* Astronomy

Thermionic emission is the heat-induced flow of charge carriers from a surface or over a potential-energy barrier.
The phenomenon was initially reported in 1873 by Frederick Guthrie in Britain. While doing work on charged objects, Guthrie discovered that a red-hot iron sphere with a positive charge would lose its charge (by somehow discharging it into air). He also found that this did not happen if the sphere had a negative charge. Other early contributors included Hittorf (1869-1883), Goldstein (1885), and Elster and Geitel (1882-1889).
The effect was rediscovered by Thomas Edison on February 13, 1880, while trying to discover the reason for breakage of lamp filaments and uneven blackening (darkest near one terminal of the filament) of the bulbs in his incandescent lamps.
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