This is the H-R diagram for stars in a 12-billion-year-old globular cluster. Based on our understanding of stellar lives, which of the four labeled stars is currently generating energy through hydrogen fusion in a shell around an inert (nonfusing) helium core?

A) I
B) II
C) III
D) IV


C) III

Physics & Space Science

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Emission nebulae like M42 occur only near stars that emit large amounts of:

A) visible light. B) microwaves. C) ultraviolet radiation. D) infrared heat. E) X-rays and gamma rays.

Physics & Space Science

The kinetic energy of the electron in the first Bohr orbit of hydrogen is 2.18 × J

Indicate whether the statement is true or false

Physics & Space Science

The wave properties of light can limit telescope resolution by causing

A. Circular diffraction B. Scattering off impurities C. Thin film interference D. Uneven magnification

Physics & Space Science

Which is not a color?

A) yellow-green B) black C) both of these D) neither of these

Physics & Space Science