Scorpius–Centaurus association

{{Short description|Nearest OB association to Earth}} {{Infobox stellar association | name = Scorpius–Centaurus association | image = [[File:ScoCen.jpg|300px]] | caption = Scorpius–Centaurus association | credit = | constellation= [[Scorpius (constellation)|Scorpius]] [[Lupus (constellation)|Lupus]] [[Centaurus]] [[Crux]] [[Musca (constellation)|Musca]] | epoch = J2000 | ra = {{RA|16|15|0.00}}<ref name=":SIMBAD">{{Cite web|title=Sco OB2 |url=https://simbad.cds.unistra.fr/mobile/object.html?object_name=NAME%20Upper%20Sco-Cen|website=simbad.cds.unistra.fr|access-date=2026-01-30}}</ref> | dec = {{DEC|-24|11|60.0}}<ref name=":SIMBAD" /> | dist_ly = 420 [[Light-year|ly]]<ref name=":5" /> | dist_pc = 130 [[parsec|pc]] | span_ly = | span_pc = | rv = −4.1<ref name=":5">{{Cite journal|title=Kinematics of OB-associations and the new reduction of the Hipparcos data|journal=Monthly Notices of the Royal Astronomical Society|date=2009-11-21|pages=518–523|volume=400|issue=1|doi=10.1111/j.1365-2966.2009.15484.x|language=en|first1=A. M.|last1=Mel'nik|first2=A. K.|last2=Dambis |doi-access=free |arxiv=0909.0618 |bibcode=2009MNRAS.400..518M }}</ref> | uvw = | age_myr = | mass_msol = | num_members = | num_ob_stars = | subgroups = Upper Scorpius, Upper Centaurus–Lupus, Lower Centaurus–Crux | names = Sco–Cen, Sco OB2 }}

The '''Scorpius–Centaurus association''' (also known as '''Sco–Cen''' or '''Sco OB2''') is the closest [[OB association]] to the Solar System, composed of three subgroups (''Upper Scorpius'', ''Upper Centaurus–Lupus'', and ''Lower Centaurus–Crux'') and located at a distance of 420 [[light-year]]s (130 [[parsec]]s) from the Sun.<ref name=":P. T. de Zeeuw et al 1999">{{Cite journal |last1=de Zeeuw |first1=P. T. |last2=Hoogerwerf |first2=R. |last3=de Bruijne |first3=J. H. J. |last4=Brown |first4=A. G. A. |last5=Blaauw |first5=A. |date=January 1999 |title=A ''Hipparcos'' Census of the Nearby OB Associations |url=https://iopscience.iop.org/article/10.1086/300682 |journal=The Astronomical Journal |volume=117 |issue=1 |pages=354–399 |doi=10.1086/300682 |arxiv=astro-ph/9809227 |bibcode=1999AJ....117..354D }}</ref><ref name=melnik>{{cite journal|arxiv=2006.14649|doi=10.1007/s10509-020-03827-0|title=Distance scale for high-luminosity stars in OB associations and in field with Gaia DR2. Spurious systematic motions|year=2020|last1=Melnik|first1=A. M.|last2=Dambis|first2=A. K.|journal=Astrophysics and Space Science|volume=365|issue=7|page=112|bibcode=2020Ap&SS.365..112M|s2cid=220128144}}</ref> Analysis using improved [[Hipparcos]] data has brought the number of known members to 436. The cluster shows a continuous spread of stars with no apparent need for subclassification.<ref name=mnras416_3108>{{citation | last1=Rizzuto | first1=Aaron | last2=Ireland| first2=Michael | last3=Robertson | first3=J. G. | title=Multidimensional Bayesian membership analysis of the Sco OB2 moving group | journal=Monthly Notices of the Royal Astronomical Society |date=October 2011 | volume=416 | issue=4 | pages=3108–17 | doi=10.1111/j.1365-2966.2011.19256.x | doi-access=free | bibcode=2011MNRAS.416.3108R | arxiv=1106.2857 | s2cid=54510608 | postscript=. }}</ref>

The Sco–Cen subgroups range in age from 11 million years (Upper Scorpius)<ref name="Pecaut">{{Cite journal|author=Mark J. Pecaut|author2=Eric E. Mamajek|author3=Eric J. Bubar|name-list-style=amp|date=February 2012|title=A Revised Age for Upper Scorpius and the Star Formation History among the F-type Members of the Scorpius–Centaurus OB Association|journal=Astrophysical Journal|volume=746|issue=2|page=154|arxiv = 1112.1695 |bibcode = 2012ApJ...746..154P |doi = 10.1088/0004-637X/746/2/154 |s2cid=118461108}}</ref> to roughly 15 million years (Upper Centaurus–Lupus and Lower Centaurus–Crux). Many of the bright [[star]]s in the [[constellation]]s of [[Scorpius]], [[Lupus (constellation)|Lupus]], [[Centaurus]], and [[Crux]] are in fact the brightest members of the Sco–Cen association, including the [[red supergiant star]] [[Antares]] (the most massive member of Upper Scorpius), and most of the stars in the [[Southern Cross]].<ref name="Preibisch2009">{{cite journal|title=The Nearest OB Association: Scorpius-Centaurus (Sco OB2)|author=Preibisch, T.|author2=Mamajek, E.|date=2009|journal=Handbook of Star-Forming Regions|volume=2|page=0|bibcode=2008hsf2.book..235P|arxiv=0809.0407}}</ref> The total stellar population in each of the three subgroups is probably of the order 1000–2000,<ref>{{cite journal|bibcode=2002AJ....124.1670M|author=Mamajek, E.E.|author2=Meyer, M.R.|author3=Liebert, James |name-list-style=amp|date=2002|journal=Astronomical Journal|volume=124|issue=3|pages=1670–1694|title=Post-T Tauri Stars in the Nearest OB Association|doi=10.1086/341952|arxiv = astro-ph/0205417 |s2cid=16855894}}</ref> and the total number of stars in the association exceeds 10,000.<ref name=":2">{{Cite journal |last1=Damiani |first1=F. |last2=Prisinzano |first2=L. |last3=Pillitteri |first3=I. |last4=Micela |first4=G. |last5=Sciortino |first5=S. |date=March 2019 |title=Stellar population of Sco OB2 revealed by Gaia DR2 data |url=https://www.aanda.org/10.1051/0004-6361/201833994 |journal=Astronomy & Astrophysics |volume=623 |pages=A112 |doi=10.1051/0004-6361/201833994 |arxiv=1807.11884 |bibcode=2019A&A...623A.112D |issn=0004-6361}}</ref>

The stellar members of the Sco–Cen association have convergent [[proper motions]] of approximately 0.02–0.04 [[arcseconds]] per year, indicating that the stars have nearly parallel velocity vectors, moving at about 20 km/s with respect to the [[Sun]]. The dispersion of the velocities within the subgroups are only of order 1–2 km/s,<ref>{{cite journal| title=Astrometric radial velocities. III. Hipparcos measurements of nearby star clusters and associations|author=Madsen, S.|display-authors= etal|date=2002 |journal=Astronomy & Astrophysics|volume=381| issue=2|pages=446–463|bibcode=2002A&A...381..446M| doi=10.1051/0004-6361:20011458|arxiv = astro-ph/0110617 |s2cid=17596452}}</ref> and the group is most likely gravitationally unbound. Several [[supernovae]] have exploded in Sco–Cen over the past 15 million years, leaving a network of expanding gas [[superbubble]]s around the group,<ref name=":3">{{cite journal| date=1992| bibcode=1992A&A...262..258D|author=de Geus, E.J.| title=Interaction of Stars and Interstellar Matter in Scorpio Centaurus| journal=Astronomy & Astrophysics|volume=262|pages=258–270}}</ref> including the [[Loop I Bubble]].

