Download Binary Star Systems Discussion Points 1. What characteristic of a

Binary Star Systems Discussion Points
1. What characteristic of a star controls all of the other properties of the star?
2. About what % of all stars are in orbit with at least one other star around a common center of mass?
3. Give an example of 2 stars that appear to be close to each other in the sky, but are actually far apart from each other.
4. If both the stars in a binary system are visible with the naked eye or with a telescope, the system is a
binary system.
5. Give an example of a star system like that in the previous question.
6. For what 3 reasons might a binary star system be considered a spectroscopic binary system?
a)
b)
c)
7. What detail in the spectrum of a spectroscopic binary system lets us know that there are actually 2 stars present?
8. What was the first spectroscopic binary star system every observed?
9. Give an example of another spectroscopic binary star system.
10. If the total brightness of a binary star system varies in a regular way over time, the system is an
binary system.
11. How is the orbit of the 2 stars in the previous question oriented with respect to the earth?
12. What is the “classic” example of the type of star system in questions 10 & 11?
Use the light curves for six eclipsing binary star systems on the next page to answer the rest of the questions.
13. Which light curve shows a system where the two stars are the most different from one
another?
14. Which light curve shows a system where the two stars are the most similar to one another?
15. Label the primary and secondary minimums on the V809 Cygnii curve.
16. For the V809 Cygnii light curve, about what % of the light is blocked out during the primary
minimum?
17. For the V809 Cygnii light curve, about what % of the light is blocked out during the
secondary minimum?
18. For the V809 Cygnii light curve, during the primary minimum:
a) the brighter star is passing in front of the dimmer star.
b) the dimmer star is passing in front of the brighter star.
19. The V809 Cyg pair takes 213 years to orbit one another. The V986 Sgr pair orbits one another in only 10.3 days.
What does this mean about the distances between the stars within each pair?
Key to Binary Star Systems
1. The star’s mass.
2. 50-75%
3. Mizar & Alcor (the horse & rider in Ursa Major.)
4. visual
5. Albireo (the head of Cygnus the swan)
6.
a) The two stars are too close together to be resolved by a telescope.
b) The two stars are too far away to be able to separate their images.
c) One of the stars is too small or too dim to be able to see it against the glare of the larger, brighter star.
7. The spectroscopic lines periodically split and recombine.
8. Mizar in Ursa Major
9. Dubhe in Ursa Major, Capella in Auriga, Regulus in Leo
10. Eclipsing binary star
11. They are edge-on to the earth.
12. Algol in Perseus
13. BY Vel or V986 Sag.
14. ET Vel
Secondary
Primary
15.
16.
17.
18.
19.
About 50% of the light is blocked out.
About 35% of the light is blocked out.
b) The dimmer star is passing in front of the brighter star.
The pair of stars in the V809 Cyg system is very far apart from one another. The pair of stars in the V986 Sgr pair is
very close together (much closer together than the distance between Mercury and our sun!)