Final Exam Review Flashcards
(23 cards)
Where did comets that are now in the Kuiper belt originally form?
a. in the asteroid belt
b. inside Jupiter’s orbit
c. between the orbits of Jupiter and Neptune
d. near the radius at which they orbit today
e. in the Oort cloud
d. near the radius at which they orbit today
Comet Locations:
Only a tiny number of comets enter the inner Solar System
Most stay far from the Sun in one of two places:
1) Kuiper belt: in ecliptic plane; comets on orderly orbits from 30-100 AU in disk of Solar System
2) Oort cloud: “Surrounds” Solar System; comets on random orbits extending to about 50,000 AU
Comet Formation:
Kuiper belt comets
- Short-period comets: Orbital periods of 200 years/less
- Orbit Sun in the same plane and direction as the planets (on elliptical orbit)
- Formed in the Kuiper belt and stayed there (only very occasional gravitational interactions with jovian planets)
Oort cloud comets:
- Origin of long-period comets
- Orbital periods that are higher (up to millions of years).
- Can have virtual any orbit, lie in a spherical distribution
- Formed closer to the Sun, but were kicked out by gravitational interactions with jovian planets
When we see Venus in its full phase, what phase would Earth be in as seen by a hypothetical Venetian?
a. full
b. new
c. first quarter
d. third quarter
e. waning crescent
a. full
Which of the following statements about constellations is false?
a. There are only 88 official constellations.
b. Some constellations can be seen from both the Northern and Southern hemispheres.
c. Some constellations can be seen in both the winter and summer.
d. It is possible to see all the constellations from Earth’s equator.
e. Most constellations will be unrecognizable hundreds of years from now.
e. Most constellations will be unrecognizable hundreds of years from now.
The three principal sources of the internal heat of terrestrial planets are
a. conduction, differentiation, and accretion.
b. accretion, differentiation, and radioactivity.
c. accretion, differentiation, and eruption.
d. convection, differentiation, and eruption.
e. conduction, convection, and eruption.
b. accretion, differentiation, and radioactivity.
Which moon did the Huygens spacecraft land on?
a. Ganymede
b. Callisto
c. Europa
d. Titan
e. Triton
d. Titan
What effect or effects would be most significant if the Moon’s orbital plane were exactly the same as the ecliptic plane?
a. Solar eclipses would be much rarer.
b. Solar eclipses would be much more frequent.
c. Total solar eclipses would last much longer.
d. both A and C
e. both B and C
b. Solar eclipses would be much more frequent.
Think back to Moon’s orbital plane
Studies of solar vibrations have revealed that
a. the Sun vibrates only on the surface.
b. they are caused by processes similar to those that create earthquakes.
c. the Sun generates energy by nuclear fusion.
d. our mathematical models of the solar interior are fairly accurate.
e. neutrinos from the solar core reach the solar surface easily.
d. our mathematical models of the solar interior are fairly accurate.
Solar Interior: Information Source
How do we know all this?
Models
- Physical laws predict internal conditions
- Observable properties accurately match
Vibrations
- Plasma waves travel like sound waves through air
- Doppler shift tells us the small but measureable movements
- Surface vibrations infer inner conditions (cf. seismology)
Neutrinos
- Subatomic particles produced at the core detected at the Earth
You observe a star cluster with a main-sequence turn-off point at spectral type G2 (the same spectral type as the Sun). What is the age of this star cluster?
a. 10,000 years
b. 4.6 billion years
c. 10 billion years
d. 100 billion years
e. You also need to know the luminosity class of the turn-off point to determine the age.
c. 10 billion years
Think: the lifetime of our Sun is 10 billion years old, it’s age is 4.6 billion years old because we are only halfway through it’s lifetime.
Stellar Lifetime:
- You might think that a more massive star has more fuel (H) so it should last longer – not true!
