ASTR EXAM
Imagine the size (radius) of the Earth were tripled, yet the mass were to remain the same. If you step on a scale, your weight will now be?
9 times smaller
This movie is widely known as the most accurate sci-fi movies today
Interstellar
Using the same H-R Diagram once again, which of the following stars would have the smallest radius?
Sirius B
The Table will be used for the next 4 questions Star X app mag 3 abs 3 Star Y app magn 4 abs -2 Star Z app mag -1 abs 1 Which of the following stars X Y Z will be the brightest star as seen from Earth
Star Z
Which of the following is true of a satellite that is in a perfectly circular orbit around Earth?
The satellite is constantly accelerating
Imagine we live in a collapsing universe. In particular, all the galaxies observed from Earth appear to be rapidly approaching us. What would we observe in the light of these galaxies?
Their light would be blueshifted
Why are astronomers eager to build larger (and larger) telescopes?
They allow us to see fainter objects they permit higher resolution of fine details they magnify objects more A and B ALL OF THE ABOVE
As stars get hotter, what happens to the absorption lines we see?
We see more absorption lines from ionized elements, due to the extreme temperatures.
This spectral class of stars exhibits the most visibly prominent hydrogen absorption lines (ie balmer lines)
What are spectral type A stars
Law relating period and semi-major axis of an orbit
What is Keplers 3rd law
Even from Earth's surface, this kind of telescope can take data during the day time
What is a radio telescope
You examine 3 newly discovered comets, and measure their eccentricities. One of the three, which of the following is most similar to a perfect circle
a. e=0.5 b. e=0.25 c. e=0.10 Answer= C
Lets say you are somewhere between the Earth and the Moon, and you find a position where the force of gravity exerted on you by the Earth exactly cancel the force of gravity exerted on you by the moon. Where would this position be located
closer to the moon
Over the course of one year, a star exhibits a total angular shift of approximately 0.2 arcseconds. What is the approximate distance to this star?
10 parsecs
Approximately how many hydrogen atoms are there in the sun?? (order of magnitude works here) Hint the sun is 2x10 to the 30th power kg, and 70% of that mass is H atoms).
1x10 to the 57th power of atoms
image the mass of the Earth were triples, yet the size (radius) were to remain exactly the same. If you step on a scale, your weight will now be?
3 times bigger
Which of the following could be the mass of a main sequence star that would likely end its life in a supernova explosion? (Recall: 1 solar mass = the mass of our sun)
30 solar masses
We talked about the extremely massive star Eta earlier this semester. It is one of the most luminous stars in our milky way. What is its approximate luminosity, in "solar luminosities"? (ie how many times more luminous than the sun)
4,000,000
Which of the following electron energy-level transitions corresponds to the shortest wavelength of light being emitted?
5 to 2
A planet in another solar system orbits a star of 2 solar masses (M=2). If this planets semi-major axis is 4AU, how long is this planets orbital period?
5.7 YEARS
The wavelength of "H-alpha" radiation we observe in the lab on Earth is 656 nanometers (nm) If we observed H-Alpha being emitted by the Andromeda Galaxy, what is the most likely wavelength at which we would observe it?
655 The Andromeda galaxy is slightly blueshifted, so light observed at shorter wavelengths
The wavelength of a prominent hydrogen emission line (called H-Alpha) is 656 nm. Which of the following wavelengths could represent H-alpha emission from an object moving away from you the fastest?
675 nm
In the "Parallax and Distance" Lecture-Tutorial, what was the last month represented in the succession of images on Page 43? (Remember, you can use your class materials during this exam. Yes, I fully realize this is the easiest question on the exam, provided you actually obtained your Lecture-Tutorial book. If that's the case, thank you!)
August 2001
Annie Jump Cannon famously contributed to the field of astronomy by accomplishing which of the following?
By painstakingly cataloging hundreds of thousands of stars, and classifying them based on the strength of their hydrogen absorption lines., By delivering the best comeback imaginable to that 7th grader in the planetarium who kept making those damn "Uranus" jokes. (From planetariums worldwide: "Sick burn, Annie!!!")
Movie adaptation of Carl Sagans book where Jodi Foster travels through a worm hole
Contact
You observe a red star, of spectral class M. With only this information, you can conclude this star will be placed low (towards the bottom) on the H-R Diagram.
