Answer to Question 1
D
Answer to Question 2
(1 ) Astronomers create mathematical models that use the laws of physics and the Sun's observed composition, mass, and age to compute its internal conditions. Therefore, we believe that our models are accurate if they can reproduce the characteristics of the Sun that we can observe (such as its radius and luminosity). (2 ) By measuring Doppler shifts of material on the Sun's surface, we observe vibrations of the surface that are created deep within the Sun. We can learn about the densities and other characteristics of the various layers within the Sun by studying how the waves propagate throughout the Sun. (3 ) Another way that we can learn about the interior of the Sun is by detecting solar neutrinos that are produced by the nuclear fusion reactions occurring in the Sun's core.
Asteroid Orbits
Asteroid 1994 XM1
The Orbit and Tails of a Comet
A photograph of Commodore Matthew Perry in 1855 juxtaposed with a Japanese portrait of him. When Per
Crewed mission spacecraft
The first pioneer species arrived less than a decade after the eruption.