- More mass does mean more fuel for nuclear fusion, but it also means higher fusion rates, so higher consumption of fuel
- More massive stars die younger
Age of a Star Cluster
- The most massive stars die first, so after 10 million years, the most massive stars are less than 10 solar masses
- An HR diagram would be missing the high-mass stars (because the stars are gone)
- Thus, the “turn-off” point determines the age of the cluster
Ages of Open Clusters
- Open clusters have different ages
- Oldest open cluster about lifetime of the Sun
Age of Globular Clusters
- Generally much older than open clusters
- Age of M13 globular cluster is about 13 billion years
- Must have formed shortly after the Big Bang
If we use 1 millimeter to represent 1 light-year, how large in diameter is the Milky Way Galaxy?
a. 100 millimeters
b. 100 meters
c. 1 kilometer
d. 100 kilometers
e. 1 million millimeters
b. 100 meters
Universe: 100 000 light years
100 000 mm
10 000 cm
100 m
How do the size and mass of Jupiter’s core compare to the size and mass of Earth?
a. It is the same size and mass.
b. It is about 10 times larger both in size and mass.
c. It is about 10 times larger in size and the same mass.
d. It is about the same size but is 10 times more massive.
e. Jupiter doesn’t have a core—it is made entirely from hydrogen and helium.
d. It is about the same size but is 10 times more massive.
Jupiter is mostly made of mass, it’s actual core is likely the size of Earth. Pillow Analogy.
Jovian Planet’s Masses compared to Earth’s Mass:
Jupiter: 300
Saturn: 100
Uranus/Neptune: 15
If the Moon is setting at noon, the phase of the Moon must be
a. full.
b. first quarter.
c. third quarter.
d. waning crescent.
e. waxing crescent.
c. third quarter.
What do astronomers mean when they refer to “gaps” in the asteroid belt between Mars and Jupiter?
a. There are very few asteroids with diameters between 1 and 100 kilometers, creating a “gap” in the size distribution.
b. Asteroids typically cluster together and this creates “gaps” on the sky.
c. Asteroids seem to avoid certain orbits around the Sun, creating “gaps” in the orbits that asteroids can have.
d. There is a large population of asteroids too faint to see called the “gap” asteroids.
e. There are either pure metal or pure rock asteroids, but no mixtures. Thus there is a “gap” in the composition of asteroids.
c. Asteroids seem to avoid certain orbits around the Sun, creating “gaps” in the orbits that asteroids can have.
Bird’s eye view: Kirkwood Gaps…
Why an Asteroid Belt and Not a Planet? Answer: Jupiter
In the past:
- Present-day asteroid belt region used to have enough mass present to build another terrestrial planet
- Jupiter and planetesimals had unstable orbital resonances (two objects repeatedly line up with each other at the same positions in their orbits)
- Planetesimals kicked out of orbit, and belt region lost lots of mass (heavy bombardment)
Jupiter’s Disturbance
- Jupiter prevented accretion;
asteroid belt is not the
remains of a destroyed
planet
In the present-day
- Asteroid orbits today
are nudged such they
avoid - unstable orbital
resonances
- Empty orbits known as Kirkwood gaps
- Still possible that Jupiter throws us a large object every 105 years or so
Approximately how many other planetary systems have been discovered to date?
a. ten
b. about three hundred
c. about three thousand
d. tens of thousands
e. millions
c. about three thousand
NASA Exoplanet Archive:
3431 confirmed planets confirmed as of 1 Dec 2016
Conservative estimates:
70% of stars have at least one planet
Milky Way has 100 billion stars
Therefore 70 billion planets (7 x 1010) in our Galaxy alone
Recall how many galaxies in the Universe (about 100 billion or 1011)
Total planets in the Universe: 7 x 1021
What are the two main differences between extrasolar planetary systems discovered to date and our Solar System?
a. Extrasolar planets tend to be more massive and dense than Jupiter.
b. Extrasolar planet orbits tend to be more eccentric and inclined than in our Solar System.
c. Extrasolar planet orbits tend to be closer and more eccentric than in our Solar System.
d. Extrasolar planet orbits tend to be closer and more circular than in our Solar System.
e. Extrasolar planets tend to be bigger and denser than Jupiter.
c. Extrasolar planet orbits tend to be closer and more eccentric than in our Solar System.
Exoplanet Orbits
- Close in to stars (even though some are Jupiter-sized or bigger – “hot Jupiters” )
- Might be selection effects (a.k.a. data bias)
- Eccentric orbits
- Planets orbit more than one star
Which of the following statements about electrons is false?
a. Electrons orbit the nucleus rather like planets orbiting the Sun.
b. Within an atom, an electron can have only particular energies.
c. Electrons can jump between energy levels in an atom only if they receive or give up an amount of energy equal to the difference in energy between the energy levels.
d. An electron has a negative electrical charge.
e. Electrons have very little mass compared to protons or neutrons.
a. Electrons orbit the nucleus rather like planets orbiting the Sun.
