Astronomy Final review
The center of the Milky Way is 30,000 light years from the Sun. When was light that we see from the center of the Milky Way now emitted?
30,000 years ago.
As of August 1, 2021 there are 4,081 known "expolanets" - planets that orbit stars other than the Sun. Which of these expresses this number in correct reduced Scientific notation?
4.081×10^3
The Solar System is _________ years old. We know this from measurements of __________.
4.5 billion measurements of radioactive decay in very old rocks
Suppose the average human lives for 100 years. You observe a random, but representative sample, of 100 humans. About how many would you expect to be teen-agers (age 13-19), on average?
5
About how long would it take to send a radio message to the nearest star to the Sun, (Proxima Centauri) and then hear back if it is about 4 light years away?
8 years
What is the HR diagram?
A plot of temperature or color index versus luminosity for stars.
Betelgeuse is 100,000 times more luminous than the Sun. Its surface glows a red color. Which of these statements is true? Pick ALL that apply.
Betelgeuse has a much, much bigger size than the Sun. Betelgeuse has a lower surface temperature than the Sun.
A star is in Thermal Equilibrium when the amount of energy generated in the core is balanced by the transport of that energy to the surface to be radiated away as starlight.
True
The Sun is a star.
True
Evidence that our Solar System formed from a thin rotating disk of gas and dust comes from the fact that
the spin of the Sun and the orbits of most of the Solar System bodies are in the same direction. we observe disks of gas and dust around other stars. all of the planets have orbital planes around the Sun that are very close to the ecliptic plane.
One of the central postulates of Special Relativity is that
uniformly moving observers agree on the laws of physics.
An object in orbit experiences acceleration _____ caused by _____ .
Toward the other body in orbit Gravity
The 'spiral nebula' Andromeda is
the most nearby massive spiral galaxy, like the Milky Way.
The Drake Equation expresses
the number of intelligent civilizations in the Milky Way
Does fusing Helium release energy? Is Helium fusion more or less efficient than Hydrogen fusion?
Yes. Less.
A neutron star has about 1.5 times Sun's mass and is about the size of
a city like Columbus, OH
Galileo showed that massive bodies in the gravitational field of the Earth fall with
constant acceleration, independent of mass.
ALL Main Sequence stars
convert Hydrogen to Helium via fusion in their cores.
A star whose spectrum peaks in the infrared range of the electromagnetic spectrum is
cooler than the Sun.
Two stars are at the same distance and have the same temperature, but they have different radii. The larger star will be
dimmer
The Hubble constant (given the symbol H0) can be found by
dividing a galaxy's radial velocity by its distance.
The ideal gas law states that the pressure of a gas
increases as density or temperature increase.q
One method of finding planets around other stars is by direct detection. This method is biased towards finding
large planets at large semi-major axes.
Compared to low mass stars, high mass stars are
less common, hotter, and shorter lived.
One of the central postulates of Special Relativity is that
the speed of light is the same for all observers.
How would you write "one one-millionth" (a number much smaller than 1) in scientific notation? (The answer is the power of 10) 1×10^-6
-6
About how high is University Hall?
100 feet
How old is the Universe?
About 14 billion years.
The Fermi paradox may imply that
All of these are correct
What is a "standard candle"? Why are they useful?
An astrophysical object whose luminosity is known. We can use this information and the observed brightness to derive the distance to objects.
What is most abundant form of the matter in the universe?
Dark matter.
What supports a white dwarf star against gravitational collapse?
Electron degeneracy pressure.
Humans have been existed for a majority of the history of the Solar System.
False
What basic obstacle has to be overcome to fuse two atomic nuclei?
The repulsion of the positive charges of the nuclei.
What causes stars to rise and set in the sky each night?
The rotation of the Earth on its axis.
What causes a white dwarf star to explode as a supernovae?
The white dwarf collides with another star or "accretes" matter from a companion star.
One major success of the Big Bang model for the formation of the Universe is that it predicts the
abundance of helium in metal-poor stars.
Compared to the gravitational force exerted by the Sun on the Earth, the Earth exerts __________ gravitational force on the Sun.
precisely the same
Retrograde motion is the apparent ________ on the sky with respect to background stars over the course of _________.
"backward" motion of planets, Earth's year.
Suppose the average human lives for 100 years. You observe a random, but representative sample, of 100 humans. About how many will be infants (ages 0-1), on average?
1
Order the scale of the following structures that we live in/on from 1 (smallest) to 5 (largest).
1 (smallest) Earth (planet) 2 Solar System 3 Milky Way (galaxy) 4 (largest) Universe
Big Bang nucleosynthesis took place when the universe was approximately
1 minute old.
