| 词条 | FG Sagittae |
| 释义 |
epoch=J2000.0 (ICRS) | constell=Sagitta | ra={{RA|20|11|56.05947}}| dec={{DEC|+20|20|04.3672}}| appmag_v=9.45[3]}}{{Starbox astrometry | parallax = 0.7630 | p_error = 0.2302 | parallax_footnote = [4] }}{{Starbox character | class=B4Ieq-K2Ib[5]| b-v=+1.21[3]| u-b=+0.75[3]| }}{{Starbox catalog | }}{{Starbox reference | Simbad = FG+Sagittae }}{{Starbox end}} FG Sagittae, is a supergiant star in the constellation Sagitta at a distance of 8000 light-years. When first noted in 1943, it was identified to be a variable star, and its spectrum was registered as of B4Ieq ("blue") in 1955. Since then it has expanded and reddened to G ("yellow") in 1991,[8] and then further to about K ("orange"). FG started to pulsate when becoming an A-type star (soon after being registered as B4Ieq) with a period of 15 days, now the period has increased to over 100 days. FG Sagittae is the central star of the planetary nebula Henize 1-5. Since 1992 the star has exhibited fadings and recoveries similar to that of a R Coronae Borealis variable star; this behavior is emphasized by a hydrogen deficiency typical for this class of stars.[9] It has been proposed that this star has undergone a "late thermal pulse" (LTP) of helium fusion after having left the asymptotic giant branch (AGB) to move towards the hottest end of the "white dwarf cooling track". This thermal pulse is believed to have revived this aged star to once again, for a short time, behave as an AGB star.[9] See also
References1. ^1 2 3 {{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|author1=Ducati|first1=J. R.|year=2002}} [1][2][3][4][5]2. ^1 {{cite journal|bibcode= 2011ARep...55...31S|title= Search for and study of hot circumstellar dust envelopes|journal= Astronomy Reports|volume= 55|pages= 31|author1= Shenavrin|first1= V. I.|last2= Taranova|first2= O. G.|last3= Nadzhip|first3= A. E.|year= 2011|doi= 10.1134/S1063772911010070}} 3. ^1 {{cite web|url=https://www.newscientist.com/article/mg13117862-100/ |publisher=Newscientist |title=Life and times of a chameleon star |accessdate=2017-09-27}} 4. ^1 2 {{cite journal|bibcode=2003ApJ...583..913L|title=Sakurai's Object, V605 Aquilae, and FG Sagittae: An Evolutionary Sequence Revealed|journal=The Astrophysical Journal|volume=583|issue=2|pages=913|author1=Lawlor|first1=T. M|last2=MacDonald|first2=J|year=2003|doi=10.1086/345411}} 5. ^1 {{cite DR2|1828750899461025536}} }} External links
6 : Variable stars|Sagitta (constellation)|Objects with variable star designations|Supergiants|Hipparcos objects|2MASS objects |
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