Midterm II Review:

Give subjects and questions.


  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“)


  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)