Astronomy:Delta2 Lyrae
  | |
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Lyra |
| Right ascension | 18h 54m 30.28269s[1] |
| Declination | +36° 53′ 55.0317″[1] |
| Apparent magnitude (V) | 4.22 – 4.33[2] |
| Characteristics | |
| Evolutionary stage | AGB[3] |
| Spectral type | M4 II[2] |
| U−B color index | +1.65 |
| B−V color index | +1.68 |
| Variable type | SRc?[2] |
| Astrometry | |
| Radial velocity (Rv) | −25.55 km/s |
| Proper motion (μ) | RA: −6.598[1] mas/yr Dec.: 1.953[1] mas/yr |
| Parallax (π) | 4.2352 ± 0.2951[1] mas |
| Distance | 770+68 −42 ly (237+21 −13 pc) |
| Absolute magnitude (MV) | −3.3[4] |
| Details | |
| Mass | 4.5±1[5] M☉ |
| Radius | 293+19 −22[6] R☉ |
| Luminosity | 10,248±1,500[6] L☉ |
| Surface gravity (log g) | 0[7] cgs |
| Temperature | 3,394±32[6] K |
| Age | 75[8][lower-alpha 1] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Delta2 Lyrae (δ2 Lyr), also named Jiantai,[9] is a 4th magnitude star in the constellation Lyra, approximately 770 light years away from Earth. It is visible to the naked eye. It is one of the M4II spectral standard stars.[10]
Nomenclature
Delta2 Lyrae (Latinized from δ2 Lyrae, abbreviated δ2 Lyr) is the star's Bayer designation. In Chinese astronomy, this star is part of the asterism Jiàn Tái (Clepsydra Terrace, 渐台), which represents timekeeping with water clocks. The IAU Working Group on Star Names adopted the name Jiantai for this star on 18 June 2026, after this Chinese constellation.[9]
Characteristics
It began life as a hot blue main sequence star, but now is a large cool asymptotic giant branch star with a degenerate carbon-oxygen core. It is a semi-regular variable star that has its brightness change by 0.2 magnitudes over an ill-defined period.[8] Delta2 Lyrae was a 5.0 M☉ star when still in the main sequence, but due to stellar mass loss it has lost 0.5 solar masses.[5] The star's photosphere has expanded to 290 times the size of the Sun, and is now radiating 10,200 times the luminosity of the Sun. It has cooled to 3,394 K (3,121 °C),[6] giving Delta2 Lyrae a reddish hue typical of M-type stars.[11]
It is the brightest member of the scattered open cluster Stephenson 1, also known as the δ Lyrae Cluster. Other known members include δ1 Lyrae, a handful of 8th-9th magnitudes stars, and at least thirty other stars down to 14th magnitude.[12][4]
Variability
δ2 Lyrae is a variable star, probably a semiregular variable. It has a magnitude range of 4.22 to 4.33.[2]
Companion stars
Delta2 Lyrae was once thought to form a visual binary with the star Delta1 Lyrae, but it does not, only appearing to do so if seen from Earth's direction.[8]
Notes
- ↑ For a mass of 6 solar masses.
References
- ↑ 1.0 1.1 1.2 1.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 2.0 2.1 2.2 2.3 Samus, N. N. et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S 1. Bibcode: 2009yCat....102025S.
- ↑ Ragland, S.; Traub, W. A.; Berger, J. -P.; Danchi, W. C.; Monnier, J. D.; Willson, L. A.; Carleton, N. P.; Lacasse, M. G. et al. (2006). "First Surface-resolved Results with the Infrared Optical Telescope Array Imaging Interferometer: Detection of Asymmetries in Asymptotic Giant Branch Stars". The Astrophysical Journal 652 (1): 650. doi:10.1086/507453. Bibcode: 2006ApJ...652..650R.
- ↑ 4.0 4.1 Eggen, O. J. (April 1968). "Photometric evidence for the existence of a delta Lyrae cluster". Astrophysical Journal 152: 77. doi:10.1086/149525. Bibcode: 1968ApJ...152...77E.
- ↑ 5.0 5.1 Halabi, Ghina M.; Eid, Mounib El (2015). "Exploring masses and CNO surface abundances of red giant stars". Monthly Notices of the Royal Astronomical Society 451 (3): 2957. doi:10.1093/mnras/stv1141. Bibcode: 2015MNRAS.451.2957H.
- ↑ 6.0 6.1 6.2 6.3 Baines, Ellyn K.; Thomas Armstrong, J.; Clark, James H.; Gorney, Jim; Hutter, Donald J.; Jorgensen, Anders M.; Kyte, Casey; Mozurkewich, David et al. (2021). "Angular Diameters and Fundamental Parameters of Forty-four Stars from the Navy Precision Optical Interferometer". The Astronomical Journal 162 (5): 198. doi:10.3847/1538-3881/ac2431. Bibcode: 2021AJ....162..198B.
- ↑ Levesque, E. M.; Massey, P.; Olsen, K. A. G.; Plez, B.; Josselin, E.; Maeder, A.; Meynet, G. (2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not as Cool as We Thought". The Astrophysical Journal 628 (2): 973–985. doi:10.1086/430901. Bibcode: 2005ApJ...628..973L.
- ↑ 8.0 8.1 8.2 Kaler, Jim. "DELTA-2 LYR (Delta-2 Lyrae).". http://stars.astro.illinois.edu/sow/delta2lyr.html.
- ↑ 9.0 9.1 9.2 "IAU Catalog of Star Names". https://exopla.net/star-names/modern-iau-star-names/.
- ↑ Garcia, B. (1989). "A list of MK standard stars". Bulletin d'Information du Centre de Données Stellaires 36: 27. Bibcode: 1989BICDS..36...27G.
- ↑ "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html.
- ↑ Stephenson, C. B. (1959). "A Possible New Galactic Cluster Involving δ Lyrae". Publications of the Astronomical Society of the Pacific 71 (419): 145. doi:10.1086/127349. Bibcode: 1959PASP...71..145S.
- ↑ "/ftp/cats/more/HIP/cdroms/cats". Strasbourg astronomical Data Center. https://cdsarc.cds.unistra.fr/viz-bin/ftp-index?/ftp/cats/more/HIP/cdroms/cats.
Cite error: <ref> tag with name "b-j" defined in <references> is not used in prior text.
<ref> tag with name "wds" defined in <references> is not used in prior text.
 |  |
