Fr.: AG de la Carène
A → Luminous Blue Variable star in the constellation → Carina; also known as HD 94910. AG Carinae lies about 6 kpc (20,000 → light-years) away and is surrounded by a → nebula. It is also a → spectroscopic variable, with the variability on time-scale of years. During the epochs of minimum in the visual → light curve (mV ~ 8.1), the star is relatively hot and has a → WN11 spectral type, showing strong He I, H I, and N II → emission lines, weak He II 4686 Å emission, and Si IV 4088-4116 Å absorption. During the maximum epochs of the light curve (mV ~ 6.0), the star is cooler, and the spectrum is reminiscent of extreme A-type → hypergiants, with a strong emission of H I, Fe II, and T III lines. The transition between both phases is characterized by the appearance of peculiar features in the spectrum, such as absorption-line splitting, strong → electron-scattering wings in He I and Fe II lines, and apparent → inverse P Cygni profiles in He I lines. The presence of a massive → bipolar nebula around AG Car testifies to a recent (t< 104 years) phase of high → mass loss. The morphology and kinematics of the nebula suggest a → dynamical age of 8.5 × 103 years and a high mass of → ionized nebular material (~ 4.2 Msun), which is likely composed of → ejecta from the central star. The nebular abundances show evidence of moderate nitrogen → enrichment. Properties of the → circumstellar nebula, studied in the → mid-infrared and → far-infrared, reveal an incredibly high dust mass of ~ 0.25 Msun, → dust temperature between 76 and 99 K, and the presence of large → dust grains of ~ 1 μm, as deduced from far-→ infrared excess. Assuming a normal → gas-to-dust ratio of 100, the total nebular mass of AG Car could be as high as ~ 30 Msun which would be of the order of, or even higher than, the mass of the → Homunculus nebula around → Eta Carinae. At the time when the AG Car nebula was ejected, the → interstellar bubble around the central star likely contained a negligible amount of material compared to the total mass of the nebula, implying that most of the nebular mass was ejected by the central star (Groh et al., 2009, ApJ 698, 1698).
AG, as used in the → variable star designation system; → Carina.
Canopus (α Carinae)
Soheyl (#), Agast (#), Parak (#)
The brightest star in the → constellation → Carina and the second brightest star in the sky with a → visual magnitude -0.72. Also called α Carinae and HD45348. Canopus is not visible from latitudes above 37 degrees north. It is an evolved star, a → supergiant of type F0 II (Smiljanic et al., 2006, A&A 449, 655). Canopus lies 310 → light-years (96 → parsecs) from the Solar System; this is based on its → Hipparcos → parallax measurement of 10.43 mas (5% accuracy). From this distance a → luminosity 13,300 times that the → solar luminosity is derived, and a radius of 73 times solar, in agreement with the → angular size (6.95 ± 0.15 mas) measured using → interferometry (Cruzalèbes et al., 2013, arXiv:1306.3288). These observations also yield an → effective temperature of about 7400 K. The star's mass is estimated to be about 8 Msun. Canopus possesses an extremely hot magnetically heated → corona. Canopus's corona is some 10 times hotter than the → solar corona and produces both observable → X-rays and → radio emission. According to calculations by J. Tomkin (1998, Sky & Telescope 95, 59), using → Hipparcos data, Canopus has, in the past, been the brightest star during three periods: from 3,700,000 to 1,370,000 years ago, from 950,000 to 420,000 years ago, and from 160,000 to 90,000 years ago. It will, once more, become the brightest star in 480,000 years and will remain such for 510,000 years.
Canopus, from Gk. kanobos, perhaps from Coptic language Kahi Nub "golden earth."
Soheyl, from Ar. Suhail.
afzal, šâh-taxté (#)
The Keel. A major → constellation in the southern sky, home to → Canopus (α Carinae), the second brightest star after → Sirius. Approximate position: RA 9h, Dec. -60° The constellation resulted from the division of a very large constellation representing → Argo Navis, the mythological Jason's ship. The partition into the constellations → Carina, → Puppis, → Vela, and → Pyxis appeared first on a sky map by Nicholas Louis de Lacaille (1763). Carina represents the bottom of the Ship Argo. Abbreviation: Car; genitive form: Carinae.
L. carina "the keel of a ship, i.e. the principal structural member of a ship, running lengthwise along the center line from bow to stern, to which the frames are attached."
Afzal "keel" in the jargon of the Caspian sea fishermen of Gilan province. Šâh-taxté "main plank."
Fr.: bras de Carène
A → spiral arm in the Milky Way galaxy seen at its best in the → constellation → Carina, but also crossing the constellations → Vela, → Crux, and → Centaurus. It may be a continuation of the → Sagittarius arm; the combined feature is called Sagittarius-Carina arm.
Fr.: Nébuleuse de la Carène
One of the most prominent → massive star formation regions of the → Milky Way, also known as NGC 3372. It is associated with a giant → H II region of the same name, which spans about 4 square degrees on the sky and is split by a remarkable V-shaped → dust lane. The Carina Nebula harbors several → star clusters, mainly → Trumpler 14, → Trumpler 16, and Collinder 228, including more than 60 known → O-type stars in addition to the extreme → LBV star → Eta Carinae. This gas and dust complex is associated with a → giant molecular cloud extending over about 130 pc. Large cavities within the molecular cloud are supposed to be carved out by the massive star clusters. There are also several → Herbig-Haro objects and → bipolar outflows.
Fr.: Eta de la Carène
The most luminous and the most extensively studied of → Luminous Blue Variables. Known also as HD 93308, it lies in the → Trumpler 16→ star cluster of the → Carina Nebula and is about 7,500 to 8,000 → light-years away. η Carina probably began its life as a → very massive star with an initial mass of about 150 → solar masses, and has a current estimated mass of about 90-100 solar masses. The difference has been lost in sudden giant eruptions in the past few thousand years. The so-called → Homunculus Nebula results from the mass ejection by η Carinae during its giant outburst around 1843 when it reached a magnitude of -1 and became the second brightest star in the southern sky. About 1880 it reached magnitude 7 and has remained at this level, although with fluctuations. The 1843 event ejected at least 12 solar masses of gas moving at speeds of up to 650 km s-1 with a kinetic energy of almost 1050 erg. The double-lobed remnant has a mass of about 2.5 solar masses. It is divided by a → torus of cold dust (110 K), about 5 → light-years in radius and 15 solar masses, which was ejected in an earlier event some 1000 years ago. There is strong evidence that η Carinae is a → binary system with a period of about 5.5 years and a projected separation less than 30 → astronomical units (about 0.013 arcsec). A colliding-wind binary is suggested by the → hard X-ray spectrum. The main component has an estimated → mass loss rate of 10-3 solar masses per year.
Eta (η), Gk. letter of alphabet; the → Carina constellation.