A Main Sequence star that is about 10 times more massive than the Sun is about 10,000 times more luminous. Its Main Sequence lifetime is therefore approximately
1,000 times shorter than the Sun's.
How much time does it take light to travel 103 light-years?
1,000 years
How many bucks is a gigabuck?
1,000,000,000
The distance from the Sun to the Earth is 150,000,000,000 meters. Express this in kilometers in reduced scientific notation.
1.5×10^8
What is the following product, written in scientific notation? 2×10^4×8×10^15=
1.6 x 10^20
For what fraction of the history of the Universe has the Sun existed? Roughly
1/3
Roughly. what is the shape and size of the Milky Way? It has about [ Select ] stars and is about [ Select ] across.
100 billion 100,000 light years
About how old is the Universe?
14 billion years
About how old is the Universe?
14 billion years.
About when was the telescope invented?
1600
There are about 200 billion stars in the Milky Way Galaxy. There are about 100 billion galaxies like the Milky Way in the observable universe. If each star in each galaxy has 1 billion comets, how many comets are there in the observable universe?
2 x 10^31
There are about 200 billion stars in the Milky Way Galaxy. It is estimated that roughly 1 out of every 100 stars formed will explode (as a supernova) shortly after it forms. How many total stars have exploded in the Milky Way over the course of its history?
2 x 10^9
Convert 2,190,000,000 kilometers to meters and express your answer in reduced scientific notation.
2.19 x 10^12
The value of the Hubble constant is about H0 = 20 km/sec/million light years. The Perseus Cluster of galaxies is at a distance d = 200 million light years. How fast is the Perseus Cluster moving away from us?
4,000 km/sec
How many arcseconds are there in 1 degree?
60 x 60
Proxima Centauri is the nearest star to our Sun. It is 4 light years from Earth. How long would it take to send a light signal to Proxima Centauri and then "hear back"? Assume aliens on a planet orbiting Proxima Centauri immediately send a response when they receive our signal.
8 years.
What is the Milky Way?
A band of light in the sky at night that is our home galaxy viewed from within its disk.
In measuring the angle of the Sun relative to a vertical stick in Alexandria at noon on the day of the summer solstice, Eratosthenes found 7 degrees and 12 arcminutes. Imagine that everything about that experiment was the same, except that the angle measured was smaller (for example: 3 or 5 degrees). What would that smaller angle imply?
A larger value for the Earth's circumference.
What is the HR diagram?
A plot or graph of luminosity versus temperature (or color index) for stars.
What sits at the very center of the Milky Way Galaxy and other large galaxies? [ Select ] How do we know? [ Select ]
A supermassive black hole. We observe stars orbiting a massive invisible object.
Object A has a mass of 10 kg. Object B has a mass of 1000 kg. If the same force is applied to both,
A will accelerate 100 times more than B.
Roughly how old is the Universe?
About 14 billion years.
The speed of light is 300,000 km/s . The distance from the Earth to Mars at closest approach is about 50,000,000 km. How much time does it in seconds take a radio signal sent from a rover on Mars to reach Earth?
About 200 seconds
A famous galaxy called "the Pinwheel" is about 21 million light years away. A few years ago, we saw a new bright flash in that galaxy that indicated that a star had exploded (a "supernova" had occurred). When did that star actually explode?
About 21 million years ago.
About how old is the solar system? How do we know?
About 4.5 billion years. Radiometric dating of rocks.
My car goes 100 km/hour. Suppose we are on a "road" trip (in space). How many years would it take make the 50,000,000 km trip to Mars at closest approach? Hint: First use distance = rate * time to find the time to make the trip in hours, then divide by the number of hours in a day. Then divide by the number of days in a year (365).
About 60 years.
The Voyager satellite is moving at roughly 60,000 km/h away from the Sun. It ran out of fuel long ago. It is far enough away from the Sun and other stars that the effect of gravity is small and we can say that Voyager is not being acted on by any gravitational force or any other force. If you check back in on Voyager in 100,000 years what would you expect its speed to be?
About the same, 60,000 km/h.
On the FM dial, the frequencies run from 88 - 107 MHz (million cycles per second). On the AM dial, the range is 570 - 1600 kHz (thousand cycles per second). Which statements are true?
All of these statements about FM photons are true.
If an object is moving in a circular orbit and you speed it up, giving it a bit more speed (but not enough to escape) what will its new orbit look like?
An ellipse with a bigger long ("semi-major") axis than the current orbit.
