Good tracers of the spiral tracers are all I. very old. II. very young. III. very luminous. IV. moving with large radial velocities
a. I & III
b. I & IV
c. II & III
d. II & IV
e. I, III, & IV
C
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Which of the following objects is considered to possibly contain a black hole?
a. the central star of the Crab nebula b. the Orion nebula. c. LMC X-3 d. Algol e. PSR 1257+12
The amount of light received at Earth from a star is called luminosity
a. True b. False Indicate whether the statement is true or false
If the Moon formed out of the same cloud of material from which Earth formed, what can we predict about the composition of moon rocks collected by Apollo astronauts?
A. Moon rocks should have a completely different composition than rocks found on and inside Earth. B. Moon rocks should have the same composition as rocks found on Earth. C. Moon rocks should have a composition that is the same as Earth's crust. D. Moon rocks should have some similar and some different compositional characteristics.
At present, what is the primary way that the search for extraterrestrial intelligence (SETI) is carried out?
A) by using radio telescopes to search for signals from extraterrestrial civilizations B) by analyzing high-resolution images of nearby stars in search of evidence for structures that could not have developed naturally C) by searching for planets around distant stars D) by using x-ray telescopes to search for exhaust from interstellar spacecraft E) by seeking access to the secret records and alien corpses kept at the military's Area 51 in Nevada