Sextans B

{{Short description|Dwarf irregular galaxy in the constellation Sextans}} {{Infobox Galaxy | name = Sextans B | image =File:Sextans_B.jpg | caption = Sextans B, imaged by the 4-meter Telescope at [[Kitt Peak National Observatory]] | epoch = [[J2000]] | type = ImIV–V<ref name="ned">{{cite web |title=NASA/IPAC Extragalactic Database |work=Results for Sex B |url=http://nedwww.ipac.caltech.edu/ |accessdate=2006-12-13}}</ref> | ra = {{RA|10|00|00.1}}<ref name="ned" /> | dec = {{DEC|+05|19|56}}<ref name="ned" /> | dist_ly = [[1 E23 m|4.44 ± 0.23]] [[light-year|Mly]] (1.36 ± 0.07 [[parsec|Mpc]])<ref name="karachentsevetal2004">{{cite journal |author=I. D. Karachentsev |author2=V. E. Karachentseva |author3=W. K. Hutchmeier |author4=D. I. Makarov |title=A Catalog of Neighboring Galaxies |journal=Astronomical Journal |date=2004 |volume=127 |issue=4 |pages=2031–2068 |doi=10.1086/382905 |bibcode=2004AJ....127.2031K|doi-access=free }}</ref><ref name="Karachentsevetal2006">{{cite journal |author=Karachentsev, I. D. |author2=Kashibadze, O. G. |title=Masses of the local group and of the M81 group estimated from distortions in the local velocity field |journal=Astrophysics |date=2006 |volume=49 |issue=1 |pages=3–18 |doi=10.1007/s10511-006-0002-6 |bibcode=2006Ap.....49....3K|s2cid=120973010 }}</ref> | z = 301 ± 1 km/[[second|s]]<ref name="ned" /> | appmag_v = 11.9<ref name="ned" /> | size_v = 5.1{{prime}} × 3.5{{prime}}<ref name="ned" /> | size = ~{{convert|2.73|kpc|ly|abbr=on|lk=on|order=flip}} (estimated)<ref name ="ned" /> | constellation name = [[Sextans]] | notes = | names = {{odlist | UGC= 5373 | PGC= 28913 | name= [[David Dunlap Observatory Catalogue|DDO]] 70 | MCG= +01-26-005 | CGCG= 036-012}} }}

'''Sextans B''' (also known as '''UGC 5373''' and '''DDO 70''') is an [[irregular galaxy|irregular]] [[galaxy]] that may be part of the [[Local Group]], or lie just beyond it. The earliest known reference to this galaxy is from a 1954 paper by [[Edison Pettit]] in [[The Astrophysical Journal]], where it was listed as "Wilson Dwarf".<ref>{{cite journal|bibcode=1954ApJ...120..413P |title=Magnitudes and Color Indices of Extragalactic Nebulae Determined Photoelectrically |last1=Pettit |first1=Edison |journal=The Astrophysical Journal |date=1954 |volume=120 |page=413 |doi=10.1086/145932 }}</ref>

Sextans B is 4.44 million [[light-year]]s away from [[Earth]] and thus is one of the most distant members of the Local Group, if it is indeed a member. It forms a pair with its neighbouring galaxy [[Sextans A]].<ref name="SandageCarlson1985"/> It is a type Ir IV–V galaxy according to the [[galaxy morphological classification]] scheme.<ref name="vandenBergh2000"/> Sextans B may also be gravitationally associated with the galaxies [[NGC 3109]] and the [[Antlia Dwarf]].<ref name="vandenbergh1999"/>

Sextans B has a uniform stellar population,<ref name="TosiEtAl1991"/> but the interstellar medium in it may be inhomogeneous.<ref name="KniazevEtAl2005"/> Its mass is estimated to be about 2{{e|8}} times the mass of the [[Sun]], of which 5.5{{e|7}} is in the form of atomic [[hydrogen]].<ref name="TosiEtAl1991"/> Star formation in the galaxy seems to have proceeded in distinct periods of low intensity, separated by shorter periods of no activity.<ref name="TosiEtAl1991"/> The existence of [[Cepheid variable]]s in the galaxy implies that Sextans B contains at least some young stars.<ref name="vandenBergh2000"/> The [[metallicity]] of Sextans B is very low, with a value of approximately Z = 0.001.<ref name="TosiEtAl1991"/> Sextans B is receding from the [[Milky Way]] with a speed of approximately {{convert|300|km/s|mi/s}},<ref name="KniazevEtAl2005"/> and probably lies just outside the edge of the [[Local Group]], so as its neighbour [[Sextans A]].<ref name="AlloinGieren"/>

Five [[planetary nebula]]e have been identified in Sextans B, which is one of the smallest galaxies where planetary nebulae have been observed. These appear point-like and can be identified by their spectral emission lines.<ref name="MagriniEtAl2002"/> It also contains a massive [[globular cluster]].<ref name="SharinaEtAl2007"/>