To it has been hypothesized that a nearby [[supernova]], possibly a member of Sco–Cen, exploded in the [[Sun]]'s vicinity roughly 3 million years ago,<ref>{{cite journal| date=2005| bibcode=2005ApJ...621..902F| author=Fields, Brian D.| author2=Hochmuth, Kathrin A.| author3=Ellis, John| title=Deep-Ocean Crusts as Telescopes: Using Live Radioisotopes to Probe Supernova Nucleosynthesis| journal=Astrophys. J.| volume=621| issue=2| pages=902–07| doi=10.1086/427797|arxiv = astro-ph/0410525 | s2cid=17932224}}</ref> causing the [[Pliocene–Pleistocene boundary marine extinction]]<ref>{{cite journal| date=2005| author=Benítez, N.| author2=Maíz-Apellániz, J.| author3=Canelles M.| title=Evidence for nearby supernova explosions| journal=Phys. Rev. Lett.| volume=88| issue=8| article-number=081101| doi=10.1103/physrevlett.88.081101| pmid=11863949|arxiv = astro-ph/0201018 |bibcode = 2002PhRvL..88h1101B | s2cid=41229823}}</ref> and leaving [[radioactive]] 60[[Iron#Isotopes|Fe]] in deep ocean ferromanganese crusts and in biogenic magnetite crystals within Pacific Ocean sediments.<ref name="LudwigBishop2016">{{cite journal|year=2016|title=Time-resolved 2-million-year-old supernova activity discovered in Earth's microfossil record|journal=Proceedings of the National Academy of Sciences|volume=113|issue=33|pages=9232–9237|doi=10.1073/pnas.1601040113|issn=0027-8424|last1=Ludwig|first1=Peter|display-authors=etal|pmid=27503888|pmc=4995991|arxiv=1710.09573|bibcode=2016PNAS..113.9232L|doi-access=free}}</ref> However, other findings cite the distance at which this supernova occurred at more than 100 parsec, maintaining that it is not likely not to have contributed to this extinction through the mechanism of what is known as an ultra-violet B (UV-B) catastrophe.<ref name="LudwigBishop2016" /><ref>{{Cite journal|last=Cockell|first=CS|date=1999|title=Crises and extinction in the fossil record—A role for ultraviolet radiation?|journal=Paleobiology|volume=25|issue=2|pages=212–225|doi=10.1017/S0094837300026518|bibcode=1999Pbio...25..212C |s2cid=132108580 }}</ref> In 2019, researchers found interstellar iron in Antarctica which they relate to the [[Local Interstellar Cloud]], which might have been formed near the Sco-Cen association.<ref name="Interstellar Iron">{{cite journal |title=Interstellar 60Fe in Antarctica |volume = 123|issue = 7|article-number = 072701|first1=D. |last1=Koll |first2=al. |last2=et. |journal=Physical Review Letters |year=2019 |doi=10.1103/PhysRevLett.123.072701|pmid = 31491090|bibcode = 2019PhRvL.123g2701K|s2cid = 201868513|hdl=1885/298253|hdl-access=free}}</ref>

The Scorpius-Centaurus Association is one of the most conspicuous and easily recognizable galactic structures in the entire celestial vault, as well as, in terms of apparent size, the largest OB association visible from Earth. It extends for over fifty degrees and includes a large number of very bright blue stars, whose apparent magnitudes can reach first magnitude, making them visible even from the centers of large cities.<ref name=":4">{{Cite web |last=Gonzaga |first=Shireen |date=2023-07-27 |title=The Scorpion's Crown and its stellar neighborhood |url=https://earthsky.org/favorite-star-patterns/scorpions-crown-scorpius-centaurus-association/ |access-date=2026-02-09 |website=earthsky.org |language=en-US}}</ref> Generally speaking, it can be said that almost all the bright stars that make up the constellations of Lupus, the northern part of Scorpius, Centaurus and the Southern Cross belong to this association; only a few stars are exceptions, such as [[Alpha Centauri]], [[Gacrux]], [[Theta Centauri]] and [[Iota Centauri]], which appear in this region of the sky only due to visual perspective, as they are located in the foreground with respect to the association. The association appears tangent to the luminous trail of the Milky Way, inclined, with respect to it, by more than 20°.<ref name=":P. T. de Zeeuw et al 1999" />

The Scorpius-Centaurus Association lies entirely in the Southern Celestial Hemisphere. The northernmost part, coinciding with the Antares region, lies at an average declination of −23° and is visible without excessive difficulty—even from much of the Northern Hemisphere. The central segments, coinciding with the constellations of Lupus and Northern Centaurus, lie on average at 40°S and can only be observed from lower temperate, Mediterranean, and subtropical latitudes.<ref name=":P. T. de Zeeuw et al 1999" /> The southern section extends into the southernmost part of Centaurus and the Southern Cross, until it touches Musca and ends in Carina with the bright [[open cluster]] of [[IC 2602]] (the Southern Pleiades). The southern section is only easily observable from tropical regions, and it is no coincidence that from the Southern Hemisphere it appears to be circumpolar and extend throughout the extratropical belt.<ref name=":P. T. de Zeeuw et al 1999" />

Due to its wide extension across the starry sky, a complete and clear view of the association can only be obtained from regions in the Southern Hemisphere, where the portion of the Milky Way affected by its presence, which coincides with the southernmost part, appears high on the horizon. Global views are also possible north of the equator, in the lower tropical zone, provided the southern horizon is completely clear of obstacles.<ref name=":4" /> The ideal time for its observation in the evening hours is between March and June, its presence high in the sky during southern nights indicates the advance of the autumn season, while in the Northern Hemisphere, the northern parts of Centaurus and Scorpius appearing in the southeast indicate the imminent arrival of the summer season.<ref>{{Cite journal |last1=Murphy |first1=Simon J. |last2=Lawson |first2=Warrick A. |last3=Bento |first3=Joao |date=2015-11-01 |title=New members of the TW Hydrae Association and two accreting M-dwarfs in Scorpius–Centaurus |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=453 |issue=3 |pages=2221–2232 |doi=10.1093/mnras/stv1745 |doi-access=free |issn=0035-8711|arxiv=1507.08002 }}</ref>

