Sagitta#Mythology

File:Sidney Hall - Urania's Mirror - Delphinus, Sagitta, Aquila, and Antinous.jpg in this plate from Urania's Mirror (1825).]]

The ancient Greeks called Sagitta {{lang|grc|Oistos}} 'the arrow', and it was one of the 48 constellations described by Ptolemy. It was regarded as the weapon that Hercules used to kill the eagle ({{lang|la|Aquila}}) of Jove that perpetually gnawed Prometheus' liver.{{cite web |url=http://www.theoi.com/Text/HyginusAstronomica.html#15 |title=Astronomica |author=Hyginus |translator=Mary Grant |website=Theoi Project |access-date=31 January 2020}} Sagitta is located beyond the north border of Aquila, the Eagle. An amateur naturalist, polymath Richard Hinckley Allen proposed that the constellation could represent the arrow shot by Hercules towards the adjacent Stymphalian birds (which feature in Hercules' sixth labour) who had claws, beaks, and wings of iron, and who lived on human flesh in the marshes of Arcadia—denoted in the sky by the constellations Aquila the Eagle, Cygnus 'the Swan', and Lyra 'the Vulture'—and still lying between them, whence the title Herculea.{{cite book|first=Richard Hinckley | last=Allen|title=Star-Names and Their Meanings|pages =349–351 | url=https://books.google.com/books?id=l8V2DY3tQMgC&q=Star-Names+and+Their+Meanings | year=1963 | orig-date=1899 | publisher=Dover Publications |location=New York | isbn=978-0-486-21079-7 }} Greek scholar Eratosthenes claimed it as the arrow with which Apollo exterminated the Cyclopes. The Romans named it Sagitta.{{Cite book|title=The Star Atlas Companion: What You Need to Know about the Constellations|last=Bagnall|first= Philip M. |date=2012|publisher=Springer |pages= 386–389 | location=New York | isbn=978-1-4614-0830-7|oclc=794225463}} In Arabic, it became al-sahm 'arrow', though this name became Sham and was transferred to Alpha Sagittae only. The Greek name has also been mistranslated as {{lang|el-latn|ὁ istos}} 'the loom' and thus in Arabic al-nawl. It was also called al-'anaza 'pike/javelin'.{{cite journal |url= http://opar.unior.it/473/1/P._Kunitzsch_pp.19-28_pdf.pdf |title= Albumasariana |journal=Annali dell'Università degli studi di Napoli "L'Orientale" |publisher=Rivista del Dipartimento di Studi Asiatici e del Dipartimento di Studi e Ricerche su Africa e Paesi Arabi |first=Paul |last= Kunitzsch |volume=62 |page=4 |date=2002 |issn=0393-3180 }}

The four brightest stars make up an arrow-shaped asterism located due north of the bright star Altair.{{Cite book |last=Moore |first=Patrick |title=The Observer's Year: 366 Nights in the Universe |publisher=Springer Science & Business Media |year=2005 |isbn=978-1-85233-884-8 |location=New York |page=10 |author-link=Patrick Moore}} Covering 79.9 square degrees and hence 0.194% of the sky, Sagitta ranks 86th of the 88 modern constellations by area. Only Equuleus and Crux are smaller. Sagitta is most readily observed from the late spring to early autumn to northern hemisphere observers, with midnight culmination occurring on 17 July.{{cite book|title=Illustrated Guide to Astronomical Wonders: From Novice to Master Observer|author1=Thompson, Robert Bruce|author2=Barbara Fritchman|url=https://books.google.com/books?id=ymt9nj_uPhwC&pg=PA392|page=392|isbn=978-0-596-52685-6|publisher=O'Reilly Media, Inc.|location=Sebastopol, California|year=2007}} Its position in the Northern Celestial Hemisphere means that the whole constellation is visible to observers north of 69°S.{{cite web| url=http://www.ianridpath.com/constellations2.html | title=Constellations: Lacerta–Vulpecula | work= Star Tales |author=Ridpath, Ian | access-date= 22 May 2015| author-link=Ian Ridpath }}{{efn|1=While parts of the constellation technically rise above the horizon to observers between the 69°S and 73°S, stars within a few degrees of the horizon are to all intents and purposes unobservable.}} Sagitta is bordered by Vulpecula to the north, Hercules to the west, Aquila to the south, and Delphinus to the east. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Sge"; American astronomer Henry Norris Russell, who devised the code, had to resort to using the genitive form of the name to come up with a letter to include ('e') that was not in the name of the constellation Sagittarius.{{cite journal | last=Russell | first=Henry Norris |author-link=Henry Norris Russell | title=The New International Symbols for the Constellations | journal=Popular Astronomy | volume=30 | page=469 | bibcode=1922PA.....30..469R | year=1922 }} The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of twelve segments (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between {{RA|18|57.2}} and {{RA|20|20.5}}, while the declination coordinates are between 16.08° and 21.64°.{{Cite web | title=Sagitta, Constellation Boundary | publisher=International Astronomical Union | url=https://www.iau.org/public/themes/constellations/#sge | access-date=20 October 2020 }}

