Transcript Atmosphere
Astronomy 2 Most of human history, people thought sun burned some type of fuel to make energy Not until the 21st century did scientists figure out where sun’s energy comes from Electromagnetic energy is a type of energy that can travel through space an example is visible light Light travels in wavelengths There are many things that travel in wavelengths (radio waves, microwaves, ultraviolet rays, x-rays) The electromagnetic spectrum breaks visible light down into the colors that make it up When you shine light through a prism you can see the different colors of visible light Visible light is composed of red, orange, yellow, green, blue and violet – like a rainbow 1. 2. 3. Core Inner zones Atmosphere Inner zones and atmosphere divided into more layers Continuous – gradual change between layers Makes up 10% of sun’s diameter Diameter = 1,300,000 km Temp at core is 15,000,000 ℃ No liquid or solid can exist – entirely plasma Sun’s mass 300,000 times bigger than Earth’s mass So, gravity is greater Center of sun – 10 times more dense than iron Pressure and heat of sun change structure of atoms in core Most atoms are nucleus surrounded by electrons Heat and pressure of sun strips electrons from nuclei plasma Nuclei can be changed by nuclear reactions Hydrogen fused into helium Nuclei of hydrogen atoms are primary elements in fusion of sun Hydrogen made of 1 proton, 1 electron Electron ripped off, so only protons remain 1. 2. 3. 4. 5. Two hydrogen nuclei (protons) collide and fuse One of the protons changes to neutron Another proton combines with proton-neutron pair making a nucleus of 2 protons Two of these nuclei collide and fuse Resulting group throws off two protons Remaining combination of 2 protons and 2 neutrons is nucleus of helium atom During each step, energy given off Helium nucleus has about 0.7% less mass than hydrogen nuclei that combined to form it Loss in mass converted to energy Hoover Dam provides energy to most of Western US 2,080 megawatts 380 billion billion megawatts EVERY SECOND 380,000,000,000,000,000,000 Before reaching sun’s atmosphere, energy made in core moves through two inner zones Radiative zone surrounds core Temp is about 2,500,000℃ Energy moves from atom to atom as radiation Electromagnetic radiation transfers energy through space Convective zone around radiative zone Temp about 1,000,000℃ Energy made in core moves by convection transfer of energy by moving liquids or gases Hot gases carry heat energy to sun’s surface As atoms of hot gases move out and expand, they radiate and lose heat Cooling gases become denser than other gases Sink to bottom of convection zone There, cooled gases heated by radiative zone and rise again Heat transferred to surface as gases rise and sink 1. 2. 3. Surrounds convective zone Atmosphere uppermost area of solar gases Has 3 layers Photosphere Chromosphere Corona Photosphere innermost layer of solar atmosphere Made of gases bubbling up from convective zone Temp about 6,000℃ Layer has grainy appearance called granulation Results from gases rising and sinking Much of energy given off is as visible light It’s what we see from earth So, photosphere is considered “surface” of the sun Chromosphere “color sphere” above photosphere Thin layer of gases that glows with reddish light Temp ranges from 4,000-50,000℃ Gases of chromosphere move away from and toward photosphere In upward movement, they sometimes form narrow jets of hot gas that shoot out from chromosphere then fade Sometimes these jets reach 16,000 km high Corona “crown” outermost layer of sun’s atmosphere Huge cloud of gas heated by sun’s magnetic field to temp of about 2,000,000℃ Relatively thin Prevents most atomic particles from sun’s surface from escaping into space Some electrically charged particles (ions) leak into space through holes in corona Particles are called solar wind Chromosphere and corona not seen from earth b/c of brightness of blue sky during the day During solar eclipse – moon blocks sun – can see corona Solar Activity Gases of inner zones and atmosphere are in constant motion Energy made in sun’s core and force of gravity combine to cause rising and falling of gases Gases also move because sun rotates on its axis Because the sun is plasma/gas, not solid, different parts rotate at different speeds Closest to sun’s equator take only 25.3 earth days to make one rotation Points near poles take 33 earth days Average = 27 earth days Combination of up-anddown movement of gases in convective zone and movement of sun’s rotation produces magnetic fields These fields slow down activity in convective zone Slower convection means less gas is transferring heat from core to photosphere So, regions of photosphere near strong magnetic fields are up to 3,000℃ cooler than surrounding areas Cooler areas appear darker than areas around them Sunspots cool, dark areas of gas within photosphere that are caused by magnetic fields Large sunspots can be more than 100,000 km in diameter (several times the size of earth) Astronomers found that sunspots first appear in groups midway between sun’s equator and poles As they disappear, new ones seems to appear near sun’s equator Shift of sunspots was one of first indications that sun rotates Number of sunspots also changes according to average 11-year cycle called the sunspot cycle Sunspot cycle begins when number of sunspots is very low but is starting to increase May not see any for several weeks Gradually see more and more Increases