Download ASTR 1102 final Exam 2025 | Updated Questions and Correct Answers | Already Graded A+ and more Exams Astronomy in PDF only on Docsity!
ASTR 1102 final Exam 2025 | Updated Questions
and Correct Answers | Already Graded A+ |
verified Answers | Just Released
What is Astronomy? A) Fortune-telling based on looking at the positions of stars and planets B) A law discipline C) The study of relationship between food and culture D) A natural science ---------CORRECT ANSWER-----------------D I am a theoretical astrophysicist. Where do you think I spend most of my time? A) Looking through a telescope at night B) Instructing an automated telescope to take digital images for me C) Working in the office during the night D) Working in the office during the day ---------CORRECT ANSWER-----------------D My friend Tabby is an observational astronomer. Where do you think she spends most of her time? A) Looking through a telescope at night B) Instructing telescopes to take digital images for her C) Working in the office during the night D) Working in the office during the day ---------CORRECT ANSWER-----------------D What is the necessary condition for Universe to exist?
A) A set of natural laws that work together in harmony B) A living consciousness to study and interpret its laws C) LSU Football ---------CORRECT ANSWER-----------------A and B Which star, from the following, in the constellation of Cygnus is brighter? A) Delta (δ) Cygni B) Zeta (ζ) Cygni C) LL Cygni D) Epsilon (ε) Cygni E) Theta (θ) Cygni ---------CORRECT ANSWER-----------------A How many stars are there are in the Milky Way Galaxy A) None, all stars are outside the Milky Way Galaxy B) One, the Sun C) 200 D) 200 million E) 200 billion ---------CORRECT ANSWER-----------------E How is the "ecliptic" defined? A) The apparent path of the moon in the night sky B) The apparent path of the sun across the celestial sphere going through the 12 "zodiac" constellations C) The line connecting the brightest stars in the sky D) It corresponds to the plane of the Milky-Way galaxy ---------CORRECT ANSWER-- ---------------B
B) Cooler than the sun C) at the same temperature as the sun ---------CORRECT ANSWER-----------------B The Sun has a lifetime of 10 billion years. If a B star has a mass of 10 M◉ and a luminosity of 10,000 L◉, how long will it live for? A) 1 billion years B) 100 million years C) 10 million years D) 1 million years ---------CORRECT ANSWER-----------------C An A5 star has 5x the mass of the Sun, but 15x the luminosity. How long will it live? A) 1/3rd of the Sun's lifetime B) 1/5th of the Sun's lifetime C) 3 times the Sun's lifetime ---------CORRECT ANSWER-----------------A Why is the sun gradually and very slowly get's brighter during its lifetime in the main-sequence? A) Because newly made helium in the core of the sun produces more nuclear energy via fusion during the main-sequence. B) Because as hydrogen converts to helium in the core, the pressure slowly decreases and gravity slowly compresses the core making it hotter therefore producing more luminosity.
C) Because it continues to burn hydrogen in a thin shell around the core. --------- CORRECT ANSWER-----------------B Which of the following reaction rates is more sensitive to temperature? A) The CNO cycle B) The 3α process C) The proton-proton (pp) chain ---------CORRECT ANSWER-----------------B Which of the following reaction pairs burn hydrogen to helium? A) The CNO cycle and the 3α process B) The 3α process and the pp chain C) The proton-proton (pp) chain and the CNO cycle ---------CORRECT ANSWER------- ----------C How do red giant stars generate energy? A) Fusion of hydrogen in their core B) Fusion of hydrogen in a shell around their core C) Fusion of helium in their core D) Fusion of helium in a shell around their core E) Fusion of carbon ---------CORRECT ANSWER-----------------B Why after the 'helium flash' stars become less luminous in the HR diagram? A) Because a hydrogen-burning shell around the core does not produce as much energy as hydrogen-core burning, therefore luminosity drops.