How would the Hubble Law look different for someone living in the distant galaxy "Arp 220," which is on the other side of the Virgo Cluster from us?
An observer in Arp 220 would see the same Hubble Law that we do.
Which of these is the best description of parallax?
An observer shifts position and nearby objects appear to move relative to the background.
What is (9×10^9)/(3×10^4)? (The answer includes the coefficient and the power of 10) Answer here: 3 ×105 .
Answer 1:3 Answer 2:5
What is a black hole?
Any object dense enough that light cannot escape from it.
Two stars A, B have the same mass, but A has smaller radius than B. Which has the HIGHER escape velocity? Two planets C, D orbit the same star, but C has a smaller semi-major axis than D. Which has the SMALLER orbital circular velocity?
B,C
In Aristarchus's measurement of the Earth-Sun distance when the Moon is half-illuminated, why is the angle between the Moon-Earth-Sun so close to 90 degrees?
Because the Sun is far away compared to the Earth-Moon distance.
In the case of a planet-star system, which of these is always true?
Both the star and the planet orbit the common center of mass.
How does the Hubble law tell us about the age of the Universe?
By "reversing" the observed expansion we can tell when all galaxies were next to each other.
Think about two space shuttles, OHIO and CLEVELAND. Both orbit the Earth in an approximately circular orbit. Space shuttle OHIO orbits at four times larger distance compared to space shuttle CLEVELAND (i.e., CLEVELAND is much closer to the Earth). What can you say about their relative orbital speeds? Hint: Look at the formula for orbital velocity in a circular orbit.
CLEVELAND has an orbital speed two times faster than OHIO.
What is the ultimate fate of a star like the Sun that is about 1 solar mass and not in a binary star system? It will end up as a
Carbon-Oxygen white dwarf
A star that starts out equal in mass to the Sun will end its life as a [ Select ]. A star that starts out with 15 times the mass of the Sun will end its life as a [ Select ].
Carbon-Oxygen white dwarf neutron star or black hole
Which of the following was a empirical argument used by Aristotle for why the Earth is a sphere.
Constellations that were low in the sky when viewed from northern latitudes were higher in the sky when viewed from more southern latitudes. During a lunar eclipse, the shadow cast by the Earth on the Moon is a circle. The Moon shows phases indicating it is a sphere.
Match the following players in the Copernican revolution to one of their major contributions.
Copernicus Proposed that the Earth goes around the Sun. Tycho Brahe Obtained pre-telescopic observations that could distinguish between the Earth- and Sun-centered models. Kepler Constructed a mathematical model and a set of orbital laws that explain planetary motions around the Sun. Galileo First deployed the telescope for astronomy.
One piece of evidence supporting the idea that our Universe went through "Inflation" at a very early epoch in its history is that the
Cosmic Microwave Background is highly smooth & uniform.
Two objects separated by a distance d are pulled apart to a distance of 10d. How has their gravitational force changed?
Decreased by a factor of 100
What is our preferred explanation for the Hubble Law?
Each unit of empty space expands over time. The empty space in the universe is expanding.
In general, what is the shape of the orbits of planets or comets around the Sun?
Ellipses.
Which of these best describes the Earth's motion in space?
Every day the Earth spins once on its axis. Every year the Earth orbits the Sun once.
Two planets, NEARPLANET and FARPLANET, orbit the same star on near-circular orbits. The orbit of FARPLANET has an orbital semi-major axis three times larger than that of NEARPLANET. What can you say about the orbits of the two planets?
FARPLANET has a slower orbital speed, and a longer orbital period than NEARPLANET.
Because X-rays have higher energy than radio waves, they move faster through space than than radio waves.
False
In Newtonian physics, a planet in a perfectly circular orbit at constant orbital speed experiences no force.
False
The difference in the semi-major axis between Mercury's and Earth's orbit is about the same as the difference between Mars's and Neptune's.
False
How do we measure the luminosity of a star? Pick the most direct answer.
From the apparent brightness and distance (from parallax).
How do we think elliptical galaxies form?
From the merger or collision of two or more spiral galaxies with random or oppositely directed spins.
You are standing on the Oval at Ohio State facing due south, at the moment of sunset. The Moon rises just as the Sun sets. What phase is the Moon? What direction does it rise from?
Full Moon. East.
What common behavior is shared by all main sequence stars (like the Sun)?
Fusion of hydrogen into helium in the core.
How do we infer the existence of dark matter? Pick the simplest, most direct answer.
Galaxies spin too quickly to be explained just by the matter than we can see.
What is one way that we infer the existence of dark matter? Pick the simplest, most direct answer.
