Title: Final Exam
Course: ASTRON103: The Evolving Universe: Stars, Galaxies, and Cosmology (001) DHH SU18

Q: From where on Earth could you observe all of the stars during the course of a year? What fraction of the sky can be seen from the North Pole?

Q: What is an asterism? Can you name an example?

Q: Why don’t lunar eclipses happen during every full moon?

Q: If a star rises at 8:30 p.m. tonight, approximately what time will it rise two months from now?

Q: Parallaxes of stars were not observed by ancient astronomers. How can this fact be reconciled with the heliocentric hypothesis?

Q: Why do sunspots look dark?

Q: What is the ultimate source of energy that makes the Sun shine?

Q: Describe the two main ways that energy travels through the Sun.

Q: What two factors determine how bright a star appears to be in the sky?

Q: Order the seven basic spectral types from hottest to coldest.

Q: Why have we learned a lot about star formation since the invention of detectors sensitive to infrared radiation?

Q: Why are star clusters so useful for astronomers who want to study the evolution of stars?

Q: Astronomers find that 90% of the stars observed in the sky are on the main sequence of an H–R diagram; why does this make sense? Why are there far fewer stars in the giant and supergiant region?

Q: If the formation of a neutron star requires a supernova explosion, explain why only three of the hundreds of known pulsars are found in supernova remnants.

Q: How is a nova different from a type Ia supernova? How does it differ from a type II supernova?

Q: Describe the main distinguishing features of spiral, elliptical, and irregular galaxies.

Q: What evidence do we have that the luminous central region of a quasar is small and compact?

Q: If a quasar has a redshift of 3.3, at what fraction of the speed of light is it moving away from us?

Q: When astronomers make maps of the structure of the universe on the largest scales, how do they find the superclusters of galaxies to be arranged?

Q: What is the evidence that star formation began when the universe was only a few hundred million years old?

Q: According to Kepler’s second law, where in a planet’s orbit would it be moving fastest? Where would it be moving slowest?

Q: A body moves in a perfectly circular path at constant speed. Are there forces acting in such a system? How do you know?

Q: Explain how we can deduce the temperature of a star by determining its color.

Q: Explain why astronomers use the term “blueshifted” for objects moving toward us and “redshifted” for objects moving away from us.

Q: What is meant by “reflecting” and “refracting” telescopes?

Q: What is the key distinguishing feature that a star can claim, that a brown dwarf cannot?

Q: The AU is defined as the average distance between Earth and the Sun, not the distance between Earth and the Sun. Why does this need to be the case?

Q: Which of the following can you determine about a star without knowing its distance, and which can you not determine: radial velocity, temperature, apparent brightness, or luminosity? Explain.

Q: Why can’t we use visible light telescopes to study molecular clouds where stars and planets form? Why do infrared or radio telescopes work better?

Q: Estimate the maximum and minimum time it takes a radar signal to make the round trip between Earth and Venus, which has a semimajor axis of 0.72 AU.

Q: Describe in your own words, what an Event Horizon is.

Q: You are standing on a weighing machine in an elevator when the cable snaps, sending the elevator car into free fall. Before the automatic brakes stop your fall, you glance at your weight reading. Does the weighing machine show your real weight? If not, how is it different?

Q: Explain where in a spiral galaxy you would expect to find globular clusters, molecular clouds, and atomic hydrogen.

Q: The Sun orbits the center of the Galaxy in 225 million years at a distance of 26,000 light-years. Given that a3=(M1+M2)×P2, where a is the semimajor axis in AU and P is the orbital period in years, and M1 and M2 are the masses in Solar Masses, estimate is the mass of the Galaxy within the Sun’s orbit?

Q: What evidence do we have that we have a Super Massive Black Hole at the center of our Galaxy

Q: Which formed first: hydrogen nuclei or hydrogen atoms? Why?

Q: Suppose the Hubble constant were not 22 but 44 km/s per million light-years. By what factor would the critical density change?

Q: Describe in your own words, what the habitable zone means. How are the inner and outer radius defined?

Q: Does all life on Earth require sunshine? How else can an organism receive the energy it needs?

Q: The moons of Jupiter and Saturn do not lie in the traditional habitable zone of the Sun, yet they are often considered potential places to find life in our Solar System. How does these planets receive their energy to maintain liquid water?