Astro 7N Exam 1 Overview

Astro 7N Exam 1 The force of gravity by the Sun keeps the planet in orbit around it, but how do the planets affect the sun? They exert an equally strong pull on the sun, causing it move slightly An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Newton's First Law ex: if the sun suddenly disappeared, the Earth would continue in the direction that it was traveling in its orbit at that time The acceleration of a body due to a force will be in the same direction as the force, with magnitude directly proportional to its mass Newton's Second Law Force = mass x acceleration A smaller mas will move faster, if the same force is applied to it For every action there is an equal and opposite reaction Newton's Third Law The Sun exerts force on planets, and they orbit it - he planets exert equal force on Sun, but it only moves slightly because of its very large mass relative to the planets the strength of gravity: g = m/r^2 where M is the mass of the planet and R is its radius. Note the radius is squared but the mass is not. More mass = more gravity. - If the mass of a planet were twice that of another, but they had the same radius, the gravity felt on the surface of the more-massive one would be twice as strong. Larger separation = less gravity. - If the radius of a planet were twice that of another, the gravity is 1 / (2) 2 = 1/4 as strong. Surface Gravity on a Planet Putting the effects of mass and radius together, you should be able to gure out the surface gravity of Mars, relative to the Earth. - Mars has 1/10 the mass of the Earth and 1/2 the radius of Earth. So for Mars, g = (1/10) / (1/2) 2 = (1/10) / (1/4) = 4/10 Mars has a surface gravity 4/10 that of Earth. You will need to be able to do this type of estimate for the test, given the numbers for mass and radius. If I apply exactly the same amount of force to a pebble and a boulder, what will happen the pebble will move faster If the Earth were moved to half its current distance from the sun, how would the force of gravity by the sun on the earth change? it would become 4 times weaker As the mass of the planet increases, the jump height does decreases by the same factor Mass As the mass of the planet decreases, the jump height does increases by the same factor According to Newton's Second law of motion, if the net force acting on the object increases while the mass of the object remains constant, what happens to acceleration acceleration increases If the earth were moves to half its current distance from the Sun, how would the force of gravity by the Sun on the Earth change it would become four times weaker 1 / 18 What did newton's law of universal gravitation tell us about how gravity works the force of gravity from the sun will be stronger on object with more mass If you were to sit on the ground, there would be a force due to gravity pulling you toward the earth. which of the following is true you are pushing the earth away from yourself with the same force according to newton's third law what would happen to the earth sun's gravity somehow turned off it would continue to move in the line in the same direction it was instantaneously moving when the gravity turned off Newton's Universal Law of Gravitation This law gives the force of gravity between any two objects in the Universe. The force of gravity is proportional to (mass of object 1) × (mass of object 2) divided by the distance between the two objects squared: F M1 x M2 / d 2 Again, more mass = stronger gravity. If the objects were moved 2 times closer (or, to half of their initial distance between), ... F M1 x M2 / (1/2) 2 = M1 x M2 / (1/4) = 4 (M1 x M2) ... so, the gravitational attraction would become 4 times as great. Q: What causes day and night? A: Rotation of the Earth on its axis. Q: How does the Sun appear to move in the sky in the course of a day? A: East to West, because of Earth's rotation. The stars and planets move in the same way from our point of view, also, because of Earth's rotation. Q: What happens to the Earth in one year? A: It orbits the Sun, once (also referred to as one complete revolution about the Sun). The Seasons, Day & Night Q: Why do we have seasons? A: The tilt of the Earth's axis of rotation, with respect to the plane of its orbit around the Sun (and not because of changing distance from Sun). The Earth's tilt is about 23 degrees. Q: How is the Earth's axis tilted when we have summer in the Northern hemisphere? A: With the North pole toward the Sun. Q: What season is it in the Southern hemisphere when it