Galaxies spin too quickly to be explained just by the matter we can see.
What causes light to shine from some black holes?
Gas heats up due to as it accretes onto the black hole, producing radiation.
In the horizontal branch/red clump phase of low-mass stellar evolution, which element undergoes nuclear fusion in the stellar core?
Helium
The Sun will spend about 10 Gyr on the Main Sequence, but only 100 Myr on the Horizontal Branch/Red Clump. Why?
Helium fusion is less efficient than Hydrogen fusion.
Most of the atoms in the Universe are
Hydrogen and helium.
During the evolution of a low-mass star up the red giant branch on the HR diagram, the star burns
Hydrogen in a shell and has an inert Helium core.
I am gently spinning in my swivel chair with my arms extended holding two weights. I bring the weights in close to my chest. What happens?
I will spin faster.
Where is most of the mass in the Solar System?
In the Sun.
What type of light does my dog glow in (i.e., what type of light does my dog give off)?
Infrarred light
If the Earth vanished suddenly, and the force of gravity acting between the Earth and the Moon were shut off, what would happen to the Moon?
It would fly off in a straight line along its current direction of motion.
Over the course of an orbit of each planet around the Sun, space stations on Mercury, Earth, and Jupiter measure the parallax angle of a nearby star. Which measures the LARGEST parallax angle?
Jupiter
What is the cosmic microwave background? What are we looking at when we observe it?
Light emitted when the universe was full of hot opaque gas, that has been traveling through space since then.
We often say that telescopes are "time machines" or that they "look back into the past." Which of these statements correctly explains this phenomenon?
Light takes time to cover astronomical distances, so we see distant objects as they appeared when they emitted that light.
The rocky, terrestrial planets of the Solar System consist of
Mercury, Venus, Earth, Mars
Of the eight planets in the Solar System, which has the fastest orbital velocity around the Sun? Which has the slowest?
Mercury. Neptune.
Which of these best describes the orbits of the planets and smaller Solar System bodies?
Most orbits lie the same plane and proceed in the same direction.
Why do we expect neutrino emission from the Sun?
Neutrinos are a by-product of hydrogen fusion
Does the Moon always appear to be the same size from Earth? Does the Moon rotate?
No. Yes.
Two bodies (A and B) have the same angular size from your position, but B is twice as far away as A. Which is physically larger?
Object B.
Consider two identical new planets found in the outskirts of our Solar System: planet "Brutus" and planet "Buckeye". Both planets have the same physical diameter in kilometers. But, Planet Buckeye is two times farther from Earth than Planet Brutus. Planet Brutus has a smaller orbital semi-major axis than Planet Buckeye. Which of the following statements is true about apparent angular size (diameter measured in degrees) of the two planets?
Planet Brutus appears two times larger than Planet Buckeye.
Which of these statements describes the position of the planets in the sky compared to the background stars?
Planets move in a complex way relative to the background stars, showing loops and back-and-forth motion.
Which of these statements describes the position of the planets in the sky compared to the background stars?
Planets move relative to the background stars; the path is complex, showing loops and back-and-forth motion.
Kepler's 2nd law of orbital motion ("equal areas in equal times") means that
Planets orbiting the Sun speed up in their orbits when they are closest to the Sun and slow down when they are furthest away.
Which will have a longer main sequence life time, Proxima Centauri (0.2 solar masses) or Sirius (2 solar masses)?
Proxima Centauri
We know the age of the Solar System and Earth quite precisely. How?
Radioactive dating of rocks provides very precise estimates.
The accelerated expansion of the universe as a result of Dark Energy causes very distant galaxies to have
Recession velocities smaller than the linear Hubble Law would predict.
Near-infrared light has a wavelength 3 times longer than that of red light. How do the frequency of near-infrared light and red light compare?
Red light has a frequency 3 times larger than that of near-infrared light.
How can light from stars most directly tell us about their composition?
Sharp features (dark or light bands) in the spectrum reflect the unique quantum mechanical structure of the atoms that makes up the object.
The planets in the Solar System orbit ________ . This reflects that we think that they formed ________ .
Some plain and direction from a thin, spinning disk of gas and dust. from a thin, spinning disk of gas and dust
An RR Lyrae is an example of a __________. RR Lyraes in globular clusters were used by Shapley to investigate the size and shape of __________.
Standard candle. The Milky Way.
Two Cepheid stars A & B have the same apparent brightness, but A has a pulsation period 5 times longer than B. From this information you can conclude that
Star A is further away than star B.
Two stars, A and B, have the same intrinsic luminosity, but star B is two times further away than star A. Which star is brighter and by how much?
