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In August 1908, a white mob attacked Springfield, Illinois’s Black community, destroying homes and businesses and lynching two Black men. National outrage over the violence helped spur the movement that created the NAACP the following year.
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
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Taurus |
| Right ascension | 04h 34m 55.42019s[2] |
| Declination | +24° 28′ 53.0336″[2] |
| Apparent magnitude (V) | 12.2 to 16.1[3] |
| Characteristics | |
| Spectral type | K7Ve[4] |
| Variable type | T Tauri-type?[4] |
| Astrometry | |
| Radial velocity (Rv) | 16.98±0.04[5] km/s |
| Proper motion (μ) | RA: +5.323 mas/yr[2] Dec.: −20.680 mas/yr[2] |
| Parallax (π) | 7.4255±0.0868 mas[2] |
| Distance | 439 ± 5 ly (135 ± 2 pc) |
| Details | |
| Mass | 0.76[6] M☉ |
| Radius | 1.81[6] R☉ |
| Luminosity | 0.8[6] L☉ |
| Temperature | 4,060[6] K |
| Rotational velocity (v sin i) | 12.8±1.1[5] km/s |
| Age | 2.4[6] Myr |
| Other designations | |
| AA Tau, GCRV 55202, GSC 01833-00851, IRAS F04318+2422, 2MASS J04345542+2428531, XEST 25-026, AN 196.1930, CSI+24-04319, MHA 259-17, 2E 0431.8+2422, UBV 4396, 2E 1098, XEST 25-OM-003[7] | |
| Database references | |
| SIMBAD | data |
AA Tauri is a young variable star in the equatorial constellation of Taurus, located in the Taurus-Auriga star-forming region. It is too faint to view with the naked eye, having an apparent visual magnitude that varies from 12.2 down to 16.1.[3] The star is located approximately 439 light-years (135 parsecs) away from the Sun based on parallax, and is drifting further away with a radial velocity of +17 km/s.[5]
The stellar classification for this object is K7Ve,[4] matching a K-type main-sequence star that displays emission features. It is an eruptive variable of the T Tauri type[3] with an estimated age of 2.4 million years. The object has 76% of the mass of the Sun, 181% of the Sun's radius,[6] and is spinning with a projected rotational velocity of 13 km/s.[5] AA Tauri is radiating 80% of the luminosity of the Sun at an effective temperature of 4,060 K.[6]
AA Tauri shows brightness variations of one to two magnitudes over an 8.2-day period. The brightness has been described as "roughly constant, interrupted by quasi-cyclic fading episodes".[9] The periodic variations are ascribed to eclipses of the star by a warped dust disk around it.[10]
In 2011, AA Tauri faded by about two magnitudes and has remained at the fainter level since then. The star also became significantly more reddened. The eight-day variations continue, with a maximum brightness now around magnitude 14 and magnitude 16.5 at its faintest. It is theorised that the root cause of this dimness is a warp in the accretion disk, located at a distance of 7.7 AU or more from the centre, that was brought into the line of sight by its elliptical motion around the central star.[8]
In their 2003 paper, Bouvier et al. invoked the possible presence of a substellar object to explain peculiar and periodic eclipses occurring to the young star every 8.3 days, though they considered it unlikely that such a companion could be responsible for said variability.[9] They inferred a mass of 20 times that of Jupiter for the perturbing object and an orbital separation of 0.08 Astronomical Units. Later studies found no evidence for a planet, instead finding multiple rings with accretion streams between them.[10]
Gaia astrometry shows evidence of a proper motion anomaly, suggesting the presence of a stellar companion.[1]
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
AA Tauri is a young variable star in the equatorial constellation of Taurus, located in the Taurus-Auriga star-forming region. It is too faint to view with the naked eye, having an apparent visual magnitude that varies from 12.2 down to 16.1. The star is located approximately 439 light-years (135 parsecs) away from the Sun based on parallax, and is drifting further away with a radial velocity of +17 km/s. The stellar classification for this object is K7Ve, matching a K-type main-sequence star that displays emission features. It is an eruptive variable of the T Tauri type with an estimated age of 2.4 million years. The object has 76% of the mass of the Sun, 181% of the Sun's radius, and is spinning with a projected rotational velocity of 13 km/s. AA Tauri is radiating 80% of the luminosity of the Sun at an effective temperature of 4,060 K.
Theta Tauri (θ Tauri, abbreviated Theta Tau, θ Tau) is a wide double star in the constellation of Taurus and a member of the Hyades open cluster. θ Tauri is composed of two 3rd magnitude stars, designated Theta1 Tauri (Theta Tauri B) and Theta2 Tauri (Theta Tauri A). Theta² is brighter, hence the pair are sometimes referred to as Theta Tauri B and A, respectively. They are separated by 5.62 arcminutes (0.094°) on the sky. Based upon parallax measurements, Theta¹ Tauri is located at a distance of 152 ly (47 pc), while Theta² Tauri is at a distance of 157 light-years (48 parsecs). θ Tauri A and B are both spectroscopic binaries; the four components are designated Theta Tauri Aa (formally named Chamukuy ), Ab, Ba, and Bb.
Xi Tauri (ξ Tau, ξ Tauri) is a hierarchical quadruple system in the constellation Taurus. Xi Tauri is a spectroscopic and eclipsing quadruple star. It consists of three blue-white B-type main sequence stars and an F-type main sequence star. Two of the stars form an eclipsing binary system and revolve around each other once every 7.15 days. These in turn orbit the third star once every 145 days. The fourth star is a F star that orbits the other three stars in a roughly fifty-year period and has been resolved optically. The best-fit orbital fit would require it to be a binary system itself, with a semi-major axis of 0.020 au. The brightest and most massive of the four stars is the "third" star, although the eclipsing pair have a greater combined mass and hence are generally considered to be the primary. The typical combined apparent magnitude of the system is +3.73, but because the two inner stars eclipse one another during their orbits, it is classified as a variable star, and its brightness varies from magnitude +3.73 to +3.81. Xi Tauri is approximately 210 light years from Earth. Nomenclature for the four stars varies. Some sources refer to the faint resolved companion as component C, while others refer to it as B. Similarly, the inner three stars are respectively Aa, Ab, and B, or Aa, Ab, and Ac.
Tau Tauri, also named Gaja, is a quadruple star system in the constellation Taurus. It is visible to the naked eye as a faint point of light with a combined apparent visual magnitude of 4.33. The distance to this system is approximately about 400 light years based on parallax. The system is moving further from the Earth with a heliocentric radial velocity of +14.6 km/s, and it is a member of the Taurion OB association, located between Orion and Taurus. It is located 0.7 degree north of the ecliptic, and thus is subject to lunar occultations. The blue-white hued primary, component Aa, is a B-type main-sequence star with a stellar classification of B3V. It was found to be a close spectroscopic binary in 1903 by American astronomers Edwin B. Frost and Walter S. Adams. The pair have an orbital period of 2.96 days and eccentricity of 0.05. A second companion, white-hued component Ab, has magnitude 6.97 and angular separation 0.2" from the primary in a 58-year orbit. This is a probably A-type main-sequence star with a class of A0V–A2V. The more distant component B is a type A1V star with magnitude 7.2 and separation 62.8".
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 →Joe Louis.
