What observations demonstrate the existence of an interstellar medium?
What will be an ideal response?
One way to investigate properties of the ISM is to measure its effects on the starlight that passes through it. Astronomers observe that distant stars appear fainter than they should for their distances and luminosities, an effect called interstellar extinction. Distant stars also appear redder than they should for their spectral types, an effect called interstellar reddening. Astronomers also observe interstellar absorption lines in the spectra of stars. Lines that cannot be produced in stars must be produced by atoms located between the stars and Earth.
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What does molten rock solidify into?
a. basalt b. marble c. sandstone d. quartzite e. travertine
How has Earth's interior remained warm over its geological history?
A. the greenhouse effect B. tidal stresses from the Moon C. Earth's proximity to the Sun D. leftover heat from formation E. radioactive decay
A 20 solar mass star will stay on the main sequence for 10 million years, yet its iron core can exist for only a
A) day. B) week. C) month. D) year. E) century.
An airplane flies in a horizontal circle of radius 500 m at a speed of 150 m/s. If the plane were to fly in the same 500-m circle at a speed of 300 m/s, by what factor would its centripetal acceleration change?
a. 0.25 b. 0.50 c. 1.00 d. 2.00 e. 4.00