PHYS 2022 Week 5 Notes
PHYS 2022 Week 5 Notes PHYS 2022
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This 2 page Class Notes was uploaded by HellFire on Saturday February 6, 2016. The Class Notes belongs to PHYS 2022 at Georgia Institute of Technology - Main Campus taught by James R Sowell in Winter 2016. Since its upload, it has received 17 views. For similar materials see Stars, Galaxies and the Universe in Physics 2 at Georgia Institute of Technology - Main Campus.
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Date Created: 02/06/16
Observatories Key parameters to successful telescopes o Must be in a dark location with mild weather o Clear atmosphere with minimal pollution (light pollution or smog) o “Steady air”—crisp, low humidity air with minimal interference “Seeing” (units: arcseconds) describes how easily visible one can see through the air in astronomy terms The Sun 100x larger than earth 1,000,000x as massive as earth Surface temperature of 10,500 F (5800 K) Completes 1 rotation every 30 days Takes 8.32 mins for light to travel from the sun to the earth o Distance from sun to earth is 150,000,000 km or 1 AU (astronomical unit) Solar atmosphere o Photosphere (light region) Part of the sun we see; surface is not solid 400 km thick, 5800 – 4500 K temps Covered in granules, i.e. Texas-sized bubbles that are around 100 K hotter than the surrounding surface; last for around 8 mins Convection creates granules as hot air rises and cold sinks o Chromosphere (color region) Helium (red) resides in this region, was discovered during solar eclipses 2000 – 3000 km thick, 4500 K – 10000 K temps Covered in spicules, i.e. 10000 km high wave-like splashes that can rise to extreme temperatures (1,000,000 K); last for around 15 mins o Corona (crown) Heated by magnetic field lines, is usually a violent region Best viewed with x-rays Millions of km thick at millions of degrees K Differential rotation: the sun rotates faster at the equator than it does at the poles, unlike Earth Eclipses o Lunar eclipse: the earth casts a shadow on the moon Lunar plane is offset around 5 degrees from the earth-sun plane, resulting in eclipses that occur around once every six months Lunar eclipses are reddish in color because of some interference within the earth’s atmosphere that skews the light from the sun as it hits Earth and the moon behind o Solar eclipse: the moon casts a shadow on the earth Annular eclipse: the moon’s positioning can sometimes cause the moon to not completely block out the sun even if the moon is right in front of it Sunspots o Live in the photosphere, significantly larger than granules around it o 1500 K cooler than the surrounding surface o Last for a couple of months o Like to cluster in groups of around 2-20 members, individual size is usually 3-4 times larger than earth in diameter Solar cycle: 11 years (used for sunspot prediction) o Spots will typically appear equidistant above and below the equator, starting at +-30 degrees latitude and moving to +- 10 degrees latitude at the end of their lifetimes o 11 years for the minimum number of sunspots to appear, then the max, then return to min until all sunspots are gone at the end of the cycle o Magnetic fields occur within groups of sunspots with one sunspot with high magnetic field and the other with low magnetic field Above the equator, the leading edge is low magnetic field (i.e. the low magnetic field spot is on the right) while below the equator the leading edge is high magnetic field. This flips every cycle (every 11 years) however. Huge flares on the sun’s surface are the result of magnetic field lines anchored between sunspots o Solar magnetic cycle: 22 years to account for the flip Filaments and Prominences in the chromosphere o They’re actually the same thing—prominences are typically seen in front of a cool gas while filaments are seen in front of hot surfaces o Prominences erupt in the form of a magnetic field loop anchored between sunspots Coronal activity o Coronal holes: driven by massive changes in magnetic flux o Flares: possibly due to prominences interacting with each other, very explosive Giant explosions of energy primarily in the x-ray spectrum o Coronal Mass Ejections (CMEs) are large expulsions of hot gases from the outer edge of the sun These can knock out power grids and most electronics occasionally Our magnetic field protects us from CMEs, but not completely: the particles that come around our magnetic field are looped back into Earth’s atmosphere and form the gases/energy that make up the Aurora Borealis/northern lights
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