{{short description|Stellar classification}} {{see also|Stellar classification#Class}} {{Infobox astronomical formation| |image=Star-Vega.png |caption=Vega, the second-brightest star in the northern celestial hemisphere, is an A-type main-sequence star (field of view approx. 1°). |thing=Class of moderate-large main-sequence star |commonscat=White main-sequence stars |qid=Q471805 |Mass=1.63–2.33 ''M''<sub>☉</sub> |temp=7,400–9,700 K |luminosity=8–38 ''L''<sub>☉</sub> |head=|name=}} An '''A-type main-sequence star'''{{efn|also called an "A-type dwarf" or "white main-sequence star" to distinguish it from a white dwarf.}} is a main-sequence (core hydrogen burning) star of spectral type A. The spectral luminosity class is {{rn|V}}.<ref>{{Cite web |date=2020–2026 |title=Glossary term: Luminosity Class |url=https://astro4edu.org/resources/glossary/term/503/ |access-date=2026-01-15 |website=IAU Office of Astronomy for Education (OAE) – astro4edu.org}}</ref><ref>{{Cite web |date=2020–2026 |title=Glossary term: Dwarf Star |url=https://astro4edu.org/resources/glossary/term/88/ |access-date=2026-01-15 |website=IAU Office of Astrononomy for Education (OAE) – astro4edu.org}}</ref> These stars have spectra defined by strong hydrogen Balmer absorption lines.<ref>{{cite web |url=http://hyperphysics.phy-astr.gsu.edu/hbase/starlog/staspe.html |title=Stellar Spectral Types |website=hyperphysics.phy-astr.gsu.edu |access-date=June 19, 2007 }}</ref> They usually measure between 1.7 and 2.1 solar masses ({{solar mass}}), have surface temperatures between 7,600 and {{val|fmt=commas|10,000|ul=K}}, and live for about a quarter of the lifetime of the Sun. Bright and nearby examples are Altair (A7), Sirius A (A1) and Vega (A0). A-type stars do not have convective zones and thus are not expected to harbor magnetic dynamos. As a consequence, because they do not have strong stellar winds; they lack a means to generate X-ray emission.
==Spectral standard stars== thumb|left|The Morgan-Keenan spectral classification
{| class="wikitable floatright" style="text-align:center; font-size:smaller;" |+ Properties of typical A-type main-sequence stars<ref>{{cite journal |last1=Pecaut |first1=Mark J. |last2=Mamajek |first2=Eric E. |title=Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-main-sequence Stars |journal=The Astrophysical Journal Supplement Series |date=1 September 2013 |volume=208 |issue=1 |pages=9 |doi=10.1088/0067-0049/208/1/9 |issn=0067-0049|arxiv=1307.2657 |bibcode=2013ApJS..208....9P |s2cid=119308564 }}</ref><ref>{{cite web |last1=Mamajek |first1=Eric |title=A Modern Mean Dwarf Stellar Color and Effective Temperature Sequence |url=https://www.pas.rochester.edu/~emamajek/EEM_dwarf_UBVIJHK_colors_Teff.txt |publisher=University of Rochester, Department of Physics and Astronomy |access-date=5 July 2021 |date=2 March 2021}}</ref><ref>{{cite book | first1 = Dale A. |last1=Ostlie | first2 = Bradley W. |last2=Carroll | date = 2007 | title = An Introduction to Modern Stellar Astrophysics | publisher = Pearson Addison-Wesley | pages = | isbn = 978-0-8053-0348-3 | url = https://books.google.com/books?id=BNpFAQAAIAAJ}}</ref><ref>{{cite journal|bibcode=1981A&AS...46..193H|title=Empirical bolometric corrections for the main-sequence|journal=Astronomy and Astrophysics Supplement Series|volume=46|pages=193|last1=Habets|first1=G. M. H. J.|last2=Heintze|first2=J. R. W.|year=1981}}Tables VII, VIII</ref><ref name=Schroeder2007>{{cite journal | title=X-ray emission from A-type stars | last1=Schröder | first1=C. | last2=Schmitt | first2=J. H. M. M. | journal=Astronomy and Astrophysics | volume=475 | issue=2 | pages=677–684 | date=November 2007 | doi=10.1051/0004-6361:20077429 | bibcode=2007A&A...475..677S | doi-access=free }}</ref> |- !Spectral<br/>type !Mass ({{Solar mass|link=y}}) !Radius ({{Solar radius|link=y}}) !Luminosity ({{Solar luminosity|link=y}}) !Effective<br/>temperature<br/>(K) !Color<br/>index<br/>{{nowrap|(B − V)}} |- | A0V | 2.33 | 2.193 | 38.37 | style="background-color:#{{Color temperature|9700|hexval}}"|9,700 | 0.00 |- | A1V | 2.17 | 2.136 | 30.76 | style="background-color:#{{Color temperature|9300|hexval}}"|9,300 | 0.04 |- | A2V | 2.06 | 2.117 | 24.21 | style="background-color:#{{Color temperature|8840|hexval}}"|8,840 | 0.07 |- | A3V | 1.92 | 1.861 | 17.06 | style="background-color:#{{Color temperature|8600|hexval}}"|8,600 | 0.10 |- | A4V | 1.88 | 1.794 | 13.43 | style="background-color:#{{Color temperature|8250|hexval}}"|8,250 | 0.14 |- | A5V | 1.86 | 1.785 | 12.36 | style="background-color:#{{Color temperature|8100|hexval}}"|8,100 | 0.16 |- | A6V | 1.83 | 1.775 | 11.12 | style="background-color:#{{Color temperature|7910|hexval}}"|7,910 | 0.19 |- | A7V | 1.76 | 1.750 | 10.00 | style="background-color:#{{Color temperature|7760|hexval}}"|7,760 | 0.21 |- | A8V | 1.67 | 1.747 | 9.12 | style="background-color:#{{Color temperature|7590|hexval}}"|7,590 | 0.25 |- | A9V | 1.63 | 1.747 | 8.24 | style="background-color:#{{Color temperature|7400|hexval}}"|7,400 | 0.27 |} The revised Yerkes Atlas system<ref>{{cite journal |bibcode=1953ApJ...117..313J |title=Fundamental stellar photometry for standards of spectral type on the Revised System of the Yerkes Spectral Atlas |last1=Johnson |first1=H. L. |last2=Morgan |first2=W. W. |journal=The Astrophysical Journal |year=1953 |volume=117 |page=313 |doi=10.1086/145697 }}</ref> listed a dense grid of A-type dwarf spectral standard stars, but not all of these have survived to this day as standards. The "anchor points" and "dagger standards" of the MK spectral classification system among the A-type main-sequence dwarf stars, i.e. those standard stars that have remained unchanged over years and can be considered to define the system, are Vega (A0 V), Phecda (A0 V) and Fomalhaut (A3 V).<ref name="Garrison">{{cite web |url=http://www.astro.utoronto.ca/~garrison/mkstds.html |title=MK Anchor Points |first=Robert F. |last=Garrison |access-date=2022-01-05 |archive-date=2019-06-25 |archive-url=https://web.archive.org/web/20190625094716/http://www.astro.utoronto.ca/~garrison/mkstds.html |url-status=dead }}</ref><ref name="MK73">{{cite journal |bibcode=1973ARA&A..11...29M |title=Spectral Classification |last1=Morgan |first1=W. W. |last2=Keenan |first2=P. C. |journal=Annual Review of Astronomy and Astrophysics |year=1973 |volume=11 |page=29 |doi=10.1146/annurev.aa.11.090173.000333 }}</ref> The seminal review of MK classification by Morgan & Keenan (1973)<ref name="MK73"/> did not provide any dagger standards between types A3 V and F2 V. HD 23886 was suggested as an A5 V standard in 1978.<ref name="MK78">{{cite book |bibcode=1978rmsa.book.....M |year=1978 |title=Revised MK Spectral Atlas for stars earlier than the sun |last1=Morgan |first1=W. W. |last2=Abt |first2=Helmut A. |last3=Tapscott |first3=J. W. }}</ref>
Richard Gray & Robert Garrison provided the most recent contributions to the A dwarf spectral sequence in a pair of papers in 1987<ref name="GrayGarrison87">{{cite journal| bibcode=1987ApJS...65..581G | title=The Early A-Type Stars: Refined MK Classification, Confrontation with Stroemgren Photometry, and the Effects of Rotation | last1=Gray | first1=R. O. | last2=Garrison | first2=R. F. | journal=The Astrophysical Journal Supplement Series | year=1987 | volume=65 | page=581 | doi=10.1086/191237 | doi-access=free }}</ref> and 1989.<ref name=GrayGarrison89>{{cite journal |bibcode=1989ApJS...70..623G |title=The Late A-Type Stars: Refined MK Classification, Confrontation with Stroemgren Photometry, and the Effects of Rotation |last1=Gray |first1=R. O. |last2=Garrison |first2=R. F. |journal=The Astrophysical Journal Supplement Series |year=1989 |volume=70 |page=623 |doi=10.1086/191349 |doi-access=free }}</ref> They list an assortment of fast- and slow-rotating A-type dwarf spectral standards, including HD 45320 (A1 V), HD 88955 (A2 V), 2 Hydri (A7 V), 21 Leonis Minoris (A7 V) and 44 Ceti (A9 V). Besides the MK standards provided in Morgan's papers and the Gray & Garrison papers, one also occasionally sees Zosma (A4 V) listed as a standard. There are no published A6 V and A8 V standard stars.
