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Astronomy Final

Terms in this set (147)

Which of the images is the youngest?
There are no craters in this image.
What is at the center of our solar system
the sun
How old is the Earth estimated to be based on radiometric dating?
4.6 Billion years old (average surface age is 200 million years old)
What is the structure of Earth and Venus?
Thin atmosphere over rocky crust, mantle, and core.
What feature are the pink arrows pointing to in Image C?
A dry river bed
The 3 most massive things in our solar system (the Sun, Jupiter, and Saturn) are made mostly of...
Hydrogen
What is the structure of Europa and Ganymede?
Ice crust over a water ocean over a rocky mantle and core.
About how old is the surface of Image A?
Under a few million years old as there are no craters.
Since terrestrial planets have crusts which are lighter than their cores, what else can I infer?
They have differentiated, and so must have been liquid (molten) at some time in the past.
Planets with densities near 5.0 g/cc are mostly made of while planets with densities near
1.0 g/cc are made mostly of
Rock gas
What causes Earth's seasons?
The tilt of the Earth's spin axis.
Aristarchus measured the relative sizes of the Earth, Moon, and Sun using eclipses and phase
timings. Since the Moon is smaller than the Earth and orbits the Earth and the Earth is smaller
than the Sun, he deduced that the Earth must orbit the Sun. This last phrase is what part of the
scientific method?
Theory. (He is explaining something.)
About how old is the surface of Image B?
4-4.5 billion years old. It is saturated with craters.
All items listed below are an important part of science, except...
An expert says it is correct.
Why is Mars' atmosphere so thin compared to Venus', even though it is made of the same
stuff and Venus is hotter?
Mars' mass (escape velocity) is much lower than Venus'.
Our Moon, Mars' moons, and Io all show that our solar system is...
dynamic and always changing, even though most changes are quite slow.
If I observe a moon that has a similar composition as its planet's crust, has a small core, and
orbits nearly over the spin equator, how did that planet most likely get that moon?
Spun off the surface of the planet.
List 3 observations of Image D and describe what they mean
Many possibilities:
1) Well-defined features so a solid surface.
2) Several craters, so probably about 1-2 Gyrs old.
3) Little change in color, so probably composed of mainly one material.
4) The roughly area looks like higher elevation, and the split looks like a broken continent, which could
indicate plate tectonics.
5) etc.....
Estimate the surface age of Image C and describe how you do it
About 1-2 Gyrs old, based on the number of craters present. The image looks fairly close up, yet there
are 10-20 craters present, though it is far from saturated.
Put the images in order from youngest to oldest.
A, C or D, B
In two sentences, describe the object in Image B.
This is a solid, old, heavily cratered object. There is no evidence of an atmosphere or any form of
erosion.
What does the coloring of Image A tell us?
There is a reddish color in between the lighter colored hills and the plain on the right is also lighter
colored. I would presume this difference is composition, as the plain and the red regions seem to be at
the same level
What is the structure of the terrestrial planets?
Thin atmosphere over rocky crust, mantle, and core.
What do we use to infer the age of a planet or moon's surface (other than the Earth and the Moon)?
The numbers of craters present.
The surface in Image 2A is mostly likely...
A solid.
A planet with a density near 5.0 g/cc is most likely...
A Terrestrial-like planet.
What is at the center of our solar system?
The Sun.
In Image 1A the letters a, b, and c are roughly in the center of three craters. Which crater is likely the
oldest?
Crater a.
Our solar system can best be described as...
a place where change is always occurring, but usually very slowly
In Image 1B, the yellow arrows are pointing to ...
a dry river bed.
If I see an object with active volcanoes, what else can I assume?
It has an atmosphere.
Which factor is not important to determine if an object has an atmosphere and its composition?
How many moons the object has.
What is the structure of icy moons (warm interior) like Europa and Ganymede?
Ice crust over a water ocean over a rocky mantle and core.
