Alpha Ceti
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Template:Location mark Location of α Ceti (circled) | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cetus |
| Right ascension | Template:RA[1] |
| Declination | Template:DEC[1] |
| Apparent magnitude (V) | 2.53[2] |
| Characteristics | |
| Evolutionary stage | AGB[3] |
| Spectral type | M1.5 IIIa[4] |
| U−B Template:Engvar | +1.93[2] |
| B−V Template:Engvar | +1.64[2] |
| Astrometry | |
| Radial velocity (Rv) | Script error: No such module "val".[5] km/s |
| Proper motion (μ) | RA: Script error: No such module "val".[1] mas/yr Dec.: Script error: No such module "val".[1] mas/yr |
| Parallax (π) | 13.09±0.44 mas[1] |
| Distance | Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc) |
| Absolute bolometric magnitude (Mbol) | Script error: No such module "val".[4] |
| Details | |
| Mass | Script error: No such module "val".;[6] 1.465–1.933[7] Template:Solar mass |
| Radius | Script error: No such module "val".[7] Template:Solar radius |
| Luminosity | Script error: No such module "val".[7] Template:Solar luminosity |
| Surface gravity (log g) | Script error: No such module "val".[7] cgs |
| Temperature | Script error: No such module "val".[7] K |
| Metallicity [Fe/H] | Script error: No such module "val".[7] dex |
| Rotational velocity (v sin i) | 6.9[8] km/s |
| Metallicity [Fe/H] | {{{metal_fe2}}} dex |
| Other designations | |
| Menkar, 92 Ceti, HR 911, BD+03°419, HD 18884, SAO 110920, FK5 107, HIP 14135 | |
| Database references | |
| SIMBAD | data |
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Alpha Ceti (α Ceti, abbreviated Alpha Cet, α Cet), officially named Menkar Template:IPAc-en,[9][10] is the second-brightest star in the constellation of Cetus. It is a cool luminous red giant estimated to be about 250 light years away based on parallax.
Nomenclature
Alpha Ceti is the star's Bayer designation. It has the traditional name Menkar, deriving from the Arabic word منخر manħar "nostril" (of Cetus). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[11] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[12] included a table of the first two batches of names approved by the WGSN; which included Menkar for this star.
This star, along with γ Cet (Kaffaljidhma), δ Cet, λ Cet (also Menkar), μ Cet, ξ1 Cet and ξ2 Cet were Al Kaff al Jidhmah, "the Part of a Hand".[13]
In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Circular Celestial Granary, refers to an asterism consisting of α Ceti, κ1 Ceti, λ Ceti, μ Ceti, ξ1 Ceti, ξ2 Ceti, ν Ceti, γ Ceti, δ Ceti, 75 Ceti, 70 Ceti, 63 Ceti and 66 Ceti. Consequently, the Chinese name for α Ceti itself is Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx.)[14]
Characteristics
Despite having the Bayer designation α Ceti, at visual magnitude 2.54 this star is actually not the brightest star in the constellation Cetus. That honor goes instead to Beta Ceti at magnitude 2.04. Menkar is a red giant with a stellar classification of M1.5 IIIa.[4] It has more than twice the mass of the Sun[6] and, as a giant star, has expanded to about 100 times the Sun's radius.[7] The large area of the photosphere means that it is emitting about 1,765 times as much energy as the Sun, even though the effective temperature is only Script error: No such module "val". (compared to Script error: No such module "val". on the Sun).[7] The relatively low temperature gives Menkar the red hue of an M-type star.[17]
Menkar has evolved from the main sequence after exhausting the hydrogen at its core. It has also exhausted its core helium, becoming an asymptotic giant branch star,[3] and will probably become a highly unstable star like Mira before finally shedding its outer layers and forming a planetary nebula, leaving a relatively large white dwarf remnant.[18] It has been observed to periodically vary in brightness, but only with an amplitude of about one hundredth of a magnitude.[16]
Namesakes
Menkar (AK-123) was a United States Navy Crater class cargo ship named after the star.
References
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- ↑ a b c d e f g h Script error: No such module "Citation/CS1". Menkar's database entry at VizieR.
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- ↑ Star Name - R.H. Allen p.160
- ↑ Template:In lang AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日 Template:Webarchive
- ↑ Script error: No such module "citation/CS1".
- ↑ a b Script error: No such module "citation/CS1".
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