Exam 12: Characterizing Stars

A particular star in a binary star system orbits the other in an elliptical orbit with a semimajor axis of 3 au and a period of 5 years. What is the sum of the masses of the two stars in the system?

A star of apparent magnitude -2 appears _____ than a star of apparent magnitude -3.

The ancient Greek astronomer Hipparchus introduced the magnitude scale on which he called the brightest stars "first magnitude". Today, the brightest star in the night sky is Sirius, with a magnitude of -1.4, considerably brighter than first magnitude. Why the discrepancy?

Which of these molecules produces the strong absorption bands in the spectrum of a cool M-type star, as can be seen in Figure 12-5 in the text?

How many times brighter is a star with an apparent magnitude of +1.0 than a star with an apparent magnitude of +6.0?

Which sentence describes the relationship between mass and luminosity of stars on the main sequence?

The star Elnath is classified as B7 III and the star Al Na'ir is classified as B7 IV. Compared with Al Na'ir, Elnath has about the same

Three stars have the following absolute (M) and apparent (m) magnitudes. Star A: M = 1.8 m = 3.8 Star B: M = 2.5 m = 9.5 Star C: M = 7.6 m = 15.1 Which star is closest to Earth?

Absorption lines in the spectra of some binary stars are seen to change periodically from single to double lines and back again. Explain.

How much can astronomers learn about a star from a measurement of its apparent magnitude?

Rigel, the bright star in the knee of Orion, has a surface temperature of about 12,000 K. Through which filter will it appear brightest?

The star $\alpha$ Centauri C and the star Groombridge 34 B have the same apparent magnitude, but $\alpha$ Centauri C is 1.3 pc away from Earth and Groombridge 34 B is 3.5 pc away. What is the luminosity of Groombridge 34 B compared with $\alpha$ Centauri C?

To determine the sum of the masses of a visual binary star system, what needs to be measured?

Two stars, one classified A4 V and the other F8 V, have the same apparent magnitude. There is no significant amount of absorption of starlight by interstellar material. From this information one knows that the A4 V star is _____ the F8 V star.

If astronomers measure the parallax of a star against the background stars and conclude that the star has a parallax of 0.004 arcsec, how far is the star from Earth?

Why is there a limited range of stellar surface temperatures around 10,000 K at which neutral hydrogen gas absorbs visible light in the Balmer series?

The light intensity from a particular star remains essentially constant except for short and regular decreases, after which it increases again to its constant value. What is the MOST plausible explanation for this phenomenon?

The star Rigel, in the constellation Orion, appears brighter through a blue filter than it does through a yellow filter. Suppose that a second star is found that is slightly brighter than Rigel through the yellow filter but is much brighter than Rigel through the blue filter. From this information, one can say conclusively that the second star has

A particular star is 20 pc away from Earth. What is the stellar parallax for this star?

Which of these possible factors MOST seriously limits the accuracy of spectroscopic parallax?