Astronomy:Westerhout 3

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Westerhout 3
Emission nebula
H II region
Westerhout 3
Image of Westerhout 3
Observation data: J2000.0 epoch
Right ascension 02h 27m 4.1s[1]
Declination61° 52′ 22″[2]
Distance6,000[3] ly
ConstellationCassiopeia
DesignationsW3, Sh 2-157
See also: Lists of nebulae

Westerhout 3 (also known as W3) is a giant molecular cloud and a star-forming region in the Perseus arm of the Milky Way Galaxy, first identified by the Dutch Astronmer Gart Westerhout. It is one of the most active sites of massive star formation in the outer parts of our galaxy, located in the constellation Cassiopeia at a distance of approximately 6,000 light-years from Earth. W3, with W4 and W5, forms part of the larger W3/W4/W5 complex, associated with the Heart and Soul Nebula, and corresponds specifically to the bright emission nebula Fish Head Nebula (IC 1795) within the Heart Nebula (Sh 2-190).[4][5][6]

Herschel Image of W3/W4/W5 Complex

Star Formation

W3 is a prolific star-forming region, hosting both massive O and B-type stars and lower-mass pre-main-sequence (PMS) stars in embedded clusters. Star formation appears to occur sequentially, triggered by feedback from previous generations of massive stars, including expanding ionization bubbles and stellar winds that compress surrounding gas. Ultracompact H II regions, protostellar outflows, and young stellar objects (YSOs) with circumstellar disks are common, as observed by telescopes like Chandra and Spitzer. The region exemplifies how massive stars accrete material in dense environments despite radiative feedback, with detections of large organic molecules like methanol in vast clouds.[7][8][9]

Subregion

Westerhout 3 Comprises several distinct subregions, each with unique star-forming characteristics, often studied via multi-wavelength data to map embedded clusters, H II regions, and molecular outflows. These include W3 Main, W3(OH), and others such as W3 East and W3 West, illustrating dynamic interactions within the GMC.

  • W3 Main: W3 Main is the central subregion, spanning about 7 parsecs and containing a nearly spherical cluster of around 900 X-ray-detected stars, including ultracompact H II regions and high-mass protostars. It features dense cores, filaments, and a southern cavity likely formed by stellar feedback. Intense star formation involves O-type stars and PMS objects, with infrared excesses indicating disks. Herschel observations highlight warmer, heated material in this area.[10][11][12][13][14]
Image of W3 Main
  • W3(OH): Located east of W3 Main, W3(OH) is a compact H II region known for OH and Methanol maser emissions, signaling early high-mass star formation. It exhibits an optically thick spectrum below 15 GHz, with embedded cores, outflows, and hot gas. Protostellar clusters form here, potentially triggered by cloud collisions involving three overlapping molecular clouds. Additional star-forming sites lie south of W3(OH), contributing to the HDL's diversity. It is one of W3's most luminous compact sources, as per Herschel and JCMT data.[15][16][17][18][19]
  • Other subregions includes W3 East and W3 West with full widths at half maximum under 0.45 parsecs, showing high densities and protostellar activity akin to the main areas. They exemplify sequential star formation driven by expanding bubbles from prior stellar generations.[20]

Observation and Research

W3 has been extensively observed across wavelengths to study its kinematics, gas properties, and stellar populations. Key instruments include the Herschel Space Observatory for far-infrared imaging, the Chandra X-ray Observatory for stellar clusters, and the Spitzer Space Telescope for infrared excesses in YSOs. Research focuses on the interplay between stellar feedback and cloud evolution, making W3 a model for obscured star formation processes.[21][22]

