Westerhout 49

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Westerhout 49, also known as W49, is a strong galactic thermal radio source characteristic of an HII region. It was discovered by Gart Westerhout in 1958. Its distance is estimated to be about 14-15 kpcs and it lies in the galactic plane about the same distance from the galactic centre as does the Sun. It has been compared to the giant HII region NGC 3603 which is about half as distant. Non-thermal radiation has been found which is believed to be from an old supernova remnant. Gaseous molecular outflows have been detected as well as H₂O (water) masers . No optical counterpart has yet been discovered. While this is partly due to interstellar absorption, any tight clustering of stars at such a great distance in the galactic plane would be scarcely distinguishable from the general background.

[edit] References

A Survey of the Continuous Radiation from the Galactic System at a Frequency of 1390 Mc/s, G. Westerhout, Bull. Astron. Inst. Neth.14, 215, 1958.

A Distant HII Region in the Galaxy, K. Akabane and F. J. Kerr (Frank John Kerr), Aust. J. Phys. 18, 91, 1965.

Galactic HII Regions. The nature of the Radio Source W49, P. G. Mezger and J. Schraml, Astropys. J.150, 807,1967.

High Resolution Observations of the Radio Source W49, C. G. Wynn-Williams, Mon. Not. R. astr. Soc. 142, 453 1969.

High Resolution Far-infrared Observations of HII Regions: Sagittarius B2, W49, DR 21- W75, P. M. Harvey, M. F. Campbell and W. F. Hoffman, Astrophys. J. 211, 786, 1977.