Why does a star grow larger after it exhausts its core hydrogen?
A) The outer layers of the star are no longer gravitationally attracted to the core.
B) The internal radiation generated by the hydrogen fusion in the core has heated the outer layers enough that they can expand after the star is no longer fusing hydrogen.
C) Helium fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward.
D) Helium fusion in the core generates enough thermal pressure to push the upper layers outward.
E) Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward.
Question 2
What is astrometry?
A) measuring the positions of stars on the sky
B) measuring the velocities of stars via the Doppler effect
C) using metric units for distance (e.g., meters rather than light years)
D) measuring distances to stars
E) searching for planets around stars
Betelgeuse star (Hubble)
Circumpolar Star Trails
Jupiter’s and Saturn’s Upper Layers
The Structure of an Old Low-Mass Star
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