Astro 5 Midterm #1 Review

Topics Covered So Far


Cosmology:

History of the universe:

the Big Bang, Hubble's Law, expanding universe, nucleosynthesis,

Geometry of the universe:

open, closed, flat; the density parameter r (rho), deflection of light

Doppler effect, dark matter

Four fundamental forces:

electricity-magnetism, strong nuclear force, weak nuclear force, gravity


Stellar birth, death, and evolution:

pp chain, metallicity, stellar nucleosynthesis, metal production, H-R diagram, hydrostatic equilibrium

Planetary Systems:

collapse of molecular cloud, fragmentation, angular momentum conservation, formation of planetesimals and planets


Primitive Earth:

Conditions of primitive earth,

Source of primitive atmosphere:

primordial atmosphere, outgassing, collisions with planetesimals

Major geological eras, conditions for primitive life, radioactive dating


Origin of Life

28 monomers of life, definition of life,

4 models to explain the origin of life

special creation, spontaneous generation, panspermia, chemical evolution

Chemical evolution:

necessary conditions, origin of reducing atmosphere


Equations to keep in mind

(know which symbol means what)


doppler effect : delta lambda / lambda = v/c


Hubble's law: v = Hd


angular momentum: spin = mvr


energy: E = mc^2




Please fill in these definitions


Universe: whole body of things and phenomenon observed and postulated

universal clock: a way of measuring time that everyone in the universe can agree to

dark matter: non-luminous matter, which we can observe by their gravitational interaction with luminous matter

super Copernican principle: in addition to the Earth/Sun not being the center of the universe, even the material that we are made of (i.e. matter) is not the dominant material of the universe

dark energy: according to quantum mechanics, the energy density of vacuum

Anthropic principle: (weak) our presence as intelligent observers restrict the allowable conditions in the universe

hydrostatic equilibrium: a condition where the inward gravitational force is balanced by an outward pressure force

kill radius of supernova: the radius interior of which a supernova explosion would wipe away life

angular momentum: the amount of "spin" a given body has around either its axis or some external axis

TTauri star: pre-main sequence young stars with a large infra-red excess indicative of an accretion disk

radioactive dating: using the radioactive properties of certain isotopes to infer the age of the material

monomers: the basic units that make up all life on Earth, there are 28 monomers

panspermia: the idea that life on Earth originated elsewhere

entropy: a measure of the randomness of a system

evolution: a fight between disorder introduced by copying mistakes, cosmic rays etc. and order introduced by selection of the fittest.


Questions you should be able to answer:

I'm providing a bare-bones answer. Yours should be more detailed


1) What are some observations of the universe that are supported by the Anthropic principle?

(density of the universe, relative strengths of the strong force to the e-m force)

2) Describe the evolutionary pathway of a 2 solar mass star and draw the path on an HR diagram.

(proto-star --> main sequence --> red giant --> white dwarf)

3) What are the main constituents of interstellar dust grains?

(silicon, carbon, iron)

4) What wavelengths do interstellar dust particles scatter best and why?

(blue light, on the order of their size)

5) Why is the finding of molecules such as HCN and formaldehyde in the interstellar medium important?

(shows that the universe "knows" how to do organic chemistry)

6) How do we find these molecules, i.e. what property of these molecules allows us to observe them?

(rotational emission causes spectral lines)

7) Why are so many astronomical objects pancake shaped?

(collapse from spherical clouds, conservation of angular momentum flattens it into a disk)

8) Name three ways of getting rid of excess angular momentum

(fragmentation, ejection of material, friction)

9) Name three evidences for a Mars-sized object impact on earth during its formation

(composition of the moon, tilt in earth's spin axis, evaporation of primordial atmosphere)

10) Give some examples of processes that increase entropy

(dropping a vase, digesting dinner, expansion of the universe)

11) Give some examples of free energy. Why do we need free energy to form life?

(sunlight, geothermal energy. We need a source of energy to do chemistry in the early earth)

12) What are some ways to make the primitive earth atmosphere more reducing?

(volcanic gases, meteoritic material, oxidation of rocks)