02 HELMI. 2005
Julkaisupäivä
798
Katselukerrat
1824: On 22 February 1824, Pierre Jules-César Janssen was born.
Janssen was a French astronomer who in 1868 devised a method for observing solar prominences without an eclipse.
Janssen observed the total solar eclipse in India. Using a spectroscope, he proved that the solar prominences are gaseous, and identified the chromosphere as a gaseous envelope of the Sun. He noted an unknown yellow spectral line in the Sun in 1868, and told Lockyer (who subsequently recognised it as a new element he named helium, from Greek "helios" for sun).
Janssen was the first to note the granular appearance of the Sun, regularly photographed it, and published a substantial solar atlas with 6000 photographs.
Mediamodaali
20 February
1962: On 20 February 1962, US Marine Colonel John Glenn became the first American to orbit Earth.
18 February
2004: On 18 February 2004, ESA scientists announced they had seen a super-massive black hole ripping apart a star and consuming a portion of it.
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