Possible Short Answer Essay Questions:
1. Sketch a face-on view of the Milky Way, marking and labeling the location of
at least three components.
2. List three key differences between spiral and elliptical galaxies
3. Describe three consequences of galaxy mergers
4. Why is it extremely rare for stars to collide even when their galaxies collide?
5. Describe the standard Big Bang model in a few sentences.
6. List four observations that support the Big Bang model, and very briefly
explain how each supports the model.
7. Describe where (or when) most of the (a) hydrogen, (b) the helium, and (c)
the uranium in the universe was made.
8. What is inflation? Describe one observation not well explained by the
standard Big Bang model, but which might be explained by inflation.
9. Describe the stage that the sun is in right now, and the stages it will go
through in the future. Your answer should name the stages, include what is
happening to the core and outer parts of the star, and list the energy source
in the core.
10. For each of the following, draw a sketch showing the locations of the Earth,
Moon and Sun. Be sure to label each object. For some, if the Moon can be in
more than one location, please indicate both locations.
a. The full Moon
b. A lunar eclipse
c. The tides are most extreme (in other words, the highest tides of the
month)
11. List three consequences of tidal forces on the spin and orbits of the Earth
and Moon.
12. In two or three sentences, discuss the mechanism that results in Venus
having the hottest surface in the solar system.
13. Hubble was the first astronomer to systematically study galaxies. He
determined they were huge collections of stars, often with gas and dust, far
beyond the limits of our galaxy.
a. What advancement made it possible for Hubble to make these
discoveries?
b. Describe how Hubble determined the distance to the “Andromeda
spiral nebula.”
c. How did Hubble discover/develop the relationship known as Hubble’s
law? (State this relationship in words)
14. A galaxy is discovered in a cluster that shows a measurable spiral diameter
that is 1/10 the size of the Andromeda galaxy. Assuming that these galaxies
have similar dimensions and that the distance to Andromeda is 2 million
light years, how far away is this newly discovered galaxy? Be sure to show
your work.
15. Consider another galaxy discovered in this same cluster that appears as
bright to us as the Andromeda galaxy. What is the luminosity of this galaxy?
16. You notice a “fuzzy” object on the Palomar sky survey print. You suspect
that it may be a quasar. What would you do to confirm your suspicions?
(What observation would you make next, and why?)
17. Quasars are connected to black holes. Make a sketch showing the model and
explain how quasar’s energy is generated.
18. What conditions (give three) on Earth are considered to be crucial for “life as
we know it”?
19. Why are main sequence stars near one solar mass considered by many
astronomers to be the BEST candidates for supporting planets that have
given rise to intelligent lifeforms who have developed a technology similar to
or more advanced than ours?
20. Why do astronomers believe that Mars and Earth had similar past histories?
21. Explain why astronomers can’t use optical (visible light) to completely map
out the structure of our Milky Way galaxy.
22. Radio astronomers have mapped the galaxy more completely using 21 cm
radiation. Describe how this radiation is produced.
23. Given this HR diagram for a star cluster, what would you conclude about the
cluster’s age? Explain your answer.
24. Giant elliptical galaxies are usually found at the center of a cluster of
galaxies. Explain why.
25. Describe how clusters of galaxies are arranged in space. (This was referred
to as “large scale structure.”)
26. Given the Hubble Diagram below, estimate the distance to a galaxy whose
velocity of recession is 40,000 km/sec.
27. Astronomers use a supermassive black hole model to account for the
observation made of quasars. Sketch this model and label the important
parts. Describe below your drawing how Xrays are produced and why a jet
might be observed.
28. Sketch the appearance of the Milky Way Galaxy. Where would you find a
globular cluster; an open star cluster; a cool, cloud of hydrogen; a hot, young
O main sequence star; and the Sun. Explain why it has only been possible to
make such maps since the 1950s.
29. The Sun and stars produce absorption spectra. Using what you know about
the conditions that lead to the three different types of spectra, explain why
we see an absorption spectrum for the Sun and other stars.
30. You read in a magazine that an astronomer has determined that the bright
star Sirius is approaching the Earth at a velocity of 8 km/sec. How was this
information determined? Describe the method.
31. Even using telescopes located above the atmosphere, stellar parallaxes cannot
be measured for stars that are farther than 10000 parsecs. Explain why.
32. What is a meteor? What causes an unusually large number to be seen
during a meteor shower?
33. Describe the surface of Jupiter’s closest large moon, Io. Explain why Io is
different than the other jovian satellites.
34. Should Pluto be classified as a planet or Kuiper Belt Object? Justify your
answer.
35. Discuss the relevance of Einstein’s equation E=mc2 as you explain the source
of the Sun’s energy.
36. What will happen inside the Sun that will cause it to evolve into a red giant
star? Describe the changes that take place in the core.
37. Name the final stage of stellar evolution for the Sun.
38. Account for a pulsar’s radio wave variations using a neutron star model.
Include a labeled sketch with your written explanations of how the radio
waves are produced and why there are regular variations/pulses.
39. What can you say for sure about the mass of a neutron star?
40. How would the evolution of a 25 solar mass star differ from that of the Sun?
41. Describe and account for the physical changes that we see from Earth as a
comet approaches the Sun.
42. Asteroids have been photographed by spacecraft. Describe what one looks
like.
43. Which observations support the theory that the planets in our Solar System
formed out of a rotating, thin disk? Give 2 observations and describe how
they favor this theory.
