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The Final Frontier 1st – Lets get a perspective on how large and far away things in space are…. Facts: Sun = 109 X larger than Earth Earth = 3.7 X larger than Moon Moon = 30 X farther from Earth than Earth’s diameter Sun = 400 X farther away than Earth is from the Moon 1st – Calculate the diameters of Earth and Sun using a scale in which the Moon’s diameter = 1 cm 2nd – Use step 1’s answers to calculate the distance between Earth and Moon, Earth and Sun 3rd – Cut out circles of the correct diameter to represent Earth, Moon, Sun and glue them down at the correct scaled distance apart. Astronomers must analyze LIGHT that comes to the Earth from distant objects in Space = Electromagnetic Radiation that travels as a wave Electric and Magnetic disturbances Wavelength = distance from two parts on the wave that are the same (crest-crest/troughtrough) Frequency (f)= # of waves passing a point in 1 second All Light travels at the same speed = speed of light = 3.0X108 m/s Our eyes have only evolved to be able to “see” VISIBLE light…that’s why we call it visible! Not all light coming from space is visible, and its so far away its hard for our eyes to see…therefore, we use TELESCOPES to see these different forms of light Telescopes Detect different wavelengths of light Collect more light than our eyes are able to (larger openings) Can collect light over periods of time = create photographs that allow us to observe changes out in space Focus light at a point where an image can be studied (our eyes do this too, but only with visible wavelengths) Largest observatory in Hawaii – Mauna Kea We also send SATELITES and PROBES into space to collect information Why?? Our atmosphere blocks certain wavelengths of light (IR, UV, X ray, Gamma) so it doesn’t allow us to study everything coming from space Our atmosphere also blurs images because it doesn’t allow all wavelengths to pass Break down of Space Universe All existing matter and space AKA: The Cosmos Galaxy System of millions or billions of stars with gas and dust held together by gravitational attraction We live in the Milky Way Galaxy Solar System Collection of planets and their moon in orbit around a sun Also contain smaller bodies (asteroids, meteoroids, comets) How did it all begin…or did it even have a beginning?? 1930-1965…the scene: debating astrophysicists…aka: largest nerds on the planet 2 Theories have Emerged to explain the beginning of our Universe Big Bang Theory Proposed by George Lemaitre (a priest, astronomer, and Prof. of Physics) States that the universe orginated when a “primeval cosmic egg” exploded Universe has been expanding ever Steady – State Theory Proposed by Fred Hoyle, Herman Bandi, and Tommy Gold Stated that the Universe looks the same from all points and has not changed -There was no beginning -Matter is continuously created to fill space left behind as universe expands Major Points of Debate that eventually lead to an accepted theory Religion’s Part Pope Pious XII, 1952 – announces that the Big Bang Theory affirms the idea of a creator, thus this theory was in harmony with Christianity Steady-State becomes associated with Atheism and the Communist Party because it says there was no beginning Major Points of Debate that eventually lead to an accepted theory Miscalculations Early On A miscalculation within the Big Bang Theory showed that our solar system was older than our universe…this caused some doubt in the theory early on This was later figured out and fixed – new calculations showed the universe as 2X as old as the solar system Nail in the Steady-State Coffin… Cosmic Microwave Background Radiation is discovered! Cosmic Microwave Background Radiation…….. What tha heck is that?! Faint glow of light that fills the Universe Falls on Earth from all directions, at all times, with the same intensity Residual heat from the creation of the Universe…afterglow of the Big Bang (Its like heat that comes off of a sun warmed rock at night) Oldest light we can pick up = Shows us the farthest back in time…14 byo From a time when the Universe wasn’t cold and dark…it was a firestorm of radiation and elementary particles which these later form the planets & galaxies As the Universe was stretched through expansion… so were the wavelengths of the light from the explosion…currently is has stretched to the size of MICROWAVES and cooled to a