Star B is 4 times brighter than Star A.
Consider two main sequence stars, star CAT and star DOG. Star CAT has a luminosity 100 times higher than that of star DOG. Star CAT has a mass 2 times larger than that of star DOG. How does the lifetime of star CAT compare to that of star DOG?
Star CAT lives 50 times LESS than star DOG.
You measure the parallax of two stars (i.e., you measure their angular shift between June and December as the Earth goes around its orbit). Star SCARLET shows a parallax angle that is two times bigger than Star GRAY. What can you say about the two?
Star GRAY is two time farther away than star SCARLET.
Parallax is the apparent angular motion of relatively nearby stars compared to background stars over the course of a year on Earth, as our perspective on those nearby stars changes. Which of these statements is true about the parallax of nearby stars?
Stars that show a smaller parallax angle are farther away.
The Copernican heliocentric system violated which ancient Greek idea?
That the Earth is fixed and unmoving.
If Dark Energy is a Cosmological Constant, what is the current best idea for the future history of our universe?
The Big Chill.
You apply the same force pushing two otherwise identical objects: an EMPTY WAGON and a FULL WAGON with five times the mass of the empty wagon. How will the acceleration of the two wagons compare?
The EMTPY WAGON will accelerate five times MORE than the FULL WAGON.
The Great Debate contrasted which hypotheses about the universe?
The Nebular and Island Universe hypotheses.
Saturn's semi-major axis is about 10 astronomical units from the Sun. Compare the apparent brightness of the Sun from Earth to the apparent brightness of the Sun from Saturn.
The Sun appears 100 times fainter at Saturn than at Earth.
Jupiter's semi-major axis is 5 astronomical units. How does the apparent brightness of the Sun from the orbit of Jupiter compare to the apparent brightness of the Sun from the orbit of Earth?
The Sun appears 25 times fainter from the orbit of Jupiter than from the orbit of Earth.
What was Copernicus's revolutionary idea concerning the solar system?
The Sun is at its center, the planets orbit the Sun.
Potassium-40 is a radioactive isotope that decays to Argon-40 with a half-life of about 1.25 billion years. If a sample of rock forms in the early solar system without any Argon-40, but with some Potassium-40, what happens?
The amount of Potassium-40 decreases, and the amount of Argon-40 increases, with about half of the Potassium converted into Argon in 1.25 billion years.
Earth has just gained a new moon! This moon (named Brutus by popular vote) has exactly the same physical size as our current Moon. Brutus is three times farther away from us than our current Moon. What can you say about the apparent (or angular) size of Brutus compared to our current Moon?
The apparent size of Brutus is 1/3 that of the Moon.
Gamma rays have higher energies than radio waves. Both are emitted by a nearby star at the same time. Which arrives first?
The arrive at the same time
What is an AU (astronomical unit)?
The average distance between the Earth and the Sun.
Which of the following is an experimental verification of General Relativity?
The bending of light around massive bodies
If you moved the Earth *three* times further away from the Sun than it is now (that is, you increased the semi-major axis of the Earth's orbit from 1AU to 3AU), what would happen to the force of gravity between the Earth and the Sun?
The force of gravity would decrease by a factor of 9.
The apparent change in the Sun's position in the sky relative to the background stars over the course of the year depends mainly on ...
The location of the Earth in its orbit around the Sun.
Mars is in a nearly circular orbit about the Sun. We measure the semi-major axis of its orbit (about 1.5 AU) and its orbital speed (about 25 km/s). What other piece of information could we figure out from these quantities?
The mass of the Sun.
Venus is in a very nearly circular orbit about the Sun. We measure the size of its orbit (about 0.7 AU) and its orbital speed (about 35 km/s). What other piece of information could we figure out from these quantities?
The mass of the Sun.
We measure the rotation speed of a galaxy at a radius, R. What can we infer from this information?
The mass of the galaxy inside the radius R.
What is the basic observation that we call the "Hubble Law"?
The more distant a galaxy is the faster it appears to recede away from us.
We think that the differences in composition between the inner "terrestrial" and outer "jovian" planets reflects that ...
The outer planets formed where cold temperatures made ices available to help build planets.
The stars Proxima Centauri and Betelgeuse have the same surface temperature. However, the luminosity of Betelgeuse is 1,000,000 times the luminosity of Proxima Centauri. What can you say about the relative size of Betelgeuse and Proxima Centauri?
The radius of Betelgeuse is 1,000 times the radius of Proxima Centauri.
What causes stars to rise and set in the sky over the course of a night?
The rotation of the Earth on its axis.