44. Describe the method of heliocentric parallax to determine distances and
discuss the limitations of this method.
45. What conditions on Jupiter’s moon Europa support the hypothesis that
extraterrestrial life might have developed there?
46. Explain why auroras usually aren’t observed in College Park, MD, but are
common in Alaska.
47. If a large asteroid (~10 kilometers in diameter) were to hit Earth, describe
how a global mass extinction could result.
48. Where does cosmic microwave background radiation come from? What
does it tell us about the early universe?
49. Why are the atmospheres of Venus and Earth very different? Explain what
happened.
50. Describe the leading hypothesis that explains the Moon’s origin.
51. Make a clearly labeled sketch showing the positions of the Sun and the Earth
on the summer solstice (June 21). What seasons does each hemisphere
experience at this time? Explain why.
52. What is an epicycle and how was it used?
53. The North Star has changed from Thuban (3000 BC) to Polaris (2005 AD).
Why?
The SHORT LIST
Important historical figures
1. Copernicus – HELIOCENTRIC, planets orbit around the Sun – all in circles –
still needed Epicycles
2. Eratosthenes – determined size of Earth (longest day of year in Syene and
Alexandreia)
3. Aristarchus – determined distance to Moon (time to cross Earth’s shadow,
Earth’s size and distance), estimated distance to Sun with quarter moons
4. Ptolemy – model for planet motion – GEOCENTRIC – many epicycles
5. Galileo – made and used telescope – did not invent it. See his separate list.
6. Newton – Gravity! 3 important laws – see his separate list.
7. Kepler – Used Brahe’s data to come up with his laws of planetary motion.
See his separate list.
8. Brahe – systematic/accurate observations of planets, Sun and Moon for 20+
years – believed in Earth-centered Solar System
9. Einstein – relativity – cosmological constant (biggest blunder), E = mc2
10. Hubble – his law – galaxies are receding
Newton’s three laws
1. Inertia
2. F = ma
3. equal and opposite
Kepler’s three laws
1. planets travel in elliptical orbits with sun at one focus
2. equal area, equal time
3. P2 = a3
Galileo’s Observations with his telescope
1. stars in the Milky Way
2. sunspots
3. craters on the Moon
4. phases of Venus
5. moons of Jupiter
Tycho Brahe’s contributions
1. 20+ years of very accurate planetary positional information
2. He did this with the naked eye – did not yet have a telescope
Evolution of a low mass star
1. protostellar cloud collapses
2. H fusion – main sequence stage – longest stage
3. Red Giant
4. Planetary Nebula
5. White Dwarf (1.4 Msun)
Evolution of a high mass star
1. protostellar cloud collapses
2. H fusion – Main sequence
3. Super giant
4. Fusion of heavier and heavier elements
5. Iron Core - SUPERNOVA
a. Neutron Star – Pulsar
b. Black Hole
Types of Supernova
1. From a high mass star – Hydrogen evident in spectra
2. From a white dwarf that has accreted more mass from a companion
Doppler Effect – moving away (redshift), towards (blueshift)
1. information about spectroscopic binaries
2. evidence the universe is expanding
The main parts of the Milky Way (about 100,000 light-years in diameter)
1. Disk – lots of gas and dust, star formation, young (hot, blue) stars, about 1,000
light-years thick
2. Bulge
3. Globular Cluster halo – older, redder stars
4. Dark Matter halo
5. Sun’s location in the Milky Way ~28,000 ly from center or about 8.5 kpc
How do we know the size and shape of the Milky Way?
1. We are not at the center of the galaxy – Globular clusters are in sky all
centered around the region where Sgr A* is located
2. Most stars in a plane in the sky - the Milky Way – showing us that we are in a
disk
3. Other observations, such as radio observations of neutral Hydrogen (HI),
discovered in 1951, give information on the gas in the disk and the spiral arms
4. We DON’T have a picture of the Milky Way from the outside! All pictures
you see are artistic renditions or of other galaxies.
Fusion – What makes a star? The heat of battle, the pressure of a big game, and the
ability to shine.
1. heat & pressure – nuclei have a net positive charge. So, naturally they will
repel based on Coloumb forces. They must be forced close enough together
for the strong nuclear force to overpower the weaker Coulomb force and for
fusion to occur. The fusion of heavier elements requires HOTTER and
DENSER conditions in the nucleus of a star.
2. ability to shine: E = mc2 – a little bit of mass is converted to a lot of energy
How is energy transported to surface of a star?
1. radiative zone
2. convective zone
3. conductive zone
Binary Star Systems
1. Visual
2. Spectroscopic
3. Eclipsing
Diagrams you should be able to draw
1. HR diagram
2. Milky Way galaxy - edge on & face on
3. Continuous, absorption and emission spectra
4. Wien’s Law
5. Lunar phases
6. Epicycles
7. Parallax
8. Our place in the universe
9. What causes seasons?
10. Electromagnetic Spectrum
Distance Ladder
1. hands-on
2. radar ranging
3. parallax
4. Main-Sequence fitting for stellar clusters (using HR diagram)
5. Cepheid variables
6. white dwarf supernovas
7. Hubble’s Law
Four expansion patterns for the Universe
1. Recollapsing Universe – will end in the BIG CRUNCH
2. Critical Universe – will expand infinitely, slowing, but never halting. FLAT
geometry.
3. Coasting Universe – expansion forever with little change in rate of expansion
4. Accelerating Universe – if dark energy is a repulsive force – expansion will
continue to accelerate