Partial preview of the text
Download Astro 1 final exam psu.pdf and more Exams Astronomy in PDF only on Docsity!
ASTRO 1 FINAL EXAM PSU (ACTUAL 2025/2026) | 100 QUESTIONS WITH 100% VERIFIED CORRECT ANSWERS | | LATEST UPDATE What is a light year? distance that light travels in 1 year What is the closest star to Earth besides the Sun? (4.2 ly away) proxima centauri What is the age of the universe? 14 billion years What is our cosmic address? What is the Local Group? Earth, solar system, milky way galaxy, local group, local supercluster what is angular resolution? ability to distinguish clearly between two small points in the sky Why does using a camera (detector or an astronomical instrument) in conjunction with the telescope enable you to see fainter objects than you would with your eye? detectors gather much more light than our eyes, can take images with longer exposure time than our eyes Why do we put telescopes in space? earths atmosphere can distort the images since the photons are traveling through the atmosphere and being redirected into the telescope What wavelengths is the Earth's atmosphere transparent to? visible and radio What wavelengths is the Earth's atmosphere partly opaque? infrared and uv What wavelengths is the Earth's atmosphere completely opaque? x ray and gamma rays characteristics of Jovian vs. Terrestrial planets surprising that there were so many other planets outside our solar system What is nuclear fusion? Why do the nuclear fusion reactions in the Sun produce energy? atoms being fused together into a bigger one, thermonuclear reactions in the core release energy Write out the nuclear fusion reaction occurring in the core of the Sun right now 4H-->He+2v(neutrinos)+6y(gamma photons) Why are the minimum and maximum masses of stars? Low mass: .08-8Msun (too small and no fusion) High mass: 8-150Msun (too large and extreme radiation causes explosions) How will the Sun end its life? as a white dwarf that released a planetary nebula Which stars end up as white dwarfs; which as black holes or neutron stars? white dwarfs: death of main sequence stars black holes: core > 3MSun neutron stars: core < 3MSun Which phase of stellar evolution lasts the longest? main sequence phase Supernovae - what are the two types? What remains after each? Type 1: white dwarf releasing matter into space type 2: large mass star exploding and either becoming a neutron star or black hole What are pulsars? neutron star that beams radiation along a magnetic axis (sweeps through space like a lighthouse) What are planetary nebulae? outer layers of white dwarf star expand and drift away, propelled by thermal pulses (envelope of gas size of solar system) Why are lives of low mass stars longer than those of high mass stars? Which stars on an H-R diagram will someday go supernova? Giants and supergiants Why can nothing escape a black hole? gravity inside is so strong that not even light can escape What is a Black Hole? a neutron star that has collapsed to size zero, and has infinite density What is Schwarzschild Radius? radius of event horizon, how far away you have to be to get sucked in What do we mean by the event horizon of a black hole? point of no return, not even something going as fast as the speed of light can escape What would happen to an object that comes close to a black hole? depends on how close you get. If you are within the schwarzchild radius you could get sucked in What would happen to the time when one gets close to a black hole? times slows down to infinity What happens to light when it gets too close to a black hole? it gets sucked in and can never escape, which is why you can't see black holes How do we know that black holes exist? 1.) observe gravitational influence on objects orbiting it 2.) observe high energy emission from an accretion disk (black hole sucking in stuff, best method) 3.) detect gravitational waves: ripples in spacetime What does an object falling into a black hole appear like to an outside observer? the object approaches the black hole slowly and eventually so much light is sucked in that there is no reflection off of it anymore and you never see what happens to it What are the two types of clusters? Where are they found in our galaxy? How do we know that there is a supermassive black hole in the center of our galaxy? Which constellation is it in? Sagittarius A -very bright radio source -lots of supernova remnants, gas clouds -hundreds of stars orbiting it Why do stars in the halo of the galaxy have almost no heavy elements such as carbon, nitrogen, and oxygen? they are the oldest stars in the galaxy, and formed early on in the age of the universe when there was only hydrogen and helium to form from We have an expert-written solution to this problem! What evidence is there for dark matter in our own galaxy? Other galaxies? there is missing mass that accounts for a large amount of our galaxy, dark matter is the cause of pushing other galaxies and causes movement we only notice through visible objects in space What is a rotation curve? milky way galaxy's rotation curve is flat, rotating too fast compared to the predicted curve that does not account for dark matter How much dark matter is there in the Milky Way? 90% What could dark matter be made of? exotic particles not yet discovered What is the role