== Planets == A-type stars are young (typically few hundred million years old) and many emit infrared (IR) radiation beyond what would be expected from the star alone. This IR excess is attributable to dust emission from a debris disk where planets form.<ref name=apj124_1_514>{{cite journal | last1=Song | first1=Inseok | last2=Weinberger | first2=A. J. | last3=Becklin | first3=E. E. | last4=Zuckerman | first4=B. | last5=Chen | first5=C. | title=M-Type Vega-like Stars | journal=The Astronomical Journal | date=2002 | volume=124 | issue=1 | pages=514–518 | doi=10.1086/341164 | bibcode=2002AJ....124..514S | arxiv=astro-ph/0204255 | s2cid=3450920 }}</ref> Surveys indicate massive planets commonly form around A-type stars although these planets are difficult to detect using the Doppler spectroscopy method. This is because A-type stars typically rotate very quickly, which makes it difficult to measure the small Doppler shifts induced by orbiting planets since the spectral lines are very broad.<ref name="atype">{{cite journal |arxiv=0704.2455 |doi=10.1086/519677 |title=Retired a Stars and Their Companions: Exoplanets Orbiting Three Intermediate-Mass Subgiants |year=2007 |last1=Johnson |first1=John Asher |last2=Fischer |first2=Debra A. |last3=Marcy |first3=Geoffrey W. |last4=Wright |first4=Jason T. |last5=Driscoll |first5=Peter |last6=Butler |first6=R. Paul |last7=Hekker |first7=Saskia |last8=Reffert |first8=Sabine |last9=Vogt |first9=Steven S. |journal=The Astrophysical Journal |volume=665 |issue=1 |pages=785–793 |bibcode=2007ApJ...665..785J |s2cid=15076579 }}</ref> However, this type of massive star eventually evolves into a cooler red giant which rotates more slowly and thus can be measured using the radial velocity method.<ref name="atype"/>
As of early 2011 about 30 Jupiter-class planets have been found around evolved K-giant stars including Pollux, Gamma Cephei and Iota Draconis. Doppler surveys around a wide variety of stars indicate about one in six stars having twice the mass of the Sun are orbited by one or more Jupiter-sized planets, compared to about one in sixteen for Sun-like stars.<ref name="JAJohnson"> {{Cite journal |last=Johnson |first=J. A. |date=2011 |title=The Stars that Host Planets |journal=Sky & Telescope |volume=121 |issue=April|pages=22–27 |bibcode=2011S&T...121d..22J }}</ref> A-type star systems known to feature planets include HD 15082, Beta Pictoris and HR 8799.<ref name=":0">{{Cite web |title=NASA Exoplanet Archive |url=https://exoplanetarchive.ipac.caltech.edu/ |access-date=2025-11-20 |website=exoplanetarchive.ipac.caltech.edu}}</ref>
Examples of A-type main-sequence stars with circumstellar disc and exoplanets:
{| class="wikitable sortable “wikitable”" ! Name ! Spectral<br/>type ! Mass<br/>(''M<sub>☉</sub>'') ! Radius<br/>(''R<sub>☉</sub>'') ! Disk extent<br/>(AU) ! Exoplanets |- | Vega | {{StarA|A0V<ref name=Gray2003/>}} | 2.15<ref name=monnier2012/> | 2.73<ref name=monnier2012/> | 170<ref name=apj628_1_487>{{cite journal | display-authors=3 | last1=Su | first1=K. Y. L. | last2=Rieke | first2=G. H. | last3=Misselt | first3=K. A. | last4=Stansberry | first4=J. A. | last5=Moro-Martin | first5=A. | last6=Stapelfeldt | first6=K. R. | last7=Werner | first7=M. W. | last8=Trilling | first8=D. E. | last9=Bendo | first9=G. J. | title=The Vega Debris Disk: A Surprise from ''Spitzer'' | journal=The Astrophysical Journal | date=2005 | volume=628 | issue=1 | pages=487–500 | doi=10.1086/430819 | bibcode=2005ApJ...628..487S|arxiv = astro-ph/0504086 | s2cid=18898968 }}</ref> / 815<ref name=Su2024>{{cite journal | last1 = Su | first1 = Kate Y. L. |first2=Andras |last2=Gaspar |first3=George H. |last3=Rieke |first4=Renu |last4=Malhotra |first5=Luca |last5=Matra |first6=Schuyler Grace |last6=Wolff |first7=Jarron M. |last7=Leisenring |first8=Charles |last8=Beichman |first9=Marie |last9=Ygouf | date = 31 Oct 2024 | title = Imaging of the Vega Debris System using JWST/MIRI | journal = The Astrophysical Journal | volume = 977 | issue = 2 | page = 277 | doi = 10.3847/1538-4357/ad8cde | doi-access = free | arxiv = 2410.23636 | bibcode = 2024ApJ...977..277S}}</ref> | Vega b (candidate)<ref name="Hurt2021">{{cite journal |last1=Hurt |first1=Spencer A. |last2=Quinn |first2=Samuel N. |last3=Latham |first3=David W. |last4=Vanderburg |first4=Andrew |last5=Esquerdo |first5=Gilbert A. |last6=Calkins |first6=Michael L. |last7=Berlind |first7=Perry |last8=Angus |first8=Ruth |last9=Latham |first9=Christian A. |last10=Zhou |first10=George |title=A Decade of Radial-velocity Monitoring of Vega and New Limits on the Presence of Planets |journal=The Astronomical Journal |date=21 January 2021 |volume=161 |issue=4 |page=157 |doi=10.3847/1538-3881/abdec8 |arxiv=2101.08801 |bibcode=2021AJ....161..157H |s2cid=231693198 |doi-access=free }}</ref> |- | Fomalhaut | {{StarA|A3V<ref name=Gray2006/>}} | 1.92<ref name=age_mam/> | 1.84<ref name=age_mam/> | 209<ref name="Kalas2013">{{cite journal|title=STIS Coronagraphic Imaging of Fomalhaut: Main Belt Structure and the Orbit of Fomalhaut b|author1=Kalas, Paul |author2=Graham, James R. |author3=Fitzgerald, Michael P. |author4=Clampin, Mark |date=2013|journal=The Astrophysical Journal|volume=775|issue=1|article-number=56|doi=10.1088/0004-637X/775/1/56|bibcode=2013ApJ...775...56K|arxiv=1305.2222|s2cid=62877509 }}</ref> | Fomalhaut b (controversial<ref>{{Cite web |title=Planet Fomalhaut b – Exoplanet.eu – Encyclopaedia of exoplanetary systems |url=https://exoplanet.eu/catalog/fomalhaut_b--291/ |access-date=2025-12-16|website=exoplanet.eu}}</ref>),<ref name="Kalas2008">{{cite journal | last = Kalas | first = Paul | author-link = Paul Kalas |display-authors=etal | title = Optical Images of an Exosolar Planet 25 Light-Years from Earth | journal = Science | volume = 322 | issue = 5906 | pages = 1345–8 | date = 2008-11-13 | arxiv = 0811.1994 | doi = 10.1126/science.1166609 | pmid = 19008414 |bibcode = 2008Sci...322.1345K | s2cid = 10054103 }}</ref> unnamed candidate<ref name="Ygouf2023">{{cite journal |last1=Ygouf |first1=Marie |last2=Beichman |first2=Charles |display-authors=etal |title=Searching for Planets Orbiting Fomalhaut with JWST/NIRCam |journal=The Astronomical Journal |date=October 2023 |volume=167 |issue=1 |page=26 |doi=10.3847/1538-3881/ad08c8 |doi-access=free |arxiv=2310.15028 |bibcode=2024AJ....167...26Y }}</ref> |- | HR 8799 | {{StarA|A5V<ref>{{Cite journal |last1=Gray |first1=Richard O. |last2=Kaye |first2=Anthony B. |date=December 1999 |title=HR 8799: A Link between γ Doradus Variables and λ Bootis Stars |url=https://iopscience.iop.org/article/10.1086/301134 |journal=The Astronomical Journal |volume=118 |issue=6 |pages=2993–2996 |bibcode=1999AJ....118.2993G |doi=10.1086/301134}}</ref>}} | 1.43<ref>{{Cite journal |last1=Sepulveda |first1=Aldo G. |last2=Bowler |first2=Brendan P. |date=2022-02-01 |title=Dynamical Mass of the Exoplanet Host Star HR 8799 |journal=The Astronomical Journal |volume=163 |issue=2 |pages=52 |arxiv=2111.12090 |bibcode=2022AJ....163...52S |doi=10.3847/1538-3881/ac3bb5 |doi-access=free |issn=0004-6256}}</ref> | 1.44<ref>{{Cite journal |last1=Baines |first1=Ellyn K. |last2=White |first2=Russel J. |last3=Huber |first3=Daniel |last4=Jones |first4=Jeremy |last5=Boyajian |first5=Tabetha |last6=McAlister |first6=Harold A. |last7=ten Brummelaar |first7=Theo A. |last8=Turner |first8=Nils H. |last9=Sturmann |first9=Judit |last10=Sturmann |first10=Laszlo |last11=Goldfinger |first11=P. J. |last12=Farrington |first12=Christopher D. |last13=Riedel |first13=Adric R. |last14=Ireland |first14=Michael |last15=von Braun |first15=Kaspar |date=2012-12-10 |title=The Chara Array Angular Diameter of Hr 8799 Favors Planetary Masses for ITS Imaged Companions |url=https://iopscience.iop.org/article/10.1088/0004-637X/761/1/57 |journal=The Astrophysical Journal |volume=761 |issue=1 |pages=57 |arxiv=1210.0556 |bibcode=2012ApJ...761...57B |doi=10.1088/0004-637X/761/1/57 |issn=0004-637X}}</ref> | 360<ref name=Faramaz-Marino-etal-2021> {{cite journal |last1=Faramaz |first1=Virginie |last2=Marino |first2=Sebastian |last3=Booth |first3=Mark |last4=Matrà |first4=Luca |last5=Mamajek |first5=Eric E. |last6=Bryden |first6=Geoffrey |last7=Stapelfeldt |first7=Karl R. |last8=Casassus |first8=Simon |last9=Cuadra |first9=Jorge |last10=Hales |first10=Antonio S. |last11=Zurlo |first11=Alice |display-authors=6 |year=2021 |title=A Detailed Characterization of HR 8799's Debris Disk with ALMA in Band 7 |journal=The Astronomical Journal |volume=161 |issue=6 |page=271 |doi=10.3847/1538-3881/abf4e0 |arxiv=2104.02088 |bibcode=2021AJ....161..271F |s2cid=233033512 |doi-access=free }} </ref> | HR 8799 b, HR 8799 c, HR 8799 d,<ref name=Marois-etal-2008> {{cite journal |first1=Christian |last1=Marois |first2=Bruce |last2=Macintosh |first3=Travis |last3=Barman |first4=B. |last4=Zuckerman |first5=Inseok |last5=Song |first6=Jennifer |last6=Patience |first7=David |last7=Lafrenière |first8=René |last8=Doyon |date=November 2008 |title=Direct imaging of multiple planets orbiting the star HR 8799 |journal=Science |volume=322 |issue=5906 |pages=1348–1352 |doi=10.1126/science.1166585 |arxiv=0811.2606 |pmid=19008415 |bibcode=2008Sci...322.1348M |s2cid=206516630 }} </ref> HR 8799 e,<ref name=Marois-etal-2011> {{cite journal |first1=Christian |last1=Marois |first2=B. |last2=Zuckerman |first3=Quinn M. |last3=Konopacky |first4=Bruce |last4=Macintosh |first5=Travis |last5=Barman |date=December 2010 |title=Images of a fourth planet orbiting HR 8799 |journal=Nature |volume=468 |issue=7327 |pages=1080–1083 |doi=10.1038/nature09684 |bibcode=2010Natur.468.1080M |arxiv=1011.4918 |pmid=21150902 |s2cid=4425891 }} </ref> HR 8799 f (candidate)<ref name="Thompson2023">{{cite journal |bibcode=2023AJ....165...29T |title=Deep Orbital Search for Additional Planets in the HR 8799 System |last1=Thompson |first1=William |last2=Marois |first2=Christian |last3=Do ó |first3=Clarissa R. |last4=Konopacky |first4=Quinn |last5=Ruffio |first5=Jean-Baptiste |last6=Wang |first6=Jason |last7=Skemer |first7=Andy J. |last8=De Rosa |first8=Robert J. |last9=MacIntosh |first9=Bruce |journal=The Astronomical Journal |date=2023 |volume=165 |issue=1 |page=29 |doi=10.3847/1538-3881/aca1af |doi-access=free |arxiv=2210.14213 }}</ref> |- | Beta Pictoris | {{StarA|A6V<ref name=Gray2006/>}} | 1.75<ref name="Crifo1997">{{cite journal|bibcode=1997A&A...320L..29C|title=β Pictoris revisited by Hipparcos. Star properties|author=Crifo, F.