Hydrogen lines are weak in the spectra of hot O-type stars because ____
a. most of the hydrogen has been converted to helium
b. a good spectrum of these stars is difficult to obtain
c. these stars have no atmosphere
d. gravitational pressure pushes all the hydrogen lines out of the visible spectrum
e. most of the hydrogen is ionized to high energy levels
e
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ROI stands for return-on-investment.
Answer the following statement true (T) or false (F)
How old is the Galaxy? How do we know this?
What will be an ideal response?
An object accelerates when it experiences a non-zero net force. Which of the following statements is always true?
1.The object moves in the direction of the net force. 2.The object's velocity increases. 3.The object's velocity is in the same direction as its acceleration. 4.The object's acceleration is in the same direction as the net force that acts upon it.
A breeze of low-density ionized gas that streams away from the Sun through _______________ holes is called the _______________
Fill in the blank(s) with correct word