Why is the spectral sequence of stars not alphabetical?
A) The letters refer to the initials of the original discovers.
B) The original alphabetical labeling did not correspond to surface temperature and thus had to be reordered.
C) They were chosen to fit a mnemonic.
D) Because there is still uncertainty over what generates the energy in stellar cores.
E) Because it refers to stellar masses and these were difficult to measure accurately.
B
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A. 9500 K B. 5300 K C. 2500 K D. 25,000 K E. 15,000 K
Weight and g: If you stood on a planet having a mass four times that of Earth's mass, and a radius two times that of Earth's radius, you would weigh
A. the same as you do on Earth. B. two times more than you do on Earth. C. two times less than you do on Earth. D. four times more than you do on Earth.
The key to identifying a black hole candidate in a binary system is that
A) one of the two stars cannot be seen. B) the unseen companion in the system must have a sufficiently high mass. C) the unseen star is a contact binary. D) the system must be a very strong source of radio emissions. E) the visible companion must be an evolving main sequence or giant star.
The normal force is always vertical
Indicate whether the statement is true or false