temperature of 2.73oK Cosmic Microwave Background Radiation Discovery The Hulmdel Horn Antenna, 1960s, New Jersey Big Bang Theory Details Nothing left (that we know of) from before the Big Bang…so don’t ask what happened before…no one knows! The idea begins with Hubble’s Discovery, 1939 – the Universe is moving away…expanding in all directions taking galaxies with it = Hubble’s Law Thus, in reverse thought, the Universe must have been much smaller in the past It was a tiny point in existence All matter/energy existed within this small point Eventually too dense = explosion of the Universe Evidence: 1) Expansion of the Universe is seen 2) Cosmic microwave background radiation 3) Abundance of different elements were predicted and are now found (Hydrogen, Helium) 4) Lays a framework for evolution of the Universe seen today Evolution of the Universe…What can we expect? Within the Big Bang Theory, we know that there are two forces acting on the Universe Outward Momentum of Expansion Inward Pull of Gravity If this force is greater than the outward If this force is greater than momentum = expansion the pull of gravity = stops, universe starts to expansion will never stop = contract = Closed Open Universe Universe If the Forces are Equal = Expansion will slow, but contraction won’t happen = Flat Universe Most recent discoveries show that the expansion is SPEEDING UP…a force is required to make this happen Formation of the Milky Way Galaxy Starts as a spherical cloud Cloud collapses due to gravity Rotation forces the cloud into a disc shape Formed 13.5 BYA Galactic Center is surrounded by a Nuclear Bulge, surrounded by a halo = oldest stars Disk sticks out from the Bulge = Youngest stars 4 Major Spiral Arms (several minor arms) – our sun is in a minor arm Formation of Our Solar System Formed 4.5 BYA Interstellar cloud = clouds made of gas/dust that exist in between stars An interstellar cloud started to condense as a result of gravity This led to the formation of a star and planets Collapse starts slow, then accelerates If the cloud is rotating, this will cause it to spin faster until it contracts As it collapses, rotation slows, cloud flattens = Becomes a rotating disk with a dense center Formation of our Sun Starts from a SOLAR NEBULUA (disk of gas and dust) The dense concentration of hot gases at the center of the nebula became our sun Formation of our Planets The disk of gases surrounding the sun has various temperatures – hottest closest to the sun, coldest furthest from the sun As the gas cools, different substances (elements) are able to condense into liquids and solids The condensing liquids/solids begin to clump together and grow into larger bodies called Planetesimals Planetesimals collide and some clump together forming larger bodies = Planets The Sun Largest object in our solar system (99% of the mass…109 Earths to fit across it!) Because it’s the largest, it has the largest gravitational force and thus it controls the motions of all other objects in the solar system The Sun’s Fuel Source The sun’s energy comes from the process of FUSION This is the combination of light nuclei, like hydrogen Once combined, they form larger nuclei, like Helium Mass is LOST!...because it is converted into ENERGY during the process! Fission is the opposite of this process…LARGE E = mC2 NUCLEI ARE SPLIT APART by a NEUTRO, producing SMALLER, MORE STABLE NUCLEI We use it in nuclear bombs and nuclear power plants to make energy. Structure of the Sun Core the temperature at the core is 15,000,000°C it is made up entirely of gas Radiation Zone the temperature in the radiation zone is 2,500,000°C Convection Zone the temperature in the convection zone is 1,000,000 °C Atmosphere of the Sun There are 3 layers in the Sun’s Atmosphere Photosphere • the temperature is 5800 °K • it is considered the surface of the sun • it appears yellow in color = where most light is emitted Atmosphere of the Sun Chromosphere • the temperature is 30,000 ° K • it appears reddish in color • only visible to the naked eye during a solar eclipse when the photosphere is blocked • can be viewed with the use of special filters to block all wavelengths of light except for red coming from the sun Atmosphere of the Sun Corona • the temperature is 1-2,000,000 oK • it can only be seen during a total solar eclipse or with use of filters • appears white in color • flows outward @ high speeds and