Physical World Exam 4 Study Guide PDF

Physical World Exam 4 Study Guide Solar System & the Sun Q: What is a solar system? A: Solar System - star and the collection of objects gravitationally bound to it Q: How does the Sun’s mass compare with that of the entire solar system? A: The Sun is more than 99% of the Solar System’s mass...

Physical World Exam 4 Study Guide Solar System & the Sun Q: What is a solar system? A: Solar System - star and the collection of objects gravitationally bound to it Q: How does the Sun’s mass compare with that of the entire solar system? A: The Sun is more than 99% of the Solar System’s mass Q: Why is it said that the solar system is mostly empty space? A: Compared to the size of the objects in the solar system, the space between them is immense (orders of magnitude bigger). Q: What is a nebula? A: Nebula - a low density cloud of gas and dust in space Q: How does the contraction of a nebula affect its rotation? A: Nebula shrinks from gravity. The initial spin is amplified by the contraction & a rotating disk forms Q: According to the Nebula Theory, why do planets in a solar system tend to orbit in the same general plane, and mostly rotate in the same direction? A: Collisions and gravity fuse objects together at certain distances from the protostar Planets form, orbiting in same general plane, and mostly rotating in the same direction Q: What is the Sun composed of? Approximately how old is it? A: Hydrogen/helium 5 billion years old (5 billion years left in current life cycle) Planets Q: What is a planet? A: Planet - Large orbiting bodies massive enough for gravity to make them spherical, but small enough to avoid nuclear fusion Q: Which are the four inner planets, listed in order by their distance from the Sun? Which is the largest inner planet? A: Mercury Venus Earth Mars -Earth is the largest inner planet (Venus is close second) Q: Which are the four outer planets, listed in order by their distance from the Sun? Which is the largest outer planet? A: Jupiter Saturn Uranus Neptune -Jupiter is the largest outer planet Q: Between the inner planets and the outer planets, which are solid, rocky planets and which are gaseous planets? Which set has many more moons? Which set has the largest size planets? A: The inner planets (Mercury, Venus, Earth, Mars) are solid rocky planets The outer planets (Jupiter, Saturn, Uranus, Neptune) are gaseous planets The outer planets have many more moons than the inner planets The outer planets also has the largest size planets Inner Planets Q: How does Mercury’s size compare to the other planets? Does Mercury have a significant atmosphere? A: Mercury is the smallest planet (only 1.4 times the size of our Moon) Very little atmosphere Q: How does Venus’ size compare to Earth's? A: Venus is slightly smaller than Earth Q: What has allowed Venus to become the hottest planet in the solar system? A: The Runaway greenhouse effect (surface is 470 C) Q: Why is it difficult to view the surface of Venus from space? What technology has allowed us to see the surface of Venus? A: Decks of opaque clouds of sulfuric acid Remote sensing from probes (Parker Solar Probe 2022) Q: When talking of planets, what is meant by the “habitable zone”? A: Habitable zone - the range of orbits around a star within which a planetary surface can support liquid water (given sufficient atmospheric pressure) Q: Why is Earth a blue planet? A: 70% of surface is water Q: What does Earth's relatively fast rotation rate do for the planet? A: Fast rotation keeps day/night temperature difference reasonable Q: What helps protect Earth from solar wind? A: Magnetic field shields Q: How does Mars’ size compare to Earth's? What type of atmosphere does Mars have? A: About half the size of Earth (around 1/9 the mass) Thin atmosphere, mostly carbon dioxide Q: How do we know that liquid water was once abundant on Mars? A: Surface features indicate that liquid water was once abundant: Q: What would be the challenges to establishing a human settlement on Mars? A: No magnetic field No oxygen Cold temperatures (-65C) Weaker gravity Potable water Food Outer Planets Q: What is the atmosphere of the outer planets mostly composed of? Where did these gases come from? A: Mostly hydrogen and helium These gases originated from the protoplanetary disk Q: How does Jupiter’s size compare to the other planets? A: Jupiter is the largest planet Q: What is believed to be at the center of Jupiter? A: A solid sphere Q: What is a moon? A: Moon - a naturally-formed body that orbits a planet, dwarf planet, or other non-star object Q: Which of Jupiter's four largest moons is the solar system's largest moon? Which two have ice on their surfaces, with the potential of having an ocean of water underneath? Which is the most volcanically active object in the solar system? A: Ganymede is the largest moon in the solar system Ganymede and Europa are covered with ice with the potential of having an ocean of water underneath Io has the most volcanic activity Q: How does Saturn’s size compare to the other planets? What is the likely source of Saturn’s famous rings? A: Saturn is the second largest planet The rings are likely a failed moon, or