ASTR 101 Final Study Guide. about 29.5 days for the Moon to go through a complete set of phases

Transcription

1 ASTR 101 Final Study Guide I received study guides for Chapters 1, 2, 6, 7, 10, 12, and 14. Chapter 1 - What is the celestial sphere? - What is the ecliptic? - What is the zodiac? - What are the two reasons for the seasons? Why is it warmer in the summer than in the winter? - What is responsible for the annual motion of the stars? - Draw a quick sketch of the Sun, Moon, and Earth lined up for a solar and lunar eclipse. What phase does the Moon have to be in for each? - Define solstice and equinoxes Summer solstice - June 21 Autumnal equinox (Fall) - Sept. 21 Winter solstice - Dec. 21 Vernal equinox (Spring) - March 2 - Draw and label the phases of the Moon about 29.5 days for the Moon to go through a complete set of phases Phases: new, waxing crescent, first quarter, waxing gibbous, full, waning givvous, third quarter, waning crescent

2 Chapter 2 How we know Earth is round Eratosthenes Zodiac Retrograde Motion Geocentric/ Heliocentric (how it explains retrograde motion) Nicolaus Copernicus Tycho Brahe Johannes Kepler (Kepler s 1 st, 2 nd, 3 rd Law) Galileo Issac Newton

3 Chapter 6 Why is the Earth round? Exceeds the critical size needed for gravity to pull its material into a sphere. Why does Earth s equator bulge? Rotation, inertia pushes material away from a spinning objects axis. Composition of Earth s Crust: mainly oxygen and silicone silicates Density of Earth: 5.5 gm/cm 3, tells us Earth s composition which is mainly rock and metal o Average D of Rock: 3gm/cm 3 o Average D of Metal: 8gm/cm 3 How do we know Earth has a solid core within a liquid one? Seismic waves (S & P waves) tell us about the Earth s interior as they travel through it. S waves cannot travel though liquid like P waves so experimentation has shown that S waves do not make it to every part of the globe like P waves do. Why is the Inner Core solid? The core is under so much pressure that it compresses molecules together to form a solid. Why is the Earth s Core so hot? It contains radiative elements and radioactive decay releases energy. How have scientists determined the age of the Earth? Scientists find the oldest rocks possible and look at its composition. Radioactive atoms within the rock will have decayed into different elements and thus counting the daughter atoms will tell us how old a rock is because radiative decay follows a half-life. What is Convection? The movements of heat energy as hot substances rise up to the surface while cooler substances sink down to be heated moves as a cycle. What is Rifting? Makes oceans expand by spreading surface layers with the movement of hot material below the crust. What is Subduction? Creates mountains by driving one piece of crust over another. What is Plate Tectonics? Movement of the Earth s crust Origin of Earth s Magnetic Field: electric current flowing in the earth s core Troposphere: lowest layer of atmosphere Stratosphere: where the ozone is located Earth s atmospheric composition: 78% nitrogen, 21% oxygen, 1% argon, less than 1% of carbon dioxide

4 Chapter 7 - Cool, no inner activity, so there is no elements for an atmosphere - No erosion occurring - Was pelted with fragments early in its formation where smaller fragments created craters, and larger fragments created huge basins that eventually filled with lava - Highlands: bright areas that surround maria, and are mainly composed of anorthosite - Maria : large smooth areas that come from large basins that eventually filled with lava, mainly composed of basalt - Rays: out-flung material from craters - Riles: canyons, perhaps from old lava flows - thought to have come from splashed out material form a Mars sized object hitting Earth s surface. - Has a small core that is off center, an uneven crust; is thought to have been pulled off center by Earth s gravitational pull during its formation - Does not orbit directly over Earth s equator, about 5 degrees above/below the equator - Synchronous rotation - Tidally locked - Elliptical orbit - Tides: differential gravity is what causes tides, the tidal bulge causes the high and low tides - Spring tides: highest high tides, lowest low tides; during new and full moon - Neap tides: a lower than normal difference between high and low tides; during ¼ and ¾ moon - tides change every six hours, so from one tide to that same tide again it takes 12 hours - Tidal breaking: gravitational pull from the Earth slowing down the Moon s revolution

