The new age of the sun.The new age of the sun The sun's age, as measured from the time it entered the main sequence of stellar evolution stellar evolution, life history of a star, beginning with its condensation out of the interstellar gas (see interstellar matter) and ending, sometimes catastrophically, when the star has exhausted its nuclear fuel or can no longer adjust itself to a stable , can't be determined directly. It has to be inferred from the ages of the oldest meteorites Meteorites See also astronomy. aerolithology the science of aerolites, whether meteoric stones or meteorites. Also called aerolitics. astrolithology the study of meteorites. Also called meteoritics. -- a difficult task because astronomers must establish a connection between the time of the sun's birth and the formation of meterorites. Recent observations of young stars in star-forming regions are starting to supply that connection. These young stars, not yet on the main sequence of stellar evolution when they ahieve core temperatures high enough to fuse hydrogen into helium, are surrounded by disks of dust and gas, out of which meteorites form. On the basis of this evidence, David B. Guenther of Yale University Yale University, at New Haven, Conn.; coeducational. Chartered as a collegiate school for men in 1701 largely as a result of the efforts of James Pierpont, it opened at Killingworth (now Clinton) in 1702, moved (1707) to Saybrook (now Old Saybrook), and in 1716 was in New Haven New Haven, city (1990 pop. 130,474), New Haven co., S Conn., a port of entry where the Quinnipiac and other small rivers enter Long Island Sound; inc. 1784. Firearms and ammunition, clocks and watches, tools, rubber and paper products, and textiles are among the many , Conn., now calculates the sun's age at 4.49 billion years, somewhat less than the 4.7 billion years commonly used in the standard solar model The Standard Solar Model (SSM) is the best current physical model of our sun. Very generally, in the Standard Solar Model the sun is a ball of mostly hydrogen plasma which is held together through self gravitation. . Guenther reports his results in the April 15 ASTROPHYSICAL JOURNAL The Astrophysical Journal, often abbreviated to ApJ, is a scientific journal covering astronomy and astrophysics. It was founded in 1895 by George Ellery Hale and James E. Keeler. It currently (October 2006) publishes three issues per month, with 500 pages per issue. . "The well-determined ages of the meteorites, the theories describing the origin of the solar system solar system, the sun and the surrounding planets, natural satellites, dwarf planets, asteroids, meteoroids, and comets that are bound by its gravity. The sun is by far the most massive part of the solar system, containing almost 99.9% of the system's total mass. , improved to fit recent infrared and radio observations of star-forming regions, and the pre-main-sequence evolutionary calculations have all combined to permit, for the first time, a relatively precise determination of the age of the sun," Guenther says. "Because the error in the age is small and because the solar model is relatively insensitive to small changes in the age, we now have grounds for using the sun's age as a fixed parameter of the standard solar model." Guenther's calculations show that the 200-million-year difference in age between the old and new estimates has little effect on present theoretical models of how the sun has evolved. Characteristics such as the helium abundance and amount of internal mixing remain relatively unchanged. At the same time, the sunhs new age is more consistent with the age of the oldest known meteorites, which are 4.53 billion years old. Such meteorites would have formed before the sun entered the main sequence of stellar evolution. |
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