What is the approximate age of the surface in Image 1D?
4-4.5 billion years old. The surface is saturated, or nearly so.
The goal of science is to ...
understand the world (and Universe).
What type of erosion are the yellow arrows pointing to in the image?
Liquid erosion (river beds, etc)
The surface in Image 2D is most likely...
A gas.
What is the best estimate for the age of our solar system?
4.5 billion years old.
What is the pink arrow pointing to in Image 1D?
Crater.
Which is not a key point of science?
Things written in textbooks are correct.
What is the approximate age of the surface in Image 1C?
Less than a few million years old. There are no craters.
Why are there so few visible craters on the Earth?
Erosion and resurfacing erases them.
List and describe 3 observations of the object in Image 2A.
Many, but the most obvious are:
Round so it is massively huge.
There are multiple colors (blue, white, and brown-ish) which are multiple compositions
There are well-defined features on the brown, so that is a solid.
The white on top and bottom look solid, and so are likely ice caps, which means the spin must be
roughly aligned with the orbit.
Hazy around the edge, so that indicates an atmosphere.
What does the coloring in Image 2B tell us? Briefly describe the evidence you use.
The most obvious would be the difference between the blue and orange and I would suspect the
difference is composition. The blue looks smooth, and therefore a liquid while the orange has betterdefined features, and so I would presume a solid.
Put the images in Image 1 in order from youngest to oldest
C, B, A, and D
Estimate the age of the surface of Image 1A and briefly describe how you do it.
Roughly 2-3 Gyrs; There are many craters in this image, but there are also smooth, craterless areas, and
so it cannot be 4Gyrs old or older.
List and describe 3 observations of the object in Image 2D
Many, but the easiest are:
Round, so massively huge
Swirly features, which means it is made of gas.
Mostly one color (red) which means it's mostly made of one composition.
What stage of evolution is our Sun currently at?
Main Sequence.
On Figure 2, HR diagram #4, what is the region labeled C?
White dwarf.
What is the source of energy for a protostar?
Gravity.
Why do stars evolve?
They emit energy, and so use fuel which is a limited resource.
What produced all the nitrogen (#7 in the periodic table) in Earth's atmosphere?
Supernovas and Planetary nebulas
In HR4 in Figure 2, what is the difference between stars near the letter D and stars near the
letter E that causes them to be at those locations?
Mass.
In Figure 2, which of the HR diagrams shows the oldest set of stars?
HR3 It has the shortest main sequence
If our Sun became a black hole, how large would its event horizon (Schwarzchild radius) be?
3km: RSch = 3M = 3(1) = 3
What is the surface temperature of a star with a peak in its continuous spectrum at 400 nm?
7250 K: T = 2.9 × 10^6/λ = 2.9 × 10^6/400 = 7250K
The most common type of exoplanets discovered so far....
have masses between Earth's and Neptune's with short orbits.
Why does nuclear fusion only occur in the cores of stars?
Only the core is hot and dense enough.
About what fraction of stars have planets?
90%
A star with 34 times the mass of our Sun will end up as...
a black hole.
I see a red star and a blue star in a binary. The red star is brighter, what else do I know
about these two stars?
The red star is larger.
A gas cloud collapses to form 4 stars (so they all
start the main sequence at the same time and ar at the same distance). Star A is 0.08 solar masses,
Star B is 1.2 solar masses, Star C is 2.6 solar masses, and Star D is 29 solar masses.
Which star is the brightest on the main sequence?
Star D: Lms = M^3.5 so more massive = brighter.
A gas cloud collapses to form 4 stars (so they all
start the main sequence at the same time and ar at the same distance). Star A is 0.08 solar masses,
Star B is 1.2 solar masses, Star C is 2.6 solar masses, and Star D is 29 solar masses.
Which star evolves the fastest?
Star D Tms = 1 × 10^10/M^2.5
so more massive stars evolve faster.
