Astro 1 Exam 3 | 100 Questions with 100% Correct Answers | Verified | Latest Update 2024, Exams of Astrophysics

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Astro 1 Exam 3 | 100 Questions with 100% Correct Answers | Verified | Latest Update 2024 what is the sun comprised of? - Correct answer-73% hydrogen 25% helium why is the sun stable? - Correct answer-outward force of gas pressure; inward force of gravity Where does the gas pressure in the sun come from? - Correct answer-nuclear fusion reactions in the core at temperatures of 15 million degrees What is the diameter of the sun compared to earth? mass? luminosity (compared to 100W lightbulbs? - Correct answer-diameter-109x; mass-333,000; luminosity- 4 x 10^24 What percent of mass in the solar system comes from the sun? - Correct answer-99.9% how long has the sun been shining? how much longer will it shine? - Correct answer-4.5 billion years; 5.5 billion years what are sunspots? - Correct answer-slightly cooler regions on the sun's surface what causes sunspots? how long are their cycles? - Correct answer-magnetic activity preventing hot material from rising to that region. they have 11 year cycles what comprises helium-4? What does it release? What is it called? - Correct answer-4 protons combine to make helium-4 (2 protons, 2 neutrons); produces gamma rays; it is called the proton-proton chain What is the first step in Nuclear fusion? - Correct answer-two protons stick together and one changes into a neutron to produce deuterium (1 proton and 1 neutron) What is the second step in Nuclear fusion? - Correct answer-deuterium plus proton makes helium-3 (2 protons and 1 neutron bound together) What is the third step in nuclear fusion? - Correct answer-two helium-3 molecules combine to make helium-4 and 2 protons When is energy created in Nuclear fusion? - Correct answer-in every step Where does the energy in Nuclear fusion come from? - Correct answer-E= mc^2 because the mass of helium is 4 less than the mass of 4 protons What are the layers of the sun from inside to out? - Correct answer-core, radiative zone, connective zone, photosphere, chromosphere, flare, prominence, corona, solar wind What is the core of the sun like? - Correct answer-at center; high density and temperature; where nuclear reactions occur and gamma rays produced What is the radiative zone of the sun like? - Correct answer-photons are repeatedly reabsorbed and emitted, and the energy of an individual photon can take on average 170,000 years to pass through What is the connective zone of the sun like? - Correct answer-hot gas rises and cold gas sinks; more massive stars: What does it stop burning at and why? - Correct answer-stops burning at iron because iron is very stable and reactions involving iron do not produce energy more massive stars: How does it end? - Correct answer-type II supernova with core left behind; supernova makes elements heavier than iron, including gold and silver more massive stars: what happens to the core? - Correct answer-the core is 1.4-3 solar masses and becomes a neutron star=radius of 5-6 km, city sized more massive stars: what if the core is > 3 solar masses - Correct answer-it becomes a black hole, infinitesimal radius; infinite destiny black holes: Where do they come from? - Correct answer-it is the end state of a high mass star (> 40 solar masses), left behind after a supernova explosion black holes: can anything escape a black hole? can light? - Correct answer-the gravity of collapsed (very dense) object is so large that even light cannot escape black holes: do black holes suck things in? - Correct answer-black holes do not suck things in; if you are far enough away from them they act like normal objects withe the same mass black holes: what is the event horizon? - Correct answer-the sphere around a black hole from within nothing can escape black holes: what can be used to measure the mass of a black hole? - Correct answer-the speed of the orbit of a star in a binary star system with a black hole black holes: what would happen to a clock if if it was falling in a black hole? - Correct answer-intense gravity of a black hole warps space so that a clock would appear to slow as it falls down black holes: what happens to object falling into a black hole? - Correct answer-tidal forces are created near a black hole and objects are stretched because the force on the nearest part is so much larger than the force on the farthest part black holes: what is at the center? - Correct answer-a singularity, a point of infinite destiny what happens at the end of its life with if a star begins with < 8 solar masses? - Correct answer-the core becomes a white dwarf- collapse stop because of degeneracy pressure of electrons- radius same as earth what happens at the end of its life with if a star begins with 8-40 solar masses? - Correct answer-the core becomes a neutron star- collapse stops because of degeneracy pressure of neutrons- radius of 5-6 km what happens at the end of its life with if a star begins with > 40 solar masses? - Correct answer-the core becomes a black hole- collapse does not stop- mass concentrated at singularity When, where and by whom was the first