5 Ch 10 How do astronomers explain the fact that Titan was able to retain an atmosphere, while Jupiter s Ganymede did not? Titan is colder, the gas molecules above Titan s surface do not have enough speed to escape. The equatorial diameter of Jupiter is larger than its diameter through the poles. Why? Jupiter s rapid rotation causes the equatorial diameter to be larger. What causes a high magnetic field on Jupiter? The combined effect of the planet s rapid rotation and convection in the layer of liquid metallic hydrogen in the planet s interior. 20,000x stronger than Earth s. What causes the high volcanic activity of Io? The strong tidal forces of Jupiter and Europa constantly distorts Io s shape and causes friction which creates extreme heat. What are facts about Saturn s rings? The consist of numerous separate ringlets, they extend 100,000km from the planet, they consist of mostly water-ice particles ranging a few centimeters to a few meters in size, the rings are a few hundred meters thick. Low average densities of Jupiter and Saturn compared with the Earth s suggest what? Jupiter and Saturn contain large quantities of light elements, such as hydrogen and helium. What is the Roche limit? The distance from the planet at which a moon held together by gravity will be broken apart by its planet s gravitational attraction How rings form around planets. What source of energy allows Jupiter and Saturn to radiate more heat than they receive from the Sun? Gravitational energy of sinking material. What makes astronomers think that Uranus was hit by a large body in its history? Its rotation axis has such a large tilt. Like other gas giants, Neptune s rotational period is closest to two-thirds of an Earth? Day

6 All Jovian s- large mass/diameters, low density, all have rings and moons, rock/iron cores, hydrogen/helium gases, do not have solid surfaces Jupiter Saturn Uranus Neptune. ED AU ) What are Jupiter s internal heat source? -due to heat left over from its creation -shrinking in size converting gravitational energy into heat 2.) What sorts of atmospheric motion and activity are observed in Jupiter? -adjacent belts, with different relative speeds, create vortices of various colors -the largest being the Great Red Spot, which has persisted for over 300 years. 3.) What sort of activity has been seen in Io? What causes the interior of Io to be hot? -volcanic plumes and lava flows -the gravitational tidal forces induced from Jupiter and Europa keeps Io s interior hot 4.) What is the interior of Saturn made of? -molecular hydrogen gas, liquid metallic hydrogen, water and rock and iron core 5.) What creates the large gaps between Saturn s rings? -large gaps are due to complex interaction between ring particles and tiny moon rings 6.) What is the Roche Limit? -any object held together solely by gravity will break by tidal forces if it gets too close to the planet. 7.) Why are Uranus and Neptune blue? -methane gas and ice causing the blue color of both planets atmosphere 8.) Why are the outer planets so large? -low temperature of solar nebula allowed condensing bodies to capture hydrogen and helium gases 9.) How do Jupiter s radius and mass compare with Earth? -11x Earth s diameter; -300x the mass 10.) How do astronomers know what lies inside the outer planets? -their average density is composed of ~1 g/cm3-indicating that the interior is composed of very light elements.

7 Chapter 12 How big is the Sun? The Sun is 109 Earth Diameters and 333,000 in Earth Masses What is hydrostatic equilibrium? The internal balance of gravitational force which is trying to pull into a smaller ball, and the pressure force which is trying to expand it. Why must the interior of the sun be so hot? The interior of the sun is hot due to nuclear fusion, and must be hot in order to not collapse in on itself. Be able to identify and place the thermo-nuclear core, radiative zone, convective zone, chromosphere, photosphere, and corona in a cross section. What do Solar Neutrinos tell us? Tell us what is going on in the core of the Sun and the rate of nuclear reactions What is the difference between a solar flare and a solar prominence? Solar flares are sudden and violent releases of energy and matter. A solar prominence are slow arcs following magnetic lines. How hot is the Suns core? 15,000,000 K What is the Sun s density? What does that tell us about its composition? The Sun s density is 1.4 g/cm cubed, and is composed of hydrogen, helium, and trace amounts of other elements. How does the Sun produce energy/ where does its energy come from? The energy comes from nuclear fusion when hydrogen turns into helium which makes the Sun lose mass. Why are sunspots so dark? The sunspots are relatively cool compared to the surrounding gasses, so they appear darker. What is a solar cycle? The number of sunspots increase and decrease over time in a regular, approximately 11- year cycle.