is summer in the Northern hemisphere? A: Winter Winter begins on or about Dec. 21 = in the Northern hemisphere, the nights are longer than days Spring begins on or about March 21 = days and nights have equal length The Seasons, Day & Night pt2 Summer begins on or about June 21 = days longer than nights in the North Fall begins on or about Sept. 21 = days and nights have equal length Seasons would not happen if the Earth's axis were not tilted. The distance between the Earth and the Sun does not change very much over the course of a year, so the temperature does not change much for that reason. Without the tilt of Earth's axis there 2 / 18 would be no seasons on Earth. Mars has a similar tilt to its rotation axis as Earth does. if earth rotated on it axis more slowly than it does now; days would be longer if earth had its orbit changed so that all points along its orbit it were always the same distance from the sun (circular orbit), how would this affect the seasons on earth? they would be the same as they are now a new planet orbits its star faster than the earth orbits the sun and the new planet has a shorter year than earth and a longer day than it rotates more slowly than he earth rotates. which is true earth what time of year is it dark all (and night) at the south pole of earth? June When the northern hemisphere is tilted TOWARDS the Sun the average daily temperature is marked as____, suggested that the northern hemisphere is experiencing____ warm;summer And, on the opposite site of the orbit, when the northern hemisphere is tilted the farther away from the sun, the average daily temperature is marked as____, suggesting that the norther hemisphere is experiencing___ cool;winter in the southern hemisphere its___in late june, and__is in late december winter;summer the longest day of the year in the Northern Hemisphere is on or about____ and the shortest is, again, six months later near___, when the earth is at the opposite point in its orbit around the sun June 21 and December 21 These are called summer solstice and winter solstice March 21 and September 21 Two dates are on opposite sides of the earth's orbit near these are called the Vernal Equinox and Autumnal equinox (equal night) Q: What happens to the moon in 1 month? A: It moves once around the Earth. Q: What causes the phases of the Moon? A: The Sun is lighting up different fractions of the part of the Moon we see from Earth. Q: What is the order of the phases of the Moon? A: New - Waxing Crescent - First Quarter - Waxing Gibbous - Full - - Waning Gibbous - Third Quarter - Waning Crescent - New (and repeat...) Q: When is the full moon visible? A: Only at night. It transits (is highest in the sky, or overhead) at midnight; the full moon rises 6 hours earlier (at sunset), and sets 6 hours later (at sunrise). Moon Phases and Eclipses Q: When is the new moon visible? A: The new moon is visible during the day. It transits at noon; it rises 6 hours earlier (at sunrise), and sets 6 hours later (at sunset). Q: How are the Sun, Earth, and Moon positioned when it is new Moon? A: in a straight line: Sun — Moon — Earth Q: How are the Sun, Earth, and Moon positioned when it is full Moon? A: Sun — Earth — Moon Q: What is a solar eclipse? A: The Moon is blocking the Sun's light, or a location on the Earth's surface is passing under the Moon's shadow. 3 / 18 The outer ring of Moons shows the orientation of the Sun-illuminated half its surface; the inner ring of Moons shows how the Moon appears in our sky at those times. The Moon phase directly away from a point on the Earth's surface can be said to be "overhead" at the time of day that corresponds to that direction (e.g., a full Moon at midnight, rst quarter at sunset, a waning crescent at 9:00am, etc.) Moon Phases and Eclipses pt2 A Moon phase rises about 6 hours before it is overhead, and then sets about 6 hours later. Q: How are the Sun, Earth, and Moon positioned when it is a solar eclipse? A: Sun — Moon — Earth (as in a new Moon). Q: What is a lunar eclipse? A: Earth's shadow passes across the Moon. Q: How are the Sun, Earth, and Moon positioned when it is a lunar eclipse, and what phase is the Moon in? A: Sun — Earth — Moon (as in a full Moon). Q: Why do eclipses not occur every month on Earth? A: The Moon orbits the Earth in a slightly different plane than the Earth orbits the Sun. Moon phases Q: What about eclipses of the moons of Mars? A: Mars has two small moons, Phobos and Deimos. Relative to Earth's Moon, they are tiny, and closer to their planet and orbiting