The source of energy that keeps the Sun shining today is ________.
A) gravitational contraction B) nuclear fusion
C) chemical reactions D) nuclear fission
Question 2
The number of confirmed extrasolar planets
A) is about 600, and is not expected to rise very much.
B) is about 800, and is rising slowly, as observations are quite difficult.
C) was about 800 at the time of publication but is rising rapidly due to new observations by the Kepler spacecraft.
D) has been decreasing as some observations thought to be planets have been disproven.
E) is zero; there are observations thought to be of extrasolar planets but none has yet been confirmed.
Diagrams showing the multiple energy shells and orbitals of a nitrogen atom
Activation energy of uncatalyzed and catalyzed chemical reactions
Measles rash. (© Lowell Georgia/Science Source/Photo Researchers, Inc.)
Kyo and jitsu-concept of energy deficiency and excess from shiatsu.
Activation energy
A piece of glass has a thin film of gasoline floating on it. A beam of light is shining ...