| Revision as of 23:06, 30 September 2010 editRothorpe (talk | contribs)Extended confirmed users, Pending changes reviewers104,418 editsNo edit summary← Previous edit | Revision as of 18:06, 27 October 2010 edit undoLightmouse (talk | contribs)Pending changes reviewers148,333 edits Mostly units using AWB (7290)Next edit → | ||
| Line 35: | Line 35: | ||
| | luminosity_bolometric = 5,800<ref name=m07 /> | | luminosity_bolometric = 5,800<ref name=m07 /> | ||
| | rotational_velocity = 375<ref name=m07 /> | | rotational_velocity = 375<ref name=m07 /> | ||
| | rotation = 12 |
| rotation = 12 h<ref group=note>From equatorial rotational velocity of 470 km/s and radius of 4.8 R<sub>☉</sub>.</ref><ref name=m07 /> | ||
| }} | }} | ||
| {{Starbox catalog | {{Starbox catalog | ||
| Line 61: | Line 61: | ||
| It is a ] ] approximately 240 ] from the ], with an ] which varies between 2.76<sup>m</sup> and 2.90<sup>m</sup>.<ref name=sb0 /><ref name=bsc1 /> | It is a ] ] approximately 240 ] from the ], with an ] which varies between 2.76<sup>m</sup> and 2.90<sup>m</sup>.<ref name=sb0 /><ref name=bsc1 /> | ||
| Like other Be stars, Alpha Arae rotates quickly, rapidly enough in fact to be surrounded by a equatorial disk of material ejected from the star.<ref>, ESO press release 35/06, September 20, 2006. Accessed on line December 12, 2008.</ref> In 2003 and 2005, Alpha Arae was observed by ] ], using the MIDI and AMBER instruments at the ]. The results, published in 2005 and 2007, appear to show that Alpha Arae has an equatorial rotational speed of about 470 |
Like other Be stars, Alpha Arae rotates quickly, rapidly enough in fact to be surrounded by a equatorial disk of material ejected from the star.<ref>, ESO press release 35/06, September 20, 2006. Accessed on line December 12, 2008.</ref> In 2003 and 2005, Alpha Arae was observed by ] ], using the MIDI and AMBER instruments at the ]. The results, published in 2005 and 2007, appear to show that Alpha Arae has an equatorial rotational speed of about 470 km/s, that it is surrounded by a dense equatorial disk of material in Keplerian (rather than uniform) rotation, and that it is losing mass by a polar ] with a terminal velocity of approximately 1,000 km/s. There is also some evidence that Alpha Arae is orbited by a companion at 0.7 AU.<ref name=m07>First direct detection of a Keplerian rotating disk around the Be star α Arae using AMBER/VLTI, A. Meilland et al., ''Astronomy and Astrophysics'' '''464''', #1 (March 2007), pp. 59–71, {{doi|10.1051/0004-6361:20064848}}, {{bibcode|2007A&A...464...59M}}. See Tables 1 and 4 for parameters of the star, circumstellar disk, and polar winds.</ref><ref>First VLTI/MIDI observations of a Be star: Alpha Arae, O. Chesneau et al., ''Astronomy and Astrophysics'' '''435''', #1 (May 2005), pp. 275–287, {{doi|10.1051/0004-6361:20041954}}, {{bibcode|2005A&A...435..275C}}.</ref> | ||
| {{-}} | {{-}} | ||
Revision as of 18:06, 27 October 2010
 α Arae in the constellation Ara. | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Ara |
| Right ascension | 17 31 50.4933 |
| Declination | −49° 52′ 34.121″ |
| Apparent magnitude (V) | 2.76 to 2.90 |
| Characteristics | |
| Spectral type | B3Ve |
| U−B color index | −0.69 |
| B−V color index | −0.17 |
| R−I color index | −0.24 |
| Variable type | BE |
| Astrometry | |
| Radial velocity (Rv) | 0 km/s |
| Proper motion (μ) | RA: −31.27 mas/yr Dec.: −67.15 mas/yr |
| Parallax (π) | 13.46 ± 0.95 mas |
| Distance | 240 ± 20 ly (74 ± 5 pc) |
| Absolute magnitude (MV) | −1.5 |
| Details | |
| Mass | 6.8 M☉ |
| Radius | 4.4 R☉ |
| Luminosity (bolometric) | 5,800 L☉ |
| Temperature | 19,000 K |
| Rotation | 12 h |
| Rotational velocity (v sin i) | 375 km/s |
| Other designations | |
| Choo, CD−49°11511, FK5 651, HD 158427, HIP 85792, HR 6510, NSV 8999, SAO 228069. | |
| Database references | |
| SIMBAD | data |
Alpha Arae (α Arae, α Ara) is the second brightest star in the constellation Ara.