faster — and closer to the orbital plane of Mars around the Sun. This leads to more frequent eclipses visible from Mars. sunset occurs 6 hours before the full moon transits. Now, when does the full moon set? full moon will set at 6am (sunrise) - sun rises at the moon sets When does the waxing crescent moon rise at 9 am when does the waning gibbous set at 9am waning crescent so what time must the moon be so the observers on earth will see the mood overhead at 9am. And where on the sky does the moon the moon sets on the west side, and rises on the east side (east set? to west) Both the mood and the sun rise for the same reason, it is b/c of: the rotation of the earth the moon's orbit around earth is actually tipped about 5 degrees to earth's orbit around the sun so the moon isnt always in the right plane for an eclipse to occur moon and earth Phobos eclipses: every orbit Mars had a one degree inclination, which is different from Earth's Moon's inclination of 5 degrees. That inclination of Earth's Moon's orbit explain why eclipses are very rare on earth 4 / 18 If Earth's Moon was Full on May 1,2007. When was it next in the First Quarter phase after this Full Moon? May 22 How much of the total surface area of the Moon is illuminated by Sunlight during the Full Moon phase? one half At approximately what time does the third quarter Moon rise? sunrise 6am full moon approximately two weeks after a solar eclipse, what phase will the moon be in? it takes about a month to get a new moon - so a full moon is the half mark (2 weeks) A moon orbits is exactly the same plane as the planet orbits its star. How often does this planet experience a solar eclipse? once every orbit of its moon (its month) constellation = large dened areas of the sky (like states in a map of a country) - anything visibly within that region is considered "in" that constellation - there are 88 of them, in all (dividing up the total celestial sphere) • Stars in the same constellation are likely to be at very different distances from us. Not necessarily close to each other, though they appear close projected on our sky. • Different constellations are visible at different times of year; e.g., "Orion the Hunter" is prominent in the Winter — because as the Earth travels around the Sun, its nighttime side faces different regions of space. • ecliptic = the apparent path of the Sun over the course of a year, with respect to the distant stars — also refers to the plane in which the Earth orbits the Sun. Constellations • Zodiac constellations = the 12 (or 13) constellations that lie along the ecliptic. • The Sun is inside a Zodiac constellation at all times = in each one for about a month, each year. - During that time you cannot see that constellation since it is behind the Sun all day and not on the nighttime side of Earth. • The Sun was in the constellation of your Zodiac "sign" during the month you were born. (You cannot see it at night at that time of year; you must wait six months.) • Winter Zodiac constellations = ones opposite the Sun in the winter • Summer Zodiac constellations = ones opposite the Sun in the summer At winter solstice, december 21, at noon, the sun is in sagittarius At midnight on March 21, we would be looking at___assuming the sky is clear virgo a small group of stars that are used to form a picture or represent an object Ibig dipper) Asterisms drawn by connecting the brightest, easiest-to-see, starts as seen from earth brightest start tends to be the one closest to earth from earth, in which constellation might you find the planet Saturn 5 / 18 Tarus Why don't we see the constellation Orion at night throughout the year? As the earth orbits the sun, its nighttime side points to different constellations at different points along its orbit when is the best time for you to be able to see the constellation that is your sign of the zodiac at middnight sex months after your birthday Constellations close to the north pole of earth___ Move in a circle around the North star, Polaris, over the course of a single night. There are a total of 88 constellations. Roughly how many of these can be seen at any given time from a single location on a clear night? 