What causes stars to rise and set in the sky?
The rotation of the Earth on its axis.
An ice skater (or figure skater) spins with their arms extended. Then they bring their arms in towards their body. What happens to their rate of spin (in revolutions per minute)?
The skater spins faster.
A comet, say Halley's Comet, is on a very long, very elliptical and elongated orbit. What can you say about the speed of the comet at various points in its orbit?
The speed is higher when the comet is close to the Sun.
What is the main cause of seasons on Earth?
The tilt of the Earth's axis relative to its orbit about the Sun.
What is the main cause of the seasons on Earth?
The tilt of the Earth's axis relative to its orbit about the Sun.
We measure the rotation speed, V, of a galaxy at a radius, R, from the center of that galaxy. What can we infer from this information?
The total mass of the galaxy inside the radius R.
If you measure the orbital period of a binary star system (two stars in an orbit around each other) and the semi-major axis of the orbit, what property of the system can you calculate from Newton's generalization of Kepler's 3rd Law?
The total mass of the whole system (both stars).
You observe some infrared light and some visible light. The visible light has a 10 times larger frequency than the infrared light. How do the wavelengths of the infrared and visible light that you observed compare?
The wavelength of the infrared light is 10 times larger than that of the visible light.
You observe some infrared light and some visible light. The visible light has a 10 times higher frequency than the infrared light. How do the wavelengths of the infrared and visible light that you observed compare?
The wavelength of the infrared light is 10 times larger than that of the visible light.
What common behavior is shared by all "main sequence" stars?
They all fuse hydrogen into helium in their core.
Gamma-ray photons have higher energy than optical photons. Both gamma-ray and optical photons are emitted simultaneously by a nearby star. Which arrives at our detector on Earth first?
They arrive at the same time.
Ultra-violet photons have higher energies than microwave photons. Both types of photons are emitted by a nearby star at precisely the same time. Which arrives first?
They arrive at the same time.
Which of the following is NOT a property of main sequence stars?
They undergo Helium fusion in their cores.
Where do "heavy" elements like carbon, oxygen, and iron come from?
They were created by nuclear processes inside of stars.
Carbon-Oxygen white dwarfs are the remnants of low mass (stars less than 4 times the mass of the Sun) stellar evolution.
True
Helium fusion is less efficient than Hydrogen fusion. This is why the duration of the red clump/horizontal branch phase of stellar evolution is shorter than the main sequence phase.
True
Hydrostatic equilibrium is a balance between pressure and gravity.
True
Low mass stars (< 4 times the mass of the Sun) do not undergo fusion of Carbon and Oxygen.
True
Neutron stars and black holes are the product of high mass (>8 times the mass of the Sun) stellar evolution.
True
Oxygen-Neon-Magnesium white dwarfs are the remnants of intermediate mass (4-8 times the Sun's mass) stellar evolution
True
Stars on the main sequence are in hydrostatic equilibrium.
True
Stars on the main sequence are in thermal equilibrium.
True
Stars on the main sequence are powered by the fusion of Hydrogen into Helium.
True
White dwarf stars and neutron stars shine only by residual heat.
True
Saturn is about 10 times the size of Venus (i.e., it has 10 times the diameter of Venus). When both planets are at closest approach to the Earth, Saturn is about 30 times farther away from the Earth than Venus. How does the angular size or apparent size (i.e., the angular diameter) of Saturn at closest approach compare to that of Venus at closest approach?
Venus has an apparent size 3 times bigger than Saturn.
Venus, the Earth and Jupiter are all on approximately circular orbits around the Sun. Rank their circular orbital velocities around the Sun from largest to smallest.
Venus, Earth, Jupiter
What part of the electrogmagnetic spectrum does the Sun's spectrum peak in?
Visible.
At the moment of sunrise, you are facing due south, standing in the middle of the Oval at Ohio State. The Moon is directly south, and half illuminated. Is the Moon waxing or waning? If you went to that spot, at sunrise on the *next* day, would the Moon have moved to the east or west of where it was the previous day?
Waning. East.
How do we measure the "rotation curve" of a spiral galaxy?
We measure the Doppler shift/radial velocity of stars or gas towards or away from us across the galaxy.
Three stars are on the HR diagram. All three stars have the same temperature (color index). Star X has the lowest luminosity. Star Q has the highest luminosity. Star D is in between Star X and star Q, with intermediate luminosity. List the stars in order of INCREASING physical radius FROM SMALLEST TO LARGEST.
X, D, Q.
Is there any maximum mass limit for a neutron star?