8 o Size of the Sun relative to the Earth? o 108 Earths across. o 1/3 of a million in mass. o Surface temperature of the Sun? Sun s core temperature? o 5780 K (or 6000 K). 15 million K. o What is the density of the Sun? What is it composed of? o 1.4 density, Hydrogen and Helium o How do we know the structure and numerical properties of the Sun? o Solar Models, Wien's law uses colors to determine the temperature of a star, and Neutrinos can tell how hot it is in the center, and the composition inside the Sun. Know what those are and why. o Know the cross-section/ structure of the Sun. Thermonuclear core, Radiative zone, Convection zone, Photosphere, Chromosphere and Corona. Know the properties of these layers. o What is Hydrostatic Equilibrium? o The balance between the internal pressure of the sun and the gravitational pressure. o What are the two forces keeping the Sun together? o Pressure and Gravity. o What is solar seismology? o Know the different types of Solar Magnetic Activity, such as sunspots, prominences, solar flares, and coronal mass ejections, how do these things affect things on Earth? Our satellites, radiation for the space station, sometimes the power grid, etc. o How much power does the Sun output in watts? 400 trillion trillion watts. o How does the sun produce energy? o The loss of mass when Hydrogen turns into Helium is creating energy. o How does the solar cycle work? o The cycle varies 6-16 years, every 11 year cycle the sun s field and polarity reverses. o What was the little ice age in Europe and North America called, and what caused it? o The Maunder Minimum, and too few sunspots from

9 Sun s radius: 100 x Earth s radius Sun s mass: 300,000 x Earth s mass 2.The distance from Earth to Sun is measured by Triangulation or Radar. 3.Sun s surface temperature: about 6,000K and Core temperature 15 million K. 4.Composition of Sun: Hydrogen is 71% and Helium 27%. 5.Solar Interior: ThermonuclearCore > Radiative Zone > Convection Zone > Photosphere > Chromosphere > Corona. 6.Granulation: visible evidence that sun has a convection zone. It is on photosphere. 7.Hydrostatic Equilibrium: The balance of the outward pressure force and the inward gravitational force. 8.Nuclear fusion: the solar energy generation process. 9.Sunspots: darkappearing regions, cooler than other region(4,500k) due to stronger magnetic fields. 10.Prominence:huge gas plumes from lower chromosphere into the Corona. 11.Solar Flares:Sunspots give birth to Solar Flares, eruption of hot gas in the chromosphere. due to strong twisting of magnetic field. 12.Coronal Mass Ejection:Shoot gas across the Solar System, Spectacular auroral displays. 13.Solar Cycle: Sunspot, flare, and prominence activity change yearly in a pattern(every 11 years). 14.Differential Rotation: result of Solar Cycle. Equator 25days 30days at Poles. Drives the wind up and wind down of solar activity. 15.Solar neutrinos tells Nuclear Reaction Rate. 16.We can plot the magnetic fields of the Sun using ZEEMAN splitting of spectral lines. 17.The primary method astronomers use to measure oscillations on the surface of the Sun is by: DOPPLER EFFECT.

10 Chapter 14 Gravity drives stellar evolution. The sun began its life as an interstellar cloud, a tenuous, cold, dark mass of gas drifting around the Milky Way. Gravity holds a star together, while pressure supports a star against gravity. Stars form from the matter in interstellar clouds, but also return much of that matter back to space once they live and die out. Interstellar matter is mostly hydrogen, with some helium as well as a tiny amount of silicates, carbon, and iron compounds. Interstellar gas is generally cold. As a star forms, the infalling material causes violent changes in brightness and color. The high temperature at the core of a massive star allows it to fuse its hydrogen into helium. The properties of a stars core depend greatly on the mass of the star. A star s life begins when its core temperature rises above about 5 million K. A star like the sun may increase in luminosity by a factor of 3 over about 10 billion years as it consumes the hydrogen in its core. A red giant is when the star s radius grows by a factor of anywhere from five to several hundred, depending on the star s mass. Helium nuclei are sometimes called alpha particles, and so this reaction is sometimes called the triple alpha process, or simply, helium burning. Not all stars have a constant luminosity. Stars that change in brightness are called variable stars, and many of these are associated with stages in the evolution of a star. Once the sun becomes a yellow giant, it will be nearing the end of its life. As the core burns its helium into Carbon, its radius will once again shrink, compressing and heating it. Astronomers call the glowing shell of gas around a dying star a planetary nebula. A supernova is when a star s pressure surges and lifts the outer layers away in a titanic explosion. Supernova explosions mark the death of stars. A supernova emits more than just light, most of the energy of its blast is carried by a burst of neutrinos, which are highly charged particles generated in the Sun as it converts hydrogen into helium.