A gas cloud collapses to form 4 stars (so they all
start the main sequence at the same time and ar at the same distance). Star A is 0.08 solar masses,
Star B is 1.2 solar masses, Star C is 2.6 solar masses, and Star D is 29 solar masses.
Which stars will become white dwarfs?
Stars A, B, and C
Which star in the image is the brightest?
Star A: it has the largest dot.
Which star is the hottest?
Star B: it is the most blue
If Star C and Star D in the image are at the same distance and have the same apparent luminosity, what else do we know about these two stars?
Star C is larger than Star D.
Here is a list of stages of stellar evolution for most stars:
A: Main Sequence B: Horizontal Branch C: White dwarf D: Red Giant Branch E: Protostar
Here is a list of energy sources:
I: Fusion of H into He II: Fusion of He into C III: Gravity IV: Electron Degeneracy Pressure
V: Neutron Degeneracy Pressure VI: Supernova
Put the steps of stellar evolution (just write the letters) in the correct order from beginning
to end for regular (not high-mass) stars.
Next to each step put the roman numeral of its support mechanism (energy in most cases)
E III
A I
D III
B II
C IV
Put the HR diagrams 1-3 of Figure 2 in order from youngest to oldest.
1, 2, 3.
Put the labeled stars in Figure 1 in order from hottest to coolest.
E or B (both blue), D (white), A (yellow), C (orange)
Compared to Blue light, Yellow light ....
is colder.
The 3 most massive things in our solar system (the Sun, Jupiter, and Saturn) are
made mostly of,
Hydrogen (the lightest gas).
What is the temperature of a star if the peak of its spectrum is 800nm (very red)?
3625 K.
Since terrestrial planets have crusts which are lighter than their cores, what else can
I infer?
They have differentiated, and so must have been liquid (molten) at some time in the past
Aristarchus measured the relative sizes of the Earth, Moon, and Sun using eclipses
and phase timings. Since the Moon is smaller than the Earth and orbits the Earth and
the Earth is smaller than the Sun, he deduced that the Earth must orbit the Sun. This
last phrase is what part of the scientific method?
Theory.
Which star in the image is the brightest?
Star A
Which star is the hottest?
Star B
If Star B and Star D in the image are at the same distance and have the same apparent luminosity,
what else do we know about these two stars?
Star D is larger than Star B.
Stars B and E in the image have the same sized dots. If I know that star B is four times closer then star E, what else do I know?
Star B is smaller than Star E.
Stars A and C are at the the same distance, what else do I know about these stars?
Star A is larger than Star C. and Star A is cooler than Star C. (both of these are true!)
What stage of evolution lasts the longest?
Main Sequence.
Which part of a comet will exist when the comet is outside of 5AU?
Just the nucleus.
Our sun...
-will evolve llf the main sequence when the hydrogen in the core is gone.
-is unusual in that it is not a binary.
- did not form in isolation but rather with other stars around from the same gas cloud
I take spectra of 2 main sequence stars. Star A has a peak in its continuous spectrum at
350 nm and Star B has its peak at 500 nm. What do I know about these 2 stars?
Star B is less massive than Star B (Star A is more blue)
I see stars twinkle and think it is caused by Earth's atmosphere. So above the
atmosphere stars should not twinkle. I send a cell phone above the Earth's atmosphere in a
small satellite to take a video. This last sentence is what part of the scientific method?
Observation of predictions
If two stars are in a (not eclipsing) binary, what can I learn from that?
Mass.
Use the following information for questions 16 through 21: A gas cloud collapses to
form 4 stars (so they are all the same age and at the same distance).
Star A is 0.5 solar masses on the main sequence.
Star B is 2.0 solar masses on the main sequence.
Star C is 13 solar masses on the main sequence.
Star D is 34 solar masses on the main sequence.
Which star is the brightest on the main sequence?