{{see also|List of stars in Sagitta}}

Celestial cartographer Johann Bayer gave Bayer designations to eight stars, labelling them Alpha to Theta. English astronomer John Flamsteed added the letters x, mistaken as Chi (χ), y and z to 13, 14, and 15 Sagittae in his Catalogus Britannicus. All three were dropped by later astronomers John Bevis and Francis Baily.{{cite book | last = Wagman | first = Morton | year = 2003 | title = Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others |pages=266–267, 515 | publisher = The McDonald & Woodward Publishing Company | location = Blacksburg, Virginia | isbn = 978-0-939923-78-6 }}

Ptolemy saw the constellation's brightest star Gamma Sagittae as marking the arrow's head,{{cite web |last=Ridpath |first=Ian |author-link=Ian Ridpath |title=Sagitta |url=http://www.ianridpath.com/startales/sagitta.html |access-date=22 May 2015 |work=Star Tales}} while Bayer saw Gamma, Eta, and Theta as depicting the arrow's shaft. Gamma Sagittae is a red giant of spectral type M0 III,{{cite journal|bibcode=2018A&A...612A..45S|title=PEPSI deep spectra. II. Gaia benchmark stars and other M-K standards|journal=Astronomy and Astrophysics|volume=612|pages=A45|last1=Strassmeier|first1=K. G. |last2=Ilyin|first2=I.|last3=Weber|first3=M.|year=2018|arxiv=1712.06967|doi=10.1051/0004-6361/201731633|s2cid=119244142}} and magnitude 3.47. It lies at a distance of {{val|258|4|ul=light-years}} from Earth.{{cite journal | first=F. | last=van Leeuwen | title=Validation of the New Hipparcos Reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | date=2007 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | arxiv=0708.1752| s2cid=18759600 }} With around 90% of the Sun's mass,{{cite journal

| title=Precise radial velocities of giant stars. X. Bayesian stellar parameters and evolutionary stages for 372 giant stars from the Lick planet search

| last1=Stock | first1=Stephan | last2=Reffert | first2=Sabine

| last3=Quirrenbach | first3=Andreas | last4=Hauschildt | first4=P.

| journal=Astronomy and Astrophysics

| volume=616 | pages=A33 | year=2018

| bibcode=2018A&A...616A..33S | arxiv=1805.04094

| doi=10.1051/0004-6361/201833111 | s2cid=119361866 }}{{cite journal

| last1=Neilson | first1=Hilding R. | last2=Lester | first2=John B.

| title=Determining parameters of cool giant stars by modeling spectrophotometric and interferometric observations using the SAtlas program

| journal=Astronomy and Astrophysics

| volume=490 | issue=2 | pages=807–10 | date=2008

| bibcode=2008A&A...490..807N | arxiv=0809.1875

| doi=10.1051/0004-6361:200810627 | s2cid=1586125 }} it has a radius 54 times that of the Sun and is 575 times as bright. It is most likely on the red-giant branch of its evolutionary lifespan, having exhausted its core hydrogen and now burning it in a surrounding shell.

Delta Sagittae is the second-brightest star in the constellation and is a binary. Delta and Zeta depicted the spike according to Bayer.{{sfn|Wagman|2003|p=515}} The Delta Sagittae system is composed of a red supergiant of spectral type M2 II that has 3.9 times the Sun's mass and 152 times its radius and a blue-white B9.5V main sequence star that is 2.9 times as massive as the Sun. The two orbit each other every ten years.{{cite journal|title=Winds and accretion in delta Sagittae|author=Eaton, Joel A.|author2=Hartkopf, William I.|author3=McAlister, Harold A.|author4=Mason, Brian D.|journal=Astronomical Journal|volume=109|number=4|pages=1856–1866|date=1995|bibcode=1995AJ....109.1856E|doi=10.1086/117412}} Zeta Sagittae is a triple star system,{{citation

| last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A.

| title=A catalogue of multiplicity among bright stellar systems

| journal=Monthly Notices of the Royal Astronomical Society

| volume=389 | issue=2 | pages=869–879 | date=September 2008

| bibcode=2008MNRAS.389..869E | doi=10.1111/j.1365-2966.2008.13596.x

| doi-access=free | arxiv=0806.2878 | s2cid=14878976 | postscript=. }} approximately {{val|326|u=light-years}} from Earth. The primary and secondary are A-type stars.{{citation

| last1=Christy | first1=James W. | last2=Walker | first2=R. L. Jr.

| title=MK Classification of 142 Visual Binaries | postscript=.