44 Light has some properties of a wave and other properties of a particle. - A "particle of light" is called a photon. Forms of light, from high-energy to low-energy: - gamma ray > X-ray > ultraviolet (UV) > visible > infrared (IR) > microwave > radio(DO ACRONYM) high-energy light =high frequency =low / short wavelength = a bluer color low-energy light =low frequency =high / long wavelength = a redder color Electromagnetic Radiation / Light All forms of radiation travel at the speed of light. wavelengths of radio waves = meters and centimeters wavelengths of visible light = ten-billionths of a meter (hundreds of nanometers) wavelengths of X-rays = even smaller (nanometers down to picometers) Blackbody spectrum higher temperature = more light in total, and a peak intensity at a shorter wavelength (or at a bluer color) - e.g., Object A has a temperature of 5000 kelvins while object B has kelvins of 500. Which one has blackbody spectrum peak at a shorter wavelength - Object A Which one will look brighter in the infrared wavelength region? -Object A A prism splits light into different colors by bending different wavelengths by different angles. Electromagnetic Radiation / Light pt 2 The Sun's surface temperature is about 5800 degrees Kelvin. Its spectrum peaks in the visible light region (peak around green — a "green star"!). Room temperature is about 300 degrees Kelvin; a "blackbody" at room temperature peaks in the infrared (IR) region of light. Q: What kinds of radiation get through the Earth's atmosphere? A: 6 / 18 visible and radio (so, to be able to see other kinds of light with a telescope — e.g., infrared, x-ray — you would need to place that telescope in space) photons light is particle and a wave Light is made up of little packets of energy called a blue photon does not move faster than a red photon b/c they are bot traveling at the speed of light A photon's___can be measured to determine its energy wavelengths or frequency Which one requires more energy? Long or short waves? short waves require more energy to generate A star(sun) has a surface area temperature of 50,000 kelvin, in which region of electromagnetic spectrum does its peak brightness occur? Ultraviolet Suppose I detect a star giving off more ultraviolet light than infrared light. What property of the star can I estimate with this infor? its temperature What is the relationship between wavelength and frequency? if the frequency increases the wavelength decreases Compare frequency of x-ray versus regular light The X-ray has a larger frequency than visible light. Compare the frequency and wavelength of a gamma ray with visible light: gamma ray frequency is higher and its wavelength is lower If the frequency of radiation is twice as large then its wavelength is half as large Compared to blue light, red light has longer wavelength, smaller frequency, smaller energy Which types of radiation have the lowest energy? infrared radiation and radio Where rainbows come from? a rainbow is a result of white light being split into its component parts of visible light spectrum through mist droplets in what region of the electromagnetic spectrum would an object near Absolute Zero radiate the most? radio What would you expect an object at 600 kelvin to radiate the most energy. Visible light b/c humans are about 310 kelvin continuum spectrum: light at all wavelengths absorption spectrum: shows absorption lines — dark lines in the spectrum at certain wavelengths, superimposed on a continuum spectrum— produced by a (less-energetic) gas cloud in front of a light source An absorption line is produced when the electrons in atoms absorb photons and remove light of specic energies from the spectrum. Then the electrons move from a lower to a higher energy level. Spectroscopy emission spectrum: shows emission lines — bright lines at specic wavelengths, in an otherwise empty (dark) spectrum, due to emission of photons from atoms in gas that have electrons in elevated levels (i.e., an "excited" gas) An emission line is produced when electrons jump from higher to lower energy levels, and emit photons of those specic energies. Different chemical elements have different energy levels that their electrons can occupy, and thus give rise to different placements and patterns of lines in their spectra; in other words, each chemical element has its own spectral ngerprint. 