FALSE
Astronomers can do high-quality gamma ray astronomy from the ground, provided the telescopes are far away from large cities
False
Astronomers could potentially deduce that a star is rapidly rotating if its absorption lines were thinner (narrower) than expected.
False
The gamma rays produced by fusion reactions in the sun's core escape the interior of the sun and reach the visible surface (the photosphere) in about 8 minutes.
False
We have two stars (Star A and Star B) that are born at the same time, and Star A is twice as massive as Star B. Due to this additional mass, we can conclude that Star A will have a longer lifetime than Star B.
False
When we break apart sunlight, we can observe the full spectrum of the sun. Because the sun exhibits an absorption spectrum, we can deduce that the sun must be entirely composed of low-density gas.
False
In the Binary Stars Lecture-Tutorial exercise, on page 122, what are the two spectral classes of the stars used in questions 4-6?
G and A
In 1955 movie where pod people take over Santa Maria California
Invasion of the body snatchers
If Earth were moved from its current orbit, and we now orbited the sun at a distance of 4 AU, how would this alter the intensity of sunlight we experience on Earth?
It would be 1/16 its current value
If the size (radius) of the sun were increased by a factor of 4, but the temperature of the sun were reduced to 1/2 its current value, what would happen to the sun's total luminosity?
It would remain the same
After the universe cooled, following the big bang, hydrogen condensed out of the energetic soup. And for just a brief period, the energies/densities across the universe were sufficient for fusion. This produced a bunch of helium. This is why the universe is mostly made of helium and hydrogen today. One addition element was made in trace amounts. This is the name of that element.
Lithium Lithium is never an end-product of stellar fusion, nor is it produced in supernovae, because the reaction chains skip right past lithium. So any/all lithium in existence today is leftover from the conditions of the Big Bang itself. 100% of lithium around today= big bang lithium
Which of the following properties could possibly be the same for the two stars below?
NONE OF THE ABOVE
Which of the following stars seen in the image below would appear bluest in color? (Note: the next 2 questions will refer to this same H-R Diagram)
Spica
If we consider the entire lifespan of each star above from the moment of formation until its death (i.e., no more nuclear fusion), which of the stars will have the shortest total lifespan?
Star 1
Use the data table below to answer the next 4 questions (note: the table will be reproduced for each question). Star 1 Spec Class O Solar mass 50 Star 2 Spec Class M Solar mass 40 Star 3 Spec Class A Solar mass 2 Star 4 Spec Class M Solar mass 0.2
Star 2
Which of the stars is likely to produce a planetary nebula?
Star 3
Which of the two stars below would appear red to your eye(s)?
Star B
Which of the stars is exactly 10 parsecs from the Earth?
Star X
Which of the stars is the most luminous? (i.e., which gives gives off the most total energy?)
Star Y
Which of the stars is closest to the Earth?
Star Z
How does the mass of 4 hydrogen nuclei (or protons) compare to that of one helium nucleus?
The 4 hydrogen nuclei have more total mass than the 1 helium nucleus.
Your friend asks you a question about the Earth-moon system: "Why does the moon appear to orbit the Earth, while it appears as though the Earth barely moves?" What is your fully correct response?
The gravitational forces of attraction are equal, but because the moon is less massive, it experiences a greater acceleration
Which of the following best describes what was once called the solar neutrino problem?
The instruments built to detect solar neutrinos were successful in detecting them, but were coming up short of the expected numbers.
Two stars exhibit exactly the same proper motion. With only this information, which of the following can say with certainty?
The stars appear to drift at the same rate with respect to the background stars.
As human beings, even though we don't emit visible light, our bodies produce a continuous spectrum of radiation.
True
Even though a hotter star will emit more energy per unit area on its surface, it is possible that a cooler star can have a higher total luminosity than a hotter star.
True
Light emitted by a hot, dense body, where all wavelengths are present
What is a continous spectrum? Will also accept blackbody radiation or thermal radiation)
Screenshot
What is close encounters of the third kind
The measurement of stellar distance by measuring the angle of the apparent motion of the star
What is trigonometric parallax
You note that X-rays are higher energy form of electromagnetic radiation than visible (optical) light. When comparing these two forms of light, what must also be true of X-rays?
X-rays have a higher frequency
Which of the following most accurately describes how main sequence stars generate their energy?
a series of nuclear reactions
Which of the following numbers share the same order of magnitude
a. 1,000,000-2,000,000 b. 20 and 2,000 c. 400 and .004 Answer is A.