Due to the precession of the equinoxes, the south celestial pole is slowly moving towards the southwestern part of the association, between the Southern Cross and Carina. Within a few thousand years, when the south celestial pole will point towards the Milky Way and the False Cross asterism, the stars of the Scorpius-Centaurus association will have reached their southernmost point. As the Earth's axis moves away from that region of the sky, the constellations of Scorpius and Centaurus will assume increasingly northerly declinations, until they even move partly north of the celestial equator.<ref>{{Cite web |title=La precessione |url=https://pwg.gsfc.nasa.gov/stargaze/Iprecess.htm |access-date=2026-01-29 |website=pwg.gsfc.nasa.gov}}</ref><ref>{{Cite web |last=Williams |first=Matthew |date=2011-03-26 |title=Southern Cross Constellation |url=https://www.universetoday.com/articles/southern-cross-constellation |access-date=2026-02-09 |website=Universe Today |language=en}}</ref>

==Characteristics== The Scorpius–Centaurus (Sco–Cen) association region exemplifies a medium-scale star formation process, wherein giant molecular clouds produce stars across a broad mass spectrum, before disintegrating under the influence of stellar winds and supernova explosions from its progeny—which accumulate, compact, and erode residual gas and dust to trigger additional, often marginal, star formation episodes. As the most prominent component of a vast complex of recent (<20 million years old) and ongoing star formation, the Sco–Cen OB association encompasses numerous nearby molecular clouds at distances of approximately 120–200 parsecs, including the [[Rho Ophiuchi cloud complex|Rho Ophiuchi]], [[Pipe Nebula]], [[Barnard 68]], [[Chamaeleon complex|Chamaeleon]], [[Lupus molecular clouds|Lupus]], [[Corona Australis Molecular Cloud|Corona Australis]], and [[Coalsack Nebula|Coalsack]] complexes, these peripheral clouds, aligned along the association's inclination relative to the Milky Way, host relatively subdued low-mass star formation and form the edges of the broader Scorpius–Centaurus complex, featuring western structures like the Chamaeleon and Coalsack nebulas, and eastern ones such as the Lupus, Corona Australis, Rho Ophiuchi, and Pipe nebulas, oriented toward the [[galactic bulge]]. Surrounding Sco–Cen are several less dense young stellar groups, including the ~3–5 million-year-old [[Epsilon Chamaeleontis association|Epsilon Chamaeleontis group]], ~7 million-year-old [[Eta Chamaeleontis moving group]], ~8 million-year-old [[TW Hydrae association]], ~12 million-year-old [[Beta Pictoris moving group]], and possibly the ~30–50 million-year-old [[IC 2602]] open cluster.<ref>{{Cite journal |last1=Mamajek |first1=E. E. |last2=Feigelson |first2=E. D. |date=2001 |title=The Dispersal of Young Stars and the Greater Sco-Cen Association |url=https://ui.adsabs.harvard.edu/abs/2001ASPC..244..104M/abstract |journal=Young Stars Near Earth: Progress and Prospects |language=en |volume=244 |pages=104–115 |arxiv=astro-ph/0105290 |bibcode=2001ASPC..244..104M |issn=1050-3390}}</ref><ref name="Preibisch2009" />

The three large subregions of the association are almost completely devoid of interstellar gas, which has been completely swept away. The stars present here also show a very low extinction rate, an indication of low obscuration due to dust. A complex ring-like structure has formed around the association, a low-density bubble whose edges are composed of molecular hydrogen ([[HI Region|H I]]), whose mass is around 300,000 {{Solar mass}} and could coincide with what remains of the large molecular cloud from which the association itself originated.<ref name=":1">{{Cite journal |last1=Geus |first1=De |last2=J |first2=E. |date=August 1992 |title=Interactions of stars and interstellar matter in Scorpio Centaurus. |url=https://ui.adsabs.harvard.edu/abs/1992A&A...262..258D/abstract |journal=Astronomy and Astrophysics |language=en |volume=262 |pages=258–270 |bibcode=1992A&A...262..258D |issn=0004-6361}}</ref>

Compared to other regions of the Galaxy of more or less contemporary origin, the Scorpius-Centaurus association hosts a higher percentage of double or multiple systems, up to a rate 1.16 times higher than the average, and this percentage increases significantly if low-mass [[pre-main sequence star]]s, such as [[red dwarfs]], are considered. A study conducted on almost 200 members of the first spectral classes (i.e. the blue-white stars of class B and A) located mainly in the northernmost part of the association, showed the presence of 176 companion stars, of which at least eighty are physically linked to the major stars around which they have been observed. On average, the masses of these minor stellar and substellar components identified vary from 0.03 to 1.2 {{Solar mass}}.<ref>{{Cite journal |last1=Köhler |first1=R. |last2=Kunkel |first2=M. |last3=Leinert |first3=C. |last4=Zinnecker |first4=H. |date=April 2000 |title=Multiplicity of X-ray selected T Tauri stars in the Scorpius-Centaurus OB association |url=https://ui.adsabs.harvard.edu/abs/2000A&A...356..541K/abstract |journal=Astronomy and Astrophysics |language=en |volume=356 |pages=541–558 |bibcode=2000A&A...356..541K |issn=0004-6361}}</ref><ref>{{Cite journal |last1=Kouwenhoven |first1=M. B. N. |last2=Brown |first2=A. G. A. |last3=Zinnecker |first3=H. |last4=Kaper |first4=L. |last5=Portegies Zwart |first5=S. F. |date=January 2005 |title=The primordial binary population. I. A near-infrared adaptive optics search for close visual companions to A star members of Scorpius OB2 |url=https://ui.adsabs.harvard.edu/abs/2005A&A...430..137K/abstract |journal=Astronomy and Astrophysics |language=en |volume=430 |pages=137–154 |doi=10.1051/0004-6361:20048124 |arxiv=astro-ph/0410106 |bibcode=2005A&A...430..137K |issn=0004-6361}}</ref>

===Evolution=== [[File:ScoCendynamics.png|thumb|The possible dynamics of the star formation processes that led to the formation of the Scorpius-Centaurus association. Areas where star formation has ceased are shown in red, those where it is still active are shown in green, and inactive clouds are shown in gray]]

The dynamics that led to the formation of the various subgroups of the association are very complex and partly still unknown. Specifically, the processes that took place in the northern part of the association, visible in the direction of Scorpius, are known, while those that generated the two southernmost subgroups remain almost completely unknown. It is known that the age of the stars in the association increases as one proceeds in a westerly direction, a sign that the oldest star formation phenomena took place mainly in the region occupied by the constellation of Centaurus, it is also known that the stars located north of the galactic equator have a younger age (about 12 million years) than those located to the south (about 17 million years). Furthermore, the southern part appears to be at a distance of 109 parsecs, slightly closer than the northern part, located at 123 parsecs.<ref name=":P. T. de Zeeuw et al 1999" />