7 / 18 Reecting telescopes — use a mirror to collect and focus light Refracting telescopes — use a lens to collect and focus light Important qualities of telescopes: light-gathering power, angular resolution, and the quality of the instruments. The magnication is not so important. light-gathering power: Telescopes collect light in proportion to the area of their mirrors: - The area of circle is proportional to its diameter squared. example: a 2m-diameter telescope collects 2 x 2 = 4 times as much light as a 1m-diameter telescope (1 x 1 = 1) - or, a a 2m-diameter telescope collects the same amount of light as a 1m-diameter telescope in 1/4 the time Telescopes angular resolution: the ability to distinguish or separate two nearby light sources (with good angular resolution) • Earth's atmosphere limits angular resolution, or "seeing," for ground-based telescopes — makes stars twinkle magnication: zooms in on a smaller portion of the sky, to see more detail (but also observes a smaller overall area of the sky) Telescopes above Earth's atmosphere are better because: - certain kinds of radiation cannot get through atmosphere all the way to the surface (X-ray, gamma-ray, UV, IR) - conditions give clearer images without atmospheric blurring; i.e., better seeing • Telescopes pt 2 Telescopes above Earth's atmosphere are worse because: - it is hard (and expensive) to get a very large light-collecting area launched into space 1st law: The planets orbit the Sun in elliptical orbits with the Sun at one focus. These ellipses tend to be nearly circular for the planets in our Solar System. 2nd law: "A line joining a planet and its star sweeps out equal areas during equal intervals of time." Or, a planet's speed is fastest when the planet is closest to the Sun (at a point called perihelion), and slowest when it is farthest away (aphelion). Kepler's Laws 3rd law: P^2 = a 3, where P is the orbital period (a planet's year, given as a mulitple of Earth years) and a is the semimajor axis (average distance from Sun, given in AU). the density of water is 1 gram per cubic cm. What about the density of most gases? much less than 1 gram per cubic cm what would the density of mercury be most like? Solids like iron and aluminum Where are aurorae likely to be seen most frequently? at locations near the pole what would happen if the ozone layer was completely destroyed? uv radiation from the sun would get through the atmosphere and cause damage to life The densities of the 4 terrestrial planets are similar to each other. This means they are made of similar substances 8 / 18 greyish w/ numerous craters looks a like Earth's moon, but does not have prominent maria, the dark "seas," like the Moon does • Can only see close to Sun — and hard to do with the naked eye. Displays phases. Mercury is much smaller than Earth. It is similar to Mars in mass and radius, and only a bit bigger than Earth's Moon; surface gravity less than on Earth Temperature is extremely high on the day side and extremely low on the night side, due to lack of an atmosphere to distribute heat evenly around the planet (or to retain that heat on the night side) Many craters, like the Moon, including a few permanently-shadowed craters near the poles that are cold enough all the time as to hold persistent ice deposits; shadows in other craters may be cold, even on the hot/daytime side Mercury Rotates very slowly — 59 Earth days to rotate; has a short year — 88 Earth days to orbit the Sun Mercury has no signicant atmosphere; the sky appears black (can see in to deep space), even in daytime — except for the exact position of the Sun Density = mass / volume - density is related to what substance(s) something is made of - Mercury's average density is 5 grams per cubic centimeter, similar to metals and rock Closest planet to Earth; visible in western sky in evenings near the Sun, and in the eastern sky just before sunrise; looks like a very bright star. Also shows phases, like the Moon. Just slightly smaller than Earth in mass (82%) and in radius (95%)• Venus has a longer rotational period (243 days) than its year (225 Earth days) - Venus' rotation is in the opposite direction to its orbit around the Sun — i.e., it rotates clockwise when viewed from above (Earth & most other planets rotate counter-clockwise). - The combination of these factors leads to a day/night cycle on Venus of about 117 Earth days; also, the Sun travels "west to east" ("backwards") across the sky. Dense atmosphere — mostly carbon dioxide — of gases produced by volcanic outgassing, but not dissolved in ocean like on Earth, also sulfuric acid in clouds 9 / 18 Venus' surface is very hot (> 700 K, hotter than Mercury), because of the presence of large amounts of greenhouse gases (mostly CO2) in its atmosphere to contain heat. Density of Venus is about 5.2 grams per cubic centimeter — similar to Mercury — and made of metals/rock Active volcanoes, huge lava ows and channels, some large craters, but small meteors burn up in the thick atmosphere before they can impact to leave small craters. venus fairly