definition of Wikipedia
Epoch J2000.0 Equinox J2000.0
|Right ascension||16h 21m 11.31571s|
|Declination||–25° 35′ 34.0515″|
|Apparent magnitude (V)||+2.88|
|Spectral type||B1 III + B1 V|
|U−B color index||–0.70|
|B−V color index||+0.13|
|Radial velocity (Rv)||–0.4 km/s|
|Proper motion (μ)||RA: –10.60 mas/yr
Dec.: –16.28 mas/yr
|Absolute magnitude (MV)||–4.12 ± 0.34 / −3.32 ± 0.34|
|Primary||σ Sco A|
|Companion||σ Sco B|
|Period (P)||33.010 ± 0.002 days|
|Semimajor axis (a)||3.62 ± 0.06 mas|
|Eccentricity (e)||0.3220 ± 0.0012|
|Inclination (i)||158.2 ± 2.3°|
|Longitude of the node (Ω)||104 ± 5°|
|Periastron epoch (T)||34889.0 ± 1.0 MJD|
|Argument of periastron (ω)
|283 ± 5°|
|σ Sco A|
|Mass||18.4 ± 5.4 M☉|
|Radius||12.7 ± 1.8 R☉|
|Luminosity||(2.9 ± 0.8) × 104 L☉|
|Surface gravity (log g)||3.85|
|Temperature||26,150 ± 1,070 K|
|Metallicity [Fe/H]||–0.20 ± 0.20 dex|
|Rotational velocity (v sin i)||25 km/s|
|Age||8.0 ± 0.2 Myr|
|σ Sco B|
|Mass||11.9 ± 3.1 M☉|
|Luminosity||(1.6 ± 0.4) × 104 L☉|
Sigma Scorpii (σ Sco, σ Scorpii) is a star system in the constellation Scorpius. It has the traditional name Al Niyat, although this name is sometimes also applied to Tau Scorpii, or to the asterism formed by both Sigma and Tau. This system has a combined apparent visual magnitude of +2.88, making it one of the brighter members of the constellation, although greatly outshone by its neighbor Antares. Based upon parallax measurements made during the Hipparcos mission, the distance to Sigma Scorpii is roughly 696 light years (214 parsecs). North et al. (2007) computed a more accurate estimate of 568+75
−59 light years (174+23
The brightest component of the system is a double-lined spectroscopic binary, which means that the pair has not been resolved using a telescope. Instead, their orbit is determined by changes in their combined spectrum caused by the Doppler shift. This indicates that the pair complete an orbit every 33.01 days and have an orbital eccentricity of 0.32.
The primary component of the spectroscopic binary, σ Scorpii A, is an evolved giant star with a stellar classification of B1 III. It has around 18 times the mass of the Sun and 12 times the Sun's radius. This star is radiating about 29,000 times the luminosity of the Sun from its outer envelope at an effective temperature of 26,150 K. This is a variable star of the Beta Cephei type, causing the apparent magnitude to vary between +2.86 and +2.94 with multiple periods of 0.2468429, 0.239671, and 8.2 days. During each pulsation cycle, the temperature of the star varies by 4,000 ± 2,000 K.
The other member of the core pair, σ Scorpii B, is a main sequence star with a classification of B1 V. Orbiting this binary at a separation half an arcsecond, or at least 120 Astronomical Units (AU), four times the Sun–Neptune distance, is the magnitude +5.2 σ Scorpii C, which has an orbital period of over a hundred years. Even farther out at 20 arcseconds, or more than 4500 AU, is σ Scorpii D with a magnitude of +8.7. It is classified as a B9 dwarf.
The Sigma Scorpii system is a likely member of the Gould Belt with an 83% probability. In particular, it is a candidate member of the Upper Scorpius group of the Scorpius-Centaurus Association (Sco OB2) of stars that share a common motion through space. Hence, these stars probably formed in the same molecular cloud at about the same time. The Upper Scorpius group has an estimated age of 8–10 million years based upon their evolutionary tracks, which is a match for the age estimate of this star system.
Dictionary and translator for handheld
New : sensagent is now available on your handheld
A windows (pop-into) of information (full-content of Sensagent) triggered by double-clicking any word on your webpage. Give contextual explanation and translation from your sites !
With a SensagentBox, visitors to your site can access reliable information on over 5 million pages provided by Sensagent.com. Choose the design that fits your site.
Improve your site content
Add new content to your site from Sensagent by XML.
Crawl products or adds
Get XML access to reach the best products.
Index images and define metadata
Get XML access to fix the meaning of your metadata.
Please, email us to describe your idea.
Lettris is a curious tetris-clone game where all the bricks have the same square shape but different content. Each square carries a letter. To make squares disappear and save space for other squares you have to assemble English words (left, right, up, down) from the falling squares.
Boggle gives you 3 minutes to find as many words (3 letters or more) as you can in a grid of 16 letters. You can also try the grid of 16 letters. Letters must be adjacent and longer words score better. See if you can get into the grid Hall of Fame !
Change the target language to find translations.
Tips: browse the semantic fields (see From ideas to words) in two languages to learn more.