Other Free Encyclopedias » Online Encyclopedia » Encyclopedia - Featured Articles » Contributed Topics from P-T

Russell, Henry Norris

star spectral magnitude diagram

(1877–1957) US astronomer: inferred stellar evolution from spectral type/luminosity relationship.

Russell’s interest in astronomy probably began when, as a 5-year-old, his parents showed him a transit of Venus. After graduating from Princeton and a period in Cambridge, Russell spent his working life in Princeton. In 1913 he discovered that the absolute magnitude (the magnitude a star would have at 10 parsec distance from the Sun) of stars correlate well with their spectral class, which is indicative of surface temperature and related to their colour. He displayed his findings on a diagram of absolute magnitude vs spectral class, now known as the Hertzsprung–Russell (or H–R) diagram–had obtained similar results a few years earlier but his publication in an obscure journal had received little attention. Russell went on to suggest that the diagram represented an evolutionary path, with stars evolving into hot, bright blue-white giants and ending as cooler red dwarfs. Although this simple theory was soon abandoned, the diagram has remained a key tool in astrophysics. In the modern view, a star is formed from a cloud of gas (mainly hydrogen) and dust which contracts through gravity, eventually becoming dense enough for the heat developed by contraction to initiate nuclear fusion reactions which convert its hydrogen into helium. Its place in the main sequence, and its later fate, depend on its mass. A star of the Sun’s mass will spend 10 10 years in the main sequence before new core reactions begin, and the star becomes a red giant. The next stage is that of a white dwarf, but for heavier stars it may explode as a supernova, leaving a neutron star.Hertzsprung–Russell diagram–schematic colour-magnitude diagram for many stars. The Sun, spectral type G, lies in the main sequence.

Russell also studied chemical abundances in the Sun (a yellow dwarf) from the solar spectrum, concluding in 1929 that hydrogen makes up 60% of the Sun’s volume, at the time a surprisingly large figure, but now known to be an underestimate by over 20%.

Russell, Kurt - Actor, Career, Sidelights [next] [back] Ruska, Ernst August Friedrich

User Comments

Your email address will be altered so spam harvesting bots can't read it easily.
Hide my email completely instead?

Cancel or