The age of the Milky Way galaxy has been estimated to be at least 13 billion years based on
a. observations of globular clusters.
b. observations of open clusters.
c. 21-cm radiation from H I regions.
d. the rotation curve of the galaxy.
e. the energy produced by Sagittarius A.
.E
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Graphical Addition: Vectors 
and 
obey the equation 
+ 
= 0. These vectors satisfy which one of the following statements?
A. Vectors 
and 
are at right angles to each other.
B. Vectors 
and 
point in the same direction.
C. Vectors 
and 
have the same magnitudes.
D. The magnitude of 
is the negative of the magnitude of 
.
Explain Occam's Razor
What will be an ideal response?
Although the Sun's core has a density much greater than rock, it is considered a gaseous object because
A. the Sun formed from the Solar nebula which itself was a large gas and dust cloud. B. the Sun's high internal temperature prevent the atoms from bonding together to form a liquid or a solid. C. it is composed mostly of hydrogen. D. a large fraction of the Sun's interior is made of electromagnetic radiation (light).
A cloud fragment too small to collapse into a main sequence star becomes a:
A) white dwarf. B) pulsar. C) T Tauri object. D) brown dwarf. E) planet of another star.