References

  1. ↑ "Simbad - Object view". https://simbad.cds.unistra.fr/mobile/object.html?object_name=W3. 
  2. ↑ "Simbad - Object view". https://simbad.cds.unistra.fr/mobile/object.html?object_name=W3. 
  3. ↑ "ESA Science & Technology - Herschel's view of the W3/W4/W5 complex". https://sci.esa.int/web/herschel/-/59538-herschel-s-view-of-the-w3w4w5-complex. 
  4. ↑ "ESA Science & Technology - Herschel's view of the W3/W4/W5 complex". https://sci.esa.int/web/herschel/-/59538-herschel-s-view-of-the-w3w4w5-complex. 
  5. ↑ "New Theory of How Giant Stars Grow Unveiled" (in en). 2013-03-27. https://www.space.com/20406-how-stars-grow-massive.html. 
  6. ↑ "Things Unseen: The Westerhout radio sources | Galaxy Map". http://galaxymap.org/drupal/node/32. 
  7. ↑ Kiminki, Megan M.; Kim, Jinyoung Serena; Bagley, Micaela B.; Sherry, William H.; Rieke, George H. (2015-11-01). "THE O- and B-TYPE STELLAR POPULATION in W3: Beyond the HIGH-DENSITY LAYER". Astrophysical Journal 813 (1): 42. doi:10.1088/0004-637X/813/1/42. ISSN 0004-637X. Bibcode: 2015ApJ...813...42K. https://www.scopus.com/pages/publications/84946772167. 
  8. ↑ GaryABC, Stuart (2013-03-28). "Massive stars built in stellar nurseries" (in en-AU). http://www.abc.net.au/science/articles/2013/03/28/3724967.htm. 
  9. ↑ "ESA Science & Technology - Herschel's view of the W3/W4/W5 complex". https://sci.esa.int/web/herschel/-/59538-herschel-s-view-of-the-w3w4w5-complex. 
  10. ↑ "Chandra :: Photo Album :: W3 Main :: 18 Dec 06". https://chandra.harvard.edu/photo/2006/w3/. 
  11. ↑ "W3 star-forming region – Herschel Space Observatory" (in en-GB). 2013-03-27. https://herscheltelescope.org.uk/results/w3-star-forming-region/. 
  12. ↑ "How to build a really, really big star | University of Toronto" (in en). https://www.utoronto.ca/news/how-build-really-really-big-star. 
  13. ↑ Polychroni, Danae; Moore, Toby J. T.; Allsopp, James (2012-02-22), "The gas properties of the W3 giant molecular cloud: A HARP study", Monthly Notices of the Royal Astronomical Society 422 (4): 2992–3003, doi:10.1111/j.1365-2966.2012.20803.x, Bibcode: 2012MNRAS.422.2992P 
  14. ↑ Feigelson, Eric D.; Townsley, Leisa K. (2008-01-20). "The Diverse Stellar Populations of the W3 Star-forming Complex" (in en). The Astrophysical Journal 673 (1): 354–362. doi:10.1086/524031. ISSN 0004-637X. Bibcode: 2008ApJ...673..354F. https://iopscience.iop.org/article/10.1086/524031. 
  15. ↑ "W3(OH) · NRAO/AUI Archives". https://www.nrao.edu/archives/items/show/33495. 
  16. ↑ Colley, D. (1980). "1980MNRAS.193..495C Page 495". Monthly Notices of the Royal Astronomical Society 193: 495. doi:10.1093/mnras/193.3.495. Bibcode: 1980MNRAS.193..495C. 
  17. ↑ Yamada, Rin I; Sano, Hidetoshi; Tachihara, Kengo; Enokiya, Rei; Nishimura, Atsushi; Fujita, Shinji; Kohno, Mikito; Bieging, John H et al. (2024-10-03). "A kinematic analysis of the giant molecular complex W3: Possible evidence for cloud–cloud collisions that triggered OB star clusters in W3 Main and W3(OH)" (in en). Publications of the Astronomical Society of Japan 76 (5): 895–911. doi:10.1093/pasj/psae056. ISSN 0004-6264. https://academic.oup.com/pasj/article/76/5/895/7720735. 
  18. ↑ "Astronomers find alcohol cloud spanning 288 billion miles" (in en). https://phys.org/news/2006-04-astronomers-alcohol-cloud-spanning-billion.html. 
  19. ↑ "HERSCHELOBSERVATIONS OF THE W3 GMC: CLUES TO THE FORMATION OF CLUSTERS OF HIGH-MASS STARS - McMaster Experts" (in en). https://experts.mcmaster.ca/display/publication188538. 
  20. ↑ "HERSCHELOBSERVATIONS OF THE W3 GMC: CLUES TO THE FORMATION OF CLUSTERS OF HIGH-MASS STARS - McMaster Experts" (in en). https://experts.mcmaster.ca/display/publication188538. 
  21. ↑ "ESA Science & Technology - Herschel's view of the W3/W4/W5 complex". https://sci.esa.int/web/herschel/-/59538-herschel-s-view-of-the-w3w4w5-complex. 
  22. ↑ "How to build a really, really big star | University of Toronto" (in en). https://www.utoronto.ca/news/how-build-really-really-big-star. 



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