| journal=Publications of the Astronomical Society of the Pacific

| volume=81 | issue=482 | page=643 | date=October 1969

| doi=10.1086/128831 | bibcode=1969PASP...81..643C | doi-access=free }}{{citation | display-authors=1

| last1=Cowley | first1=A. | last2=Cowley | first2=C.

| last3=Jaschek | first3=M. | last4=Jaschek | first4=C.

| title=A study of the bright A stars. I. A catalogue of spectral classifications

| journal=Astronomical Journal | postscript=.

| volume=74 | pages=375–406 | date=April 1969

| doi=10.1086/110819 | bibcode=1969AJ.....74..375C }}

In his Uranometria, Bayer depicted Alpha, Beta, and Epsilon Sagittae as the fins of the arrow.{{sfn|Wagman|2003|p=515}} Also known as Sham, Alpha is a yellow bright giant star of spectral class G1 II with an apparent magnitude of 4.38, which lies at a distance of {{val|382|8|u=light-years}} from Earth.{{cite DR2|1824277055360974720}} Four times as massive as the Sun, it has swollen and brightened to 21 times the Sun's radius and 340 times its luminosity.{{cite web| first=James B. | last=Kaler | title=Sham | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/sham.html | access-date=22 May 2015}} Also of magnitude 4.38, Beta is a G-type giant located {{val|420|10|u=light-years}} distant from Earth.{{cite DR2|1823991938300446336}} Estimated to be around 129 million years old, it is 4.33 times as massive as the Sun,{{cite journal | title=The Lithium Abundances of a Large Sample of Red Giants | display-authors=1 | last1=Liu | first1=Y. J. | last2=Tan | first2=K. F. | last3=Wang | first3=L. | last4=Zhao | first4=G. | last5=Sato | first5=Bun'ei | last6=Takeda | first6=Y. | last7=Li | first7=H. N. | journal=The Astrophysical Journal | arxiv=1404.1687 | volume=785 | issue=2 | id=94 | page=12 | date=2014 | doi=10.1088/0004-637X/785/2/94 | bibcode=2014ApJ...785...94L | s2cid=119226316 }} and has expanded to roughly 27 times its radius.{{cite journal | title=Supergiant temperatures and linear radii from near-infrared interferometry | journal=Monthly Notices of the Royal Astronomical Society | volume=394 | issue=4 | page=1925 | year=2009 | last1=Van Belle | first1=G. T. | last2=Creech-Eakman | first2=M. J. | last3=Hart | first3=A. | bibcode=2009MNRAS.394.1925V | arxiv=0811.4239 | doi=10.1111/j.1365-2966.2008.14146.x | doi-access=free | s2cid=118372600 }} Epsilon Sagittae is a double star whose component stars can be seen in a small telescope.{{cite book|last=Consolmagno|first=Guy |title=Turn Left at Orion: Hundreds of Night Sky Objects to See in a Home Telescope – and How to Find Them|publisher=Cambridge University Press|location=Cambridge, United Kingdom|year=2019 | orig-date=1989 |page=138 |isbn=978-1-108-45756-9|url=https://books.google.com/books?id=D2JjDwAAQBAJ&pg=PA139}} With an apparent magnitude of 5.77, the main star is a 331-million-year-old yellow giant of spectral type G8 III around 3.09 times as massive as the Sun,{{cite journal | title=Spectroscopic study on the beryllium abundances of red giant stars | journal=Publications of the Astronomical Society of Japan | volume=66 | issue=5 | page=91 | year=2014 | last1=Takeda | first1=Yoichi | last2=Tajitsu | first2=Akito | doi=10.1093/pasj/psu066 | bibcode=2014PASJ...66...91T | arxiv=1406.7066| s2cid=119283677 }} that has swollen to {{val|18.37|0.65|0.88}} its radius. It is {{val|580|10|u=light-years}} distant.{{Cite DR2|4321830946398475776}} The visual companion of magnitude 8.35 is 87.4 arcseconds distant,{{cite journal| last1=Mason | first1=B. D. | last2=Wycoff | first2=G. L. | last3=Hartkopf | first3=W. I. | last4=Douglass | first4=G. G. | last5=Worley | first5=C. E. | title=The Washington Visual Double Star Catalog | journal=Nature | year=2014 | volume=122 | issue=6 | page=3466 | bibcode=2001AJ....122.3466M | doi = 10.1086/323920 | doi-access=free }} but is an unrelated blue supergiant around {{val|7000|fmt=commas|u=light-years}} distant from Earth.{{cite DR2|4321830980758181760}}

Eta Sagittae is an orange giant of spectral class K2 III{{citation

| title=The Spectra of the Bright Stars of Types F5-K5

| last=Roman | first=Nancy G. | postscript=.

| journal=Astrophysical Journal

| volume=116 | page=122 | date=July 1952

| doi=10.1086/145598 | bibcode=1952ApJ...116..122R | doi-access=free }} with a magnitude of 5.09.{{citation

| last=Argue | first=A. N. | postscript=.

