. Comet Halley has an orbital period of 75 years and when it enters the inner Solar System, it passes within a few AU of the Sun.

 

 A.  Determine the average distance of Comet Halley in AU.

 

 B.  Right now, Comet Halley is just about past the orbit of Neptune, which has an average distance from the sun of about 30 AU. Explain how this is possible given the average distance you found from its orbital period.

 

2. HIPPARCOS (an acronym for HIgh Precision PARallax COllecting Satellite was a scientific mission of the European Space Agency (ES       A., launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to astrometry, the accurate measurement of star positions, distances from us, parallaxes, and proper motions.

 

 A.  If the measured parallax shift of star A was 0.1 arcsecs and the parallax shift of star B was 0.05 arcsecs, which star was farther away from the Earth, why?

 

 B.  What is the distance of the farthest star in parsecs?

 

 C.  What is the distance of the farthest star in light-years?

 

3. There are two optical telescopes operating at the exact same frequency.

 The first telescope is a 10 m telescope that is planned to be located at the L2 Lagrangian point 1.5 million kilometers past the orbit of the Earth. The second telescope is a 2 m telescope that is planned to be placed on the far side of the moon (average distance to the moon is 380,000 km from the Earth..

 

 A.  Which of the two telescopes will have the greater light gathering power (10 m or 2 m)?

 

 B. Explain your answer to part (A).

 

If the 10m telescope were placed on the Earth on top of Mauna Kea in Hawaii at 14000 feet instead of at L2, which telescope NOW has the greater light gathering power, by what factor

 

            C.. The 10 m telescope has a _____ (greater/smaller. light gathering power )

 

            D.. by a factor of _____ times.

 

            E.  Compare your answers to parts C. and  D. to your answer to part   A.. Explain any differences.

 

4. There was a great debate concerning the value of the Hubble constant. (NOTE: The presently accepted value of the Hubble constant is 72 km/s/Mpc as listed in your formula sheet.. One party believed the Hubble constant (Ho. was closer to 50 km/s/Mpc and the other party believed the Hubble constant was closer to 100 km/s/Mp       C. Assuming you measure a recessional velocity of a galaxy of 10,000 km/s, what is the distance to that galaxy given the two different Hubble constants

 

 A.  Distance to galaxy using 100 km/s/Mpc = _____ Mpc

 

 B.  Distance to galaxy using 50 km/s/Mpc = _____ Mpc

 

 C.  How do the different Hubble constants affect the calculated age of the universe?

 

5. If you triple the distance between two celestial objects, how does the resultant gravitational force between the two objects compare to the original force? (for example, 2 times, 10 times, 100 times?.

 

 A.. The force is _____ times    B. _____ (greater/weaker)..

 

6. Two stars have the same radius but have very different temperatures. The red star has a surface temperature of 3000 K and the blue star has a surface temperature of 15,000 K. By what factor is the blue star more (or less. luminous compared to the red star? (for example, 2 times, 10 times, 100 times?.

 

  A. The blue star is _____ times    B.   _____ (more/less) luminous.