of dark matter in forming galaxies? gravity of dark matter is what caused protogalactic clouds to contract early in time What is the difference in ages of stars for each type of galaxy? spiral: new and old stars elliptical: only old stars irregular: lots of star formation Why are elliptical galaxies more common in galaxy clusters and spiral galaxies rare? When galaxies collide, what is it that actually collides? dark matter halos, then gas and dust within the galaxies gets disrupted Why are galaxy collisions more frequent than collisions of stars? stars have a much further proportional distance from one another when compared to the distance between galaxies Why do spiral galaxy mergers often trigger starbursts? dusty molecular clouds collide and compress to trigger star formation How did galaxies look billions of years ago? How do we know this? hubble ultra deep field show that the first galaxies were small and irregularly shaped, they merged to form the galaxies we see today When two spirals merge (collide), what is the most likely outcome? elliptical large scale structure superclusters and clusters of galaxies form filaments and sheets, while voids simply have no matter at all (empty space) what is hubble's law and its significance? A law of cosmology stating that the rate at which astronomical objects in the universe move apart from each other is proportional to their distance from each other. Current estimates of the value of this proportion, known as Hubble's constant, put its value at approximately 71 kilometers per second per megaparsec. How does the age of the universe depend on Hubble's constant, and why the larger the constant, the younger the universe. larger value means universe is expanding faster (it took less time to reach its current size) what is the order of events as the universe started expanding? 1.) big bang marks beginning of expansion 2.) all forces unified 3.) inflation (explosively rapid expansion of space time) 4.) energy spontaneously turning into matter and antimatter and vice versa 5.) nuclei begin to fuse (first elements H and He) 6.) atoms form and cosmic microwave background radiation starts streaming through the universe What did WMAP measure? temperature of the universe Why do we expect the cosmic background radiation to be almost, but not quite, the same in all directions? some regions had to be denser in order for galaxies to form In principle, if we could see all the way to the cosmological horizon we could see the Big Bang taking place. However, our view is blocked for times prior to about 380,000 years after the Big Bang. Why? before atoms were formed, they were completely ionized, dense, and extremely difficult to see through We have an expert-written solution to this problem! Why didn't the Big Bang produce heavier elements than helium? nuclei were not stable enough What evidence do we have for the existence of dark energy? One set of evidence comes from observations of Type Ia supernovae (white dwarf supernovae) from distant galaxies. The first observations of these objects showed that the Type Ia supernovae were systematically fainter than expected at high redshifts (recall that high redshift means large distance). The only explanation for this is if the expansion of the universe is accelerating. Another set of evidence for dark energy comes from the observations of the Cosmic Microwave Background radiation (CMB). The WMAP observations of CMB predict that normal matter only makes up approximately 4%, 23% is dark matter and 72% of the universe is dark energy. What is cosmological redshift? the part of the redshift of celestial objects resulting from the expansion of the universe. What is the actual fate of the universe? It will expand forever at an accelerated pace. We know this because an accelerating universe best fits the supernova data. Furthermore, the spatial geometry of the universe has been measured by the WMAP spacecraft to be nearly flat. What is the reason that we have seasons on Earth? tilt of the earth's axis determines what hemisphere leans towards the sun If Earth's orbit were a perfect circle, how would this affect seasons? Would not because earth's orbit is already very close to a perfect circle moon phases in order new moon, waxing crescent, first quarter moon, waxing gibbous, full moon, waning gibbous, third quarter moon, waning crescent How long does it take to complete all the phases? 29.5 days What are the two types of eclipses (only solar and lunar) and what phase does the Moon need to be in for each one of the eclipses to occur? lunar: earth blocks sunlight from moon, full moon solar: moon passing directly in front of sun, new moon We have an expert-written solution to this problem! If you see that the Moon is full, what phase will someone in Australia see? What about someone on the Moon looking at Earth? the same phase, the moon will just look upside down people on the moon wouldn't see earth (new earth) Kepler's laws 1.) a§3=p*2(M1+M2) 2.) when planet is closer to sun, it moves faster in its orbit 3.) planets further from sun orbit slower How can you tell a color of a star based on its blackbody curve? peak of curve in visible spectrum order of different types of electromagnetic radiation by wavelength gamma, x ray, uv, visible, infrared, microwave, radio 