Which of the following is equivalent to 3.87x10 to the -5 power
a. 38,700 b. 387, 000 c. 0.00000000387 d. 0.0000387 Answer is D
You observe a comet in our solar system. What is the semi-major axis of the comet if its orbit period is 300 days?
a. 44.8 AU b. 5,200 AU c. 0.745 AU d. 0.877 AU Answer: D
Which of the following quantities is the largest distance?
a. 50 light years b. 25,000,000 miles c. 30 AU d. 1 parsec Answer: 50 light years
Using the Planck/blackbody curves below, determine which of the following statements is true:
a. Star B is larger than Star C. b. Star B is hotter than Star A. c. Star C is the smallest star. d. All of these stars are of a different size. Answer: D
Which of the following pop culture, TV, and sports icons have we referenced in class thus far this semester? (Oh, and if you've somehow forgotten -- the correct answer is the first letter of the adjective we use to describe the shape of all planetary orbits in our solar system!)
a. The Fonz (of Happy Days) b. Aaron Rodgers (of the Green Bay Packers) c. Zack Morris (of Saved by the Bell) d. Uncle Rico (of Napolean Dynamite) e. all of the above Answer: all of the above
You are standing at a distance, and a car is moving toward you at constant velocity. The driver lays on the car horn, which emits a constant tone from the driver's point of view. As the observer, what is true of the Doppler shift you would detect?
a. The pitch (frequency) of the sound is higher, and constantly increases to an even higher pitch as the car approaches you. b. The sound you hear is at a lower pitch (or frequency) than what the driver hears, and it remains at this same low pitch as the car approaches you. c. Because the Doppler effect does not apply to sound waves, you will not detect a Doppler shift as the car moves toward you. d.The volume (amplitude) that you perceive from the car horn will remain constant as it approaches. e. None of the above are true. Answer: None of the above are true
Which of the following statements does NOT agree with Kepler's Three Laws of Planetary Motion?
a. all planets in our solar system have elliptical orbits around the sun b. more massive planets take longer to go around the sun c. for a given planet, it will travel at its slowest speed when it is farthest from the sun d. more distant planets will take longer to orbit the sun Answer: B
Which of the following is a true statement regarding Astronomical Units (AU)
a. an AU is larger than a light-year b. an AU is the light-travel time between earth and the sun c. an AU is approximate distance between the Earth and the sun d.an AU is equivalent to the diameter of our solar system Answer is C.
Which of the following is occurring at the precise instant that an electron is absorbing light?
a. it moves to a higher energy state b. it moves closer to the atom c. it moves to a lower energy state d. it moves to the ground state Answer: A
Which of the following is true regarding Kepler's 2nd Law?
a. planets move fastest when they are closest to the sun b. planets speed up as they move away from the sun c. the speed of a given planet is constant d. planets accelerate only when they are near the sun Answer: A
Which of the following statements about parallax is correct?
a. some stars are too close to us for parallax to be used in determining distance b. some stars are too distant from Earth for us to reliably use parallax in determining distance c. the parsec, like the light-year, is a unit of time d. as the distance to a star increases, its parallax angle increases Answer: B
Which of the following does not have any effect on the Doppler shift observed when viewing an object?
a. the velocity of the source being observed b. the distance between the source and the observer c. the velocity of the observer d. whether the two objects are approaching one another or moving apart Answer: B
Which of the following is NOT a reason why NASA might choose to fund space telescopes? (in other words, pick the false statement)
a. water vapor absorbs certain wavelengths of light b. radio waves cannot reach the surface of Earth due to atmospheric absorption c. the turbulence of our atmosphere results in lower resolution (blurring) of ground-based images d. our atmosphere absorbs certain wavelengths of light, such as X-rays Answer: B
The light curve below corresponds to the observations of an eclipsing binary system involving a sun-like star and a red giant star. Which of the following best describes why the eclipses observed are of a different depth?
because the two stars are of a different temperature
Using the blackbody curves below, how could you determine which of the two stars below is hotter? (Note: the next 3 questions will refer to this same picture below -- it will be reproduced in each question)
by comparing the wavelengths (on the x-axis) at which the peaks occur
How do astronomers know there is sodium present in the sun?