a moon that was torn apart Q: How big is Saturn's moon Titan compared to the other moons of the solar system? What is notable about the behavior of methane on Titan? A: Titan is the second largest moon in our solar system. Only Jupiter's moon Ganymede is larger, by just 2 percent. Titan is bigger than Earth's moon, and larger than even the planet Mercury On Titan, methane behaves like water on Earth, existing as a liquid on the surface, forming lakes and rivers Q: How does the temperature of Uranus compare to the other planets? What is unusual about Uranus that helps it be so cold? A: Uranus has no internal heat source, very cold (significantly lower temperature average than the other planets) Extreme axle tilt Q: What is unusual about Uranus’ axis of rotation? Know that Uranus has a ring system and many moons A: Uranus’ axis of rotation is tilted 98 degrees compared to its orbital plane (lies on its side) Q: Where is Neptune’s location compared to the other planets? What is notable about the winds observed on Neptune? A: Neptune is the farthest planet from the sun in our solar system Neptune has the strongest winds of the solar system, greater than 1200 mph (2000 kph) Q: What does it mean when a moon has a retrograde orbit? How common is this? What does it likely indicate about the origin of Neptune's moon Triton that it has a retrograde orbit? A: Retrograde orbit - when a moon orbits in the opposite direction to its planet’s rotation No, they are uncommon in our solar system A retrograde orbit for Neptune's moon Triton strongly indicates that it was likely captured by Neptune from elsewhere in the solar system, most probably originating from the Kuiper Belt Earth’s Moons Q: Earth’s moon has the approximate size of which of the planets? What part of the Earth shares the same composition as the Moon? Know that the Moon does not have a significant atmosphere. A: The moon is close to the size of Mercury The earth’s mantle No significant atmosphere (too small) Q: According to the Giant Impact Theory of the Moon’s formation, what was it that struck the Earth early in the solar system’s history? How did the Moon come about from this collision? A: A Mars sized body called Theia The debris from this impact collected in an orbit around Earth to form the Moon Q: Why does the Moon's appearance change cyclically over the course of 29-30 days? The Moon's appearance changes cyclically over 29-30 days because as it orbits the Earth, different parts of its surface are illuminated by the Sun, creating the illusion of changing shapes, known as "phases of the Moon” Q: What happens with the Moon to produce a solar eclipse? A: A solar eclipse happens when the Moon passes between the Sun and Earth, blocking at least some of the Sun and casting a shadow on Earth Dwarf Planets, Asteroids, Comets, and Planet 9 Q: What is a dwarf planet? A: Dwarf planet: planetary mass object that orbits the Sun Massive enough for gravity to have made it spheroid But... does not dominate its region of space Q: How many dwarf planets have been recognized? Where are dwarf planets located? A: 5 dwarf planets The Asteroid belt in and the Kuiper belt Q: What is the Asteroid Belt? A: Between Mars and Jupiter Millions of solid, irregularly shaped rocks, of many sizes Total mass would be around 4% that of the Moon Has 1 dwarf planet, Ceres Q: What is the Kuiper Belt? A: Like the asteroid belt, but more than 20 times more massive Four recognized dwarf planets, and likely many more Q: What is a comet? How does a comet change in its orbit around the Sun? A: Comet: Large objects of dust, rock and ices Orbit the Sun A few miles to tens of miles wide Approaching the sun, they heat up and spew gases and dust Material forms a tail; tail can be planet size -A comet's orbit around the Sun changes primarily when it gets close to the Sun, causing its icy material to vaporize and release gas and dust, which acts like a small "rocket engine" slightly altering its trajectory, potentially making its orbit slightly shorter or longer depending on the direction of the expelled material Q: What has been observed that has led scientists to believe there is another planet in the outer solar system? A: Scientists believe there might be another planet in the outer solar system, often called "Planet Nine," due to the unusual clustering of orbits exhibited by several Trans-Neptunian Objects (TNOs) in the Kuiper Belt Q: If there is likely another planet (planet 9), what would have made it difficult to find up to now? How big do scientists think it is? A: It’s extreme distance from the sun, likely reflects very little light and there is a massive area of space where it could be at the moment Would be 8 to 12 times Earth’s mass Comparable in size to Neptune and Uranus Constellations & Star Motions Q: What is a constellation? A: constellation - group of stars named over antiquity, close to each other in the night sky Q: How are the stars that form a constellation related to each other? A: Relationship between stars in a constellation? Often nothing in common, other than their proximity in the night sky Q: Why does the big dipper change its position in the night sky over the course of an