thick atmosphere, mostly composed of nitrogen and oxygen molecules; atmosphere causes sky to appear bright during the daytime; this is the scattered light from the Sun — otherwise the sky would appear dark aurora caused by solar wind particles that hit atmospheric gas and lead to emission of different colors; they are prominent near the north and south poles plate tectonics = rocky plates on the surface of Earth oat on denser but more-uid rocky material, and move around — leads to continental drift, mountains caused by collisions of plates; plates sliding past each other cause faults, quakes Earth ozone (three oxygen atoms bonded together) layer (in stratosphere at 6 - 30 miles above the surface) protects Earth from solar "Greenhouse Effect": Energy from Sun heats Earth. Earth's surface radiates this heat back towards space by giving off infrared radiation. • Earth pt 2 - Particular gases (including water vapor and CO2) in the Earth's atmosphere recapture and redirect this heat back towards the surface, preventing it from escaping to space. - This trapped heat is redistributed back on Earth. The naturally abundant greenhouse gases in the Earth's atmosphere act like a thermal blanket keeping Earth warm. - Without greenhouse gases Earth's surface would be about 33 degrees Centigrade cooler. When humans produce large amounts of greenhouse gases, it leads to extra heating, potential extra rein10 / 18 forcing feedback loops — i.e., global warming — beyond stabilized longer-term temperatures. terra (Latin for "land"): light-colored features, heavily-cratered, high peaks; geologically older; highlands uplifted from impacts in early solar system maria (Latin for "seas"): dark-colored, less cratered, valleys; geologically younger; lled by lava 1 to 4 billion years ago regolith = powdery dust and rocky debris that covers the Moon; broken apart by small meteorites hitting moon continuously impact craters = gouged out from explosions, asteroids or comets that hit the moon Earth's moon (luna) The Moon rotates on its own axis with exactly the same period that it takes to travel once around the Earth; consequentially, the same side of the Moon always faces Earth — this is known as "tidal locking" Moon lacks as much high-density material such as iron — no large iron core 1/4 diameter of Earth Moon has no atmosphere; daytime sky is dark Surface gravity is 6 times stronger on the Earth than on the Moon. Mars' days and nights are similar in length to those on Earth About half Earth's diameter; 1/10th Earth's mass > 12 spacecraft have visited Mars; rovers explored surface No thick atmosphere, but does have thin one that causes orangish sky; mostly carbon dioxide; only modest Greenhouse effect because the atmosphere is so thin • Average surface temperature about -65 ÚC, but can be warmer at its equator • mars Iron oxide ("rust") in surface rocks gives Mars its red color Has two moons, Phobos and Deimos, but they are tiny — only 0.3 % of Mars' size Olympus Mons (large volcano on Mars; do not need to remember name) is 3 times higher than Earth's highest mountain; Martian volcanos appear dormant • Valles Marineris (do not need to remember name) is the deepest canyon in Solar System — about 300 times size of the "Grand Canyon" on Earth • 11 / 18 Water once existed on the surface of Mars, but it is not owing regularly there at present; permafrosts = water ice locked beneath Martian soil Dust storms are common; occasionally make it hard to see surface features. A few kilometers in size • Made of ice (both water ice and "dry ice") and dust — remnants of Solar System formation • Tails pointing away from the Sun develop due to the solar wind • Shine by reected sunlight — i.e., comets do not produce light of their own Comets • Highly-elliptical orbits that take them far from the Sun; as would be predicted by Kepler's 2nd Law, comets spend most of their time in the outer reaches of the Solar System — they zip by the inner Solar System and travel back out very quickly • Comets move slowly across the sky from our perspective on Earth • Short-period comets have periods < 200 years • long-period comets have much longer periods (can be 1,000s of years) and come from the Oort cloud, as much as 50,000 AU from Sun • Halley's Comet is a famous short-period comet that returns every 76 years — its last visit to the inner Solar System was in 1986; the next return will be in 206 • remnants of the Solar System's formation — rocks left over when the planets form • many are in the "Asteroid Belt" between Mars and