LSU ASTR 1102: Astronomy Exam Questions and Answers, Exams of Engineering

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LSU ASTR 1102

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LSU ASTR 1102

Parsecs are used to measure: A) Distance B) Time C) Speed A Star A is seen at a parallax angle of 0.2 arcsec while Star B at an angle of 1.2 arcsec. Which star is further away and by how much/less? A) Star A is 6 times further away B) Star B is 6 times away C) Star A is 10 times further away D) They are both at the same distance A Mars is approximately twice as far from the Sun as Venus. How much dimmer does the Sun appear from Mars? A) Half as bright B) One third as bright C) One quarter as bright D) One sixteenth as bright C

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 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 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 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? 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? A) +4. B) Higher than +4. C) Lower than +4. D) Meh...another one bites the dust! C Star A and Star B have the same temperature. Star A is a lot more luminous than Star B. A) Star A is much larger than star B B) Star A is much smaller than star B C) Star A is closer than star B D) Star A is further away than star B A Star 1 has temperature 10,000 degrees and radius 5 Rsun. Star 2 has temperature 5,000 degrees and radius 10 Rsun. What is the ratio of their luminosities (L1/L2)? A) 1 B) 2 C) 4 D) 16 C

B) G star C) M star D) F star E) K star 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 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 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 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% C If you were around for 5 more billion years to watch the sun evolve to its death, how would it move as it ages on top of the HR diagram? A) From the main-sequence, to the blue supergiant class, then down to become a white dwarf B) From the main-sequence, to the red giant class, then down to become a white dwarf C) From the main-sequence directly to the white dwarf class B What type of stars ionize hydrogen in HII regions (nebulae)? A) G type stars (like the sun) B) O and B-type stars C) K-type stars D) F-type stars B

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 E 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 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 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. 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 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 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

A) The CNO Cycle B) The pp-chain C) The 3α process C What type of nuclear burning is going on in the sun right now? A) CNO cycle B) pp-chain C) Triple-alpha 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 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 A or B

Which type of cluster should have the highest abundance of heavy elements (metals)? A) Open cluster B) Globular cluster 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 A If a star is expanding: A) Gravity is overcoming pressure B) Gravity and pressure are in balance C) Pressure is overcoming gravity 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 C

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 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 C) Uranium D) Helium A What is the difference between Horizontal Branch (HB) and Asymptotic Giant Branch (AGB) stars? A) HBs fuse hydrogen in their cores while AGBs fuse helium in their cores B) HBs fuse helium in their core and hydrogen in a shell while AGBs have a carbon-oxygen core and fuse helium and hydrogen in shells around that core C) HBs are more luminous than AGBs D) HBs are older than AGBs B What portion of the entire core-collapse energy remains in the star and is available to be used to lift-off the stellar envelope in the context of a supernova?

A) 10%

B) 99%

C) 1%

D) 0.1%

C

Which of the following elements is synthesized in a supernova explosion? A) Carbon B) Silicon C) Neon D) Plutonium E) Magnesium F) Oxygen 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. C

What did LGM in LGM-1 stand for? A) Luminous Gyrating Mass B) Large Gravitational Mass C) Livid Green Monkey D) Little Green Men D What are pulsars? A)White dwarfs B)Neutron stars C)Black holes B What's the difference between white dwarfs and pulsars? A) The progenitor stars of white dwarfs are not exploding as SNe B) White dwarfs are supported by electron degeneracy pressure while pulsars from neutron degeneracy pressure C)Pulsars are much smaller in size, rotate faster and possess larger magnetic fields D) Say whaaaa? B Why do we miss most GRBs? A) They happen so fast, that we can't catch them all.

B) We don't have good enough telescopes. C) The "jets" formed during the explosion happen not to point to our direction. C In a binary system, the primary star is a massive 15-solar mass star and the secondary star has mass about the same as the sun. What will this binary system evolve to when the massive star dies? A) A red giant star accreting mass onto a white dwarf B) A main sequence star accreting mass onto a white dwarf C) A red giant star accreting mass onto a neutron star or a black hole C What's a main difference between X-ray bursts and Novae? A) XRBs require onto accretion a black hole while novae accretion onto white dwarfs B) XRBs are less frequent than Novae C) XRBs last for a few days while novae for up to a minute D) XRBs are due to the explosive burning of helium while Novae due to the explosive burning of hydrogen D What's a main difference between core-collapse and Type Ia supernovae?