| title=UBV photometry of 550 F, G and K type stars

| journal=Monthly Notices of the Royal Astronomical Society

| volume=133 | pages=475–493 | year=1966

| issue=4 | bibcode=1966MNRAS.133..475A | doi=10.1093/mnras/133.4.475| doi-access=free}} Located {{val|155.9|0.9|u=light-years}} from Earth, it has a 61.1% chance of being a member of the Hyades–Pleiades stream of stars that share a common motion through space.{{cite journal| last1=Famaey | first1=B. | last2=Jorissen | first2=A. | last3=Luri | first3=X. | last4=Mayor | first4=M. | last5=Udry | first5=S. | last6=Dejonghe | first6=H. | last7=Turon | first7=C. | title=Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters | journal=Astronomy and Astrophysics | volume=430 | pages=165–186 | date=2005 | doi=10.1051/0004-6361:20041272 | bibcode=2005A&A...430..165F | arxiv=astro-ph/0409579 | s2cid=17804304 }} Theta Sagittae is a double star system, with components 12 arcseconds apart visible in a small telescope. At magnitude 6.5, the brighter is a yellow-white main sequence star of spectral type F3 V,{{cite journal |last=Abt |first=Helmut A. |title=Visual multiples. VIII. 1000 MK types |journal=The Astrophysical Journal Supplement Series |date=1985 |bibcode= 1985ApJS...59...95A |volume=59 |pages=95–112 |doi=10.1086/191064|doi-access=free }} located {{val|146.1|0.2|u=light-years}} from Earth.{{cite DR2|1829590548393010560}} The 8.8-magnitude fainter companion is a main sequence star of spectral type G5 V. A 7.4-magnitude orange giant of spectral type K2 III is also visible {{val|91|ul="}} from the binary pair, located {{val|842|9|u=light-years}} away.{{cite DR2|1829590410954063744}}

Image:Wolf-Rayet 124 (NIRCam and MIRI composite image).tif image of WR 124 in Sagitta. NIRCam and MIRI composite]]

Variable stars are popular targets for amateur astronomers, their observations providing valuable contributions to understanding star behaviour.{{cite web |last=Tooke |first=Owen |title=Variables: What Are They and Why Observe Them? |url=https://www.aavso.org/variables-what-are-they-why-observe-them |publisher=AAVSO | date=24 August 2017 |access-date=14 October 2020}} R Sagittae is a member of the rare RV Tauri variable class of star. It ranges in magnitude from 8.2 to 10.4.{{cite book|last=Levy|first=David H.|title=Observing Variable Stars: A Guide for the Beginner|publisher=Cambridge University Press|location=Cambridge, United Kingdom|date=1998|pages=152–153|isbn=978-0-521-62755-9|url=https://books.google.com/books?id=5-O2cd937FMC&pg=PA153}} It is around {{val|8100|fmt=commas|u=light-years}} distant.{{cite DR2|1808748613981554176}} It has a radius {{val|61.2|12.4|9.9}} times that of the Sun, and is {{val|2329|744|638|fmt=commas}} as luminous, yet most likely is less massive than the Sun. An aging star, it has moved on from the asymptotic giant branch of stellar evolution and is on its way to becoming a planetary nebula.{{cite journal |doi=10.3847/1538-4357/aafc24 |title=Physical Properties of Galactic RV Tauri Stars from Gaia DR2 Data |journal=The Astrophysical Journal |volume=872 |issue=1 |page=60 |year=2019 |last1=Bódi |first1=A. |last2=Kiss |first2=L. L. |bibcode=2019ApJ...872...60B |arxiv=1901.01409 |s2cid=119099605 |doi-access=free }} FG Sagittae is a "born again" star, a highly luminous star around {{val|4000|fmt=commas|u=light-years}} distant from Earth.{{cite DR2|1828750899461025536}} It reignited fusion of a helium shell shortly before becoming a white dwarf, and has expanded first to a blue supergiant and then to a K-class supergiant in less than 100 years.{{cite journal |bibcode=1999NewAR..43..415J |title=The remarkable evolution of the post-AGB star FG Sge |last1=Jurcsik |first1=Johanna |last2=Montesinos |first2=Benjamín. |journal=New Astronomy Reviews |year=1999 |volume=43 |issue=6 |page=415 |doi=10.1016/S1387-6473(99)00098-6 |url=http://real.mtak.hu/2086/1/K.pdf }} It is surrounded by a faint (visual magnitude 23) planetary nebula, Henize 1–5, that formed when FG Sagittae first left the asymptotic giant branch.{{cite journal |bibcode=2015Ap.....58...46R |title=Photometry, Spectrometry, and Polarimetry of FG Sge in the Active State |last1=Rosenbush |first1=A. É. |last2=Efimov |first2=Yu. S. |s2cid=121128187 |journal=Astrophysics |year=2015 |volume=58 |issue=1 |page=46 |doi=10.1007/s10511-015-9365-x }}