Yes
Kepler's 2nd law of orbits states that the line between the Sun and a planet sweeps out equal areas in equal times. Newton showed this behavior is a consequence of
angular momentum conservation and gravity.
Immediately after it finishes life on the main sequence, the Sun will
ascend the red giant branch.
In Einstein's General Relativity, the mass of a black hole is located
at the singularity.
Einstein's principle of Homogeneity means that, when viewed on the universe's largest scales, the
average density of the universe is the same everywhere.
Two stars are at the same distance and have the same temperature, but they have different radii. The physically larger star (with bigger radius) will be
brighter
In a binary star system, star A has 5 times the mass of star B. The center of mass of the system lies
closer to star A than to star B.
spiral galaxy's spheroid is a two-part structure consisting of a ________ and a __________.
compact bulge, diffuse halo
From the law of gravitation, Newton deduced that the shape of an orbit is always a _______ with the _______ at one focus.
conic section, center of mass
Galileo showed that massive bodies in the gravitational field of Earth fall with
constant acceleration, independent of mass.
A light-year is a unit of
distance
The idea of a "standard candle" is important as a way of measuring.
distance
The nightly motion of the stars in the sky is predominantly __________ and is a result of _________.
east-to-west. Earth's rotation.
Andrea Ghez and Reinhard Genzel won the Nobel Prize for their work to
establish the nature and mass of the Milky Way's central supermassive black hole.
White dwarf supernova explosions are [ Select ]. They occur in [ Select ]. They produce and disperse [ Select ].
events in which runaway nuclear fusion consumes a whole white dwarf star binary star systems heavy elements, especially things like iron
Compared to the gravitational force exerted by the Earth on the Sun, the gravitational force exerted by the Sun on the Earth is:
exactly equal.
If the density parameter Omega_0 was much SMALLER than 1, and if there was no Cosmological Constant (dark energy), the universe would be expected to
expand forever, but at an ever-decreasing rate.
If the density parameter Ω0 was SMALLER than 1, and if there was no Cosmological Constant (dark energy), the universe would be expected to
expand forever, but at an ever-decreasing rate.
The apparent recession velocities we measure for the majority of galaxies in the universe are due to the
expansion of spacetime between galaxies.
Through a telescope, Venus appears __________ when _________ and appears as a _________ when _________.
fullest, furthest away; crescent, closest to Earth
Collisions between galaxies are common because
galaxy separations are only about 20x their diameters.
General Relativity is a theory of
gravity.
Which of the following is an experimental verification of General Relativity?
he bending of light around massive bodies.
We see many hot, luminous stars in the disks of spiral galaxies. These stars must be
high mass, short lived, and so have formed recently.
You are facing due south in Columbus at 10pm. The constellation Scorpius is front of you, near the horizon. You are instantly transported due south 1000 miles. Scorpius now appears
higher in the sky relative to the horizon.
In the past, the universe was
hotter, denser, smaller, younger.
Compared to low-mass main sequence stars, high-mass main sequence stars are
hotter, more luminous, and shorter lived.
What is the Sun made of mostly?
hydrogen and helium
Before any stars or galaxies formed, normal matter in the Universe consisted of ...
hydrogen and helium and not many heavier elements.
In following the Main Sequence on the H-R diagram in the direction of increasing temperature (from cooler to hotter), one is also following a sequence of
increasing mass.
In following the Main Sequence on the H-R diagram in the direction of increasing MASS (from low mass stars to high mass stars), one is also following a sequence of
increasing temperature
What type of light does my dog glow in?
infrared light
Hydrogen gas emits radiation with a wavelength of 21 cm in your laboratory on Earth. You observe the same Hydrogen spectral feature in a distant star's spectrum at 26 cm. From this, you can conclude that the star
is moving away from Earth at high velocity.
When we compare the true total mass of a galaxy cluster with the mass measured by adding up all the stars in all the galaxies of the cluster, we find that the true cluster mass
is much larger than its stars would suggest.
What happens when a white dwarf exceeds the "Chandrasekhar mass limit" due to either collision/merger with another white dwarf, or via accretion from a stellar companion?
it may explode in a white dwarf supernova.
Galileo's observations of the Sun strongly indicated that
it rotates.
One method of finding planets around other stars is to look for transits. This method is biased towards finding
large planets at small semi-major axes.
