When does a protostar become a main-sequence star?
A) when the rate of hydrogen fusion becomes high enough to balance the rate at which the star radiates energy into space
B) when a piece of a molecular cloud first begins to contract into a star
C) when it becomes luminous enough to emit thermal radiation
D) at the instant that the first hydrogen fusion reactions occur in the protostar's core
A
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________________ absorbs most of the ultraviolet radiation coming from the Sun
Fill in the blank(s) with correct word
The Hope Diamond weighs 44.5 carats. There are 200 mg per carat. How many kilograms does the Hope Diamond weigh?
A) 0.000890 kg B) 0.00890 kg C) 0.0890 kg D) 0.890 kg E) 8.90 kg
Which of the following picture might best describe a soap or detergent?
A) a B) b C) c D) d E) none of the above
Why should one not stare at the Sun during a partial eclipse?
A) Because, whether there is an eclipse or not, the Sun's intense radiation can easily damage our eyes. B) Because the eclipse event itself creates a lensing effect, which greatly magnifies and intensifies the Suns rays. C) Because Sunspots, which are excited by the eclipse event, can easily erupt during the eclipse. D) Because Ultraviolet radiation is intensified during the event. E) Because coronas and corneas are always a bad mix.