{{Short description|Star in the constellation Boötes}} {{Starbox begin}} {{Starbox image | image = {{Location mark | image=Boötes IAU.svg | alt= | float=center | width=200 | label= | position=right | mark=Red circle.svg | mark_width=10 | mark_link=β Boötis | x%=39.8 | y%=31.9 }} | caption = A [[star chart]] showing the position of β Boötis (circled) }} {{Starbox observe | epoch = J2000 | equinox = J2000 | ra = {{RA|15|01|56.7623}}<ref name="DR3"/> | dec = {{DEC|+40|23|26.047}}<ref name="DR3"/> | appmag_v = 3.488<ref name=apjss52_7/> | constell = [[Boötes]] }} {{Starbox character | type = [[Yellow giant]] | class = G8IIIa Fe-0.5<ref name=perkins/> | b-v = +0.94<ref name=apjss52_7/> | u-b = +0.75<ref name=apjss52_7/> | variable = [[Flare star]]<ref name=mnras365_3_1050/> }} {{Starbox astrometry | radial_v = −18.35{{±|0.21}}<ref name=aj135_1_209/> | prop_mo_ra = −40.708 | prop_mo_dec = −30.168 | pm_footnote = <ref name="DR3"/> | parallax = 13.878 | p_error = 0.131 | parallax_footnote = <ref name="DR3"/> | absmag_v = −0.70<ref name=pasj60_4_781/> }} {{Starbox detail | mass = {{val|3.23|0.07}}<ref name=jofre2015/> | radius = {{val|18.44|0.19}}<ref name=Baines2018/> | luminosity = {{val|188|10}}<ref name=Baines2018/> | temperature = 4,997<ref name=Gray2019/> | metal_fe = –0.086<ref name=Gray2019/> | gravity = {{val|2.45|0.03}}<ref name=jofre2015/> | rotational_velocity = {{Val|4.1|1.0}}<ref name=mnras365_3_1050/> | rotation = {{val|200|10}}<ref name=mnras365_3_1050/> days | age_myr = {{val|320|20}}<ref name=jofre2015/> }} {{Starbox catalog | names = {{odlist | name=Nakkar | name2=Nekkar | name3=Merez | name4=Meres | name5=Merets | B=Beta Boo, β Boo | F=42 Boötis | BD=+40°2840 | FK5=555 | HD=133208 | HIP=73555 | HR=5602 | SAO=45337 | GC=20226 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = bet+Boo }} {{Starbox end}}
'''Beta Boötis''' is a [[star]] in the northern [[constellation]] of [[Boötes]]. Its name is a [[Bayer designation]] that is [[Romanization of Greek|Latinized]] from '''β Boötis''', and abbreviated Beta Boo or β Boo. The star has the official name '''Nekkar''', pronounced {{IPAc-en|'|n|ɛ|k|ɑr}}, which is derived from an [[Arabic]] name for 'the Herdsman'.<ref name="IAU-LSN"/> It has an [[apparent visual magnitude]] of 3.5,<ref name=apjss52_7/> making it visible to the [[naked eye]] and one of the brighter members of the constellation. In the modern constellation, it marks the head of Boötes the herdsman.<ref name=allen1899/> Based upon [[stellar parallax|parallax]] measurements obtained by the [[Gaia (spacecraft)|Gaia]] spacecraft, this star is approximately {{Convert|235|ly|pc|abbr=off|lk=on}} from the Sun.<ref name="DR3"/> It is drawing closer to the Sun with a [[radial velocity]] of −18 km/s.<ref name=aj135_1_209/> The magnitude of the star is reduced by 0.06 from [[Extinction (astronomy)|extinction]] caused by intervening gas and dust.<ref name=pasj60_4_781/>
==Nomenclature== ''β Boötis'' ([[Latinisation of names|Latinised]] to ''Beta Boötis'') is the star's [[Bayer designation]].
