Midterm II Review:

Give subjects and questions.

Math!

  1. 100: How many times greater is the Schwarzschild radius of a 12 solar mass black hole than a 6 solar mass black hole? (2x)
  2. 200: If the parallax of a star is 0.5“, how far away is it? (2 pc)
  3. 300: Star A and Star B have the same luminosity, but Star A is 3x further away than Star B. How many times brighter in our sky is Star B than Star A? (9x)
  4. 400: Star A has a mass 3 times that of Star B. How luminous is Star A in comparison to Star B? (81x brighter)
  5. 500: A star has a parallax of 0.1” as seen from Earth. If you were to view this star from Neptune, at 30 a.u. from the sun, what would its new parallax be? (3“)

Exoplanets

  1. $100 : (Give a rough estimate) How many exoplanets have been discovered to date? (about 400)
  2. $200 : (Give a rough estimate) Describe the masses of most exoplanets. (Jupiter-sized to super-Earth-sized)
  3. $300 : True or False: Exoplanets typically have eccentric orbits. (False)
  4. $400 : Describe how the Doppler Shift can be used to spot an exoplanet. (Radial velocity method..)
  5. $500 : Describe the Transit Method of finding exoplanets. (Light curves)

Asteroids , Meteors, Space Debris

  1. $100 : Name a region in which comets originate from. (Kuiper Belt, Oort Cloud)
  2. $200 : This occurs when Earth passes through a broken up comet. (meteor shower)
  3. $300 : This is the reason why no planet was formed from the asteroids in the asteroid belt. (gravitational pull of Jupiter)
  4. $400 : Why does a comet's tail always face away from the sun? (Solar wind from the Sun pushes particles away)
  5. $500 : During one orbit, where do comets spend most of their time? (Away from the Sun b/c of Kepler's second law)

Explosions! (Supernovae and Novae)

  1. $200 : This is the type of stellar explosion that does not have any hydrogen lines (Type I Supernova)
  2. $400 : This is the type of stellar explosion that leaves a neutron star or black hole (Type II Supernova or Type Ib/c)
  3. $600 : This is the process that creates recurring “explosions” on the surface of a white dwarf in a binary system (Novae ; Material from companion star fills the Roche lobe and falls onto the WD's surface)
  4. $800 : This is the cause of Type I supernovae. (WD exceeds 1.4 solar masses, entire WD explodes)
  5. $1000 : These two things generate the force/ needed to create the explosion in a Type II supernova. (neutrinos and rebound of the core collapsing)

Nuclear Burning

  1. $100 A pre-main sequence star becomes a main sequence star when it's the temperature of it's core becomes hot enough to fuse this element into heavier elements. (hydrogen)
  2. $200 This element is the next element that will be used as fuel when a star leaves the main sequence. (helium)
  3. $300 This is the last element a massive star (whose initial mass is greater than 8 solar masses) will form by nuclear fusion reactions because fusing this element requires an input of energy. (iron)
  4. $400 This type of star is not massive enough for it’s core to attain a high enough temperature to produce enough hydrogen fusion to support itself, but it does undergo a “little bit” of fusion. (brown dwarf)
  5. $500 A white dwarf can attain enough mass from a companion star causing it to explode in a supernova. What is the physical process that creates the explosion. (A runaway chain of nuclear fusion reactions of carbon and oxygen)

Black Holes

  1. $100 This theory of gravity predicted the existence of black holes. (Einstein’s Theory of General Relativity)
  2. $200 This is the radius known as the “point of no return” of a black hole, where not even light can escape. (Schwarzschild radius / event horizon)
  3. $300 This type of force, felt by you as you approach a black hole, is stronger for low mass black holes than high mass black holes. (tidal forces)
  4. $400 These types of black holes are located in the center of many galaxies, including our own, and can have masses of more than a million solar masses! (supermassive black holes)
  5. $500 Black holes can radiate energy via this process. (Hawking Radiation: creation of electron-positron pairs by borrowing “energy” from the black hole where one of the particles escapes causing the mass to decrease)

Pulsars and Neutron Stars

  1. $100 This is the only explanation for the extremely regular bursts of pulsars (rotating neutron star)
  2. $200 This what holds up a neutron star from further collapse (Neutron degeneracy pressure)
  3. $300 These are produced in great quantity when the core of a supermassive star collapses into a neutron star (Neutrinos).
  4. $400 This is the typical size of a neutron star in km (diameter ~ 10 km)
  5. $500 This is a typical period for a pulsars rotation (period ~ 1 second, or down to millisecond for some pulsars)

Potent Potables (Misc.)

  1. 100: I am sometimes mistaken as a “shooting star.” (Meteor)
  2. 200: In a helium white dwarf, the helium is being supported against gravity by what? (elec. deg. pressure; any WD is supported by elec. deg. pressure)
  3. 300: I am emitted when two massive objects orbit one another with a VERY small period. (gravitational waves)
  4. 400: How did Mercury help Einstein's General Theory of Relativity? (GR was able to account for the 43 arcseconds of percession / century that Mercury's orbit undergoes)
  5. 500: O B A F G K M L T is the sequence of classes for stars. From O to T, what property of the star is decreasing? (Temperature ; if you just talk about main sequence stars, then Luminosity and Radius decrease as well)