Eta Apodis
 Location of η Apodis (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Apus |
| Right ascension | 14h 18m 13.89774s[1] |
| Declination | −81° 00′ 27.9300″[1] |
| Apparent magnitude (V) | +4.89[2] |
| Characteristics | |
| Spectral type | A2MA7-F2[3] or A2(m) CrEu[4] |
| U−B color index | +0.11[5] |
| B−V color index | +0.25[5] |
| Astrometry | |
| Radial velocity (Rv) | −9.4[2] km/s |
| Proper motion (μ) | RA: −19.47[1] mas/yr Dec.: −64.51[1] mas/yr |
| Parallax (π) | 23.62 ± 0.18[1] mas |
| Distance | 138 ± 1 ly (42.3 ± 0.3 pc) |
| Details | |
| Mass | 1.77[6] M☉ |
| Radius | 2.13[6] R☉ |
| Luminosity | 15.5[6] L☉ |
| Temperature | 7,860 ± 20[6] K |
| Rotational velocity (v sin i) | 17.2 ± 0.3[7] km/s |
| Age | 250 ± 200[6] years |
| Other designations | |
Eta Apodis (η Aps, η Apodis) is a star in the southern circumpolar constellation Apus. Based upon parallax measurements from the Hipparcos mission, it is approximately 138 light-years (42 parsecs) from Earth.[1] With an apparent visual magnitude of +4.9,[2] it can be viewed with the naked eye from the southern hemisphere.
This star has about 1.77 times the mass of the Sun and 2.13 times the Sun's radius. It is radiating 15.5 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 7,860 K.[6] Eta Apodis is a young star with an age of about 250 million years.[6]
The stellar classification of Eta Apodis shows this to be an Am star, which means the spectrum shows chemically peculiarities. In particular, it is an A2-type star showing an excess of the elements chromium and europium. The spectrum displays magnetically-induced features indicating an estimated surface field strength of roughly 360 G.[4] Based upon observations with the Spitzer Space Telescope, this system is emitting an excess of 24 μm infrared radiation. This may be caused by a debris disk of dust orbiting at a distance of more than 31 astronomical units from the star.[6]
Naming
In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, 異雀 (Yì Què), meaning Exotic Bird, refers to an asterism consisting of η Apodis, ζ Apodis, ι Apodis, β Apodis, γ Apodis, δ1 Apodis, α Apodis and ε Apodis. Consequently, η Apodis itself is known as 異雀七 (Yì Què qī, English: the Seventh Star of Exotic Bird.)[9]
References
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- ↑ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 29 日