According to some very simplified models, star formation would have initially taken place in the northern part of the upper Centaurus-Lupus group, about 17 million years ago, and would have then extended southwards, to the lower Centaurus-Crux group, reaching its peak about 12 million years ago; the new stars would have been initially concentrated in small clusters and filaments surrounded by gas, containing tens or hundreds of stars. The residual gas of the progenitor molecular cloud would have subsequently been swept away by the combined action of the stellar wind and the supernova explosions of the most massive components, which completed their life cycle very quickly. About 6 million years ago these generative processes extended to the clouds located south of the galactic equator, in particular in the regions of the Chameleon Cloud and stars [[Epsilon Chamaeleontis|Epsilon]] and [[Eta Chamaeleontis]].<ref name="Preibisch2009" />

Starting from 12 million years ago, the bubble formed by the wind of the young stars of the upper Centaurus-Lupus group began its expansion, perhaps further accelerated by the explosion of some supernova at a later time. About 5 million years ago, the expansion front of the bubble generated pressure and compressed the molecular cloud corresponding to the current group of stars that form the head of Scorpius, generating the youngest part of the association, the upper Scorpius group, also catalogued as Scorpius OB2. Through the knowledge of the physical distance between the two groups of the association, equal to about 60 parsecs, it has been calculated that the expansion velocity of this bubble was about 25 km/s.<ref name=":1" />

The burst of star formation in the Northern Scorpius Cloud generated approximately 2,500 stars, including some particularly massive ones with masses exceeding 10 {{Solar mass}}. These stars rapidly evolved and subsequently exploded as supernovae, generating, among others, the pulsar [[PSR J1932+1059]]. The powerful shock waves generated by these explosions almost completely swept away the residual gas of the ancient molecular cloud, whose remnants are visible in the delicate filaments known as [[Sh 2-1]] and [[Sh 2-7]]. The shock waves also impacted the adjacent Rho Ophiuchi Cloud over the last million years, fueling the intense star formation activity in the region that can still be observed today. The same shock waves may also be responsible for the initiation of stellar genesis phenomena in the Lupus Molecular Cloud, where the oldest stellar components show an age less than 1 million years.<ref>{{Cite journal |last1=Motte |first1=F. |last2=Andre |first2=P. |last3=Neri |first3=R. |date=August 1998 |title=The initial conditions of star formation in the rho Ophiuchi main cloud: wide-field millimeter continuum mapping |url=https://ui.adsabs.harvard.edu/abs/1998A&A...336..150M/abstract |journal=Astronomy and Astrophysics |language=en |volume=336 |pages=150–172 |bibcode=1998A&A...336..150M |issn=0004-6361}}</ref><ref>{{Cite journal |last1=Tachihara |first1=Kengo |last2=Toyoda |first2=Shuichiro |last3=Onishi |first3=Toshikazu |last4=Mizuno |first4=Akira |last5=Fukui |first5=Yasuo |last6=Neuhäuser |first6=Ralph |date=December 2001 |title=12CO Molecular Cloud Survey and Global Star Formation in Lupus |url=https://ui.adsabs.harvard.edu/abs/2001PASJ...53.1081T/abstract |journal=Publications of the Astronomical Society of Japan |language=en |volume=53 |issue=6 |pages=1081–1096 |doi=10.1093/pasj/53.6.1081 |bibcode=2001PASJ...53.1081T |issn=0004-6264}}</ref>

==Structure== The Scorpius-Centaurus association is traditionally divided into three groups, which show slightly different ages and characteristics. The northern section is called Upper Scorpius (US) and includes all the blue stars in the northwestern part of Scorpius, including Antares. The central section, the largest, is called Upper Centaurus-Lupus (UCL) and includes almost all the stars of Lupus and most of the northern and central stars of Centaurus. The southernmost part of the association is called Lower Centaurus-Crux (LCC), and lies in the wake of the Milky Way. It includes the southern part of Centaurus, excluding [[Alpha Centauri]], and the Southern Cross, excluding [[Gacrux]]. The southwestern edge of the association coincides with the bright cluster of the [[IC 2602|Southern Pleiades]] (IC 2602).<ref name="Preibisch2009" />

===Upper Scorpius association=== [[File:Antaresmoving.jpg|thumb|Upper Scorpius association]]

The '''Upper Scorpius Association''' (US) is the youngest part of the Scorpius-Centaurus Association. It formed about 5 million years ago and contains about 120 massive stellar components, dispersed over a 35 parsec region that is about 145 parsecs from the Sun. The spectral class of these components varies between B0.5 and G5, and most of them lie on the main sequence—although there are some stars already in an advanced evolutionary phase, among which the red supergiant [[Antares]] (α Scorpii) stands out. Despite the young age of the group, no star formation is currently taking place in the region, which is instead active in the adjacent Rho Ophiuchi cloud. Of the original components, the most massive have already completed their life cycle and exploded as supernovae. The most massive among them was probably the progenitor of the [[pulsar]] [[PSR J1932+1059]], which exploded about 1.5 million years ago, and whose original mass was probably around 50 {{Solar mass}}. Although it was speculated that this star was the larger companion of the runaway star [[Zeta Ophiuchi]], subsequent measurements suggest that the two stars were separated from their origin.<ref>{{Cite journal |last1=Hoogerwerf |first1=R. |last2=de Bruijne |first2=J. H. J. |last3=de Zeeuw |first3=P. T. |date=January 2001 |title=On the origin of the O and B-type stars with high velocities. II. Runaway stars and pulsars ejected from the nearby young stellar groups |url=https://ui.adsabs.harvard.edu/abs/2001A&A...365...49H/abstract |journal=Astronomy and Astrophysics |language=en |volume=365 |issue=2 |pages=49–77 |doi=10.1051/0004-6361:20000014 |arxiv=astro-ph/0010057 |bibcode=2001A&A...365...49H |issn=0004-6361}}</ref><ref>{{Cite journal |last1=Chatterjee |first1=S. |last2=Cordes |first2=J. M. |last3=Vlemmings |first3=W. H. T. |last4=Arzoumanian |first4=Z. |last5=Goss |first5=W. M. |last6=Lazio |first6=T. J. W. |date=2004-03-20 |title=Pulsar Parallaxes at 5 GHz with the Very Long Baseline Array |url=https://iopscience.iop.org/article/10.1086/381748 |journal=The Astrophysical Journal |language=en |volume=604 |issue=1 |pages=339–345 |doi=10.1086/381748 |arxiv=astro-ph/0312044 |bibcode=2004ApJ...604..339C |issn=0004-637X}}</ref><ref name=":P. T. de Zeeuw et al 1999" />