|year=1997|journal=Astronomy and Astrophysics|volume=320|pages=L29–L32|display-authors=etal}}</ref> | 1.73<ref name="Kervella2003">{{cite conference|title=VINCI/VLTI Observations of Main Sequence Stars|author=Kervella, P.|year=2003|editor1=A.K. Dupree |editor2=A.O. Benz |publisher=Astronomical Society of the Pacific|conference=IAUS 219: Stars as Suns: Activity, Evolution and Planets|book-title=Proceedings of the 219th symposium of the International Astronomical Union|location=Sydney, Australia|pages=80|bibcode = 2003IAUS..219E.127K}}</ref> | 1835<ref name="Larwood2001">{{cite journal|bibcode=2001MNRAS.323..402L|title=Close stellar encounters with planetesimal discs: the dynamics of asymmetry in the β Pictoris system|author1=Larwood, J. D. |author2=Kalas, P. G. |name-list-style=amp|journal=MNRAS|volume=323|issue=2|pages=402–416|year=2001|doi=10.1046/j.1365-8711.2001.04212.x|doi-access=free |arxiv = astro-ph/0011279 |s2cid=1844824}}</ref> | Beta Pictoris b,<ref name="LagrangeGratadour2009">{{cite journal |last1=Lagrange |first1=A.-M. |last2=Gratadour |first2=D. |last3=Chauvin |first3=G. |last4=Fusco |first4=T. |last5=Ehrenreich |first5=D. |last6=Mouillet |first6=D. |last7=Rousset |first7=G. |last8=Rouan |first8=D. |last9=Allard |first9=F. |last10=Gendron |first10=É. |last11=Charton |first11=J. |last12=Mugnier |first12=L. |last13=Rabou |first13=P. |last14=Montri |first14=J. |last15=Lacombe |first15=F. |title=A probable giant planet imaged in the β Pictoris disk |journal=Astronomy and Astrophysics |volume=493 |issue=2 |year=2009 |pages=L21–L25 |issn=0004-6361 |doi=10.1051/0004-6361:200811325|arxiv = 0811.3583 |bibcode = 2009A&A...493L..21L |s2cid=16548235 }}</ref> Beta Pictoris c<ref name="Lagrange2019">{{cite journal|title=Evidence for an additional planet in the β Pictoris system|last1=Lagrange|first2=Nadège|last2=Meunier|first3=Pascal|last3=Rubini|first4=Miriam|last4=Keppler|first5=Franck|last5=Galland|first6=eric|last6=Chapellier |year=2019|doi=10.1038/s41550-019-0857-1|journal=Nature|volume = 3|issue = 12|pages = 1135–1142|bibcode = 2019NatAs...3.1135L|s2cid = 202126059 |url=https://hal.science/hal-02327499 }}</ref> |}
== Examples == Within 40 light-years: {| class="wikitable" ! Name ! Spectral<br/>type ! Constellation ! vis Mag ! Mass<br/>(''M<sub>☉</sub>'') ! Radius<br/>(''R<sub>☉</sub>'') ! Luminosity<br/>(''L<sub>☉</sub>'') ! Distance<br/>(ly) |- | Sirius | A0mA1 Va<ref name=Gray2003>{{cite journal |first1=R.O. |last1=Gray |first2=C.J. |last2=Corbally |first3=R.F. |last3=Garrison |first4=M.T. |last4=McFadden |first5=P.E. |last5=Robinson |year=2003 |title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of stars earlier than M0 within 40 parsecs: The Northern Sample. I. |journal=Astronomical Journal |volume=126 |issue=4 |pages=2048–2059 |doi=10.1086/378365 |arxiv = astro-ph/0308182 |bibcode=2003AJ....126.2048G |s2cid=119417105}}</ref> | Canis Major | −1.46<ref name="Hoffleit1991">{{cite book | chapter-url=https://vizier.u-strasbg.fr/viz-bin/VizieR-S?HR%202491 | chapter=Entry for HR 2491 | title=Bright Star Catalogue|edition= 5th Revised Ed. (Preliminary Version) |last1=Hoffleit|first1=D. | last2=Warren|first2= W. H. Jr. | date=1991 | publisher=CDS | url=https://vizier.u-strasbg.fr/viz-bin/Cat?V/50|bibcode= 1991bsc..book.....H}}</ref> | 2.063<ref name="bond">{{cite journal |last1=Bond |first1=Howard E. |last2=Schaefer |first2=Gail H. |last3=Gilliland |first3=Ronald L. |last4=Holberg |first4=Jay B. |last5=Mason |first5=Brian D. |last6=Lindenblad |first6=Irving W. |last7=Seitz-McLeese |first7=Miranda |last8=Arnett |first8=W. David |last9=Demarque |first9=Pierre |last10=Spada |first10=Federico |last11=Young |first11=Patrick A. |last12=Barstow |first12=Martin A. |last13=Burleigh |first13=Matthew R. |last14=Gudehus |first14=Donald |display-authors=6 |year=2017 |title=The Sirius system and its astrophysical puzzles: Hubble Space Telescope and ground-based astrometry |journal=The Astrophysical Journal |volume=840 |issue=2 |pages=70 |arxiv=1703.10625 |bibcode=2017ApJ...840...70B |doi=10.3847/1538-4357/aa6af8 |s2cid=51839102 |doi-access=free}}</ref> | {{val|1.713|0.009}}<ref name="JDavis2010">{{cite journal |last=Davis |first=J. |display-authors=etal |date=October 2010 |title=The Angular Diameter and Fundamental Parameters of Sirius A |journal=Publications of the Astronomical Society of Australia |volume=28 |pages=58–65 |arxiv=1010.3790 |doi=10.1071/AS10010}}</ref> | {{val|24.7|0.7}}<ref name="JDavis2010"/> | {{Val|8.61|0.03}}<ref name="bond"/> |- | Altair | A7 V<ref name=Gray2003/> | Aquila | 0.76<ref name=ducati>{{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|pages=0|last1=Ducati|first1=J. R.|date=2002}}</ref> | {{val|1.86|0.03}}<ref name=bouchaud2020>{{cite journal |bibcode=2020A&A...633A..78B |title=A realistic two-dimensional model of Altair |last1=Bouchaud |first1=K. |last2=Domiciano De Souza |first2=A. |last3=Rieutord |first3=M. |last4=Reese |first4=D. R. |last5=Kervella |first5=P. |journal=Astronomy and Astrophysics |year=2020 |volume=633 |pages=A78 |doi=10.1051/0004-6361/201936830 |arxiv=1912.03138 |s2cid=208857428 }}</ref> | 2.007 × 1.565<ref name=bouchaud2020/> | 10.6<ref name=peterson06>{{cite journal | doi = 10.1086/497981| title = Resolving the Effects of Rotation in Altair with Long-Baseline Interferometry| year = 2006| last1 = Peterson| first1 = D. M.| last2 = Hummel| first2 = C. A.| last3 = Pauls| first3 = T. A.| last4 = Armstrong| first4 = J. T.| last5 = Benson| first5 = J. A.| last6 = Gilbreath| first6 = G. C.| last7 = Hindsley| first7 = R. B.| last8 = Hutter| first8 = D. J.| last9 = Johnston| first9 = K. J.| last10 = Mozurkewich| first10 = D.| last11 = Schmitt| first11 = H.| display-authors=3 | journal = The Astrophysical Journal| volume = 636| issue = 2| pages = 1087–1097| arxiv = astro-ph/0509236| bibcode = 2006ApJ...636.1087P| s2cid = 18683397}} See Table 2 for stellar parameters.</ref> | 16.73<ref name=hipparcos>{{Cite journal | last1=van Leeuwen | first1=F. | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 |date=November 2007 | pages=653–664 | doi=10.1051/0004-6361:20078357 | bibcode=2007A&A...474..653V | arxiv=0708.1752 | s2cid=18759600 }}</ref> |- | Vega | A0 Va<ref name=Gray2003/> | Lyra | 0.026<ref name=bohlin>{{cite journal|bibcode=2004AJ....127.3508B|title=Hubble Space Telescope Absolute Spectrophotometry of Vega from the Far-Ultraviolet to the Infrared|journal=The Astronomical Journal|volume=127|issue=6|pages=3508–3515|last1=Bohlin|first1=R. C.|last2=Gilliland|first2=R. L.|year=2004|doi=10.1086/420715|doi-access=free}}</ref> | {{val|2.15|0.10|0.15}}<ref name=monnier2012>{{Cite journal |last1=Monnier |first1=J. D. |last2=Che |first2=Xiao |last3=Zhao |first3=Ming |last4=Ekstrom |first4=S. |last5=Maestro |first5=V. |last6=Aufdenberg |first6=J. |last7=Baron |first7=F. |last8=Georgy |first8=C. |last9=Kraus |first9=S. |last10=McAlister |first10=H. |last11=Pedretti |first11=E. |last12=Ridgway |first12=S. |last13=Sturmann |first13=J. |last14=Sturmann |first14=L. |last15=Brummelaar |first15=T. ten |date=2012-12-10 |title=Resolving Vega and the inclination controversy