over next few years until it reaches a peak At peak, 100 or more sunspots may be visible After, they decrease Cycle begins when more sunspots begin to appear Magnetic fields also create other disturbances Prominences great clouds of glowing gases Form huge arches that reach above sun’s surface Each solar prominence follows curved lines of magnetic force from one sunspot area to another Some may last for several weeks or a year One violent solar disturbance is solar flare sudden outward eruption of electrically charged atomic particles May extend upward several thousand km within minutes Few last more than 1 hour Usually occur near sunspots During peak in sunspot cycle, 5-10 solar flares can be seen each day Some particles from solar flare flung out so forcefully they escape into space These particles increase strength of solar wind As they enter atmosphere of earth, they produce sudden disturbance in earth’s magnetic field magnetic storm Interfere with communications on earth Auroras effect of magnetic storm appears in sky as bands of light When ions of solar wind approach earth, they are guided toward magnetic poles of earth by earth’s magnetosphere Magnetosphere contains the magnetic field of earth The ions hit the gas molecules in upper atmosphere, and produces green, red, blue or violet lights Usually seen near poles Also called northern lights or southern lights Auroras usually happen 100 and 1,000 km above earth’s surface Most frequent just after peak in sunspot cycle, especially after solar flares Visible about 5 times a year http://www.youtube.com/watch?v=982cTjW x_zc&feature=player_embedded Formation of the Solar System Includes sun and bodies revolving around the sun 1600-1700s scientists thought sun formed first, then threw off materials that later formed the planets 8 major bodies revolving around the sun 1796 – Marquis Pierre Simon de Laplace had a new idea The sun and planets made from same spinning nebula The entire solar system formed at about the same time Nebular theory From big bang, some matter gathered into clouds of dust and gas Cloud of gas and dust that developed into our solar system is called the solar nebula Larger than our solar system now About 4-5 billion years ago, shock waves from nearby supernova or some other force caused cloud of gas and dust to contract, forming solar nebula A star (the sun) started to form in center When temp high enough, fusion began About 99% of matter in solar nebula became part of the sun Planets formed in outer regions of solar nebula Small bodies of matter in solar nebula called planetesimals joined together through collisions Formed larger bodies called protoplanets Gravity of protoplanets acted like magnets, pulling in other planetesimals from solar nebula Eventually protoplanets condensed into existing planets and moons Moons smaller bodies that orbit the planets Both planets and moons are smaller and denser than protoplanets Distance between protoplanet and developing sun influenced the composition of the planet that formed from the protoplanet Four protoplanets closest to sun became Mercury, Venus, Earth and Mars Contained large amounts of heavier elements like iron Next four protoplanets became Jupiter, Saturn, Uranus, and Neptune These formed in the cold areas of solar nebula Icy material of outer protoplanets made of helium and hydrogen and frozen gases (water, methane, ammonia) Inner planets probably could not build up gases b/c gravity is weak Solar wind may have stripped away early atmosphere of lighter elements b/c outer planets further away from sun and have HUGE gravity, they kept most of their original gases Called the gas giants 1. 2. 3. When first formed, it was very hot 3 things contributed to heat Earth kept a lot of heat made when it collided with planetesimals Increasing weight of outer layers pressed on inner layers, making more heat Radioactive materials (radiate heat) were plenty when earth first formed Temp on young earth enough to melt iron Gravity pulled molten iron to center Denser materials flowed to center Less dense materials forced to outer layers Earth eventually separated into 3 layers Crust Mantle Core The protoplanet that became earth could not hold gases b/c gravity was too weak Collisions added more mass to protoplanet, gravity increased Eventually it captured some hydrogen and helium that were in solar nebula By the time earth was formed, the atmosphere was mostly hydrogen and helium Today these two found mostly in upper atmosphere Much of earth’s first atmosphere was probably lost as result of solar explosion or solar wind Earth’s second atmosphere results from explosions within earth about 3 billion years ago Heat in interior caused volcanoes to form Volcanic eruptions released large amounts of gases Mostly water and carbon dioxide These formed new atmosphere Sunlight probably caused ammonia and some water in atmosphere to form nitrogen, hydrogen and a little oxygen Most of hydrogen escaped to outer space (too light to be held by gravity) Early green plants – photosynthesis – increase levels of oxygen Some oxygen formed ozone (in upper atmosphere) Shielded earth from UV radiation from sun As atmosphere was developing, earth was cooling enough for liquid water to form Between 3-3.5 billion years ago water vapor started to condense Fell as rain and formed oceans in lower surface areas Ocean water absorbed carbon dioxide from atmosphere By 1.5 billion years ago, atmosphere similar to what it is today