Jupiter • asteroid orbits are typically slightly elliptical • a few major types exist: carbon-rich, metallic, and silicate (stony) Asteriods • we see asteroids by reected sunlight; they do not shine visibly on their own • the orbits of some asteroids intersect Earth's orbit, and lead to meteors • most are less than 1 kilometer in size, but some are bigger • like comets, asteroids tend to move very slowly across the sky to a viewer on Earth 12 / 18 an asteroid Vesta streak across the sky very quickly — they are also called "shooting / falling stars" (they can travel up to a hundred thousand kilometers per hour) • most meteors are tiny dust particles or grains — less than a centimeter in size — that rapidly burn up in Earth's atmosphere; pieces of Solar System debris • Meteors meteors occur when an asteroid crosses Earth's orbit, or when Earth passes through a cloud of debris left behind by a comet passing through the inner Solar System (the famous Halley's Comet is reponsible for the "Orionids" annual meteor shower) • a "reball" = very bright meteor due to larger-than-usual chunk of debris • a "meteorite" = piece of meteor that survives atmospheric entry, hits Earth's surface • asteroid collisions were more common in the younger Solar System • 65 million years ago a large meteor collision with Earth contributed to the extinction of dinosaurs (the "K/T event"); dust and smoke thrown into the atmosphere was greater cause of extinction — not so much the initial impact itself • Jupiter is about 300 times the mass of the Earth, but is on average far less dense — overall about 1.3 grams per cubic centimeter (about the density of milk); it has a radius of 11 times that of the Earth. Jupiter has a small ring system. Jupiter is made mostly of hydrogen and helium gas. - Gaseous molecules of ammonia, methane, and water vapor also present; these lead to different colors in Jupiter's stripey, swirling appearance. - Clouds of different colors are also at different altitudes. Jupiter Windspeeds can reach 360 km/hr; the "Great Red Spot" is a giant storm larger than Earth — like an anticyclone on Earth — and has lasted for at least 300 years Jupiter rotates rapidly (once every 10 hours), which stretches the clouds into long bands. It takes Jupiter 12 Earth years to orbit the Sun. Interior temperatures and pressures get very high, deep inside Jupiter's gaseous body - Hydrogen gets compressed into a liquid-metallic form. - In its very center, Jupiter is likely to have a rocky/metallic core. Magnetic elds are 10 times stronger than Earth's due to the rotating liquid-metallic region; interaction between this magnetic eld, the solar wind, and Jupiter's atmosphere leads to aurora like 13 / 18 we see on Earth Methane can convert to carbon soot, and high pressures inside Jupiter can compress that into diamonds (leading to "diamond rain" in Jupiter's atmosphere). Life forms in Jupiter's atmosphere were proposed to exist by astronomers Carl Sagan and Edwin Salpeter; these speculative creatures were referred to as "sinkers," "oaters," and "hunters." Jupiter pt 2 Jupiter has more than 50 moons; - the four largest were discovered by Galileo in the early 17th century CE; they looked like stars, but were found to orbit Jupiter — important because it helped demonstrate that Earth is not the center of Universe - Using Kepler's laws, the mass of Jupiter can be measured using the periods and semimajor axes of the orbits of Jupiter's moons; periods range from 1.8 to 17 Earth days, and Jupiter's mass is about 317 Earth masses. - You should remember the names and basic information (below) for these four largest "Galilean" moons of Jupiter the closest; mostly coppery-yellow with black dots, which are active volcanic sites; overall very volcanically active, due to "tidal heating" from Jupiter; low crater density; yellow color from sulfur Jupiter's moon Io water-ice surface; no craters — ice movement wiped them out; liquid water ocean below icy crust Jupiter's moon Europa largest moon in the Solar System (larger than the planet Mercury); icy crust; has craters so not active now, but cracks show it once was more active Jupiter's moon Ganymede 14 / 18 the farthest out of the four large Galilean moons; very heavily cratered — many young craters; does not get heated much, and has not changed much since its formation; about the size of the planet Mercury Jupiter's moon Callisto Galileo discovered its rings (although he did not know what they were, at the time). - the rings are incredibly thin; made of trillions of