B) pp-chain C) Triple-alpha ---------CORRECT ANSWER-----------------B What type of nuclear burning will take place in the hydrogen shell of the sun when it becomes a sub-giant star? A) CNO cycle B) pp-chain C) Triple-alpha ---------CORRECT ANSWER-----------------A What types of nuclear burning will take place in the hydrogen shell of the sun when it becomes a giant star? A) CNO cycle B) pp-chain C) Triple-alpha ---------CORRECT ANSWER-----------------A or B Which type of cluster should have the highest abundance of heavy elements (metals)? A) Open cluster B) Globular cluster ---------CORRECT ANSWER-----------------A There are many clusters of stars in the galaxy. All the stars in a cluster are usually the same age. Which type of cluster should appear bluest? A) Young clusters B) Middle-aged clusters C) Old clusters D) Geriatric clusters ---------CORRECT ANSWER-----------------A
If a star is expanding: A) Gravity is overcoming pressure B) Gravity and pressure are in balance C) Pressure is overcoming gravity ---------CORRECT ANSWER-----------------C Where does most carbon in the galaxy originate from? A) Fusion in red giant stars B) Supernova explosions C) Asymptotic Giant Branch (AGB) stars D) Galactic collisions ---------CORRECT ANSWER-----------------C What is the largest stage (by radius) in the life of the Sun? Hint: Think of scaling of radius in the HR diagram: we talked about this in a previous lecture. A) Main sequence B) Sub-giant C) Red giant D) Asymptotic giant branch E) White Dwarf ---------CORRECT ANSWER-----------------D Parsecs are used to measure: A) Distance
α Fic has the same mass as the Sun, but is about 100x more luminous. If the Sun has a total lifetime around 10 billion years, how long would you expect α Fic to live, to the nearest power of ten? Hint: For stars of the same mass, the life-time ranges as one over the star's luminosity (i.e. the more luminous stars live shorter lives). A) 100 billion years B) 1 billion years C) 10 billion years D) 100 million years E) 1000 billion years ---------CORRECT ANSWER-----------------D The apparent brightness of a star is 3 x 10^-10 W m-2 and it's parallax 0.05 arcsec. Estimate the star's lifetime as compared to that of the sun. Round up your final answer. Hint: Convert parsecs to meters (Google it) before using inverse-square law. The luminosity of the Sun is 3.846 x 10^26 W. A) Star will live 4 times longer than the sun B) Star will have about a quarter of the sun's lifetime C) Star will live about the same time as the sun D) Star will have about half of the sun's lifetime ---------CORRECT ANSWER----------- ------B
Star A has a magnitude of 2 while Star B a magnitude of 6. How much brighter is Star A from Star B? A) Star A is (2.5)x(2.5)x(2.5)x(2.5)x(2.5)x(2.5) brighter B) Star A is 2.5 times brighter C) Star A is 4 times brighter D) Star A is (2.5)x(2.5)x(2.5)x(2.5) times brighter ---------CORRECT ANSWER----------- ------D Parallax allows us to measure a star's distance and a ground-based telescope allows us to measure it's apparent magnitude. Do we have enough information to calculate the star's luminosity? A) Yes B) No C) Maybe - not enough information is provided ---------CORRECT ANSWER------------ -----C You are given a star's distance modulus and the information that there is a lot of dust along the line of sight. Is the distance you estimate using the distance modulus formula: A) Underestimated? B) Overestimated? C) Unaffected? ---------CORRECT ANSWER-----------------B A star has an apparent magnitude of +4.3 but it lays behind clouds of interstellar dust. What would be the apparent magnitude of the star if there was no dust along the line of sight?
B) No, it's brighter than most stars ---------CORRECT ANSWER-----------------A Which of the following stellar quantities is harder to measure? A) Temperature B) Distance C) Mass D) Brightness E) Luminosity ---------CORRECT ANSWER-----------------C Which of these stars is coolest? A) A star B) G star C) M star D) F star E) K star ---------CORRECT ANSWER-----------------C Which of these stars is hottest? A) A star B) G star C) M star D) F star E) K star ---------CORRECT ANSWER-----------------A Where are most massive of the main-sequence stars located along the main- sequence curve of the HR diagram?