S Sagittae is a classical Cepheid that varies from magnitude 5.24 to 6.04 every 8.38 days. It is a yellow-white supergiant that pulsates between spectral types F6 Ib and G5 Ib.{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=27343 |title=S Sagittae |author =Watson, Christopher |date=4 January 2010|publisher=AAVSO |access-date=22 May 2015}} Around 6 or 7 times as massive and 3,500 times as luminous as the Sun,{{cite web| first=James B. | last=Kaler | title=S Sagittae | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/ssge.html | date= 4 October 2013|access-date=22 May 2015}} it is located around {{val|5100|fmt=commas|u=light-years}} from Earth.{{cite DR2|1820309639468685824}} HD 183143 is a remote highly luminous star around {{val|7900|fmt=commas|u=light-years}} away,{{cite DR2|4323280515006629760}} that has been classified as a blue hypergiant.{{cite journal|last=Chentsov|first=E. L.|title=HD 183143: A Hypergiant|journal=Astronomy Letters|volume=30|issue=5|year=2004|pages=325–331|doi=10.1134/1.1738155|bibcode=2004AstL...30..325C|s2cid=121435951}} Infrared bands of ionised buckminsterfullerene molecules have also been found in its spectrum.{{cite journal|bibcode=2015ApJ...812L...8W|arxiv=1509.06818|title=Identification of More Interstellar C60+ Bands|journal=The Astrophysical Journal Letters|volume=812|pages=L8|last1=Walker|first1=G. A. H.|last2=Bohlender|first2=D. A.|last3=Maier|first3=J. P.|last4=Campbell|first4=E. K.|year=2015|issue=1|doi=10.1088/2041-8205/812/1/L8|s2cid=118598331}} WR 124 is a Wolf–Rayet star moving at great speed surrounded by a nebula of ejected gas.{{cite journal|bibcode=1999A&A...350.1007C|title=Wolf–Rayet nebulae as tracers of stellar ionizing fluxes. I. M1-67|journal=Astronomy and Astrophysics|volume=350|page=1007|last1=Crowther|first1=Paul A.|last2=Pasquali|first2=A.|last3=De Marco|first3=Orsola|author3-link=Orsola De Marco|last4=Schmutz|first4=W.|last5=Hillier|first5=D. J.|last6=De Koter|first6=A.|year=1999|arxiv = astro-ph/9908200 }}

U Sagittae is an eclipsing binary that varies between magnitudes 6.6 and 9.2 over 3.4 days, making it a suitable target for enthusiasts with small telescopes. There are two component stars—a blue-white star of spectral type B8 V and an ageing star that has cooled and expanded into a yellow subgiant of spectral type G4 III-IV. They orbit each other close enough that the cooler subgiant has filled its Roche lobe and is passing material to the hotter star, and hence it is a semidetached binary system.{{cite journal |last=Malkov |first=Oleg Yu |title=Semidetached double-lined eclipsing binaries: Stellar parameters and rare classes |journal=Monthly Notices of the Royal Astronomical Society |date=2020 |volume=491 |issue=4 |pages=5489–5497| bibcode= 2020MNRAS.491.5489M |doi=10.1093/mnras/stz3363|doi-access=free }} The system is {{val|900|10|u=light-years}} distant.{{cite DR2|4516549576568929408}} Near U Sagittae is X Sagittae, a semiregular variable ranging between magnitudes 7.9 and 8.4 over 196 days. A carbon star, X Sagittae has a surface temperature of {{val|2576|fmt=commas|ul=K}}.{{cite journal |last1=Taranova |first1=O.G. | first2=V. I. | last2=Shenavrin |title=JHKLM Photometry for Carbon Stars |journal=Astronomy Letters |date=2004 |volume=30 |issue=8 |pages=605–622 |doi=10.1134/1.1784497|bibcode=2004AstL...30..549T |s2cid=119984131 }}

