If the distance to the nearest star is 4.2 light-years, then
a. the star is 4.2 million AU away.
b. the light we see left the star 4.2 years ago.
c. the star must have formed 4.2 billion years ago.
d. the star must be very young.
e. the star must be very old.
b
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Many young stars in new clusters appear to be surrounded by a blue, nebulous haze. The physical process that produces this blue nebulosity is
a. mission from transitions in hydrogen atoms, predominantly in the blue part of the visible spectrum. b. the preferential scattering of blue starlight by very fine dust grains in the interstellar medium. c. emission from molecular species, particularly methane, CH4, whose emission bands are in the blue part of the visible spectrum. d. thermal (blackbody) emission from interstellar gas heated to 10,000 K by UV radiation from nearby hot, young stars
An extremely large collection of stars bound together by gravitational attraction and occupying a huge volume of space is called a _______________
a. planetary nebula b. solar system c. universe d. galaxy
Where did Thomson's model place electrons in the atom?
a. Studded throughout a positively-charged material. b. Rotating around a positively-charged core. c. Uniformly distributed in the atom. d. Clustered in the center of a positively-charged sphere. e. At the two magnetic poles of the atom.
After a skydiver reaches terminal velocity,
A. the force of gravity no longer performs work on the skydiver. B. work performed by the force of gravity is converted into gravitational potential energy. C. gravitational potential energy is no longer available to the system of the skydiver plus the Earth. D. gravitational potential energy is converted into thermal energy. E. thermal energy is converted into gravitational potential energy.