With β and σ Ara it forms the Chinese asterism Choo （pinyin: chǔ, 杵）, "pestle" in traditional Chinese astronomy. It was the second star of Choo （杵二）, but R. H. Allen used the name Choo for this star only. Patrick Moore lists Choo as a proper name for this star in his star catalogue of the constellation Ara. This name is also spelt Tchou. There is another Choo in the constellation Pegasus.
It is a variable Be star approximately 240 light-years from the Earth, with an apparent visual magnitude which varies between 2.76 and 2.90.
Like other Be stars, Alpha Arae rotates quickly, rapidly enough in fact to be surrounded by a equatorial disk of material ejected from the star. In 2003 and 2005, Alpha Arae was observed by infrared interferometry, using the MIDI and AMBER instruments at the VLT Interferometer. The results, published in 2005 and 2007, appear to show that Alpha Arae has an equatorial rotational speed of about 470 km/s, that it is surrounded by a dense equatorial disk of material in Keplerian (rather than uniform) rotation, and that it is losing mass by a polar stellar wind with a terminal velocity of approximately 1,000 km/s. There is also some evidence that Alpha Arae is orbited by a companion at 0.7 AU.
Visual companion
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Ara |
| Right ascension | 17 31 51.3 |
| Declination | −49° 53′ 24″ |
| Apparent magnitude (V) | 11.0 |
| Characteristics | |
| Spectral type | K0V |
| Position (relative to A) | |
| Epoch of observation | 2000 |
| Angular distance | 49.7″ |
| Position angle | 168° |
| Other designations | |
| HJ 4955B, CD−49°11511B, CPD−49°10052B, HD 158427B, IDS 17241-4948 B, WDS 17318-4953B. | |
| Database references | |
| SIMBAD | data |
The Be star described above has a visual companion star, CCDM J17318-4953B, located approximately 50 arcseconds away, with an apparent visual magnitude of about 11. The two stars appear close to each other by coincidence and are not physically close in space.
Notes
- From apparent magnitude and parallax.
- From equatorial rotational velocity of 470 km/s and radius of 4.8 R☉.
References
- ^ V* alf Ara -- Eruptive variable Star, database entry, SIMBAD. Accessed on line November 26, 2008.
- ^ HR 6510, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line November 26, 2008.
- ^ First direct detection of a Keplerian rotating disk around the Be star α Arae using AMBER/VLTI, A. Meilland et al., Astronomy and Astrophysics 464, #1 (March 2007), pp. 59–71, doi:10.1051/0004-6361:20064848, Bibcode:2007A&A...464...59M. See Tables 1 and 4 for parameters of the star, circumstellar disk, and polar winds.
- alf Ara, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line November 26, 2008.
- ^ Entry 17318-4953, The Washington Double Star Catalog, United States Naval Observatory. Accessed on line November 26, 2008.
- ^ Allen, R. H., (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 63. ISBN 0486210790.
{{cite book}}: CS1 maint: extra punctuation (link) CS1 maint: multiple names: authors list (link) - Moore, P., (1983). The Guinness Book of Astronomy Facts and Feats (Second ed.). Middlesex: Guinness Superlatives Ltd. p. 187. ISBN 0851122944.
{{cite book}}: Check|isbn=value: checksum (help)CS1 maint: extra punctuation (link) CS1 maint: multiple names: authors list (link) - To Be or Not to Be: Is It All About Spinning?: VLTI Discerns How Matter Behaves in Disc Around a Be Star, ESO press release 35/06, September 20, 2006. Accessed on line December 12, 2008.
- First VLTI/MIDI observations of a Be star: Alpha Arae, O. Chesneau et al., Astronomy and Astrophysics 435, #1 (May 2005), pp. 275–287, doi:10.1051/0004-6361:20041954, Bibcode:2005A&A...435..275C.
- ^ CD-49 11511B -- Star in double system, database entry, SIMBAD. Accessed on line November 26, 2008.
See also
External links
- HR 6510, entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50.
- Image of Alpha Arae from Aladin.