Although no [[supernova]]e have been observed in Sextans B, the galaxy is close enough for classical [[nova]]e to be detected. The first confirmed nova in this galaxy was discovered by [[Asteroid_Terrestrial-impact_Last_Alert_System|ATLAS]] at magnitude 18.553 on 10 November 2024, and designated AT 2024aawe.<ref>{{cite web | website=Transient Name Server | title=AT{{nbsp}}2024aawe | url=https://www.wis-tns.org/object/2024aawe | publisher = [[International_Astronomical_Union|IAU]] | access-date=12 November 2024}}</ref>

==References==

<ref name="TosiEtAl1991"> {{Cite journal | doi = 10.1086/115925 | last = Tosi | first = M | author2=Greggio, L. |author3=Marconi, G. |author4=Focardi, P. | title = Star formation in dwarf irregular galaxies – Sextans B | journal = [[Astronomical Journal]] | volume = 102 | pages = 951–974 | date = September 1991 | bibcode = 1991AJ....102..951T}}</ref>

<ref name="MagriniEtAl2002">{{Cite journal|doi = 10.1051/0004-6361:20020296|title = The Local Group Census: Planetary nebulae in Sextans B|year = 2002|last1 = Magrini|first1 = L.|last2 = Corradi|first2 = R. L. M.|last3 = Walton|first3 = N. A.|last4 = Zijlstra|first4 = A. A.|last5 = Pollacco|first5 = D. L.|last6 = Walsh|first6 = J. R.|last7 = Perinotto|first7 = M.|last8 = Lennon|first8 = D. J.|last9 = Greimel|first9 = R.|journal = [[Astronomy & Astrophysics]] |volume = 386|issue = 3|pages = 869–873|arxiv = astro-ph/0202516|bibcode = 2002A&A...386..869M| s2cid=16954005 }}</ref>

<ref name="SandageCarlson1985"> {{Cite journal | doi = 10.1086/113809 | last = Sandage | first = Allan |author2=Carlson, George | title = The brightest stars in nearby galaxies. V – Cepheids and the brightest stars in the dwarf galaxy Sextans B compared with those in Sextans A | bibcode = 1985AJ.....90.1019S | journal = [[Astronomical Journal]] | volume = 90 | pages = 1019–1026 | date = July 1985| doi-access = free }}</ref>

<ref name="KniazevEtAl2005"> {{Cite journal | doi = 10.1086/432931 | last = Kniazev | first = Alexei Y. |author2=Grebel, Eva K. |author3=Pustilnik, Simon A. |author4=Pramskij, Alexander G. |author5=Zucker, Daniel B. | title = Spectrophotometry of Sextans A and B: Chemical Abundances of H II Regions and Planetary Nebulae | journal = [[Astronomical Journal]] | volume = 130 | issue = 4 | pages = 1558–1573 | date = October 2005 | bibcode=2005AJ....130.1558K|arxiv = astro-ph/0502562 | s2cid = 14176608 }}</ref>

<ref name="SharinaEtAl2007"> {{Cite journal | last1 = Sharina | first1 = M.E. | last2 = Puzia | first2 = T. H. | last3 = Krylatyh | first3 = A. S. | title = A globular cluster in the dwarf galaxy Sextans B | journal = [[Astrophysical Bulletin]] | volume = 62 | issue =3 | pages = 209–216 | date = September 2009 | bibcode = 2007AstBu..62..209S|doi = 10.1134/S1990341307030029 |arxiv = 0704.3908 | s2cid = 119588326 }}</ref>

<ref name="vandenbergh1999"> {{Cite journal | last = van den Bergh | first = Sidney | title = Stellar Content of Local Group Galaxies – An Introduction | date = 1999 | bibcode = 1999IAUS..192....3V | volume = 192 | pages = 3 | journal = The Stellar Content of Local Group Galaxies}}</ref>

<ref name="vandenBergh2000">{{Cite book |last = van den bergh |first = Sidney|title = The galaxies of the Local Group|publisher = [[University of Cambridge]]|date = 2000 |pages = 265|url = https://books.google.com/books?id=NfOwG3cyAGIC&pg=PA265 |isbn = 978-0-521-65181-3}}</ref>

<ref name="AlloinGieren">{{Cite book |last = Alloin |first = Danielle M. |author2=Gieren, Wolfgang |title = Stellar candles for the extragalactic distance scale|publisher = University of Cambridge|date = 2000 |pages = 265|url = https://books.google.com/books?id=rpR1xfK3yFoC&pg=PA265 |isbn = 978-3-540-20128-1}}</ref>

</references>

==External links== {{commonscat}} * {{WikiSky}}

{{DEFAULTSORT:Sextans B}} [[Category:Dwarf galaxies]] [[Category:Irregular galaxies]] [[Category:Sextans]] [[Category:UGC objects|05373]] [[Category:Principal Galaxies Catalogue objects|028913]] [[Category:NGC 3109 subgroup]] [[Category:MCG objects|+01-26-005]]