Which type of radiation has been MOST effective in evaluating the spiral arm structure of the Milky Way Galaxy?
A) 21-cm radio emission from electron spin-flip transitions in cool hydrogen gas
B) Lyman-$\alpha$ultraviolet emission from hot hydrogen gas
C) synchrotron radiation from electrons spiraling in magnetic fields in the spiral arms
D) neutrinos from exploding stars in the spiral arms, since they can easily penetrate dust and gas

Question

Quizplus · Accepted Answer

21-cm radio emission from electron spin-flip transitions in cool hydrogen gas has been most effective in evaluating the spiral arm structure of the Milky Way Galaxy because it can penetrate the interstellar dust that obscures other forms of radiation, allowing astronomers to map the distribution of hydrogen and thus the spiral arms.

Which Type of Radiation Has Been MOST Effective in Evaluating α\alphaα

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