Remember: Bohr Rutherford’s diagram is false, atoms are not modelled like a Solar System but thinking of them that way helps us to understand atoms
Important to Note:
- A planet could orbit at any distance from the star
- An electron can only “orbit” the nucleus at specific distances
- Analogy: slide (planet) vs ladder (electron)
- Continuous: a planet’s possible orbital distance
- Discrete: an electron’s possible “orbital” distance
What type of star is our Sun?
a. a low-mass star
b. an intermediate-mass star
c. a high-mass star
a. a low-mass star
Main Sequence Star
Low mass stars have below 2 solar masses
Sun = 1 solar mass
Remember: Mass is Density
One light-minute is the distance light travels in one minute. The speed of light is about 300,000 km/s (3 x 105 km/s). How far is one light-minute?
a. 3 x 10 5 km
b. 1.8 x 10 6 km
c. 1.8 x 10 7 km
d. 1.8 x 10 8 km
e. 9.46 x 10 12 km
c. 1.8 x 10 7 km
Scientific Notation:
300 000 x 60 —> 3 x 6
18 000 000
1.8 x 107
or
6 x (3 x 105)
(6 x 3) x 105
18 x 105
1.8 x 107
Why is Neptune denser than Saturn?
a. It has a different composition than Saturn, including a higher proportion of hydrogen compounds and rocks.
b. It has a greater proportion of hydrogen than Saturn.
c. The extra mass of Neptune compresses its interior to a greater extent than that of Saturn.
d. Its hydrogen is molecular, whereas Saturn’s hydrogen is atomic.
e. It is not denser than Saturn.
a. It has a different composition than Saturn, including a higher proportion of hydrogen compounds and rocks.
Why the Density Difference?
- Further from the Sun, Colder, Ices Easier to form
- Ices are more dense, so we would expect density to increase as you get further from the Sun
Excluding Jupiter, this expectation is true:
- Density gets higher further out: Saturn, Uranus, Neptune
- Jupiter does not follow this trend…
Jupiter’s Density: Pillow Analogy
- Extra mass of Jupiter compresses the interior to a higher density
- Adding mass increases density
- Greater compression is why Jupiter is not much larger than Saturn even though it is three times more massive
- If you started to add more mass, you would start making Jupiter smaller
Which of the following statements about lunar phases is true?
a. The time between new moons is two weeks.
b. The time from one new moon to the next new moon is the same as the time from first-quarter moon to third-quarter moon.
c. The full moon sometimes rises around midnight.
d. It is possible to have two full moons during January, but not during February.
e. It is possible to have two full moons during November, but not during December.
d. It is possible to have two full moons during January, but not during February.
From Kepler’s third law, p2 = a3, an asteroid with an orbital period of 8 years lies at an average distance from the Sun equal to
a. 2 astronomical units.
b. 4 astronomical units.
c. 8 astronomical units.
d. 16 astronomical units.
e. It depends on the asteroid’s mass.
b. 4 astronomical units.
What quantities does angular momentum depend upon?
a. mass and velocity
b. mass, velocity, and radius
c. force and radius
d. force, velocity, and radius
e. momentum and angular velocity
b. mass, velocity, and radius
Remember: L = mvr
Angular Momentum Demo: Figure Skater
What happens when you’re spinning with your arms out, and then you pull them in?
Angular Momentum
- Angular momentum is adding up the momentum of all the parts for a spinning or orbiting object
- Depends on velocity, mass, and distribution of mass
- Angular momentum =
mass x (rotation) velocity x distance
L = mvr
What is the only force that can overcome the repulsion between two positively charged nuclei to bind them into
an atomic nucleus?
a. the strong force
b. the weak force
c. the electromagnetic force
d. the gravitational force
e. the Coriolis force
a. the strong force
Nuclear Energy
Nuclear fission versus Nuclear fusion
- Nuclear fusion naturally occurs in the Sun
- Capture one second of the Sun’s total energy, and you have enough to provide in our energy needs for 500,000 years
Forces
Electromagnetic force
- Normally, like charges will repel (e.g., two protons will repel one another)
Nuclear strong force (“particle superglue”)
- At extremely short ranges, this attractive force can overcome the electromagnetic repulsion
- Very, very short range
How to get subatomic particles so close?
- High pressures: particles close together; prevents explosion
- High temperatures: high speeds
Which of the following wavelength regions cannot be studied with telescopes on the ground?
a. radio waves
b. ultraviolet
c. X-rays
d. both B and C
e. both A and C
d. both B and C
Space-Based Telescopes
- Only radio and visible light pass easily through Earth’s atmosphere; we need telescopes in space to observe everything else
