Corona Australis Molecular Cloud

Corona Australis Molecular Cloud
Nebula
Image of Corona Australis Molecular Cloud
Observation data: J2000.0 epoch
Right ascension19h 01m 51s[1]
Declination–36° 58.9′[1]
Distance425 ly   (130 pc)
Apparent dimensions (V)16.0° × 6.5°
ConstellationCorona Australis
Physical characteristics
Radius8 ly
DesignationsCrA Dark Cloud, CrA MCLD, CrA region

The Corona Australis molecular cloud, located at a distance of 130 parsecs (~430 ly),[2][3] is a dark nebula of gas and dust and is one of the nearest star formation regions from Earth.[4] Sometimes referred to as the CrA Dark Cloud or the CrA Cloud, it hosts several reflection nebulae − NGC 6729, NGC 6726/6727, and IC 4812 being the most notable.[5] The globular cluster known as NGC 6723, which appears close by, is actually 29,000ly away, and so not part of the region.[6] The cloud is located in the constellation Corona Australis, close to the border with Sagittarius, between Gamma Coronae Australis and Epsilon Coronae Australis and stretches roughly 8ly across.

The cloud is located at about 18% below the galactic plane and covers an angular area of 16.0° × 6.5° on the celestial sphere.[4] Temperatures of the cloud ranges from 13–22 K, and there is a total of about 7,000 times the mass of the Sun in material. Over half of the mass of the complex is concentrated around a small area, and this is the most active star-forming region. There are embedded infrared sources within the complex. A total of 425 infrared sources have been detected near the L1688 cloud. These are presumed to be young stellar objects, including 16 classified as protostars, 123 T Tauri stars with dense circumstellar disks, and 77 weaker T Tauri stars with thinner disks. The last two categories of stars have estimated ages ranging from 100,000 to a million years.

Known to exhibit significant extinction, as high as 45 magnitudes at visual wavelengths (AV~45 mag), astronomers have identified 55 distinct optical members within the CrA Cloud as of 2008.[4] At the core is the Coronet protostar cluster, a loose collection of about 30 young stars with a wide range of masses at various stages of evolution.[7] Surrounding the cluster are a few late stage B stars, numerous Herbig–Haro objects, and several YSOs. At the opposite end of the mass spectrum, are two confirmed brown dwarfs along with seven more candidates.[8] There are also many embedded infrared sources within the complex. The molecular cloud has been most widely surveyed in the infrared, X-rays, radio waves and in the millimeter continuum.

Observations

In the north of the constellation is the Corona Australis Molecular Cloud, a dark molecular cloud with many embedded reflection nebulae, including NGC 6729, NGC 6726–7, and IC 4812. A star-forming region of around 7000 M☉,[9] it contains Herbig–Haro objects, T Tauri stars with dense circumstellar disks, (protostars) and some very young stars.[10] Located about 430 light years (130 parsecs) away, it is one of the closest star-forming regions to our solar system.[11] The related NGC 6726 and 6727, along with unrelated NGC 6729, were first recorded by Johann Friedrich Julius Schmidt in 1865.[12]

  • WISE infrared photo showing NGC 6723, NGC 6726-6727 and NGC 6729.
  • The R CrA region at the heart of the CrA Dark Cloud.[13][14][15]
  • Star-forming region NGC 6729 showing the dramatic birth of very young stars.[16]
  • Infrared photo of the Coronet Cluster within the R CrA region. R CrA is the bright star in the center.
  • Composite image shows the Coronet Cluster in X-rays from Chandra and infrared from Spitzer.

