Explain how giant molecular clouds give rise to spiral tracers as they move through a disk with spiral density waves
What will be an ideal response?
A spiral density wave is a stable concentration of interstellar gas and dust. Clouds of gas and dust moving at different orbital velocities approach the dense area of the wave and collide with the material in the density wave. This collision increases mass density and triggers star formation.
The young stars created in this process will include O and B stars, which will make the arms visible with their high luminosity. The OB associations will create emission nebulae, causing a wave of star formation. The newly-formed stars will continue on the orbital track of the original cloud, passing through the leading edge of the density wave and continuing through the disk. The short-lived O and B stars will go through their entire evolutionary cycle before exiting the area of the density wave, so they are only seen in the region of the wave.
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Two isotopes have the same __________ number
Fill in the blank(s) with correct word
A 1.20-kg ball is hanging from the end of a rope. The rope hangs at an angle 25.0° from the vertical when a 15.0 m/s horizontal wind is blowing. If the wind's force on the rope is negligible, what drag force does the wind exert on the ball?
A) 32.3 N B) 24.1 N C) 3.68 N D) 5.48 N E) 11.8 N
An astronaut on a strange new planet having no atmosphere finds that she can jump up to a maximum height of 27 m when her initial upward speed is 6.0 m/s. What is the magnitude of the acceleration due to gravity on the planet?
What will be an ideal response?
White dwarfs are relatively
a. hot and dim. b. cool and dim. c. hot and bright. d. cool and bright.