Corona: Star signs

The Sun's corona — a layer of plasma much hotter than the underlying surface photosphere — can be studied at optical wavelengths during total eclipses, or with the aid of a coronagraph. The high temperature of the corona cannot be explained by heating by the underlying layers, a problem that is still unresolved. While all Sun-like stars are surrounded by coronae, it has been possible to detect their thermal emission only by using X-ray satellites. Now Schmitt and Wichman report the detection of a coronal emission line in a Sun-like star using a ground-based telescope. The measurements indicate strong similarities between solar and stellar coronal heating mechanisms. The convenience and high spectral resolution of such ground-based observations opens up new avenues of research — for example, it should be possible to look for stars displaying coronal activity cycles analogous to the Sun's.

Ground-based observation of emission lines from the corona of a red-dwarf star
J. H. M. M. SCHMITT AND R. WICHMAN
Nature 412, 508-510 (2 August 2001)
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Starry aura spotted

2 August 2001 table of contents