forms SOLAR WINDS Solar Winds Solar Wind: electrically charged atomic particles (IONS) that stream out into space from holes in the corona • As particles fly past the Earth, they interact with our magnetic field and upper atmosphere = These are called VAN ALLEN BELTS • This collision with gases creates LIGHT = CALLED AURORAS The Sun’s Atmosphere CHANGES over time Changes in the sun’s atmosphere creates SOLAR ACTIVITY Solar Activity occurs on an 11 yr cycle SUNSPOTS = dark spots seen on the Sun’s surface -Actually very bright. Appear dark because surrounding areas are much cooler -Created when the Sun’s magnetic field pokes thru the photosphere -Typically last 2 months -Occur in pairs -Pairs have opposite magnetic poles The Sun’s Atmosphere CHANGES over time Changes in the sun’s atmosphere creates SOLAR ACTIVITY Prominences: cloud of glowing gases that arches high above the sun’s surface • caused by the sun’s magnetic field The Sun’s Atmosphere CHANGES over time Changes in the sun’s atmosphere creates SOLAR ACTIVITY Solar Flare: sudden outward eruption of electrically charged atomic particles Associated with sunspots May interfere with phone, TV, and radio reception Effects of Solar Activity on the Earth Scientists have evidence that solar activity affects our CLIMATE There are subtle climate variations within 11 yr periods – these correspond to the 11 yr cycles of solar activity Ex: Little Ice Age of the 1600s - Solar Activity stopped, no sunspots for nearly 60 yrs - Severe weather changes on Earth - Earth experienced a mini Ice Age – weather was very cold in Europe and North America during these years Energy from the Sun Amount of energy reaching the Earth from the Sun every day is ENORMOUS! 1354 J of Energy is received above the Earth’s atmosphere in 1 m2 /s… in other words: Thirteen 100-W lightbulbs could be operated with the energy that strikes a 1-m2 area Not all of this reaches the ground – some is absorbed and scattered by our atmosphere – this helps to PROTECT us! The Planets in our Solar System Terrestrial Planets - 4 inner planets All close to the size of Earth All are solid and rocky Mercury, Venus, Earth, Mars Gas Giants - 4 outer planets - Larger - All are gaseous and lack solid surfaces - Jupiter, Saturn, Uranus, Neptune Other Debris in our Solar System Asteroid Belt - Debris/planetisimals trapped between Jupiter and Mars - Held here because of the gravitational force between the planets Asteroids = Left over debris from the formation; range in size Meteoroids = pieces of asteroids that fall to Earth Meteor = Meteoroid that burns up in Earth’s atmsophere Meteorite = Part of the meteor that reaches the surface of the Earth; Can leave an impact crater Comets = Small, icy bodies that orbit the Sun -2 clusters/clouds of comets in our system: Kuiper Belt and Oort Cloud Haley’s Comet - Orbits into the inner system periodically (every 76 yrs) - Next time = 2061 Meteor Showers - Occur when Earth intersects the orbit of a comet - The comet burns up in our upper atmosphere - Ex: Hale-Bopp - 1997 Movement of the Planets in our Solar System Early Ideas “Earth Centered” or Geocentric Model Astronomers thought that the Sun and all other planets as well as stars orbited a stationary Earth Why did they have this idea?? When observing from the Earth, planets change their position each night relative to the stars…which made it seem like these were all moving around the Earth This couldn’t explain why the normal direction of planet motion sometimes changed Retrograde Motion = when planets move in the opposite direction across the sky.. This happens because these planets are moving around the Sun slower than the Earth Nicolaus Copernicus suggested that the Sun was at the center of the solar system and this helped to explain retrograde motion of the planets Heliocentric model Kepler’s 1st Law Johannes Kepler demonstrated that each planet orbits the Sun in the shape of an ECLIPSE…not a circle…more like an OVAL An Elliptical orbit is centered on 2 points…not just 1 Each planet’s elliptical orbit is different in size/shape These points = Foci The Sun is always 1 of the focus points Major Axis = the line between the foci that represents the maximum diameter of the ellipse Half the length of the major axis = Semimajor axis Perihelion = closest to the Sun Aphelion = furthest from the Sun Planets distance from the Sun changes with an Elliptical orbit