Located near 18 Sagittae is V Sagittae, the prototype of the V Sagittae variables, cataclysmic variables that are also super soft X-ray sources. It is expected to become a luminous red nova when the two stars merge around the year 2083, and briefly become the most luminous star in the Milky Way and one of the brightest stars in Earth's sky.{{Cite web|url=https://phys.org/news/2020-01-binary-star-sagittae-bright-nova.html|title=Binary star V Sagittae to explode as very bright nova by century's end| last= Lavalle| first= Mimi |website=phys.org|language=en-us|access-date=9 January 2020| date=7 January 2020}}{{Cite web|url=http://m.cnn.com/en/article/h_f7a7fda778b24834ac5316152cc63433|title=There will be a new brightest star in the sky, when it explodes in about 60 years|publisher=CNN|access-date=9 January 2020|date=8 Jan 2020|archive-date=13 January 2020|archive-url=https://web.archive.org/web/20200113183819/http://m.cnn.com/en/article/h_f7a7fda778b24834ac5316152cc63433|url-status=dead}} WZ Sagittae is another cataclysmic variable, composed of a white dwarf that has about 85% the mass of the Sun, and low-mass star companion that has been calculated to be a brown dwarf of spectral class L2 that is only 8% as massive as the Sun.{{cite journal | author=Steeghs, Danny | author2=Howell, Steve B. | author3=Knigge, Christian | author4=Gänsicke, Boris T. | author5=Sion, Edward M. | author6=Welsh, William F. | title=Dynamical Constraints on the Component Masses of the Cataclysmic Variable WZ Sagittae | journal=The Astrophysical Journal | volume=667 | issue=1 | pages=442–447 |date=September 2007 | doi=10.1086/520702 | bibcode=2007ApJ...667..442S|arxiv = 0706.0987 | s2cid=209833493 }} Normally a faint object dimmer than magnitude 15, it flared up in 1913, 1946 and 1978 to be visible in binoculars. The black widow pulsar (B1957+20) is the second millisecond pulsar ever discovered.{{cite journal|last1=Fruchter|first1=A. S.|last2=Stinebring|first2=D. R.|last3=Taylor|first3=J. H.|year=1988|title=A millisecond pulsar in an eclipsing binary|journal=Nature|volume=333|issue=6170|pages=237–239 |bibcode=1988Natur.333..237F|doi=10.1038/333237a0|s2cid=4337525}} It is a massive neutron star that is ablating its brown dwarf-sized companion which causes the pulsar's radio signals to attenuate as they pass through the outflowing material.{{Cite web|url=https://chandra.harvard.edu/photo/2003/b1957/|title=B1957+20: A Cocoon Found Inside the Black Widow's Web|website=Chandra|access-date=23 October 2020}}

Image:Messier 71 Hubble WikiSky.jpg globular cluster]]

HD 231701 is a yellow-white main sequence star hotter and larger than the Sun, with a Jupiter-like planet that was discovered in 2007 by the radial velocity technique. The planet orbits at a distance of {{Val|0.57|ul=AU}} from the star with a period of 141.6 days.{{cite journal | title=Five Intermediate-Period Planets from the N2K Sample | last1=Fischer | first1=Debra A. | last2=Vogt | first2=Steven S. | last3=Marcy | first3=Geoffrey W. | last4=Butler | first4=R. Paul | last5=Sato | first5=Bun'ei | last6=Henry | first6=Gregory W. | last7=Robinson | first7=Sarah | last8=Laughlin | first8=Gregory | last9=Ida | first9=Shigeru | journal=The Astrophysical Journal | volume=669 | issue=2 | pages=1336–1344 | year=2007 | arxiv=0704.1191 | bibcode=2007ApJ...669.1336F | doi=10.1086/521869 | s2cid=7774321 }} It has a mass of at least 1.13 Jupiter masses.{{cite journal

| title=Radial Velocities from the N2K Project: Six New Cold Gas Giant Planets Orbiting HD 55696, HD 98736, HD 148164, HD 203473, and HD 211810

| last1=Ment | first1=Kristo | last2=Fischer | first2=Debra A.

| last3=Bakos | first3=Gaspar | last4=Howard | first4=Andrew W.

| last5=Isaacson | first5=Howard | display-authors=1

| journal=The Astronomical Journal

| volume=156 | issue=5 | at=213 | year=2018

| arxiv=1809.01228 | bibcode=2018AJ....156..213M

| doi=10.3847/1538-3881/aae1f5 | s2cid=119243619 | doi-access=free }}

HAT-P-34 is a star {{val|1.392|0.047}} times as massive as the Sun with {{val|1.535|0.135|0.102}} times its radius and {{val|3.63|0.75|0.51}} times its luminosity. With an apparent magnitude of 10.4, it is {{val|819|9|u=light-years}} distant.{{cite DR2|1810218734055374720}} A planet {{val|3.328|0.211}} times as massive as Jupiter was discovered transiting it in 2012. With a period of 5.45 days and a distance of {{val|0.06|u=AU}} from its star, it has an estimated surface temperature of {{val|1520|60|fmt=commas|u=K}}.{{cite journal | title=HAT-P-34b – HAT-P-37b: Four Transiting Planets More Massive Than Jupiter Orbiting Moderately Bright Stars | last1=Bakos | first1=G. Á. | last2=Hartman | first2=J. D. | last3=Torres | first3=G. | last4=Béky | first4=B. | last5=Latham | first5=D. W. | last6=Buchhave | first6=L. A. | last7=Csubry | first7=Z. | last8=Kovács | first8=Géza | last9=Bieryla | first9=A. | last10=Quinn | first10=S. | last11=Szklenár | first11=T. | last12=Esquerdo | first12=G. A. | last13=Shporer | first13=A. | last14=Noyes | first14=R. W. | last15=Fischer | first15=D. A. | last16=Johnson | first16=J. A. | last17=Howard | first17=A. W. | last18=Marcy | first18=G. W. | last19=Sato | first19=B. | last20=Penev | first20=K. | last21=Everett | first21=M. | last22=Sasselov | first22=D. D. | last23=Fűrész | first23=G. | last24=Stefanik | first24=R. P. | last25=Lázár | first25=J. | last26=Papp | first26=I. | last27=Sári | first27=P. | journal=The Astronomical Journal | volume=144 | issue=1 | pages=19–32 | date=2012 | arxiv=1201.0659 | bibcode=2012AJ....144...19B | doi=10.1088/0004-6256/144/1/19 | s2cid=119291677 }}