individual orbiting objects composed of dusty water-ice crystals, of various sizes • Saturn Saturn's mass is about 100 x Earth's (about 1/3 Jupiter); diameter about 10 x Earth's. - overall average density is 0.7 grams per cubic centimeter, which is less than that of water — "Saturn could oat!" - the spin axis of Saturn is tilted about the same as Earth's - like Jupiter, Saturn is mostly made of Hydrogen and Helium; clouds arranged into belts and zones; temperatures cooler than on Jupiter. - More than 50 moons; by far the largest is Titan (remember this one) — second largest moon in Solar System; very thick nitrogen-rich atmosphere like the young Earth, but perhaps too cold for life. Saturated orange color (as opposed to Venus' pale yellow). Complete cloud cover; cannot see sharp surface features. Like with Venus, the lack of rings is a hint to help not mistake this for a gas giant. titan 15 / 18 Third-largest planet, after Jupiter (1st) and Saturn (2nd). Orbital period is about 84 Earth years. Uranus' thick atmosphere is made of gas, mostly hydrogen and helium, but some methane too that gives it the blue-green color - atmosphere does not have as continually prominent belts or zones, or bright clouds, like Jupiter - has liquid, icy core surrounding a smaller rocky core Spin axis is nearly in plane of orbit around Sun (it is kind of "rolling on its side"); probably caused by collision early in its history; leads to continual near-darkness or light for 42 Earth years in a row, at its poles Uranus Uranus has many thin, faint, dark rings made of carbon ("soot"). 27 known moons - Miranda (one of the larger moons): heavily-cratered, with weird valleys and cliffs; appearance caused by upwelling of ices - Miranda (one of the larger moons): heavily-cratered, with weird valleys and cliffs; appearance caused by upwelling of ices Uranus' moon Miranda Discovered in 1846 (do not need to memorize exact date), based on the orbit of Uranus not looking quite right Similar to Uranus, but a deeper blue color; atmosphere of hydrogen, helium, and methane (causes blue color); a solid core the size of earth; surrounded by a mantle of semi-uid ices Rapid winds and large storms/vortices; include Great Dark Spots, big storms that can come and go over the timescale of a decade Neptune Ring structure, faint and dark; made of clumps of dust 14 known moons • Triton (largest): thin atmosphere made of nitrogen and methane; rocky composition; reective icy surface; ice volcanoes with liqui d nitrogen, dust, or methane coming out of them; • unusual orbit suggests Triton may be a captured Kuiper Belt object 16 / 18 • Triton (largest): thin atmosphere made of nitrogen and methane; rocky composition; reective icy surface; ice volcanoes with liqui d nitrogen, dust, or methane coming out of them; • unusual orbit suggests Triton may be a captured Kuiper Belt object neptune moon triton Pluto was discovered in 1930; NASA's New Horizons probe passed it in July 2015 - 248 Earth-year period of orbit - orbit more highly-elliptical than any of the 8 planets, and not in the same plane; briey intersects orbi t of Neptune - icy ball of rock • Pluto is very small compared to the planets; Earth's Moon is 7 times as massive Despite its size, Pluto has 5 moons; largest is Charon, over half diameter of Pluto Pluto not considered a "planet" anymore, because ... 1. other similar objects were found farther from the Sun — Quaoar, Sedna, Eris 2. not like other outer planets / small; referred to as an "ice dwarf", which are very abundant beyond the orbit of Neptune Pluto and charon Pluto is now considered a dwarf planet, in the Kuiper belt - The Kuiper belt is a disk-shaped region beyond Neptune, ranges 30 - 55 AU. • The - Oort cloud (houses long-period comets) is out beyond the Kuiper belt. In order to be considered a planet, now, an object must 1. orbit the Sun (not be a moon around another object); 2. be massive enough to be nearly round; 3. clear the region around its orbit (Pluto does not; many other objects there). 17 / 18 1. the Solar System formed 4.5 billion years ago 2. starting with cloud of gas and dust, it collapses due to its own gravity 3. as it collapses, the spinning cloud attens and forms a di sk 4. the Sun forms at center Formation of the Solar System 5. "lumps" in the disk become planets 6. the regions around these proto-planetary clumps clear out (or material is absorbed) 7. only rocks and metals survive in inner region; outside, ices and gases also survive 8. takes a few tens of millions of years to form 18 / 18