Scorpius–Centaurus Association

OB association

The Scorpius–Centaurus Association (sometimes called Sco–Cen or Sco OB2) is a group of stars near the Sun. They are 380 to 470 light years away.[1]

Map of the Scorpius–Centaurus Association.

They are young stars which all formed from the same cloud of material. They range from 11 to 15 million years old.[2] They include the massive Antares, and most of the stars in the Southern Cross.[3]

The Sco–Cen OB association is the main part of a large complex of recent (<20 million years) and ongoing star-formation. The complex contains several star-forming molecular clouds in Sco–Cen's immediate vicinity.

The stellar members of the Sco–Cen association have nearly parallel velocity vectors, moving at about 20 km/s with respect to the Sun. The variation of velocity within the subgroups is about 1–2 km/s,[4] and the group is most likely no longer held together by gravity. Several supernovae have exploded in Sco–Cen over the past 15 million years, leaving a network of expanding gas superbubbles around the group.[5]

Iron-60 found in fossilised bacteria in sea floor sediments suggests there was a supernova near the solar system about 2,000,000 years ago.[6][7] Iron-60 is also found in sediments from 8 million years ago.[8]


  1. de Zeeuw P.T. et al 1999. "A Hipparcos census of nearby OB Associations". Astronomical Journal. 117 (1): 354–399. arXiv:astro-ph/9809227. Bibcode:1999AJ....117..354D. doi:10.1086/300682.
  2. Mark J. Pecaut, Eric E. Mamajek & Eric J. Bubar 2012. A revised age for Upper Scorpius and the star formation history among the F-type Members of the Scorpius-Centaurus OB Association. Astrophysical Journal. 746 (2): 154. arXiv:1112.1695. Bibcode:2012ApJ...746..154P. doi:10.1088/0004-637X/746/2/154 Missing or empty |title= (help)
  3. Preibisch, T. & Mamajek E. 2009. "The nearest OB Association: Scorpius-Centaurus (Sco OB2)". Handbook of Star-Forming Regions. 2: 0. arXiv:0809.0407.
  4. Madsen S. et al 2002. "Astrometric radial velocities. III. Hipparcos measurements of nearby star clusters and associations". Astronomy & Astrophysics. 381 (2): 446–463. arXiv:astro-ph/0110617. Bibcode:2002A&A...381..446M. doi:10.1051/0004-6361:20011458.
  5. de Geus E.J. (1992). "Interaction of stars and interstellar matter in Scorpio Centaurus". Astronomy & Astrophysics. 262: 258–270. Bibcode:1992A&A...262..258D.
  6. Belinda Smith (Aug 9, 2016). "Ancient bacteria store signs of supernova smattering". Cosmos.
  7. Peter Ludwig; et al. (Aug 16, 2016). "Time-resolved 2-million-year-old supernova activity discovered in Earth's microfossil record". PNAS. doi:10.1073/pnas.1601040113.
  8. Colin Barras (Oct 14, 2017). "Fires may have given our evolution a kick-start". New Scientist.