References

  1. ^ a b "CRA Dark Cloud -- Molecular Cloud". Simbad. Centre de Données astronomiques de Strasbourg. Retrieved 2012-09-01.
  2. ^ Esplin, T. L.; Luhman, K. L. (2022-02-01). "A Census of Stars and Disks in Corona Australis*". The Astronomical Journal. 163 (2): 64. arXiv:2111.14903. doi:10.3847/1538-3881/ac3e64. ISSN 0004-6256.
  3. ^ Posch, Laura; Miret-Roig, Núria; Alves, João; Ratzenböck, Sebastian; Großschedl, Josefa; Meingast, Stefan; Zucker, Catherine; Burkert, Andreas (2023-11). "The Corona Australis star formation complex is accelerating away from the Galactic plane". Astronomy & Astrophysics. 679: L10. arXiv:2310.14373. doi:10.1051/0004-6361/202347186. ISSN 0004-6361. {{cite journal}}: Check date values in: |date= (help)
  4. ^ a b c Neuhäuser, R.; Forbrich, J. (December 2008). "The Corona Australis Star Forming Region". Handbook of Star Forming Regions. II: 735. arXiv:0808.3374v1. Bibcode:2008hsf2.book..735N.
  5. ^ Malin, David (August 2010). "The Corona Australis nebula (NGC 6726-27-29)". Australian Astronomical Observatory. Retrieved 2012-09-02.
  6. ^ Jet Propulsion Laboratory (2010). "PIA13064: Star Clusters Young and Old, Near and Far". NASA/IPAC Extragalactic Database. California Institute of Technology/National Aeronautics and Space Administration. Retrieved 4 September 2012.
  7. ^ "Coronet: A Star Formation Neighbor". Chandra Multimedia Features. NASA. 2007-09-13. Retrieved 2012-09-02.
  8. ^ Martín, E. L. (2001). "Ultracool Dwarfs: New Spectral Types L and T". In Jones, Hugh R. A.; Steele, Iain A. (eds.). Spectroscopy of Young Brown Dwarfs and Isolated Planetary Mass Objects. Springer. pp. 153–167. ISBN 978-3-540-42353-9.
  9. ^ Kaler, Beta Coronae Australis.
  10. ^ Peterson, Dawn E. (January 2010). "Young Stellar Objects Identified with Spitzer in Corona Australis" (PDF). Bulletin of the American Astronomical Society. 42. American Astronomical Society, AAS Meeting #215, #429.35: 355. Bibcode:2010AAS...21542935P. Retrieved 2012-09-02.
  11. ^ Reipurth 2008, p. 735.
  12. ^ Steinicke 2010, p. 176.
  13. ^ Wang, Hongchi; Mundt, Reinhard; Henning, Thomas; Apai, Dániel (December 2004). "Optical Outflows in the R Coronae Australis Molecular Cloud" (PDF). The Astrophysical Journal. 617 (2): 1191–1203. Bibcode:2004ApJ...617.1191W. doi:10.1086/425493. Retrieved 2012-09-02.
  14. ^ "R Coronae Australis: A Cosmic Watercolour". Press Releases. European Southern Observatory. 30 June 2010. Retrieved 2012-09-02.
  15. ^ Haas, M.; Heymann, F.; Domke, I.; Drass, H.; Chini, R.; Hoffmeister, V. (September 2008). "A near-infrared survey of the entire R Coronae Australis cloud". Astronomy and Astrophysics. 488 (3): 987–996. arXiv:0807.2594v1. Bibcode:2008A&A...488..987H. doi:10.1051/0004-6361:200809949.
  16. ^ "The Drama of Starbirth". Press Releases. European Southern Observatory. 16 March 2011. Retrieved 2012-09-02.

Sources

  • Kaler, Jim. "Beta Coronae Australis". Stars. University of Illinois. Retrieved 5 July 2012.
  • Reipurth, Bo, ed. (2008). "The Corona Australis Star Forming Region". Handbook of Star Forming Regions. Vol. II: The Southern Sky. ASP Monograph Publications. Bibcode:2008hsf2.book..735N.
  • Steinicke, Wolfgang (2010). Observing and Cataloging Nebulae and Star Clusters: From Herschel to Dreyer. Cambridge University Press. ISBN 978-0-521-19267-5.
  1. 2011 June 27: Stars and Dust Across Corona Australis
  2. 2007 Sept 21: Coronet in the Southern Crown
  3. 2002 Oct 2: Star Clouds Toward the Southern Crown
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