Star D
Use the following information for questions 16 through 21: A gas cloud collapses to
form 4 stars (so they are all the same age and at the same distance).
Star A is 0.5 solar masses on the main sequence.
Star B is 2.0 solar masses on the main sequence.
Star C is 13 solar masses on the main sequence.
Star D is 34 solar masses on the main sequence.
Which star remains on the main sequence the longest?
Star A
Use the following information for questions 16 through 21: A gas cloud collapses to
form 4 stars (so they are all the same age and at the same distance).
Star A is 0.5 solar masses on the main sequence.
Star B is 2.0 solar masses on the main sequence.
Star C is 13 solar masses on the main sequence.
Star D is 34 solar masses on the main sequence.
How many of the stars will be left on the main sequence after 4 billion years?
1
List the energy source next to each step of stellar evolution.
Main sequence: Fusion H → He
Asymptotic giant branch: Gravity
Horizontal branch: Fusion He → C
A 9 solar mass main sequence star is 12,000 light years away from us. If I see a 3 solar mass main
sequence star with the same apparent brightness, how far away is it?
You have to calculate the luminosities and then compare the apparent luminosities.
LMS=M3.5 so L9=2187 and L3=46.8
Then Lap=L/d2
and since they equal each other: L9/d2
9=L3/d2
3 and we know all these numbers except for
one.
2187/(120002
) = 46.8/(d2
) → d = √(46.8*2187/(1.44x108
))= 0.26 light years. A bit unrealistic, but fine
as an exercise problem
What information can I get from an absorption line spectrum of a star?
I) composition
ii) radial velocity
iii) spin
Briefly describe the methods for finding exoplanets:
Transits: observed a planet going in front of its star and blocking some of the light. Best for short
periods and bigger planets (though, with current precision, any planet is detectable)
Radial Velocity: as the planet goes around the star, the star moves slightly and we can measure this
motion towards and away from us. Best at finding very large planets at shorter orbits.
Direct Imaging: directly sees the planet. Only good for large planets at very large (5AU+) orbits.
Which one is finding the most? Transits is finding lots more than any of the others.
Use the following information from the Big Bang theory:
A) Protons and Neutrons freeze out (stop forming).
B) Nucleosynthesis begins
C) Recombination
D) Inflation
E) Gravity separates from the other forces.
F) Nucleosynthesis ends.
G) Electrons freeze out (stop forming).
What is the age of the Universe?
14 billion years
What type of galaxy is 2 in the figure?
Elliptical
Which step in the big bang theory is the first one?
E, gravity separates from the other forces. This happens at the highest energy
Which of the following variables in the Drake equation need to be solved by biologists?
fl (the fraction of planets that develop life)
What is located in the center of our Galaxy?
a black hole.
According to astronomical clues, what is the most likely ending for our Universe?
It will expand forever.
What are the characteristics of stars in an elliptical galaxy?
Population II with random orbits.
Which is the most massive?
A neutron star.
Which statement about the Milky Way Galaxy is correct?
Our Galaxy is but one of many galaxies.
What type of galaxy is 3 in the Figure?
#1 is a spiral galaxy, #2 is an elliptical, #3 is an irregular, and #4 is a barred spira
Why is it not possible for the Universe to be ``forever and unchanging'', as once thought?
a) Because stars process H into heavier elements.
b) Because the gas within galaxies forms stars and is used up.
c) Because stars evolve into white dwarfs, neutron stars, or black holes.
d) Because gravity is a force that tries to pull massive objects together.
e) All of the above. Is the correct answer.
What makes up most of our Universe? (Not just in mass.)
Dark Energy
If you could travel at the speed of light, which of these
journeys would be the longest?
A trip to the center of the galaxy.
Which is the most massive?
Uranus.
What is the distance to a galaxy with a redshift velocity of 95,000\,km/s?
(Use Ho = 72 km/s/Mpc)
1320 Mpc.
Which of the following statements best describes the overall motion in the Universe?
