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Riga 91:
Le supergiganti rosse [[rotazione stellare|ruotano]] lentamente o molto lentamente. I modelli di evoluzione stellare indicano che anche le stelle di sequenza principale che ruotano più velocemente perdono buona parte della loro velocità di rotazione quando entrano nella fase di supergigante a causa dell'aumento di volume e delle perdite di masse. I loro nuclei continuano a ruotare più velocemente e la rotazione differenziale fra nucleo e superficie può essere molto marcata<ref name=meynet/>.
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[[File:Ssc2006-03a.jpg|left|250px|thumb|[[RSGC1]],
Le supergiganti rosse hanno al massimo 25 milioni di anni; poiché sono stelle massicce, esse si sono probabilmente formate in [[ammasso aperto|ammassi aperti]] relativamente grandi, da cui non hanno tempo di allontanarsi molto. Tuttavia, le supergiganti rosse evolvono da stelle massicce che sono rare e che hanno una esistenza più breve rispetto alle stelle meno massicce; di conseguenza, generalmente ci sono poche supergiganti rosse in ogni ammasso.
Red supergiants are necessarily no more than about 25 million years old and such massive stars are expected to form only in relatively large [[star cluster|clusters of stars]], so they are expected to be found mostly near prominent clusters. However they are fairly short-lived compared to other phases in the life of a star and only form from relatively uncommon massive stars, so there will generally only be small numbers of red supergiants in each cluster at any one time. For example, in the substantial [[Double Cluster]]s in [[Perseus]] there is just a single red supergiant, [[S Persei]], while the massive [[Hodge 301]] cluster in the [[Tarantula Nebula]] contains three.<ref name=slesnick>{{cite journal|bibcode=2002ApJ...576..880S|title=The Star Formation History and Mass Function of the Double Cluster h and χ Persei|journal=The Astrophysical Journal|volume=576|issue=2|pages=880–893|author1=Slesnick|first1=Catherine L.|last2=Hillenbrand|first2=Lynne A.|last3=Massey|first3=Philip|year=2002|doi=10.1086/341865|arxiv = astro-ph/0205130 }}</ref> Until the 21st century the largest number of red supergiants known in a single cluster was five in [[NGC 7419]].<ref name=caron>{{cite journal|doi=10.1086/377314|title=The Lack of Blue Supergiants in NGC 7419, a Red Supergiant-rich Galactic Open Cluster with Rapidly Rotating Stars|journal=The Astronomical Journal|volume=126|issue=3|pages=1415–1422|year=2003|last1=Caron|first1=Genevive|last2=Moffat|first2=Anthony F. J.|last3=St-Louis|first3=Nicole|last4=Wade|first4=Gregg A.|last5=Lester|first5=John B.|bibcode=2003AJ....126.1415C}}</ref> Most red supergiants are found singly, for example [[Betelgeuse]] in the [[Orion OB1 Association]] and [[Antares]] in the [[Scorpius-Centaurus Association]].▼
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Since 2006, a series of massive clusters have been identified near the base of the [[Crux-Scutum Arm]] of the galaxy, each containing multiple red supergiants. [[RSGC1]] contains at least 12 red supergiants, RSGC2 (also known as [[Stephenson 2]]) contains at least 26, [[RSGC3]] contains at least 8, and RSGC4 (also known as [[Alicante 8]]) contains at least 8. A total of 80 confirmed red supergiants have been identified within a small area of the sky in the direction of these clusters. These four clusters appear to be part of a massive burst of star formation 10-20 million years ago at the near end of the bar at the centre of the galaxy.<ref>{{cite journal|bibcode= 2012A&A...547A..15N|doi= 10.1051/0004-6361/201219540|title= Red supergiants around the obscured open cluster Stephenson 2|journal= Astronomy & Astrophysics|volume= 547|pages= A15|year= 2012|last1= Negueruela|first1= I.|last2= Marco|first2= A.|last3= González-Fernández|first3= C.|last4= Jiménez-Esteban|first4= F.|last5= Clark|first5= J. S.|last6= Garcia|first6= M.|last7= Solano|first7= E.|arxiv = 1208.3282 }}</ref> Similar massive clusters have been found near the far end of the galactic bar, but not such large numbers of red supergiants.<ref name=davies>{{cite journal|bibcode=2012MNRAS.419.1860D|title=A newly discovered young massive star cluster at the far end of the Galactic Bar|journal=Monthly Notices of the Royal Astronomical Society|volume=419|issue=3|pages=1860–1870|author1=Davies|first1=Ben|last2=de la Fuente|first2=Diego|last3=Najarro|first3=Francisco|last4=Hinton|first4=Jim A.|last5=Trombley|first5=Christine|last6=Figer|first6=Donald F.|last7=Puga|first7=Elena|year=2012|doi=10.1111/j.1365-2966.2011.19840.x|arxiv = 1111.2630 }}</ref>
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