evening, but Polaris (the North Star) remains fixed in position? Which of the three motions of stars that we talked about causes the motion of the big dipper over the course of an evening? A: The Big Dipper appears to change position in the night sky because it's not directly aligned with Earth's rotational axis, while Polaris, the North Star, is situated very close to that axis, making it appear nearly stationary as Earth rotates; essentially, the Big Dipper is "circling" around Polaris as our planet spins. Earth’s rotation on its axis Q: What causes the yearly motion of stars? A: Yearly motion caused by Earth’s orbit around the Sun Q: What is meant by the intrinsic motion of stars? A: Intrinsic motion - caused by the long term motion of the star itself Classifying & Comparing Stars Q: How is a star's color related to its surface temperature? Which color star (of the seven primary colors) would have the hottest surface temperature, and which would be the coolest? A: Color is related to frequency of light For stars: frequency and temperature are directly proportional Blue, indigo, violet - hotter stars Red, orange - “cooler” stars -Blue star would be the hottest, Red star would be the coolest Q: When talking about stars, what is meant by apparent brightness? A: Apparent brightness - the brightness as it appears to us Q: When talking about stars, what is meant by luminosity? A: Luminosity - the total amount of energy given off by a star (the actual amount of light it produces) Q: Are stars all about the same size, or do they vary greatly in their sizes? A: They vary greatly in size Q: What is meant by the Main Sequence when talking about stars on an H-R (Hertzsprung-Russell) diagram? A: Main sequence - stars along the diagonal; typical hydrogen-burning stars Q: What types of stars are not on the Main Sequence? A: Stars that are not on the main sequence include red giants, supergiants, white dwarfs, brown dwarfs, neutron stars, and black holes Life Cycle of Stars Q: In relation to a nebula, what is a protostar? Know that a protostar forms as gravity causes the matter of a nebula to contract. A: Protostar - the hot central bulge of a nebula Q: When a protostar “ignites” and becomes a star, what is the process that has commenced within it that causes this change? What threshold must be crossed for this process to begin? A: Nuclear fusion A temperature exceeding 100 million degrees Celsius Q: The size of stars is determined by the balance between which two forces? A: The size of a star is determined by the balance between the inward force of gravity and the outward force of radiation pressure generated by nuclear fusion within the star. Q: What happens that causes a star to enter a Red Giant or Supergiant stage? A: The star has fused most of its hydrogen Q: What are the three possible end stages of stars? A: 4a End Stage - White Dwarf (For medium size stars (e.g. the Sun) - carbon end) 4b. End Stage - Supernova and Neutron star (for stars with mass greater than 10 x mass of the Sun) 4c End Stage - Black Holes (For stars with mass greater than 40x mass of the Sun) Q: What is a white dwarf? Know that it is the likely end of our Sun. Be able to describe the process by which it will get there. A: White dwarf - a small very dense star that is typically the size of a planet. A white dwarf is formed when a low-mass star has exhausted all its central nuclear fuel and lost its outer layers as a planetary nebula When the Sun runs out of its hydrogen fuel, it will expand into a red giant, then shed its outer layers, leaving behind a hot, dense core that will cool and become a white dwarf Q: What is a supernova, and what are its characteristics? A: Supernova - a massive explosion that occurs when a star dies Characteristics: Brightness Energy Speed Q: What is a neutron star, and what are its characteristics? A: A neutron star is an extremely dense, compact stellar remnant formed when a massive star collapses at the end of its life, composed primarily of neutrons and considered one of the densest objects in the universe Neutron stars got their name because their cores have such powerful gravity that most positively charged protons and negatively charged electrons in the interior of these stars combine into uncharged neutrons. Neutron stars produce no new heat. However, they are incredibly hot when they form and cool slowly. Characteristics: Incredibly high density Strong magnetic fields Rapid rotation Relatively small size Q: What is a black hole, and what are its characteristics? A: A black hole is an astronomical object with a gravitational pull so strong that nothing, not even light, can escape it Q: What is the event horizon of a black hole? What is the photon sphere? A black hole's “surface,” called its event horizon, defines the boundary where the velocity needed to escape exceeds the speed of light, which is the speed limit of the cosmos A "photon sphere" is a region surrounding a black hole where gravity is so intense that light particles (photons) can orbit the black hole in a circular path Exoplanets Q: What is an exoplanet? About how many have so far been discovered? A: Exoplanet - any planet beyond our solar system Over 