In addition to the high-mass stars, several hundred low and medium mass stars, as well as some [[T Tauri star]]s, have been discovered. Some of these stars, however, are not physically related to the association, but are part of the Rho Ophiuchi star-forming region. A portion of the low-mass objects may fall into the category of brown dwarfs: their masses are in fact between 0.3 and 0.007 M⊙, and a dozen of these have a mass equal to or less than 15 Jupiter masses.<ref>{{Cite journal |last1=Lodieu |first1=N. |last2=Hambly |first2=N. C. |last3=Jameson |first3=R. F. |last4=Hodgkin |first4=S. T. |last5=Carraro |first5=G. |last6=Kendall |first6=T. R. |date=2007-01-01 |title=New brown dwarfs in Upper Sco using UKIDSS Galactic Cluster Survey science verification data |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=374 |issue=1 |pages=372–384 |doi=10.1111/j.1365-2966.2006.11151.x |doi-access=free |arxiv=astro-ph/0610140 |bibcode=2007MNRAS.374..372L |issn=0035-8711}}</ref>

In December 2021, around 70 new [[rogue planet]]s were discovered in the Upper Scorpius association.<ref name=eso2120>{{cite web | title = ESO telescopes help uncover largest group of rogue planets yet | url = https://www.eso.org/public/news/eso2120/ | publisher = [[European Southern Observatory]] | date = 22 December 2021 | access-date = 22 December 2021}} See also attached [https://www.eso.org/public/archives/releases/sciencepapers/eso2120/eso2120a_en.pdf research paper].</ref>

===Upper Centaurus-Lupus association=== [[File:UCLgroup.png|thumb|Upper Centaurus-Lupus association]]

The '''Upper Centaurus-Lupus association''' (UCL) constitutes the central body of the association. It includes hundreds of large and medium mass stellar components, many of which are clearly visible even to the naked eye, which make up almost the entire constellation of Lupus and part of Scorpius and Centaurus. Unlike the Upper Scorpius association, the study of this large group of stars is made more difficult by several factors: first, its position much closer to the galactic plane, which makes it more difficult to correctly determine the group's true physical components with respect to the background stars. Added to this is a greater dispersion of its stellar components and the almost total absence of pre-main sequence stars shrouded in nebulosity, due to the group's greater age. Finally, its declination means that it is only clearly visible and able to be studied by observers located at southern or, at least, tropical latitudes. The parallax measurement of the UCL components indicates a distance between approximately 90 and 200 parsecs, this large range is due to the great depth extension of the group itself, therefore some components appear to be closer and others further away.<ref name=":P. T. de Zeeuw et al 1999" /><ref name="Preibisch2009" />

The most massive components of the group belong to the spectral class B and have an apparent magnitude between 2.0 and 3.5 on average. The easternmost components are found in the central part of Scorpius, including the famous optical pair formed by the stars [[Mu1 Scorpii|Mu¹]] and [[Mu2 Scorpii|Mu² Scorpii]], and the most massive components of the group, [[Alpha Lupi|Alpha]] and [[Beta Lupi]]. These are mostly blue giants and blue subgiants, and, unlike the upper Scorpius group, there are no components of the lower spectral classes. This absence can be explained by the older age of the upper Centaurus-Lupus group, estimated at around 17 million years: the most massive components originally part of the group have already exploded as supernovae. The supernova remnants associated with these explosions coincide with a large expanding superbubble with a diameter of 200 parsecs, the edges of which are clearly visible in the neutral hydrogen (HI) band. The powerful shock wave generated by the explosions, combined with the action of the stellar wind of the hottest stars in the group, has completely dissolved the original molecular cloud that generated them.<ref name=":P. T. de Zeeuw et al 1999" /><ref name=":3" /><ref name=":2" /><ref>{{Cite journal|title=Large Supernova Remnants as Common Features of the Disk|url=https://ui.adsabs.harvard.edu/abs/1979IAUS...84..295W/abstract|journal=The Large-Scale Characteristics of the Galaxy|date=1979|issn=1743-9221|pages=295|volume=84|language=en|first=H.|last=Weaver |bibcode=1979IAUS...84..295W }}</ref>

The population of low-mass stars was detected largely in the late 1990s, when the launch of the [[ROSAT]] satellite allowed the study of the sky in X-rays, and attention was concentrated on the Lupus Cloud, adjacent to the UCL group. In this region, 136 stars with characteristics similar to T Tauri stars were identified in 1997. The stars identified in this region show different ages depending on their position: the stars scattered outside the cloud are older than those known inside it. This difference in age, 5-27 million years for the older stars and 1 million years for the younger, shows that these belong to two distinct stellar populations, and originate from different molecular clouds.<ref>{{Cite journal |last1=Krautter |first1=J. |last2=Wichmann |first2=R. |last3=Schmitt |first3=J. H.M.M. |last4=Alcalá |first4=J. M. |last5=Neuhäuser |first5=R. |last6=Terranegra |first6=L. |date=June 1997 |title=New "weak-line"–T Tauri stars in Lupus |url=http://aas.aanda.org/10.1051/aas:1997163 |journal=Astronomy and Astrophysics Supplement Series |volume=123 |issue=2 |pages=329–352 |doi=10.1051/aas:1997163 |bibcode=1997A&AS..123..329K |issn=0365-0138}}</ref><ref>{{Cite journal |last=Makarov |first=Valeri V. |date=2007-03-20 |title=The Lupus Association of Pre–Main-Sequence Stars: Clues to Star Formation Scattered in Space and Time |url=https://iopscience.iop.org/article/10.1086/511261 |journal=The Astrophysical Journal |language=en |volume=658 |issue=1 |pages=480–486 |doi=10.1086/511261 |bibcode=2007ApJ...658..480M |issn=0004-637X}}</ref>

The low and medium mass stellar components of class G and K (yellow dwarfs, like the Sun, and orange dwarfs), mostly in the pre-main sequence phase, show a large amount of [[lithium]]. Based on the study of more than fifty of these components, an average age of between 15 and 22 million years has been determined.<ref name=":P. T. de Zeeuw et al 1999" /><ref name=":2" />

===Lower Centaurus-Crux association=== [[File:LCCgroup.png|thumb|Lower Centaurus-Crux association]]

The '''Lower Centaurus-Crux association''' (LCC) is the least known and studied part of the Scorpius-Centaurus Association, although it is also the closest: its distance is estimated to be around 118 parsecs. It extends in the southwestern part of Centaurus and occupies the area of sky in the direction of the Southern Cross and the Fly, until it reaches the northeastern edge of Carina. The age of the stars in the group vary according to their position. The components in the northeastern part, the closest to the UCL group, have an age of about 17 million years, very similar to that of the central group. The more southern components have a younger age, equal to about 12 million years; this reveals that the star formation phenomena extended from north to south.<ref name=":P. T. de Zeeuw et al 1999" /><ref name="Preibisch2009" />