with CHARA/MIRC |arxiv=1211.6055 |bibcode=2012ApJ...761L...3M |journal=The Astrophysical Journal |volume=761 |issue=1 |pages=L3 |doi=10.1088/2041-8205/761/1/L3 |issn=2041-8205}}</ref> | {{val|2.726|0.006}} × {{val|2.418|0.008}}<ref name=monnier2012/> | {{val|47.2|0.2}}<ref name=monnier2012/> | 25.04<ref name=hipparcos/> |- |Fomalhaut | A3 V<ref name="Gray2006">{{cite journal |last1=Gray |first1=R. O. |last2=Corbally |first2=C. J. |display-authors=etal |date=July 2006 |title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc – The Southern Sample |journal=The Astronomical Journal |volume=132 |issue=1 |pages=161–170 |doi=10.1086/504637 |arxiv=astro-ph/0603770 |bibcode=2006AJ....132..161G|s2cid=250741593 }}</ref> | Piscis Austrinus | 1.17<ref name=ducati/> | {{val|1.92|0.02}}<ref name=age_mam/> | {{val|1.842|0.019}}<ref name=age_mam/> | {{val|16.63|0.48}}<ref name=age_mam>{{Cite journal | last1=Mamajek | first1=E.E. | title=On the Age and Binarity of Fomalhaut | journal=Astrophysical Journal Letters | volume=754 | issue=2 |date=August 2012 | pages=L20 | doi=10.1088/2041-8205/754/2/L20 | arxiv=1206.6353| s2cid=119191190 |bibcode=2012ApJ...754L..20M }}</ref> | 25.1<ref name=hipparcos/> |- |Denebola |A3 Va<ref name=Gray2003/> |Leo |2.14<ref name=gcvs>{{cite journal | display-authors=1 | last1=Samus | first1=N. N. | last2=Kazarovets | first2=E. V. | last3=Durlevich | first3=O. V. | last4=Kireeva | first4=N. N. | last5=Pastukhova | first5=E. N. | title=General Catalogue of Variable Stars | version=5.1 | journal=Astronomy Reports | year=2017 | volume=61 | issue=1 | pages=80–88 | bibcode=2017ARep...61...80S | doi=10.1134/S1063772917010085 | s2cid=125853869 }}</ref> |1.78<ref name="aaa426">{{cite journal | display-authors=1 | last1=Di Folco | first1=E. | last2=Thévenin | first2=F. | last3=Kervella | first3=P. | last4=Domiciano de Souza | first4=A. | last5=Coudé du Foresto | first5=V. | last6=Ségransan | first6=D. | last7=Morel | first7=P. | title=VLTI near-IR interferometric observations of Vega-like stars | journal=Astronomy and Astrophysics | year=2004 | volume=426 | issue=2 | pages=601–617 | bibcode=2004A&A...426..601D | doi=10.1051/0004-6361:20047189 | doi-access=free }}</ref> |{{val|1.75|0.02}}<ref name="Baines2023"> {{cite journal | last1=Baines | first1=Ellyn K. | last2=Clark | first2=James H. III | last3=Schmitt | first3=Henrique R. | last4=Stone | first4=Jordan M. | last5=von Braun | first5=Kaspar | title=33 New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble | journal=The Astronomical Journal | volume=166 | issue=6 | page=268 | date=2023-12-01 | bibcode=2023AJ....166..268B | doi=10.3847/1538-3881/ad08be | arxiv=2505.23514 | doi-access=free | issn=0004-6256 }}</ref> |{{val|12.9|0.1}}<ref name=Baines2023/> |35.8<ref name=hipparcos/> |} Sirius is the brightest star in the night sky.
== Notes == {{notelist}}
== See also == * Star count, survey of stars * B-type main-sequence star
==References== <references> <!-- Not in use <ref name=adelman2004>{{Cite journal | last1 = Adelman | first1 = S. J. | title = The physical properties of normal A stars | doi = 10.1017/S1743921304004314 | journal = Proceedings of the International Astronomical Union | volume = 2004 | pages = 1–11 | year = 2005 | doi-access = free | bibcode = 2004IAUS..224....1A }}</ref> Not in use--> </references>
{{Star|state=collapsed}} {{Portal bar|Astronomy|Outer space}} {{Commons category}}
{{DEFAULTSORT:A-type main-sequence star}} Category:Star types Category:A-type main-sequence stars