It bore the traditional name ''Nekkar'' or ''Nakkar'' derived from the [[Arabic]] name for the constellation: ''Al Baḳḳār'' 'the Herdsman'.<ref name=allen1899/> In 2016, the [[International Astronomical Union]] organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN"/> to catalogue and standardize proper names for stars. The WGSN approved the name ''Nekkar'' for this star on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.<ref name="IAU-LSN"/>
==Properties== This star had its [[angular diameter]] measured using [[interferometry|interferometric]] observations by the [[Navy Precision Optical Interferometer]]. The angular diameter, together with the star's distance, yield a radius 18 times the [[radius of the Sun]].<ref name=Baines2018/> Beta Boötis is 3.2 times more massive than the Sun. At the estimated age of {{nowrap|320 million years}},<ref name=jofre2015/> it has [[stellar evolution|evolved]] into a [[giant star]] with a [[stellar classification]] of G8 IIIa Fe-0.5. In this notation, the ''a'' indicating a slightly higher luminosity class than a typical giant and the ''Fe-05'' indicating slightly weak spectral lines of iron.<ref name=perkins/> The star is radiating around 188<ref name=Baines2018/> times as much luminosity [[solar luminosity|as the Sun]] from its [[stellar atmosphere|outer envelope]] at an [[effective temperature]] of 5,000 K.<ref name=Gray2019/> This heat gives it the yellow-hued glow of a [[G-type star]]. It has an estimated rotation period of about 200 days and the pole is inclined {{nowrap|28° ± 6°}} to the [[plane of the sky]].<ref name=mnras365_3_1050/>
In 1993, the [[ROSAT]] satellite was used to observe an X-ray flare on Beta Boötis, which released an estimated {{nowrap|1.7 × 10<sup>32</sup> [[erg]]}}. This was the first such observation for a low-activity star of this type. The flare may be explained by an as yet unobserved [[Red dwarf|M-type dwarf]] companion star.<ref name=aaa296_509/> Beta Boötis is a mild [[barium star]], which is evidence for a [[white dwarf]] companion.<ref name=Böhm-Vitense_et_al_2000/>
==References== <references> <ref name="DR3">{{cite DR3|1296713990316692096}}</ref>
<ref name=perkins>{{cite journal |bibcode=1989ApJS...71..245K |title=The Perkins Catalog of Revised MK Types for the Cooler Stars |last1=Keenan |first1=Philip C. |last2=McNeil |first2=Raymond C. |journal=The Astrophysical Journal Supplement Series |date=1989 |volume=71 |page=245 |doi=10.1086/191373 }}</ref>
<ref name=jofre2015>{{Cite journal | display-authors=1 |last=Jofré |first=E. |last2=Petrucci |first2=R. |last3=Saffe |first3=C. |last4=Saker |first4=L. |last5=Artur de la Villarmois |first5=E. |last6=Chavero |first6=C. |last7=Gómez |first7=M. |last8=Mauas |first8=P. J. D. |date=2015-02-01 |title=Stellar parameters and chemical abundances of 223 evolved stars with and without planets |journal=Astronomy and Astrophysics |volume=574 |page=A50 |bibcode= 2015A&A...574A..50J |doi=10.1051/0004-6361/201424474 |arxiv= 1410.6422 |s2cid=53666931 |issn=0004-6361}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/A%2BA/574/A50&Name=HD%20133208 Beta Boötis' database entry] at [[VizieR]].</ref>
<ref name="aj135_1_209">{{cite journal | display-authors=1 | last1=Massarotti | first1=Alessandro | last2=Latham | first2=David W. | last3=Stefanik | first3=Robert P. | last4=Fogel | first4=Jeffrey | title=Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity | journal=The Astronomical Journal | volume=135 | issue=1 | pages=209–231 |date=January 2008 | doi=10.1088/0004-6256/135/1/209 | bibcode=2008AJ....135..209M | doi-access=free}}</ref>
<ref name=Gray2019>{{Cite journal |last1=Gray |first1=David F. |last2=Kaur |first2=Taranpreet |date=2019-09-01 |title=A Recipe for Finding Stellar Radii, Temperatures, Surface Gravities, Metallicities, and Masses Using Spectral Lines |journal=The Astrophysical Journal |volume=882 |issue=2 |pages=148 |doi=10.3847/1538-4357/ab2fce |doi-access=free |bibcode=2019ApJ...882..148G |issn=0004-637X}}</ref>
