelength observed).
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Madam C.J. Walker
