Comets
The spectra of comets consist of a reflected solar spectrum from the dusty clouds surrounding the comet, as well as emission lines from gaseous atoms and molecules excited by sunlight fluorescence and/or chemical reactions. Nearby comets can even be seen in X-ray as solar wind ions flying to the coma are neutralized, and cometary X-ray spectra therefore reflect the state of the solar wind rather than that of the comet. Many organic chemicals are known to exist in comets, and it has been suggested that cometary impacts provided the Earth with much of the water for its oceans and the chemicals necessary for the formation of life. It has even been suggested that life may have been brought to earth from interstellar space by comets (the Panspermia theory).
Read more about this topic: Astronomical Spectroscopy
Famous quotes containing the word comets:
“The novel is not “a crazy quilt of bits”; it is a logical sequence of psychological events: the movements of stars may seem crazy to the simpleton, but wise men know the comets come back.”
—Vladimir Nabokov (1899–1977)
“I know
No answer to the children’s cry
Of echo’s answer and the man of frost
And ghostly comets over the raised fists.”
—Dylan Thomas (1914–1953)
“When beggars die there are no comets seen;
The heavens themselves blaze forth the death of princes.”
—William Shakespeare (1564–1616)