ASTR 1504/1514: Astronomy: Exploring the UniverseMidterm Exam 31. A 10 Solar-mass star will evolve through the same phases as a 1 Solar-mass star.• A: True• B: False2. Stars evolve primarily because t h ey run out of fuel in their cores.• A: True• B: False3. The more massive a star, the more hydrogen it has to b u r n , and the longer its main-sequence lifetime will be.• A: True• B: False4. What factor is most im portant in determining a star’s position on t h e main sequenceand subsequent evolution?• A: Temperature• B: Pressure• C: Mass• D: Radius5. A star like the Sun will eventually become an electron degenerate white dwarf star.• A: True• B: False6. What is a planetary nebula?• A: A planet surrounded by a glowing shell of gas• B: The disk of gas and dust surrounding a young star that will soon form a st a rsystem• C: The ejected envelope of a giant star surrounding the remains of a star• D: A type of young, medium-mass star7. In a white dwarf, what is the source of pressure that halts its contraction as it cool s?• A: Thermal pressure of the extremely hot gas• B: Electrons packed so closely that they become incompressible• C: Neutrons that resist being pressed further together• D: Carbon nuclei that repulse each other strongly because they each contain sixprotons8. A Type Ia supernova occurs when a white dwarf exceeds a mass of• A: 0.8 Solar Masses• B: 1.4 Solar Masses• C: 2.3 Solar Masses• D: 5.5 Solar Masses9. Special relativity says that moving clocks run slower.• A: True• B: False10. Gravity is nothing more tha n a curvature in the fabric of spacetime.• A: True• B: False11. Gravitational lensing allows us to see distant objects that would otherwise be blockedby a star or galaxy.• A: True• B: False12. We can identify only a small fraction of all t h e pulsars that exist in our galaxy because:• A: gas and dust efficiently block rad io photons• B: few swing their beam of synchrotron emission in our direction• C: most have evolved to become black holes, which emit no light• D: massive star s a r e very rare13. What would happen if mass were continually added to a 2 Sola r -mass neutron star?• A: The star’s radius would increase.• B: The star woul d eventually become a black hole.• C: The star would erupt as a nova.• D: All of the above would occur.14. The event horizon of a black hole is defined as:• A: the p oi nt of maximum gravity• B: the radius of the original neutron star before it became a black hole• C: the point at which shock waves emanate from the strong gravitational distortionthe black hole creates in the fabri c of spacetime• D: the radius at which the escape speed equals the speed of light15. If the Sun wer e to be instantly r eplaced by a 1 Solar mass b l ack hole, the gravit at i onalpull of the black hole on Earth would be:• A: much greater than it is now• B: the same as it is now• C: much smaller than it is now• D: irrelevant because Earth would be quickly obliterated by the str o n g tidal forceof the black hole16. The Cosmological Principle says th at physical laws tha t are tru e in one part of theuniverse must be true in every pa r t of the universe.• A: True• B: False17. Edwin Hubble revolutionized astronomy when he made an accurate calculation of thedistance to the Andromeda Nebula by spotting a rare Type Ia supernova.• A: True• B: False18. In the Great Debate of 1920, Curtis and Shapley argued over whether or not:• A: the Big Bang occurred• B: the age of th e universe was 14 billion years• C: the spiral nebulae were located outsi d e the Milky Way• D: life existed outside of Earth19. What do astronomers mean when they say that the universe is homogeneous?• A: All stars in all galaxies have planetary systems just l i ke ours.• B: The universe looks the same no matter where you look.• C: Galaxies are g en er al l y distributed similarly thro u ghout the universe• D: Gener al l y speaking, there is little difference between conditions on Ea r t h , inthe Sun, or in outer space.20. There is no special center to t he expansion of the universe.• A: True• B: False21. As the universe expands, the sizes of galaxies expand a measurable amount as well.• A: True• B: False22. Galaxies move away from us in all directions because:• A: the force of gr avity st r en gt hens with distance• B: the force of gr avity weakens wi t h distance• C: space is expan d i n g• D: our galaxy has expelled all ot h e r galaxies23. The current temperature of t h e co sm i c microwave background radiation is 17 K.• A: True• B: False24. The standard Big Bang theory successfully predicts that the fraction of helium by massin the primordial universe was 2 percent.• A: True• B: False25. The cosmic microwave background radiation contains photons left over from the epochin the universes history when electrons recombined with nuclei.• A: True• B: False26. To be a standard candle an object must have a constant:• A: lifetime• B: brightness• C: luminosity• D: distance27. Hubbles constant, H0, represents:• A: the rate of exp a n si on of the universe• B: the speed at which galaxies are moving away from us• C: the time it takes a galaxy to move twice as far away from us• D: the size of t h e u niverse28. We know that spiral galaxies contain dark matter because the gas in the disk rotateswith a velocity th at decreases in a way that is similar to our Solar System.• A: True• B: False29. Dark matter is dist r i b u t ed inside galaxies in exactly the same way as luminous m at t er ,although the total mass of dark m at t er is much larger than that of luminous matter.• A: True• B: False30. The disks of spiral galaxies appear blue because:• A: spiral galaxi es are moving toward us• B: spiral galax i es contain mostly hot blue stars• C: spiral galaxi es are still undergoing star form at i on• D: spiral gala xi es contain more metals that, when ionized, emit blue light31. Although elliptical and irregular galaxies have been observed in both dwarf and giantvarieties, we find only giant spiral galaxies.• A: True• B: False32. Which is not one of the three pil l ar s of Big Bang Cosmology?• A: All galaxies are moving away from the Milky Way Galaxy.• B: “Spiral Neb ula” are extragalactic objects.• C: We observe the relic of Big Bang, th e 2.73K blackbo d y radiation.• D: We observe 25% of normal matter as