<ref name="Baines2018">{{cite journal | title=Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer | last1=Baines | first1=Ellyn K. | last2=Armstrong | first2=J. Thomas | last3=Schmitt | first3=Henrique R. | last4=Zavala | first4=R. T. | last5=Benson | first5=James A. | last6=Hutter | first6=Donald J. | last7=Tycner | first7=Christopher | last8=Belle | first8=Gerard T. van | display-authors=1 | journal=The Astronomical Journal | volume=155 | at=30 | year=2018 | issue=1 | arxiv=1712.08109 | bibcode=2018AJ....155...30B | doi=10.3847/1538-3881/aa9d8b | s2cid=119427037 | doi-access=free}}.</ref>
<ref name="SIMBAD">{{cite simbad | title=bet Boo | access-date=2011-11-28 }}</ref>
<ref name="apjss52_7">{{cite journal | last1=Fernie | first1=J. D. | title=New UBVRI photometry for 900 supergiants | journal=Astrophysical Journal Supplement Series | volume=52 | pages=7–22 |date=May 1983 | doi=10.1086/190856 | bibcode=1983ApJS...52....7F | doi-access=free}}</ref>
<ref name="aaa296_509">{{cite journal| last1=Huensch | first1=M. | last2=Reimers | first2=D. | title=Detection of an X-ray flare on the low-activity G 8 III-type giant β Boo | journal=Astronomy and Astrophysics | volume=296 | pages=509–513 |date=April 1995 | bibcode=1995A&A...296..509H}}</ref>
<ref name="mnras365_3_1050">{{cite journal | display-authors=1 | last1=König | first1=B. | last2=Guenther | first2=E. W. | last3=Esposito | first3=M. | last4=Hatzes | first4=A. | title=Spectral synthesis analysis and radial velocity study of the northern F-, G- and K-type flare stars | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=365 | issue=3 | pages=1050–1056 |date=January 2006 | doi=10.1111/j.1365-2966.2005.09796.x | doi-access=free | bibcode=2006MNRAS.365.1050K |arxiv = astro-ph/0511232 | s2cid=16676999}}</ref>
<ref name="allen1899">{{cite book | first=Richard Hinckley | last=Allen | author-link=Richard Hinckley Allen | year=1899 | page=103 | title=Star-names and their meanings | publisher=G. E. Stechert | url=https://books.google.com/books?id=5xQuAAAAIAAJ&pg=RA103 | access-date=2011-11-28}}</ref>
<ref name="pasj60_4_781">{{cite journal | display-authors=1 | last1=Takeda | first1=Yoichi | last2=Sato | first2=Bun'ei | last3=Murata | first3=Daisuke | title=Stellar parameters and elemental abundances of late-G giants | journal=Publications of the Astronomical Society of Japan | volume=60 | issue=4 | pages=781–802 |date=August 2008 | bibcode=2008PASJ...60..781T |arxiv = 0805.2434 | doi=10.1093/pasj/60.4.781| s2cid=16258166}}</ref>
<ref name="WGSN">{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN) | publisher=[[International Astronomical Union]] | access-date=22 May 2016 | archive-date=10 June 2016 | archive-url=https://web.archive.org/web/20160610172014/https://www.iau.org/science/scientific_bodies/working_groups/280/ | url-status=dead }}</ref>
<ref name="IAU-LSN">{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars | publisher=IAU.org | access-date=7 March 2018 | archive-date=10 March 2025 | archive-url=https://web.archive.org/web/20250310063743/https://www.iau.org/public/themes/naming_stars/ | url-status=dead }}</ref>
<ref name=Böhm-Vitense_et_al_2000>{{cite journal | title=Do All BA II Stars Have White Dwarf Companions? | display-authors=1 | last1=Böhm-Vitense | first1=Erika | last2=Carpenter | first2=Kenneth | last3=Robinson | first3=Richard | last4=Ake | first4=Tom | last5=Brown | first5=Jeffery | journal=The Astrophysical Journal | volume=533 | issue=2 | pages=969–983 | date=April 2000 | doi=10.1086/308678 | bibcode=2000ApJ...533..969B }}</ref> </references>
==External links== * [http://aladin.u-strasbg.fr/AladinPreview?-c=15+01+56.7623%2B40+23+26.036&ident=NSV++6898&submit=Aladin+previewer Image Beta Boötis] * [https://web.archive.org/web/20080926185552/http://www.purplehell.com/riddletools/stars.htm The Constellations and Named Stars] * [http://stars.astro.illinois.edu/sow/nekkar.html Nekkar at University of Illinois]
{{Stars of Boötes}}
[[Category:G-type giants]] [[Category:Flare stars]] [[Category:Barium stars]] [[Category:Boötes]] [[Category:Bayer objects|Bootis, Beta]] [[Category:Bright Star Catalogue objects|5602]] [[Category:Durchmusterung objects|BD+40 2840]] [[Category:Flamsteed objects|Bootis, 42]] [[Category:Henry Draper Catalogue objects|133208]] [[Category:Hipparcos objects|073555]] [[Category:Stars with proper names|Nekkar]]