by the absorption lines observed that uniquely correspond to sodium
Which of the following is a true statement regarding the units we can use in the parallax equation? Reminder, the parallax equation: d = 1/p
distance is always reported in parsecs
Which of the following would result in a greater increase in the luminosity of a star?
doubling the temperature
Pink light that is seen in relatively dense, hot, gaseous, regions of the galaxy, and is emitted by a specific element
hydrogen emission
Let's say an electron in an atom emits red light when it transitions from the n = 4 to the n = 2 energy level. Hypothesize what type of light might be emitted if the electron transitions from n = 3 to n = 2.
infared light
Each second, our sun is constantly converting hydrogen into helium. For every full reaction of H--> He, a certain percentage of mass is converted directly into energy. To the nearest whole number, this is the percentage of mass lost reaction
its about .7% so 1%
Some stellar properties are difficult to determine with great precision. Fortunately, binary star systems provide astronomers the opportunity to directly determine which two properties? (Note: neither of these properties is directly measurable if the star has no companion).
mass and diameter
A main sequence star with 6 times the mass of the sun will have a rate of fusion _______ the rate of fusion in the sun.
more than 6 times
Despite being bombarded by billions of them every second, it would be a great surprise if which of the following particles did any damage to your body whatsoever?
neutrinos
Considering the sun as it is today, Which of the following does NOT play a critical role in supporting the sun's interior.
neutron degeneracy pressure
You are on a date, and you point out the star Algol, in the constellation Perseus. You note that Algol is an eclipsing binary system, and will appear noticeably dimmer in about one hour. Your date is enthralled, and asks, "Why will it appear dimmer?" What is your correct response?
one of the stars in the system is about to pass in front of the other
Which of the following types of electromagnetic radiation has the longest wavelength
radio waves
The supermassive black hole at the center of our galaxy is about 4.6 million solar masses, making it by far the most massive black hole in our galaxy. The size of its even horizon from one end to the other, is which of the following?
smaller than the orbit of mercury Its about .2 AU across So the entirety of the "hole" would comfortably fit between the sun and Mercury
Which of the stars is a low-temperature, main-sequence star?
star 4
Which of the following best describes why we see absorption spectra from stars?
stars must have hot, dense central regions surrounded by cooler gaseous layers
If you are observing a B2 spectral type star, and thats all you know about the star directly, this is the only stellar property you can confidently determine
temperature
If you observe an eclipsing binary star system you may observe two noticeably distinct eclipse events, primary and secondary. The reason a primary eclipse is more dramatic than a secondary eclipse is always due to the fact the stars differ in what stellar property?
temperature
You observe the light from a spectroscopic binary star system, and determine the two stars have different masses. Based on this knowledge, which of the following is also true?
the orbital velocity of the lower mass star will be greater
You are viewing a blackbody curve for a star's radiated intensity (I) versus wavelength. If we decrease the temperature of the star but kept its size the same, what would happen to the location of the highest point on the entire plot?
the peak would move down and to the right Remember peak wavelength increases (moves to the right) but luminosity all over will decrease ( moves down)
Which of the following best describes why a main sequence star's surface becomes cooler (reddened) as it becomes a red giant star?
the star's outer layers lose energy and cool and as they expand against gravity
If you drew a perfectly horizontal line (from left to right) on the H-R diagram, what would be true of all the stars on this line?
the would all have the same Absolute Magnitude
You see two stars in the same field of view of your telescope. One star appears very bright, and looks yellow. The other star appears very dim, and is red. What can you safely conclude?
the yellow star is hotter
The following two Plank curves were created using data from a space telescope. What is the significance of the multiple, downward-pointing spikes?
they are absorption lines from elements in the outer layers of these stars
Which of the following best explains why sunspots appear darK?
they are surface features that are slightly cooler (and therefore appear darker)
You observe a star of spectral class G2, and you correctly note this is the same spectral classification as the sun. With only this knowledge, what can you immediately say about these two stars?
they have the same temperature
If we placed Earth in an orbit that is 10 AU from the sun (like Saturn's orbit), this would increase the parallax angle for nearby stars we observe from Earth.
true
In which corner of the H-R Diagram do we find the most massive main sequence stars?
upper left
If you were to look directly at the sun using a neutral density filter (i.e., one that filters all wavelengths equally, without altering the sun's visible color), what color would it appear?
white