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Heliopolis, ancient city, Egypt

(Encyclopedia)Heliopolis hēlēŏpˈəlĭs [key] [Gr.,=city of the sun], ancient city, N Egypt, in the Nile delta, 6 mi (10 km) below modern Cairo. It was noted as the center of sun worship, and its god Ra or Re wa...

Hertzsprung, Ejnar

(Encyclopedia)Hertzsprung, Ejnar īˈnär hĕrtsˈspro͞ong [key], 1873–1967, Danish astronomer. Although trained as a chemical engineer, Hertzsprung made his career in astronomy, specializing in exacting photogr...

mass-luminosity relation

(Encyclopedia)mass-luminosity relation, in astronomy, law stating that the luminosity of a star is proportional to some power of the mass of the star. More massive stars are in general more luminous. For stars on t...

Poisson, Siméon Denis

(Encyclopedia)Poisson, Siméon Denis sēmāôNˈ dənēˈ pwäsôNˈ [key], 1781–1840, French mathematician and physicist. From 1802 he taught at the École polytechnique, Paris, and was also on the faculty of sc...

blue shift

(Encyclopedia)blue shift or blueshift, in astronomy, the systematic displacement of individual lines in the spectrum of a celestial object toward the blue, or shorter wavelength, end of the visible spectrum. The am...

Bode, Johann Elert

(Encyclopedia)Bode, Johann Elert yōˈhän āˈlĕrt bōˈdə [key], 1747–1826, German astronomer. From 1772 to 1825 he was astronomer of the Academy of Science, Berlin, and from 1786, director of the Berlin Obse...

Adams, John Couch

(Encyclopedia)Adams, John Couch, 1819–92, English astronomer, grad. St. John's College, Cambridge, 1843. By mathematical calculation based on irregularities in the motion of Uranus, he predicted the position of t...

galaxy

(Encyclopedia)CE5 Hubble classification of galaxies: Elliptical galaxies (E) are classified according to the degree of flattening of the ellipse. Spiral galaxies (S) and barred spiral galaxies (SB) are classifie...

Davis, Raymond, Jr.

(Encyclopedia)Davis, Raymond, Jr., 1914–2006, American astrochemist, Ph.D. Yale Univ. 1942. Davis, who served in the Army Air Forces from 1942 to 1946, was a researcher at Monsanto Chemical Company (1946–48) an...

Ibn al-Haytham

(Encyclopedia)Ibn al-Haytham ălhəzĕnˈ [key], 965–c.1040, Arab mathematician. Ibn al-Haytham was born in Basra, but made his career in Cairo, where he supported himself copying scientific manuscripts. Among hi...