What do we mean by a protogalactic cloud?
A) a cloud of hydrogen and helium that contracts to become a galaxy
B) a term once used historically to refer to any galaxy
C) the cloud-like halo that surrounds the disks of spiral galaxies
D) a cloud of gas that was once a galaxy
A
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A ball is rolled horizontally off a table with an initial speed of 0.24 m/s. A stop watch measures the ball's trajectory time from table to the floor to be 0.20 s. How far away from the table does the ball land? (g = 9.8 m/s2 and air resistance is negligible)
a. 0.24 m b. 0.048 m c. 0.39 m d. 0.15 m e. 0.47 m
The search for black holes involves searching for
a. single stars that emit large amounts of X-rays. b. X-ray binaries where the compact companion has a mass in excess of 3 Mo. c. large spherical regions from which no light is detected. d. pulsars with periods less than one millisecond. e. pulsars that are orbited by planets.
The two Voyager spacecraft carry a message from Earth, just in case an alien civilization ever runs across them
Indicate whether the statement is true or false
Halley's Comet returns about every ______________ years
Fill in the blank(s) with correct word