Exam 12: Characterizing Stars

The Sun's luminosity is 3.83 *10²⁶ watts. By the time this energy reaches Earth, it has spread out so that it provides only 1370 watts to each square meter. The orbit of Mars has a mean radius of 1.53 au. How many watts of the Sun's luminosity are provided to each square meter of the surface of Mars?

Which of these sequences of stellar spectral classifications is in the correct order of INCREASING temperature?

What observations of a star are necessary to determine the absolute magnitude of a star?

What fraction of the stars surrounding the Sun are main-sequence stars?

Which important stellar parameter can be derived from the study of binary stars mutually bound to each other by gravitational forces?

The radial velocity curve of a star in a binary star system is a plot against time of the

By what standard technique did astronomers in the 1930s originally determine the luminosity class (I, II, III, IV, or V) of a star?

Use the Hertzsprung-Russell diagram (Figure 12-7) and the mass-luminosity relation (Figure 12-15) in the text, to estimate the mass of Vega, an AO V main-sequence star with a surface temperature of about 10,000 K.

An astronomer is observing a binary system with two stars of masses M₁ and M₂. She determines a, the semimajor axis (also the average distance between the stars) and P, the period of their motion. Using this information in Kepler's third law she can calculate

The chemical makeup of the Sun's surface can be determined by

Which of these types of main-sequence stars would have the LARGEST mass?

As one moves upward and to the left on the H-R diagram, the stars become

Spectral classification of a star into the lettered categories, O, B, A, F, G, K, and M is carried out by

Stars of spectral type O, the hottest blue-white stars, have spectra characterized by

Which of these stars (each of which is listed with its apparent magnitude) would NOT be visible to the unaided eye on a clear night?

A particular star appears fainter seen through a blue filter than seen through a yellow filter. Which of these surface temperatures is possible for this star?

The star Spica is classified as B1 V, which means that it is a

Which of these four spectral classifications signifies the coolest stellar surface temperature?

Which of these stars (each of which is listed with its apparent magnitude) looks brightest when viewed from Earth?

The star $\gamma$ Phoenicis has an apparent magnitude of +3.4 and an absolute magnitude of -4.6. The North Star (Polaris) has an apparent magnitude of +2.0 and an absolute magnitude of -4.6. Assuming that no light has been absorbed or scattered by interstellar dust, one can say for sure that Polaris is