15 Sagittae is a solar analog—a star similar to the Sun, with {{val|1.08|0.04}} times its mass, {{val|1.115|0.021}} times its radius and {{val|1.338|0.03}} times its luminosity. It has an apparent magnitude of 5.80.{{citation

| title=XHIP: An extended hipparcos compilation

| last1=Anderson | first1=E. | last2=Francis | first2=Ch.

| journal=Astronomy Letters | postscript=.

| arxiv=1108.4971 | volume=38 | issue=5 | page=331 | year=2012

| bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015 | s2cid=119257644 }} It has an L4 brown dwarf substellar companion that is around the same size as Jupiter but 69 times as massive with a surface temperature of between 1,510 and {{val|1850|fmt=commas|u=K}}, taking around 73.3 years to complete an orbit around the star. The system is estimated to be {{val|2.5|1.8}} billion years old.{{cite journal | last1=Crepp | first1=Justin R. | last2=Johnson | first2=John Asher | last3=Fischer | first3=Debra A. | last4=Howard | first4=Andrew W. | last5=Marcy | first5=Geoffrey W. | last6=Wright | first6=Jason T. | last7=Isaacson | first7=Howard | last8=Boyajian | first8=Tabetha | last9=von Braun | first9=Kaspar | last10=Hillenbrand | first10=Lynne A. | last11=Hinkley | first11=Sasha | last12=Carpenter | first12=John M. | last13=Brewer | first13=John M. | title=The Dynamical Mass and Three-Dimensional Orbit of HR7672B: A Benchmark Brown Dwarf with High Eccentricity | journal=The Astrophysical Journal | volume=751 | issue=2 | id=97 | page=14 | date=2012 | arxiv=1112.1725 | bibcode=2012ApJ...751...97C | doi=10.1088/0004-637X/751/2/97| s2cid=16113054 }}

The band of the Milky Way and the Great Rift within it pass though Sagitta, with Alpha, Beta and Epsilon Sagittae marking the Rift's border.{{cite book|author1=Crossen, Craig |author2=Rhemann, Gerald |title=Sky Vistas: Astronomy for Binoculars and Richest-Field Telescopes|publisher=Springer|location=New York|orig-date=2004 | year=2012 | page=150 | url=https://books.google.com/books?id=3vELBwAAQBAJ&pg=PA150 | isbn=978-3-709-10626-6}} Located between Beta and Gamma Sagittae is Messier 71, a very loose globular cluster mistaken for some time for a dense open cluster. At a distance of about {{val|13000|fmt=commas|u=light-years}} from Earth,{{cite book |last1=Inglis |first1=Mike |title=Astronomy of the Milky Way: The Observer's Guide to the Northern Sky |date=2017 |publisher=Springer |location=New York |isbn=978-3-319-49082-3 |pages=83–89 |url=https://books.google.com/books?id=02DTDgAAQBAJ&q=Messier+71&pg=PA89}} it was first discovered by the French astronomer Philippe Loys de Chéseaux in the year 1745 or 1746.{{cite book | last1 = Thompson | first1 = Robert Bruce | last2 = Thompson | first2 = Barbara Fritchman | date = 2007 | title = Illustrated Guide to Astronomical Wonders: From Novice to Master Observer | page=394 | url=https://books.google.com/books?id=ymt9nj_uPhwC&pg=PA394 | publisher = O'Reilly Media | location = North Sebastopol, California | isbn = 978-0-596-52685-6 }} The loose globular cluster has a mass of around {{solar mass|53,000|link=yes}} and a luminosity of approximately 19,000 {{lo|link=yes}}.{{cite journal |last1=Dalgleish |first1=H. |last2=Kamann |first2=S. |last3=Usher |first3=C. |last4=Baumgardt |first4=H. |last5=Bastian |first5=N. |last6=Veitch-Michaelis |first6=J. |last7=Bellini |first7=A. |last8=Martocchia |first8=S. |last9=Da Costa |first9=G. S. |last10=Mackey |first10=D. |last11=Bellstedt |first11=S. |last12=Pastorello |first12=N. |last13=Cerulo |first13=P. |title=The WAGGS project-III. Discrepant mass-to-light ratios of Galactic globular clusters at high metallicity |journal=Monthly Notices of the Royal Astronomical Society |date=March 2020 |volume=492 |issue=3 |pages=3859–3871 |doi=10.1093/mnras/staa091 |arxiv=2001.01810 |bibcode=2020MNRAS.492.3859D |doi-access=free }}