5,600 Q: What are the conditions thought to be necessary for there to be life on an exoplanet? The presence of liquid water A stable atmosphere A suitable temperature range The presence of essential elements like carbon, nitrogen, and oxygen A source of energy to power chemical reactions Q: What are the three ways scientists have used to discover exoplanets? A: Transit method (detecting dips in starlight when a planet passes in front of its star) Radial velocity (observing a star's wobble caused by a planet's gravitational pull) Direct imaging (taking a picture of the planet itself) Q: What is notable about the James Webb Space Telescope as compared to other telescopes? A: Deeper infrared vision goes beyond Hubble’s infrared view to further study exoplanet atmospheres Structure of the Universe Q: What do scientists mean by a “light year”? A: Light-year is the distance light travels in one year. Light zips through interstellar space at 186,000 miles (300,000 kilometers) per second and 5.88 trillion miles (9.46 trillion kilometers) per year. Q: What is meant by the idea that when astronomers look into the sky, they are looking into history? A: Astronomers actually use the time it takes light to travel as a distance measurement - a light year, the distance light travels in one year (about 6 trillion miles). When astronomers view an object 3000 light years away, they are looking at light that left that celestial object 3000 years ago. Q: What are the three types of galaxies? A: 1. Elliptical Spherical or ovoid shape Usually older, dimmer and smaller stars 2. Spiral Central bulge and orbiting disc with “arms” Many young vibrant stars 3. Irregular Lacks a regular shape; some were deformed Q: What are the characteristics of the Milky Way Galaxy? A: Spiral Galaxy 100 billion stars 100,000 light-years across Q: When speaking of the Milky Way galaxy, what is meant by our "local group"? What are the prominent galaxies in the local group? A: The Milky Way Galaxy and its neighboring galaxies are known as the Local Group (~40 galaxies) (prominent galaxies: Andromeda, Triangulum, Large Magellanic Cloud) Between the galaxies are large regions of empty space Q: What is a galaxy cluster? A: Galaxy Cluster - gravitationally bound grouping of galaxies (containing hundreds or thousands of galaxies) Q: What is a supercluster? A: Supercluster - a large group of smaller galaxy groups or clusters As far as we can see, superclusters hold together like a foam within which there are bubbles of super large voids Q: About how old do scientists believe the universe to be? A: 14 billion years old The Big Bang Q: What is cosmology? A: Cosmology - the study of the overall structure and evolution of the universe Q: Before Hubble’s research in the 1920’s, what was the common belief about how big the universe was? A: Up to the 1920’s: Milky Way Galaxy was the universe Q: How was the Doppler effect used to determine the motion of stars? A: By analayzing the shift in the wavelengths of light they emit Q: What does it mean if the hydrogen spectrum of a star is red-shifted? A: “Blueshift" indicates a star moving towards us and a "redshift" indicates a star moving away from us Q: What did Edwin Hubble discover when he gathered data on the distance and velocity of stars from Earth? A: Hubble’s Law - Galaxies are moving away from Earth at speeds proportional to their distance Implies that the universe is expanding Also provides extremely strong evidence for theory known as the Big Bang Hubble’s Law —--------------- = Hubble’s constant Velocity X Distance Q: What is the Big Bang theory? A: Theory that our universe began with a primordial explosion some 14 billion years ago Marked the beginning of space and time Cosmic inflation - the beginning expansion was nearly in an instant Q: Use the following concept to describe the evidence in support of the big bang theory: red shift. A: "Redshift" serves as key evidence supporting the Big Bang theory because it indicates that most galaxies are moving away from us, signifying an expanding universe, which aligns with the idea that all matter originated from a single point in the distant past as described by the Big Bang theory; as space expands, light waves from distant objects are stretched out, causing a shift towards the red end of the spectrum, essentially acting as a "Doppler effect" on a cosmic scale. Q: Use the following term to describe the evidence in support of the big bang theory: cosmic background radiation. Q: Use the following elements to describe the evidence in support of the big bang theory: hydrogen and helium. 3 Strong pieces of evidence for the Big Bang: 1. Continuing expansion of the universe 2. Cosmic Background Radiation: If Big Bang => universe cooling for 14 billion years Then average temperature of space - 3 K Predicted before measured Exact temperature of microwave radiation coming from space 3. Relative abundance of light elements ➡️ Heavier elements formed by fusion of lighter elements If Big Bang not enough time to form heavy elements in large quantities Prediction: universe should be mostly hydrogen & helium Measurements indicate: hydrogen 75%, helium 25%, everything else less than 1%