Eccentricities The shape of an ellipse is determined by the distance separating the two foci. When the foci are close together, the ellipse is "rounder". When they are farther apart, the ellipse is "flatter". The shape of the ellipse is referred to as its "eccentricity" Flatter ellipses are said to have a "high eccentricity". Rounder ellipses are said to have a "low eccentricity". The eccentricity of any ellipse can be mathematically calculated and can range from 0 to .999. Low values correspond to ellipses with low eccentricities….which means they are more CIRCULAR Most planets in our Solar System have low eccentricities…less than 0.93 Comets tend to have high eccentricities ….closer to 1 Practice Questions Is the orbit illustrated in the figure representative of the orbits of planets in our solar system? No, this show high eccentricity, therefore this is more representative of a comet Describe the shape of an ellipse with an eccentricity of 0. A circle Why does the fact that the Earth is at perihelion in January prove that the distance of the Earth from the Sun is not the cause of the seasons? The eccentricity of the Earths orbit is very low so the difference between perihelion and aphelion is not very great. Also in January although it is winter in the northern hemisphere it is summer in the southern hemisphere. Kepler’s 2nd Law An imaginary line between a Sun-Planet sweeps out EQUAL amounts of AREA in EQUAL amounts of TIME Kepler’s 3rd Law Mathematical relationship between the SIZE of a PLANETS ELLIPSE (a) and its ORIBITAL PERIOD (p) 2 3 p =a p = time in Earth yrs a = semimajor axis of oribital ellipse…length in AU In words, this means that as a becomes larger (the orbit is larger), then P becomes larger too. You would expect this. A planet in a larger orbit has further to go, so it should take longer, even if it goes at the same speed Gravity and Orbits Isaac Newton observed the Moon’s motion, the planets’ orbits, and how object accelerate to Earth when falling… Realized that any 2 bodies will attract each other with a force dependent on the objects’ masses and the distance between them Called Law of Universal Gravitation Force = G (m1 m2) r2 G = gravitational constant = 6.6736 X 10-11 m3/kg/s2 M = mass r = distance between objects Basically states: Force of Gravity (attraction) between objects is directly proportional to the product of the objects’ masses and inversely proportional to the square of their distances Practice Problems 1. If one doubles the distance between two bodies, what happens to the gravitational attraction between them? Does it increase or decrease? By how much? If the distance between two bodies is increased, the attraction will decrease. If distance (d) is doubled, the attraction (F) will decrease fourfold (2^2 = 4). 2. If you reduce the distance between two bodies, what happens to the gravitational attraction between them? Does it increase or decrease? By how much? If the distance is halved, the gravitational attraction between the two bodies would increase fourfold. (2^2 = 4). 3. If you double the mass of one of the two bodies, what would happen to the gravitational attraction between them? Gravitation attraction (F) between two masses (M and m) is directly proportional to the product of their masses. If one of the masses is doubled, the product of the two masses is doubled and therefore the attraction between them is doubled. 4. Communications satellites orbit the Earth at a height of 36 000 km. How far is this from the centre of the Earth? If such a satellite has a mass of 250 kg, what is the force of attraction on it from the Earth? Center of Mass Each planet orbits a point between it and the Sun = Center of Mass AKA: Balance point between the 2 objects…like a see-saw Heavier objects will be closer to the balance point Smaller objects will be further from the balance point Earth – Moon – Sun System Daily Motions we Observe Sun, Moon, Stars rise and set every day Rise in the EAST, Set in the WEST These are the result of Earth’s ROTATION…1/day or 15o/hr around its axis Earth – Moon – Sun System Earth’s Rotation Earth spins around in an imaginary axis as it orbits the sun…orbiting = revolution 2 ways we know Earth rotates: Foucault Pendulum Pendulum swings in constant direction As Earth rotates, it will knock over pegs around a circle Coriolis Effect Flowing air and water are diverted in a N-S and E-W direction