The northern part has a higher density than the southern part, which appears more dispersed. Among the higher-mass components, several are clearly visible even to the naked eye and appear as very bright stars. These include six very massive stars, referred to as the "super Cen-Cru six", namely [[Beta Centauri|Hadar]], one of the brightest stars in the sky, halfway between the lower and central group, [[Acrux]], [[Mimosa (star)|Mimosa]], [[Delta Centauri|Delta]], [[Epsilon Centauri|Epsilon]] and [[Rho Centauri]]. Other easily observed stars include [[Gamma Centauri]], [[Alpha Muscae|Alpha]] and [[Beta Muscae]]. However, some of these stars show anomalies in their proper motion, and their exact membership in the association is still a matter of study. The southwestern edge is represented by the open cluster [[IC 2602]]. Among the massive components there are two [[Herbig Ae/Be star]]s, catalogued with the acronyms [[HD 100546]] and [[HD 100453]], of sixth and seventh magnitude respectively, with ages around 10 million years. HD 100453, seems to have a red pre-main sequence companion (class M), although its presence has not been confirmed spectroscopically.<ref name=":P. T. de Zeeuw et al 1999" /><ref name="Preibisch2009" /><ref>{{Cite journal |last1=Chen |first1=X. P. |last2=Henning |first2=T. |last3=van Boekel |first3=R. |last4=Grady |first4=C. A. |date=January 2006 |title=VLT/NACO adaptive optics imaging of the Herbig Ae star HD 100453 |url=https://ui.adsabs.harvard.edu/abs/2006A&A...445..331C/abstract |journal=Astronomy and Astrophysics |language=en |volume=445 |issue=1 |pages=331–335 |doi=10.1051/0004-6361:20054122 |bibcode=2006A&A...445..331C |issn=0004-6361}}</ref>

The group contains about 120 low-mass stellar components, whose magnitudes are between the eighth and eleventh magnitude. These are mostly main sequence, pre-main sequence, and T Tauri stars belonging to the G and K classes (yellow and orange), identified through various studies conducted since the nineties through observations made using the [[ROSAT]] satellite.<ref>{{Cite journal |last1=Torres |first1=C. A. O. |last2=Quast |first2=G. R. |last3=da Silva |first3=L. |last4=de la Reza |first4=R. |last5=Melo |first5=C. H. F. |last6=Sterzik |first6=M. |date=December 2006 |title=Search for associations containing young stars (SACY): I. Sample and searching method |url=http://www.aanda.org/10.1051/0004-6361:20065602 |journal=Astronomy & Astrophysics |volume=460 |issue=3 |pages=695–708 |doi=10.1051/0004-6361:20065602 |arxiv=astro-ph/0609258 |bibcode=2006A&A...460..695T |issn=0004-6361}}</ref><ref name=":2" /><ref name="Preibisch2009" />

== Members stars and Exoplanets == Almost all bright stars in Constellation of [[Scorpius (constellation)|Scorpius]], [[Centaurus (constellation)|Centaurus]], [[Lupus (constellation)|Lupus]] and [[Crux (constellation)|Crux]] are members of Scorpius-Centaurus association.<ref name="Preibisch2009" />

{{Clear}} {| class="wikitable sortable" |- ! class="unsortable"| Name ([[Star designation|Designation]]) ! Distance (ly) ! [[Stellar classification]] ! [[Apparent magnitude]] ! Note |- |colspan=5|''Upper Scorpius association'' |- |rowspan=2| [[Antares]] (Alpha Scorpii) |rowspan=2| 550 |style="background: {{star-color|M}};" |M1.5Iab-Ib |rowspan=2| 0.6–1.6 |rowspan=2| |- |style="background: {{star-color|B}};" |B2.5V |- |rowspan=2| [[Delta Scorpii]] (Dschubba) |rowspan=2| 470 |style="background: {{star-color|B}};" | B0.3 IV |rowspan=2| 1.59 - 2.32 |rowspan=2| |- |style="background: {{star-color|B}};" | B1-3V |- |rowspan=2| [[Beta Scorpii|Beta¹ Scorpii]] (Acrab) |rowspan=2| 400 ± 40 |style="background: {{star-color|B}};" |B0.5IV-V |rowspan=2| 2.62 |rowspan=2| |- |style="background: {{star-color|B}};" |B1.5V |- |rowspan=2| [[Mu1 Scorpii|Mu¹ Scorpii]] (Xamidimura) |rowspan=2| 500 |style="background: {{star-color|B}};" | B1.5 V |rowspan=2| 2.94 - 3.22 |rowspan=2| |- |style="background: {{star-color|B}};" | B6.5 V |- | [[Mu2 Scorpii|Mu² Scorpii]] (Pipirima) | 474 ± 8 |style="background: {{star-color|B}};" | B2 IV | 3.56 | |- |colspan=5|''Upper Centaurus-Lupus association'' |- | [[Alpha Lupi]] (Uridim) | 460 ± 10 |style="background: {{star-color|B}};" | B1.5 III | 2.30 | |- | [[Eta Centauri]] | 306 ± 6 |style="background: {{star-color|B}};" | B1.5 Vne | 2.35 | |- | [[Beta Lupi]] | 383 ± 8 |style="background: {{star-color|B}};" | B2 III | 2.68 | |- | [[Gamma Lupi]] | 420 ± 30 |style="background: {{star-color|B}};" | B2 IV | 2.77 | |- |rowspan=2| [[Kappa Centauri]] AB |rowspan=2| 400 ± 20 |style="background: {{star-color|B}};" | B2V |rowspan=2| 3.14 |rowspan=2| |- |style="background: {{star-color|B}};" |B3V |- | [[Delta Lupi]] | 900 |style="background: {{star-color|B}};" | B1.5 IV | 3.20 - 3.24 | |- | [[Epsilon Lupi]] | 510 |style="background: {{star-color|B}};" | B2 IV-V | 3.41 | |- |rowspan=3| [[Eta Lupi]] |rowspan=3| 440 ± 10 |style="background: {{star-color|B}};" | B2 IV |rowspan=3| 3.41 |rowspan=3| |- |style="background: {{star-color|A}};" |A5 Vp |- |style="background: {{star-color|F}};" |F5 V |- | [[Nu Centauri]] (Heng) | 437 ± 10 |style="background: {{star-color|B}};" | B2 IV | 3.41 | |- | [[Mu Centauri]] | 510 ± 10 |style="background: {{star-color|B}};" | B2V:e | 3.42 | |- | [[Iota Lupi]] | 338 ± 7 |style="background: {{star-color|B}};" | B2.5 IV | 3.54 | |- | [[Phi Centauri]] | 530 ± 10 |style="background: {{star-color|B}};" | B2 IV | 3.745 | |- |colspan=5|''Lower Centaurus-Crux association'' |- |rowspan=2| [[Acrux]] (Alpha Crucis) |rowspan=2| 320 ± 20 |style="background: {{star-color|B}};" | B0.5IV |rowspan=2| 0.76 |rowspan=2| |- |style="background: {{star-color|B}};" | B1V |- |rowspan=3| [[Beta Centauri]] (Hadar) |rowspan=3| 361 ± 2 |style="background: {{star-color|B}};" | B1 III |rowspan=3| 0.61 |rowspan=3| |- |style="background: {{star-color|B}};" | B1 III |- |style="background: {{star-color|B}};" | B1V |- | [[Mimosa (star)|Mimosa]] (Beta Crucis) | 280 ± 20 |style="background: {{star-color|B}};" | B0.5 III | 1.25 | |- | [[Epsilon Centauri]] | 430 ± 30 |style="background: {{star-color|B}};" | B1 III | 2.30 | |- | [[Delta Centauri]] | 410 ± 20 |style="background: {{star-color|B}};" | B2Vne or B2 IVne | 2.57 | |- | [[Alpha Muscae]] | 315 ± 3 |style="background: {{star-color|B}};" | B2 IV–V | 2.69 | |- | [[Delta Crucis]] (Imai) | 345 ± 5 |style="background: {{star-color|B}};" | B2 IV | 2.78 - 2.84 | |- |rowspan=2| [[Beta Muscae]] |rowspan=2| 340 ± 10 |style="background: {{star-color|B}};" | B2 V |rowspan=2| 3.05 |rowspan=2| |- |style="background: {{star-color|B}};" |B3 V |- | [[Lambda Centauri]] | 390 ± 10 |style="background: {{star-color|B}};" | B9 III | 3.13 | |- |rowspan=2| [[Pi Centauri]] |rowspan=2| 360 ± 10 |style="background: {{star-color|B}};" | B5Vn |rowspan=2| 3.90 |rowspan=2| |- |style="background: {{star-color|B}};" |B6V |- | [[Sigma Centauri]] | 412 ± 9 |style="background: {{star-color|B}};" | B3 V | 3.91 | |- | [[Upsilon1 Centauri|Upsilon¹ Centauri]] | 427 ± 9 |style="background: {{star-color|B}};" | B2 IV/V | 3.87 | |- | [[Rho Centauri]] | 276 ± 9 |style="background: {{star-color|B}};" | B3 V | 3.97 | |- |colspan=5|Previous Members |- | [[Zeta Ophiuchi]] | 440 ± 40 |style="background: {{star-color|O}};" | O9.5 V | 2.56 – 2.58 |The runaway star that likely originated in the association. |- |}

