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In 1968 Shirley Chisholm became the first Black woman elected to the United States Congress. In 1972 she launched a campaign for the Democratic presidential nomination, breaking another political barrier.
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
 Possible architecture for Y Sextantis' multiple system | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Sextans |
| Right ascension | 10h 02m 47.96897s[1] |
| Declination | +01° 05′ 40.1839″ |
| Apparent magnitude (V) | 9.88[2] (10.08 + 12.70)[3] |
| Characteristics | |
| Spectral type | F3/5V[4] or F5/6V[5] |
| B−V color index | 0.479±0.072[2] |
| Variable type | W UMa[6] |
| Astrometry | |
| Radial velocity (Rv) | +13.12±7.76[1] km/s |
| Proper motion (μ) | RA: +0.282[1] mas/yr Dec.: +5.112[1] mas/yr |
| Parallax (π) | 2.5554±0.2972 mas[1] |
| Distance | approx. 1,300 ly (approx. 390 pc) |
| Details[3] | |
| A | |
| Mass | 1.476±0.045 M☉ |
| Radius | 1.586±0.018 R☉ |
| Luminosity | 3.802±0.253 L☉ |
| Temperature | 6,650±163[5] K |
| B | |
| Mass | 0.288±0.033 M☉ |
| Radius | 0.750±0.008 R☉ |
| Luminosity | 0.759±0.059 L☉ |
| Temperature | 6,294±15 K |
| Other designations | |
| Y Sex, BD+01°2394, HD 87079, HIP 49217, WDS J10028+0106[7] | |
| Database references | |
| SIMBAD | data |
Y Sextantis, abbreviated as Y Sex, is a variable star system in the equatorial constellation of Sextans. The system is invisible to the naked eye with a mean apparent visual magnitude of 9.88.[2] It is located roughly at 1,300 light years from the Sun based on parallax.[1]
The variability of this system was first announced by C. Hoffmeister in 1934.[3] It was determined to be a short period, strongly-interacting eclipsing binary system.[9][10] Observations of the light variations up until 1979 were used by G. Hill to generate orbital properties, providing an orbital inclination of 76.8°±0.3°.[11]
This is a multiple star system. The two main components have apparent magnitudes of 10.08 and 12.70, and are separated by 0.50 arcseconds.[3] The brighter component is a W Ursae Majoris variable eclipsing contact binary star system,[6] whose two component stars share a common outer layer. Because the two components share their outer layers as the components of W Ursae Majoris do, they have the same stellar classification, and are classified as yellow F-type main sequence dwarfs. The components take 0.419822800 days (roughly 10 hours) to revolve around common barycentre. Orbital period variations would suggest the presence of additional perturbing objects, one of them likely substellar.
Orbital period variations suggest the presence of one more perturbing unseen object.[6] The authors He & Qian have estimated two possible orbital periods and minimum masses for unseen companions: the former cyclic oscillation would occur every 51.22 years (with amplitude of 0.0218 days) being caused by a low-mass stellar companion (likely a M dwarf star), whereas the latter would consist in a 32.1 years period and the unseen object could likely be substellar.
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
Y Sextantis, abbreviated as Y Sex, is a variable star system in the equatorial constellation of Sextans. The system is invisible to the naked eye with a mean apparent visual magnitude of 9.88. It is located roughly at 1,300 light years from the Sun based on parallax. The variability of this system was first announced by C. Hoffmeister in 1934. It was determined to be a short period, strongly-interacting eclipsing binary system. Observations of the light variations up until 1979 were used by G. Hill to generate orbital properties, providing an orbital inclination of 76.8°±0.3°. This is a multiple star system. The two main components have apparent magnitudes of 10.08 and 12.70, and are separated by 0.50 arcseconds. The brighter component is a W Ursae Majoris variable eclipsing contact binary star system, whose two component stars share a common outer layer. Because the two components share their outer layers as the components of W Ursae Majoris do, they have the same stellar classification, and are classified as yellow F-type main sequence dwarfs. The components take 0.419822800 days (roughly 10 hours) to revolve around common barycentre. Orbital period variations would suggest the presence of additional perturbing objects, one of them likely substellar.
Alpha Sextantis (α Sex, α Sextantis) is the brightest star in the equatorial constellation of Sextans. It is visible to the naked eye on a dark night with an apparent visual magnitude of 4.49. The distance to this star, as determined from parallax measurements, is around 280 light years. This is considered an informal "equator star", as it lies less than a quarter of a degree south of the celestial equator. In 1900, it was 7 minutes of arc north of the equator. As a result of Earth's axial precession, it crossed over to the southern hemisphere in December 1923. The variability of Alpha Sextantis was discovered by Aven Magded Hamadamen and included in the International Variable Star Index. The star undergoes pulsations with a period of 9.1 hours. This is an evolved A-type giant star with a stellar classification of A0 III. It has around 2.5 times the mass of the Sun and three times the Sun's radius. The abundance of elements is similar to that in the Sun, but with a large uncertainty. It radiates 90 times the solar luminosity from its outer atmosphere at an effective temperature of 9,984 K. Alpha Sextantis is nearing the end of its life as a main-sequence star; it is around 385 million years old with a projected rotational velocity of 21 km/s.
Gamma Sextantis, Latinized as γ Sextantis, is a binary star system in the equatorial constellation of Sextans. The combined apparent visual magnitude of the system is 5.05, which means it is faintly visible to the naked eye. The annual parallax shift is 11.75 mas, indicating a distance of around 280 light years. The two components orbit each other with a period of 77.6 years and a high eccentricity of 0.741. The orbital plane is inclined by 143.2° to the line of sight from the Earth. With a visual magnitude of 5.6, the brighter component Gamma Sextantis A is an A-type main sequence star with a stellar classification of A1 V. The fainter companion Gamma Sextantis B has a classification of A4 V with a magnitude of 6.0. Their combined spectrum matches a classification of A0/1 V. Their angular separation 0.4 arcseconds, so observation with a telescope requires a diameter of at least 30 centimeters. There is a magnitude 12.28 companion star Gamma Sextantis C at an angular separation of 36.9 arc seconds along a position angle of 333°, as of 2000. This separation has increased from 30.0 arc seconds in 1834. The proper motion of this star differs from the Gamma Sextantis AB system, having proper motions of −29 mas/yr and +5 mas/yr in right ascension and declination, respectively.
Beta Sextantis, Latinized from β Sextantis, is a variable star in the equatorial constellation of Sextans. With an apparent visual magnitude of 5.07, it is faintly visible to the naked eye on a dark night. According to the Bortle scale, it can be viewed from brighter lit suburban skies. The distance to this star, based upon an annual parallax shift of 8.89 mas, is around 367 light years. This star served as a primary standard in the MK spectral classification system with a stellar classification of B6 V, indicating that it is a B-type main sequence star. However, Houk and Swift (1999) list a classification of B5 IV/V, suggesting it may be transitioning into a subgiant star. Stellar evolution models support this is a main sequence star. It has served as a uvby photometric standard, but is also categorized as an Alpha2 Canum Venaticorum variable with a suspected period of 15.4 days. This lengthy a period conflicts with a relatively high projected rotational velocity of 85 km/s, leaving the explanation for the variance unresolved.
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 →Brown v. Board of Education in 1954.