Earth – Moon – Sun System Annual Motions we observe Things that change over the course of a year: Weather, Day length, Temps These are a result of Earth orbiting the Sun with a Tilted Axis Earth orbits Sun on an imaginary plane called the Ecliptic It is tilted 23.5o relative to the ecliptic 1 point of the Earth is tilted toward the Sun while the other point is tilted away. This will change as the earth revolves….creating the SEASONS This causes the Sun’s altitude to change Ex: Highest in the sky in the Northern Hemisphere during summer; lowest during winter. Earth – Moon – Sun System The Seasons Vernal Equinox = Spring March 21st Axis not pointed @ Sun – both Hemispheres get equal Sunlight. Sun is overhead @ Equator **Day and Night are Equal Winter Solstice Summer Solstice In N. Hemisphere, Sun is highest in the sky – directly overhead @ Tropic of Cancer (23.5o N Lat) **Max amount of daylight – June 21st **Sun doesn’t set @ Artic Circle/Doesn’t rise @ Antarctic Cirlce Autumnal Equinox = Fall September 21st In N. Hemisphere, Sun is lowest in the sky – directly overhead @ Tropic of Capricorn (23.5o S Lat) **Min amount of daylight – Dec 21st **Sun doesn’t set @ Antarctic Circle/Doesn’t rise @ Artic Circle Earth WOBBLES…like a toy top…while spinning on its axis Called Precession Happens because the Earth is pulled to the side by the Moon’s gravitational force It takes approx. 26,000 yrs for the Earth to go thru 1 cycle of precession Phases of the Moon Lunar Phases = Changes in the appearance of the Moon The Moon doesn’t produce light…it reflects light from the Sun When Moon is in between the Earth and Sun, we can’t see it b/c Sunlit side is away from us! Waxing = Amount of Sunlight reflected from Moon is INCREASING Waxing Cresent = less than half of Moon is seen 1st Quarter Moon = Between phases – Half of Moon is seen Waxing Gibbous = more than half of Moon is seen Phases of the Moon Waning = Amount of Sunlit side is DECREASING Waning Cresent =See LESS than half of sunlit side Waning Gibbous = See MORE than half of the sunlit side Full Moon = Earth is between Moon and Sun…so we see entire Sunlit side of the Moon 3rd Quarter Moon = Half of Moon is seen Lunar Month = Time to go through a complete cycle of phases ~ 29.5 days Takes 27.3 days to revolve around Earth…so the Moon Rises/Sets 50 min later each day b/c it has moved 13o in 24 hr..Earth has to turn an extra 13o each day! The Dark Side of the Moon The Moon has SYNCHRONOUS ROTATION = its ORBITAL and ROTATIONAL periods are the same…it spins at the same speed it orbits – so spins around 1 time as it goes around the Earth So..we only ever see 1 side of the moon…we never get to see the dark side How does the Moon Affect the Earth? Moon’s Gravity pulls on the Earth and CREATES BULGES of ocean water on the near and far sides of the Earth As Earth rotates, BULGES STAY ALIGNED WITH MOON…so person on shoreline sees ocean rise/fall every 12 hours…These are called TIDES Spring Tides = higher than normal b/c Sun and Moon are aligned in same direction – so both pull on Earth Neap Tides = lower than normal b/c Sun and Moon are @ Right angles to each other Solar Eclipses Happen when the Moon passes directly between the Sun and Earth and it BLOCKS our view of the Sun (Sun and Moon appear the same size b/c Sun is so far away) Umbra = Moon’s shadow with no direct sunlight Small portion of viewers falling in the Umbra see a TOTAL Solar Eclipse…no light Penumbra = Moon’s shadow with some direct sunlight Larger portion of viewers falling in the Penumbra see a PARTIAL Solar Eclipse Solar Eclipses Why don’t we see a Solar Eclipse each Month? Moon is tilted 5o relative to ecliptic plane…so it usually passes North or South of the Sun rather than directly in line with it! Moon’s Distance from the Earth Changes as it moves Perigee = Closest = Moon appears Larger Apogee = Farthest = Moon appear Smaller When in Apogee, can’t completely block Sun during an Eclipse = Annular Eclipse b/c you see a Ring from Sun around Moon = Annulus Lunar Eclipses When Moon passes through Earth’s Shadow Only @ time of a Full Moon, when Moon is in opposite direction from Sun If Moon falls in Earth’s Umbra = Total Lunar Eclipse If Moon falls in Earth’s penumbra = Partial Lunar Eclipse Solar and Lunar Eclipses occur in almost equal #s w/ slightly more Lunar Eclipses…Max = 7/yr which last happened in 1982 and won’t happen again until 2038