The universe is expanding faster and faster.
In one short sentence each, describe a planet, a star, and a galaxy.
A planet directly orbits a star and is not massive enough to do H fusion but is massive enough
to be the most massive thing near its orbit (so not asteroids or comets).
A star: A massive object made mostly of H and He that, at the main
energy-producing stage, undergoes nuclear fusion of H into He.
A galaxy: a congomeration of billions of stars, and possibly gas and dust,
which is at least thousands of light years across.
What is the smallest (in size) part of a spiral galaxy?
Bulge
What is dark matter?
Exotic particles that don't interact with light
Which of the following is not evidence confirming the Big Bang Theory?
90\% of the Universe is Dark Matter
What is most of the matter in our Universe made of?
H and He gas.
What is the main difference between the N (left hand side) values for the Drake and
Seager equation?
In the Drake equation, we listen only, in the Seager equation, we are actively doing the
looking.
Which factor(s) in the Drake Equation needs to be solved by sociologists?
Fc and L
What does evidence indicate is the age of the Universe?
14 billion years
Will our galaxy, the Milky Way, look as it does now (a spiral galaxy) forever?
No
What type of galaxy is 3 in the figure?
Irregular
Which of the following variables in the Drake equation need to be solved by biologists?
fl (the fraction of planets that develop life).
The regular (not dark) matter in our Universe is made mostly of
Hydrogen.
Which factor of the Drake Equation can we find clues to using places where water exists
within our own solar system?
fl (fraction of places with water that develop life)
Stars in the disk of a spiral galaxy...
have orbits that are uniform in direction
According to astronomical clues, what is the most likely ending for our Universe?
It will expand forever.
N of the Drake Equation seeks ....
to determine how many alien civilizations could be sending signals, if we just listen.
Which of the following is not in our solar system?
The star Betelguese
What is the distance to a galaxy with a redshift velocity of 230,750 km/s?
3125 Mpc
What does the phrase "the Universe is homogeneous and isotropic" mean in plain terms?
On large scales, it is the same in every direction.
N of the Seager Equation represents what?
How many places could have life, of any kind, if we look (from here).
What is the difference between N of the Drake and Seager equations?
In the Drake equation, it requires the aliens to be active participants whereas in the Seager
equation, any life is passive.
Most of the mass in a galaxy is where?
Dark matter in the Halo
Early in the Universe, before there were stars but after step F(at the top of the page), there
was/were no....
"metals"
What type of galaxy is 5 in the Figure?
Sc Spiral.
Which step of the big bang theory is responsible for making our Universe homogeneous and
isotropic (the same in all directions)?
D
What is located at the center of our Galaxy (and most other galaxies too)
a black hole
Stars in elliptical galaxies have orbits which are
unorganized and random.
Why is it not possible for the Universe to be "forever and unchanging", as once thought?
Because stars process H into heavier elements.
b) Because the gas within galaxies forms stars and is used up.
c) Because stars evolve into white dwarfs, neutron stars, or black holes.
d) Because gravity is a force that tries to pull massive objects together.
e) All of the above.
Which is most massive?
A typical galaxy.
Which of the following statements best describes the overall motion in the universe?
The universe is expanding faster and faster.
What type of galaxy is labeled 4 in the figure?
Elliptical
The Universe is made mostly of...
dark energy.
Organize these from least to most massive
Saturn, the Whirlpool Galaxy, the Moon, the Sun, a black hole.
The Moon, Saturn, the Sun, a black hole, the Whirlpool Galaxy
Organize these from largest to smallest (in size, not mass)
The Sun, a neutron star, the Milky Way galaxy, a white dwarf star, a person.
The Milky Way galaxy, the Sun, a white dwarf star, a neutron star, a person.
Organize these from closest to us, to farthest away from us.
The Moon, the Sun, Saturn, stars in the Big Dipper, the Whirlpool Galaxy
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