The Scorpius–Centaurus association contains the youngest<ref>{{Cite web |title=Planetary Systems |url=https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TblView/nph-tblView?app=ExoTbls&config=PS |access-date=2022-09-12 |website=exoplanetarchive.ipac.caltech.edu |quote=as of September 2022}}</ref> [[transiting exoplanet]]s: [[K2-33b|K2-33 b]] (11 Myrs),<ref>{{Cite journal |last1=Mann |first1=Andrew W. |last2=Newton |first2=Elisabeth R. |last3=Rizzuto |first3=Aaron C. |last4=Irwin |first4=Jonathan |last5=Feiden |first5=Gregory A. |last6=Gaidos |first6=Eric |last7=Mace |first7=Gregory N. |last8=Kraus |first8=Adam L. |last9=James |first9=David J. |last10=Ansdell |first10=Megan |last11=Charbonneau |first11=David |last12=Covey |first12=Kevin R. |last13=Ireland |first13=Michael J. |last14=Jaffe |first14=Daniel T. |last15=Johnson |first15=Marshall C. |date=2016-09-01 |title=Zodiacal Exoplanets in Time (ZEIT). III. A Short-period Planet Orbiting a Pre-main-sequence Star in the Upper Scorpius OB Association |journal=The Astronomical Journal |volume=152 |issue=3 |page=61 |doi=10.3847/0004-6256/152/3/61 |issn=0004-6256|arxiv=1604.06165 |bibcode=2016AJ....152...61M |s2cid=6552081 |doi-access=free }}</ref> [[TOI 1227 b|TOI-1227 b]] (11 Myrs)<ref>{{Cite journal |last1=Mann |first1=Andrew W. |last2=Wood |first2=Mackenna L. |last3=Schmidt |first3=Stephen P. |last4=Barber |first4=Madyson G. |last5=Owen |first5=James E. |last6=Tofflemire |first6=Benjamin M. |last7=Newton |first7=Elisabeth R. |last8=Mamajek |first8=Eric E. |last9=Bush |first9=Jonathan L. |last10=Mace |first10=Gregory N. |last11=Kraus |first11=Adam L. |last12=Thao |first12=Pa Chia |last13=Vanderburg |first13=Andrew |last14=Llama |first14=Joe |last15=Johns-Krull |first15=Christopher M. |date=2022-04-01 |title=TESS Hunt for Young and Maturing Exoplanets (THYME). VI. An 11 Myr Giant Planet Transiting a Very-low-mass Star in Lower Centaurus Crux |journal=The Astronomical Journal |volume=163 |issue=4 |page=156 |doi=10.3847/1538-3881/ac511d |arxiv=2110.09531 |bibcode=2022AJ....163..156M |issn=0004-6256|doi-access=free }}</ref> and [[HIP 67522 b]] (17 Myrs).<ref>{{Cite journal |last1=Rizzuto |first1=Aaron C. |last2=Newton |first2=Elisabeth R. |last3=Mann |first3=Andrew W. |last4=Tofflemire |first4=Benjamin M. |last5=Vanderburg |first5=Andrew |last6=Kraus |first6=Adam L. |last7=Wood |first7=Mackenna L. |last8=Quinn |first8=Samuel N. |last9=Zhou |first9=George |last10=Thao |first10=Pa Chia |last11=Law |first11=Nicholas M. |last12=Ziegler |first12=Carl |last13=Briceño |first13=César |date=2020-07-01 |title=TESS Hunt for Young and Maturing Exoplanets (THYME). II. A 17 Myr Old Transiting Hot Jupiter in the Sco-Cen Association |journal=The Astronomical Journal |volume=160 |issue=1 |page=33 |doi=10.3847/1538-3881/ab94b7 |arxiv=2005.00013 |bibcode=2020AJ....160...33R |issn=0004-6256|doi-access=free }}</ref> It also contains [[List of directly imaged exoplanets|directly imaged exoplanets]] such as [[UScoCTIO 108|UScoCTIO 108 b]] and the [[PDS 70]] system.<ref>{{Cite journal |last1=Keppler |first1=M. |last2=Benisty |first2=M. |last3=Müller |first3=A. |last4=Henning |first4=Th. |last5=van Boekel |first5=R. |last6=Cantalloube |first6=F. |last7=Ginski |first7=C. |last8=van Holstein |first8=R. G. |last9=Maire |first9=A. -L. |last10=Pohl |first10=A. |last11=Samland |first11=M. |last12=Avenhaus |first12=H. |last13=Baudino |first13=J. -L. |last14=Boccaletti |first14=A. |last15=de Boer |first15=J. |date=2018-09-01 |title=Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70 |journal=Astronomy and Astrophysics |volume=617 |pages=A44 |doi=10.1051/0004-6361/201832957 |arxiv=1806.11568 |bibcode=2018A&A...617A..44K |issn=0004-6361|doi-access=free }}</ref>