Rank the frequencies of the following types of light from 1 (lowest) to 4 (highest).
lowest red green blue Xray highest
Aristarchus used the duration of the _______ relative to the duration of the ______ to determine the distance to the Moon in terms of Earth radii.
lunar eclipse, lunar month
After formation, the main stages of evolution for a Sun-like star are
main sequence, red giant branch, red clump/horizontal branch, asymptotic giant branch, Carbon-Oxygen white dwarf
What is the main property of a star that determines where that star sits on the "main sequence"?
mass
Population III stars are a hypothesized class of stars formed from
metal-free primordial gas.
Shapley's observations of RR Lyrae stars in globular clusters neglected absorption of starlight by interstellar dust. This made the globular clusters appear
more distant than they really are.
Compared to the inner (terrestrial) planets, the outer (Jovian) planets in the Solar System are [ Select ] and [ Select ].
more massive made of more icy, gaseous material
Compared to the inner planets, the outer planets in the Solar System are ______ and ______ .
more massive made of more icy, gaseous material
Before any stars or galaxies formed, but after Big Bang nucleosynthesis, the normal matter in the Universe consisted of ...
mostly hydrogen and helium and not many heavier elements.
The largest blow Galileo dealt to the Ptolemaic (geocentric) system was to show that Venus appears
nearly full when farthest away.
Just before the epoch of Recombination, the Universe was hotter than about 3000K, and as a result
neutral hydrogen could not exist.
Massive stars end their lives as
neutron stars or black holes.
A primary piece of evidence for the existence of Dark Energy comes from the observed
non-linearity in the Hubble Diagram at high redshift.
Compared to spiral galaxies, elliptical galaxies have:
older stars, little gas and dust, few new stars, and spheroidal shapes.
As a group, Population II stars are ___________ compared to Population I stars.
older, more metal-poor, and have less ordered orbits
The distance between the Earth and the Sun is also referred to as
one "astronomical unit"
Humans have been around for
only a tiny fraction of the history of the Universe, Earth, or Solar System.
In the Copernican system, why is Venus only at most 46 degrees away from the Sun on the sky? Because Venus
orbits the Sun on a circle with radius less than 1 AU.
Hydrostatic equilibrium is a balance between
pressure and gravity.
Spiral arms are usually sites of __________ in spiral galaxies.
recent star formation
Jill watches as Jack falls toward a black hole. Jack fires a yellow laser beam that flashes every second by his watch as he falls. As Jack gets closer to the black hole, Jill sees the flashes getting
redder and fainter, and less frequent
Constellations are
regions of the sky where we associate stars with one another.
The energy radiated by solitary white dwarfs comes from
residual heat (thermal energy).
The Fermi paradox stems from the fact that
spacefaring and colonizing civilizations should cover the entire Milky Way rapidly compared to the age of the universe.
Our Galaxy, the Milky Way, is a(n)
spiral galaxy
Hydrogen gas emits at 656 nm in your laboratory on Earth. You observe the same Hydrogen spectral feature in a distant star's spectrum at 650 nm. From this, you can conclude
that the star is moving toward Earth at high velocity.
A white dwarf that accretes from a binary companion can exceed __________ and become a type of _________.
the Chandrasekhar mass, supernova
A white dwarf star is closest in size to
the Earth
The failure to detect the parallaxes of stars during Copernicus's time and before, was used as evidence that
the Earth does not move
The normal monthly phases of the Moon depend on ...
the Moon's position relative to the Sun as the Moon orbits the Earth.
From the reading, one set of ideas and theories for how the Solar System formed is called
the Nebular Hypothesis.
An early success of General Relativity was that it explained
the anomalous precession of the perihelion of Mercury.
The Hubble constant measures
the current expansion rate of the universe.
The Sun is located in what part of the Milky Way?
the disk
A "planetary nebula" is
the ejected envelope of a aging star similar in mass to the Sun.
A planetary nebula is
the ejected envelope of a aging star similar in mass to the Sun.
If you know the distance to an object and you measure its apparent brightness you can figure out:
the luminosity of the object.
Newton's law of gravitation states that the attractive force between any two masses is in proportion to the product of ________, and in inverse proportion to ________.
the two masses, the square of the distance between them
You are standing on Earth, at rest in your rest frame. Jane passes you at nearly the speed of light with a photon clock. Special Relativity says that you will see
time pass more slowly on Jane's rocket than on Earth.
On the HR diagram, three stars all have the same temperature (color index), but different luminosities. Order the three stars in order of INCREASING size, from physically smallest to physically largest.
white dwarf, main sequence blue star, blue supergiant
Three stars have surface temperatures of 10,000K. List them in order of INCREASING radius.
white dwarf, main sequence star, supergiant
If new observations showed conclusively that the Hubble constant is LARGER than previously thought, then this fact by itself would imply that the universe is
younger than we previously thought.