extrasolar planet discovered? - Correct answer-when-1992; where-in orbit around a dead neutron star; cannot support life; by whom- Penn State Prof. Alex Wolszczan What were many of the planets discovered in the late 1990's and early 2000's like? - Correct answer- planets around the mass of Jupiter, that are very close to their stars How many planets has the Kepler mission discovered using the transit method? - Correct answer- thousands; the brightness of the star decreases due to the planet passing right in front of it. How does the transit method find the distance of the planet to its star? What does this information help us discover? - Correct answer-using Kepler's law . P^2 = a^3; it helps discover i the planet is in the hospitable zone and the amount of drop in the stars brightness helps us discover the size of the planet how many extrasolar planets have been discovered in the habitable zones around their stars? - Correct answer-a dozen what is a habitable zone? - Correct answer-region around a star where liquid water could be present on a planets surface Where would the habitable zone be on a less massive star? - Correct answer-closer to the star Where would the habitable zone be on a more massive star? - Correct answer-further away from the star Is life found in extreme conditions on Earth? - Correct answer-yes, dark- ness, high radiation, acidic, underground, in methane ice, extreme heat What is drakes equation? what is it used for? - Correct answer-N =R∗×fp ×ne ×fl ×fi ×fc ×L (p,e,l,i,c are subscripts); method used to estimate the number (N) of communicating/ technological civilizations in our galaxy What is R* in Drake's equation? - Correct answer-rate of star formation, number of stars forming per year in our galaxy, around one solar mass per year What is f(subscript) p in Drake's equation? - Correct answer-percentage of stars that form planets What is n (subscript)e Drake's equation? - Correct answer-average number of planets that could support life for each star What is f(subscript)l Drake's equation? - Correct answer-percentage of those planets where life occurs What is f (subscript) i Drake's equation? - Correct answer-percentage of those planets where intelligence develops What is F(subscript)c Drake's equation? - Correct answer-percentage of intelligent species that communicates What is L Drake's equation? - Correct answer-average lifetime of a communicating species What are the properties of a star? - Correct answer-luminosity, mass, size, temperature, and age What is the closest star and how far away is it? - Correct answer-Alpha centauri, 4.3 million light years away or 1.35 parsecs, from the sun Is the nearest star to the sun a singular star system? - Correct answer-no it is a triple star system; the brightest member similar to the sun What are most of the nearest stars like and where do they fall on the H-R diagram? - Correct answer- Most of the nearest stars are cool and dim and fall on the lower right of the H-R diagram; this is because most stars have these properties. What is the brightest star in the nighttime sky? how massive is it compared to the sun? is it a singular star system? - Correct answer-sirius is twice as massive as the sun. its companion is a white dwarf how do the brightest stars fall on the H-R diagram? where do they fall? - Correct answer-brightest stars have more varied properties, red and blue, low and high luminosity, with some on the lower right of the H-R diagram, but others near where the Sun is, some on the upper left, and some on the upper right (red giant region) are the brightest stars always the closest? - Correct answer-brightest stars tend to be biased towards stars that have large luminosities, so that they appear bright to us even at large distances; we simply can't see low- luminosity stars if they are too far away What is luminosity? - Correct answer-the absolute power output at the source What is brightness? - Correct answer-apparent output as observed at some distance What determines how bright a star appears based upon its luminosity? - Correct answer-inverse square law What is the inverse square law? - Correct answer-B= L/4πd^2; b-brightness, d-distance, L- luminosity if two stars have the same luminosity and one is 10 times further away than the other, how bright will it appear? - Correct answer-it will appear 1/10^2 as bright which is 100 times fainter What is the parallax method and what is it used for? - Correct answer-used to measure distance; view stars from two locations on opposite sides of the sun (6 months apart). these locations are on opposite sides of the sun. What is the baseline of the parallax method? - Correct answer-1 AU is the radius of the orbit of earth around the sun At what angle does the star appear to move relative to distant stars in the parallax method? - Correct answer-the star appears to move (relative to distant stars) by an angle 2 times that of the parallax angle how do you determine distance in parsecs? - Correct answer-D= 1/p; p- parsecs in arcseconds; Why is a star that appears fainter sometimes closer than a star that appears brighter? - Correct answer- because the star the appears closer is more luminous