There are two notable planetary nebulae in Sagitta: NGC 6886 is composed of a hot central post-AGB star that has 55% of the Sun's mass yet {{val|2700|850|fmt=commas}} times its luminosity, with a surface temperature of {{val|142000|fmt=commas|u=K}}, and surrounding nebula estimated to have been expanding for between 1,280 and 1,600 years,{{Cite journal | doi=10.1051/0004-6361/201731788 | bibcode=2018A&A...609A.126S| title=Expansion patterns and parallaxes for planetary nebulae| year=2018| last1=Schönberner| first1=D.| last2=Balick| first2=B.| last3=Jacob| first3=R.| journal=Astronomy & Astrophysics| volume=609| pages=A126| doi-access=free}} The nebula was discovered by Ralph Copeland in 1884.{{cite web|last=Seligman|first=Courtney|title=NGC Objects: NGC 6850 - 6899|url=http://cseligman.com/text/atlas/ngc68a.htm|access-date=22 August 2015}} The Necklace Nebula—originally a close binary, one component of which swallowed the other as it expanded to become a giant star. The smaller star remained in orbit inside the larger, whose rotation speed increased greatly, resulting in it flinging its outer layers off into space, forming a ring with knots of bright gas formed from clumps of stellar material.{{cite press release |last1=Weaver |first1=Donna |first2=Ray |last2=Villard |date=11 August 2011 |title=Hubble Offers a Dazzling 'Necklace' |url=https://www.nasa.gov/mission_pages/hubble/science/necklace-nebula.html |publisher=NASA |agency=Space Telescope Science Institute |access-date=20 October 2020}} It was discovered in 2005 and is around 2 light-years wide.[https://web.archive.org/web/20111014231028/http://hubblesite.org/newscenter/archive/releases/2011/24/image/b/ Hubble Offers a Dazzling View of the 'Necklace' Nebula], news release STScI-2011-24 dated August 11, 2011, from Space Telescope Science Institute It has a size of {{Val|0.35|ul=arcminute}}.{{cite journal | display-authors=1

| title=First release of the IPHAS catalogue of new extended planetary nebulae

| last1=Sabin | first1=L. | last2=Parker | first2=Q. A.

| last3=Corradi | first3=R. L. M. | last4=Guzman-Ramirez | first4=L.

| last5=Morris | first5=R. A. H. | last6=Zijlstra | first6=A. A.

| last7=Bojičić | first7=I. S. | last8=Frew | first8=D. J.

| last9=Guerrero | first9=M. | last10=Stupar | first10=M.

| last11=Barlow | first11=M. J. | last12=Cortés Mora | first12=F.

| last13=Drew | first13=J. E. | last14=Greimel | first14=R.

| last15=Groot | first15=P. | last16=Irwin | first16=J. M.

| last17=Irwin | first17=M. J. | last18=Mampaso | first18=A.

| last19=Miszalski | first19=B. | last20=Olguín | first20=L.

| last21=Phillipps | first21=S. | last22=Santander García | first22=M.

| last23=Viironen | first23=K. | last24=Wright | first24=N. J.

| journal=Monthly Notices of the Royal Astronomical Society

| volume=443 | issue=4 | pages=3388–3401 | date=October 2014

| doi=10.1093/mnras/stu1404 | doi-access=free

| arxiv=1407.0109

| bibcode=2014MNRAS.443.3388S }} Both nebulae are around {{val|15000|fmt=commas|u=light-years}} from Earth.

• Sagitta (Chinese astronomy)

{{notelist}}

{{reflist}}

{{Commons|Sagitta}}

• [http://www.allthesky.com/constellations/vulpecula/ The Deep Photographic Guide to the Constellations: Sagitta]
• [https://iconographic.warburg.sas.ac.uk/category/vpc-taxonomy-017052 Warburg Institute Iconographic Database (ca 160 medieval and early modern images of Sagitta)]
• Bayer's [http://lhldigital.lindahall.org/cdm/compoundobject/collection/astro_atlas/id/118/show/41 Uranometria] {{Webarchive|url=https://web.archive.org/web/20201017212847/http://lhldigital.lindahall.org/cdm/compoundobject/collection/astro_atlas/id/118/show/41 |date=2020-10-17 }}, from the Linda Hall Library digital collection.

{{Stars of Sagitta}}

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