Question

1/ Alpha Centauri A is a star that is remarkably like our Sun...indeed, we can think of it as the Sun’s stellar twin. Alpha Centauri A lies at a distence of 4.4 light-years from Earth, and it has a luminosity of 5.88 x 10^26 W.

1. Calculate the apparent brightness of Alpha Centauri A

2. Suppose you have a light bulb that emits 100 W of visible light. How far away from you would you need to put that light bulb in order for it to have the same apparent brightness as Alpha Centauri A

A/ a. Alpha Centauri A has b = 2.7 x 10^-8 W/m^2

    b. you would need to put the light bulb 17168 m away from you or 17.168 km away

B/ a. Alpha Centauri A has b = 5.63 x 10^-12 W/m^2

    b. you would need to put the light bulb 1.19 x 10^6 m away from you or 1190 km away

C/ a. Alpha Centauri A has b = 5.89 x 10^-9 W/m^2

    b. you would need to put the light bulb 30400 m away from you or 30.4 km away

D/ a. Alpha Centauri A has b = 1.12 x 10^9 W/m^2

    b. you would need to put the light bulb 8.43 x 10^-5 m away from you or 84.3 um away

2/ The bright star Procyon is visible in the evenings from Jan through May. It has a luminosity of 2.66 x 10^27 W, and an apparent brightness of 1.81 x 10^-8 W/m^2. What is the distence to Procyon in light-years (ly)?

A/ 6.45 ly

B/ 5.84 x 10^17 ly

C/ 1.08 x 10^17 ly

D/ 11.46 ly

3/ Stars Moppit and Boppit have the same luminosity, but we observe Moppit to have an apparent brightness that is 16 times the apparent brightness of Boppit. Which star is further away, Moppit or Boppit? By how many times is it futher away?

A/ Moppit is 4 times further away than Boppit is

B/ Boppit is 16 times further away than Moppit is

C/ Moppit is 16 times further away than Boppit is

D/ Boppit is 4 times further away than Moppit is

4/ Star A has a luminosity that is 20 times the luminosity of star B. However, star B is 20 times closer to Earth than star A is. Compare the brightness of star A and star B

A/ bA = bB

B/ bA = 1/20 bB

C/ bA = 20 bB

D/ bA = 1/ sqrt(20) bB

5/ Use the parallax formula to calculate the distance to each of the following stars.

1. Procyon: parallax angle of 0.286 arcseconds

2. Litonya: parallax angle of 0.034 arcseconds

A/ a. d = 3.5 pc or 11.4 light years

    b. d = 29.4 pc or 95.9 light years

B/ a. d = 0.286 pc or 0.088 light years

    b. d = 0.034 pc or 0.010 light years

C/ a. d = 3.5 pc or 1.07 light years

    b. d = 29.4 pc or 9.02 light years

D/ a. d = 0.286 pc or 0.942 light years

    b. d = 0.034 pc or 0.111 light years

6/ The distance from Earth to the star Proxima Centauri is 4.08 light years. Meanwhile , the distance from Earth to Barnard’s Star is 6.52 light-years. Which of these two stars has the bigger parallax angle?

A/ Proxima Centauri

B/ Barnard’s Star

C/ Both have the same parallax angle

7/ The bright star Capella lies at a distance of 14 parsecs away from Earth. If Capella were to move to a distance of 25 parsecs away from Earth…

A/ its parallax angle would not change

B/ its parallax angle get bigger

C/ its parallax angle get smaller

8/ The stars Aldebaran and Rigel are quite prominent in the southern sky during winter months. With the naked eye, one can observe that Aldebaran has a reddish appearance. On the other hand, Rigel has a blueish appearance when viewed with the naked eye. Which star is hotter?

A/ Alebaran

B/ same temperature

C/ Need more info

D/ Rigel

9/ The star Betelgeuse has a wavelength of maximum emission of 923.5 nm, whereas the star Bellatrix has a wavelength of maximum emission of 131.8 nm. Which star is colder

A/ more info

B/ Bellatrix

C/ Betelgeuse

D/ same temperature

10/ Which of the following correctly lists the spectral sequence of stars in order of decreasing surface temperature?

A/ O,B,A,F,G,K,M

B/ M,K,G,F,A,B,O

C/ O,M,K,G,F,B,A

D/ A,B,F,G,K,M,O

11/ How is a star assigned its spectral type?

A/ The star’s spectrum is taken, and its spectral type is assigned based on the amount of green light present in its spectrum

B/ The star’s thermal energy is measured and from that its surface temperature is calculated, the value of the star’s surface temperature determines its spectral type

C/ Images of a star are taken, and its spectral type is assigned based on the star’s brightness

D/ The star’s spectrum is taken, and its spectral type is assigned based on the spectral lines observed

12/ Which of these stars has the coolest surface temperature?

A/ an A star

B/ an F star

C/ a G star

D/ a K star

13/ Which of these stars would be the most luminious?

A/ A white dwarf

B/ An A-type main sequence star

C/ A K-type main sequence star

D/ A B-type main sequence star

14/ which of these stars is the most massive ?

A/ a main sequence type T star

B/ a main sequence type G star

C/ a main sequence type M star

D/ a main sequence type A star

Answer 1

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