The blanketing effect (also referred to as line blanketing or the line-blanketing effect) is the enhancement of the red or infrared regions of a stellar spectrum at the expense of the other regions, with an overall diminishing effect on the whole spectrum. The term originates in a 1928 article by astrophysicist Edward Arthur Milne, where it was used to describe the effects that the astronomical metals in a star's outer regions had on that star's spectrum.[1] The name arose because the absorption lines act as a "blanket", causing the continuum temperature of the spectrum to rise over what it would have been if these lines were not present.[2]
Astronomical metals, which produce most of a star's spectral absorption lines, absorb a fraction of the star's radiant energy (a phenomenon known as the blocking effect) and then re-emit it at a lower frequency as part of the backwarming effect.[3] The combination of both these effects results in the position of stars in a color-color diagram to shift towards redder areas as the proportion of metals in them increases. The blanketing effect is thus highly dependent on the metallicity index of a star, which indicates the fraction of elements other than hydrogen and helium that compose it.
References edit
- ^ Milne, E. A. (1928). "The total absorption in the Sun's reversing layer". The Observatory. 51: 88–96. Bibcode:1928Obs....51...88M.
- ^ Sandage, Allan R.; Eggen, Olin J. (1959). "On the existence of subdwarfs in the (Mbol, log Te)-diagram". Monthly Notices of the Royal Astronomical Society. 119 (3): 278–296. Bibcode:1959MNRAS.119..278S. doi:10.1093/mnras/119.3.278.
- ^ Straižys, Vytautas (1992). Multicolor Stellar Photometry. Tucson: Pachart Publishing House.
External links edit
- "Line-Blanketing Effects on the uvbyβ Photometric System"; McNamara, D. H. & Colton, D. J. (1969)
- The Treatment of Line Blanketing
- David J. Darling (2004). The universal book of astronomy: from the Andromeda Galaxy to the zone of avoidance. Wiley. p. 293. ISBN 978-0-471-26569-6.
- Metallicity and the spectral energy distribution of O stars; Martín-Hernández, N. L., Mokiem, M. R., de Koter, A. & Tielens, A. G. G. M. (2002)
- Line Blanketing, Oxford Articles, May 2013