==Galactic environment== [[File:OrionSpurInner.png|thumb|350px|Close up on the [[Orion Arm]], with major [[List of nearby stellar associations and moving groups|stellar association]]s (yellow), [[List of diffuse nebulae|nebulae]] (red) and [[List of dark nebulae|dark nebulae]] ([[grey]]) [[Galactic Center|coreward]] from the [[Local Bubble]] with Sco-Cen]]

The Scorpius-Centaurus association is located on the inner edge of the [[Orion Arm]] and is part of a large ring of young stars called the [[Gould Belt]], which groups together several OB associations, including Vela OB2, Orion OB1, Perseus OB2 and Lacerta OB1. With respect to the Sun, the Sco-Cen association coincides with the closest part of this ring.<ref name=":P. T. de Zeeuw et al 1999" /><ref>{{Cite journal |last1=Strauss |first1=F. M. |last2=Poeppel |first2=W. G. L. |last3=Vieira |first3=E. R. |date=January 1979 |title=The structure of Gould's Belt. |url=https://ui.adsabs.harvard.edu/abs/1979A&A....71..319S/abstract |journal=Astronomy and Astrophysics |language=en |volume=71 |issue=3 |pages=319–325 |bibcode=1979A&A....71..319S |issn=0004-6361}}</ref><ref>{{Cite journal |last1=Comeron |first1=F. |last2=Torra |first2=J. |date=January 1994 |title=The origin of the Gould Belt by the impact of a high velocity cloud on the galactic disk. |url=https://ui.adsabs.harvard.edu/abs/1994A&A...281...35C/abstract |journal=Astronomy and Astrophysics |language=en |volume=281 |pages=35–45 |bibcode=1994A&A...281...35C |issn=0004-6361}}</ref>

Other small star groups that show a similar age to each other are linked to the association, including the [[TW Hydrae association]], the [[Beta Pictoris association]] and the [[Eta Chamaeleontis association]]. All these groups, although they are found in the proximity of the association, are not in physical contact with it. Their proper motion indicates that they are moving away from it, so they were once found in the same region. One theory suggests that these groups, now isolated and dispersed, were formed together with the association, but in the peripheral regions of the large molecular cloud from which the stars of the UCL group were also born.<ref>{{Cite journal |last1=Fernández |first1=D. |last2=Figueras |first2=F. |last3=Torra |first3=J. |date=March 2008 |title=On the kinematic evolution of young local associations and the Scorpius-Centaurus complex |url=http://www.aanda.org/10.1051/0004-6361:20077720 |journal=Astronomy & Astrophysics |volume=480 |issue=3 |pages=735–751 |doi=10.1051/0004-6361:20077720 |arxiv=0801.0605 |bibcode=2008A&A...480..735F |issn=0004-6361}}</ref>

[[TW Hydrae]] is among the star groups closest to the solar system, located at a distance of 50 parsecs. It is a group of young stars, approximately 16 million years old, which, thanks to its proximity, is of great importance in the study of the accretion phenomena that accompany the formation of stars and planets; many of its stars, in fact, are surrounded by protoplanetary disks and their current evolutionary phase is considered crucial for the subsequent formation of planets. Among its components is the young brown dwarf [[2M1207]], famous for being the first star around which an extrasolar planet was observed directly from Earth through the [[2MASS]] mapping ([[2M1207 b]]).<ref>{{Cite journal |last1=Chauvin |first1=G. |last2=Lagrange |first2=A.-M. |last3=Dumas |first3=C. |last4=Zuckerman |first4=B. |last5=Mouillet |first5=D. |last6=Song |first6=I. |last7=Beuzit |first7=J.-L. |last8=Lowrance |first8=P. |date=October 2004 |title=A giant planet candidate near a young brown dwarf: Direct VLT/NACO observations using IR wavefront sensing |url=http://www.aanda.org/10.1051/0004-6361:200400056 |journal=Astronomy & Astrophysics |volume=425 |issue=2 |pages=L29–L32 |doi=10.1051/0004-6361:200400056 |arxiv=astro-ph/0409323 |bibcode=2004A&A...425L..29C |issn=0004-6361}}</ref><ref>{{Cite journal |last=Barrado y Navascués |first=D. |date=November 2006 |title=On the age of the TW Hydrae association and 2M1207334-393254 |url=http://www.aanda.org/10.1051/0004-6361:20065717 |journal=Astronomy & Astrophysics |volume=459 |issue=2 |pages=511–518 |doi=10.1051/0004-6361:20065717 |arxiv=astro-ph/0608478 |bibcode=2006A&A...459..511B |issn=0004-6361}}</ref>

In the line of sight of the Scorpius-Centaurus association lie several bright stars and objects completely unrelated to it. This includes Alpha Centauri, whose great brightness is due exclusively to the fact that it is the closest star to the Sun, located at only 4 light-years. At about 88 light-years (27 parsecs) away lies Gacrux, a red giant that overlaps with the LCC group. Both stars exhibit a large proper motion in the direction opposite to that of the association, so Alpha Centauri will appear almost superimposed on [[Beta Centauri|Hadar]] within 4000 years, while in a few tens of thousands of years it will find itself outside the boundaries of Centaurus, and Gacrux will follow the same fate. In addition to these stars, there are also two nebulae that do not belong to the association, although they are visually aligned with it: The most notable is [[IC 2944]], visible southwest of the Southern Cross, in the direction of the LCC group. It is a large [[H II region]] located at about 2000 parsecs in the [[Sagittarius Arm]]. The second is the [[Circinus Cloud]], a dense, unilluminated clump of gas with vigorous star formation. Its distance is about 700 parsecs and it is visible just southeast of Alpha Centauri.<ref>{{Cite journal |last=Reipurth |first=B. |date=December 2008 |title=Young Stars and Molecular Clouds in the IC 2944/2948 Complex |url=https://ui.adsabs.harvard.edu/abs/2008hsf2.book..213R/abstract |journal=Handbook of Star Forming Regions, Volume II |language=en |volume=5 |pages=213 |bibcode=2008hsf2.book..213R }}</ref><ref>{{Cite journal |last1=Reipurth |first1=B. |last2=Bally |first2=J. |last3=Walawender |first3=J. |date=December 2008 |title=The Circinus Star Forming Complex |url=https://ui.adsabs.harvard.edu/abs/2008hsf2.book..285R/abstract |journal=Handbook of Star Forming Regions, Volume II |language=en |volume=5 |pages=285 |bibcode=2008hsf2.book..285R }}</ref>

== See also == * [[List of nearby stellar associations and moving groups]] * [[Beta Pictoris moving group|β Pictoris moving group]] * [[Ursa Major Moving Group]]

==References== {{reflist}}

{{DEFAULTSORT:Scorpius-Centaurus Association}} [[Category:Scorpius–Centaurus association| ]] [[Category:Stellar associations]] [[Category:Scorpius]] [[Category:Centaurus]] [[Category:Lupus (constellation)]] [[Category:Crux]]