WAVES & DOPPLER EFFECT Units 23 & 22

WAVES & DOPPLER EFFECT Units 23 & 22 Dr. John P. Cise, Professor of Physics, Austin Com. College,1212 Rio Grande St. Austin Tx. 78701 [email protected] & NYTimes June 17, 2015, by Dennis Overbye, Application dedicated to Dr. John Hart, Physics Prof. of Dr. Cise, Xavier U., Cincinnati. O. Traces of Earliest Stars That Enriched Cosmos Are Spied INTRODUCTION: Original (λ) Sound & Light produced while moving away from an observer has it’s observed wavelength λ’ lengthened. λ ‘ = λ + vT where v = object speed which produced wave T = period: original produced wave. Light speed: c = λ f, f = 1/T Thus: T = λ/c , inserting into (1) yields…. ‘ λ = λ + vλ/c = λ ( 1 + v/c) eq.(1) QUESTIONS: (a)Light(yellow) of wavelength λ = 575 nm from this distant galaxy is viewed on earth as red light of wavelength λ ‘ = 585 nm. At what speed v(in km./s. & mph) is this galaxy moving away? (b) Compare v in (a) to linear speed (in km./s. & An artist's impression of the distant galaxy CR7. Scientists say mph.) of earth at equator? light from the galaxy has been traveling to us for 12.9 billion years. HINTS: n = nano = 10-9 , c = 3.0 X 108 m/s. , use eq. (1) for (a), V = R ω , R earth = 6,371 km. , 2236.93 mph/[km./s.], ω = 2πf = 2π/T , T earth = 1 day, 24 hrs/day, 3600 s./hr. 6 ANSWER: (a) v = 5217 km/s, 11.67 X 10 mph(11,670,000 mph) (b) v earth equator = 0.463 km./s. = 1036 mph Astronomers said Wednesday that they had discovered a lost generation of ((( monster stars))) that ushered light into the universe after the Big Bang and jump-started the creation of the elements needed for planets and life before disappearing forever. Modern-day stars like our sun have a healthy mix of heavy elements, known as metals, but in the aftermath of the Big Bang only hydrogen, helium and small traces of lithium were available to make the first stars. Such stars could have been hundreds or thousands of times as massive as the sun, according to calculations, burning brightly and dying quickly, only 200 million years after the universe began. Their explosions would have spewed into space the elements that started the chain of thermonuclear reactions by which subsequent generations of stars have gradually enriched the cosmos with elements like oxygen, carbon and iron. Spotting the older stars in action is one of the prime missions of the James Webb Space Telescope, to be launched by NASA in 2018. Now, in a paper to be published in The Astrophysical Journal, an international crew of astronomers led by David Sobral of the University of Lisbon, in Portugal, and the Leiden Observatory, in the Netherlands, said they had spotted the signature of these first-generation stars in a recently discovered galaxy that existed when the universe was only about 800 million years old. Its light has been traveling to us for 12.9 billion years, while succeeding generations of stars have worked their magic to make the universe interesting. The galaxy, known as CR7, is three times as luminous as any previously found from that time, the authors said. Within it is a bright blue cloud that seems to contain only hydrogen and helium. Garth Illingworth, an astronomer at the University of California, Santa Cruz, and a veteran of the search for early galaxies, pointed out, however, that these stars were appearing far later in cosmic history than theory had predicted. Dr. Sobral and his colleagues were using the Very Large Telescope of the Southern Observatory in Chile and the W. M. Keck Observatory in Hawaii, among other big telescopes, to build on an earlier search for glowing clouds of hydrogen that might represent very early galaxies.((( Galaxy CR7 — short for Cosmos Redshift 7, after the method by which distant objects in the universe are dated — stood out. In an expanding universe, the farther away or back in time an object is, the faster it is receding, which causes the wavelength of light from it to lengthen, the way the pitch of a siren sounds lower after it passes. In astronomy, this lengthening is known as redshifting))). .

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