A) Upper left part B) Around the location of the sun C) Lower right part ---------CORRECT ANSWER-----------------A Where are the white dwarf stars located in the HR diagram? A) Upper-left corner B) Lower-right corner C) Lower-left corner D) In the middle ---------CORRECT ANSWER-----------------C In what direction in the HR diagram will a star like the sun move once it exhausts hydrogen in its core? A) Towards the lower left corner B) Towards the upper left corner C) Towards the upper right corner D) Towards the lower right corner ---------CORRECT ANSWER-----------------C You observe a star in the Milky Way galaxy. What is the change that it's not going to be in the Main-Sequence? A) 90% B) 50% C) 10% D) 20% ---------CORRECT ANSWER-----------------C
B) made of dust and gas C) as dense as the Earth's atmosphere ---------CORRECT ANSWER-----------------B Two stars are born out of the same cloud and they have the same radius and luminosity but star A has double the mass of star B. How long will it take for star A to reach the main-sequence as compared to star B? A) It will take about the same time. B) It will take twice as long C) It will take four times as long D) It will take four time less ---------CORRECT ANSWER-----------------C Which of the following processes can trigger star formation via compression of interstellar gas clouds? A) Gravitational collapse of dense cold pockets of gas in nebulae B) Compression due to a blast-wave from a nearby supernova explosion C) Collisions between giant molecular clouds D) Galactic collisions E) All of the above ---------CORRECT ANSWER-----------------E
What type of emission will be seen if one takes a spectrum of a planetary nebula? A) Continuous black-body spectrum B) Emission spectrum C) Absorption spectrum D) It depends on what part of the nebula is observed ---------CORRECT ANSWER---- -------------D What is the main reason massive stars blow up in "dirty" environments? Hint: There may be more than 1 right answer. A) They are born in nebulae, so they blow up within a dense interstellar medium B) They form a lot of dust during their evolution and eventually blow up enshrouded in a dust shell C) During the late-stages of their evolution unstable nuclear burning (in shells) can produce enough energy to eject their outer envelopes thus forming a circumstellar environment around them. D) They lose mass via strong winds during their lifetimes and in the end, they are surrounded by the remnants of these winds ---------CORRECT ANSWER----------------
- B or C or D Which one of the elements below synthesized in massive stars during their evolution is the heaviest? A) Silicon B) Carbon
D) Plutonium E) Magnesium F) Oxygen ---------CORRECT ANSWER-----------------D Why is SN 1987A so important? A) The star that exploded as SN1987A was very massive. B) It created heavier elements. C) It occurred in close distance to the Earth enabling the observations of supernova neutrinos for the first time. D) It was very bright. ---------CORRECT ANSWER-----------------C What's left behind after a supernova explosion? There could be more than 1 correct answer. A) A neutron star B) A white dwarf C) A black hole D) Nothing ---------CORRECT ANSWER-----------------A or B or D How can a supernova, though rare in our solar neighborhood, can wipe out life on Earth? A) By heating the Earth to large levels
B) By the SN ejecta directly impacting the Earth C) By showering the Earth's atmosphere with high energy radiation (X- rays/gamma-rays) destroying the ozone layer D) By radioactivity due to the decays of nickel and cobalt ---------CORRECT ANSWER-----------------C Which type of star do you think could rotate faster? A) Red giant B) Neutron star C) Main-sequence star D) White dwarf ---------CORRECT ANSWER-----------------B What did LGM in LGM-1 stand for? A) Luminous Gyrating Mass B) Large Gravitational Mass C) Livid Green Monkey D) Little Green Men ---------CORRECT ANSWER-----------------D What are pulsars? A)White dwarfs B)Neutron stars C)Black holes ---------CORRECT ANSWER-----------------B
