Discover The Universe Week 8
Discover The Universe Week 8 AST 1002
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This 7 page Class Notes was uploaded by Jocelyn on Sunday October 18, 2015. The Class Notes belongs to AST 1002 at University of Florida taught by Reyes, Francisco J in Summer 2015. Since its upload, it has received 23 views. For similar materials see Discover the Universe in Science at University of Florida.
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Date Created: 10/18/15
Thursday October 15 2015 Discover the Universe Week 8 Uranus Discovered b William Hershel in 1781 Named after the father of Saturn Barely visible to the naked eye at least 27 satellites Green Bluish color due to methane CH4 in the atmosphere Methane absorbs the red part of the spectrum and reflects the blue The deviation in its orbit led to the discovery of Neptune Faint ring system not visible with groundbased telescopes Units Distance 192 AU Diameter 40 x Earth s Mass 15 x Earth s Density 1200 kgmquot3 close to the density of water1000 Escape velocity 21 kms Surface temperature 58 K Axis tilted 98 degrees Orbital period 43 years Magnitude 57 naked eye limit 6 Neptune The OTHER planet whose gravitational pull is influencing the orbit of Uranus Mass and orbit determined in 1845 first by english John Adams and later by the french Urbain Leverrier In 1846 it was discovered by the German astronomer Johann Galle Thursday October 15 2015 At least 13 satellites The largest satellite Triton may be captured by the Kuiper belt Pluto is one of those objects It also has a bluish color due the presence of methane in the atmosphere Units Distance 30 AU Diameter 39 x Earth s Mass 17 x Earth s Density 1700 kgmquot3 denser than water pretty much gas Escape velocity 24 kms Earth is 11 Surface temperature 59 K why is this temperature so close to that of Uranus when it s farther away Sidereal orbit period 1637 years Magnitude 79 Rotational period 067 days Extreme Seasons in Uranus Due to the tilt of the 98 degree tilt of the rotational axis Ex 1986 rotational axis pointing directly at the sun northern summer solstice southern winter solstice Spacecraft Exploration of Jovian Planets Pioneer 10 and 11 reached Jupiter around 1973 Voyager 1 and 2 left Earth in 1977 and reached Jupiter in March and August in 1979 Used Jupiter s strong gravity to send them on to Saturngravity assist Voyager2 used Saturn s gravity to propel it to Uranus and then on to Neptune Studied magnetic fields and analyzed multiwavelength radiation Both are now headed into interstellar space Thursday October 15 2015 Space craft exploration of the Jovian Planets Galileo launched in 1989 and reached Jupiter in December 1995 Gravity assists from Venus and Earth Spacecraft had two components atmospheric probe and orbiter Probe descended into Jupiter s atmosphere Orbiter went through the moon system Cassini mission to Saturn arrived June 30 2994 Orbiter will orbit Saturn and its moons for 4 years presently active Huygens probe launched from the Cassini orbiter in December 2004 It landed on Saturn s moon Titan to study its atmosphere and surface Jupiter s atmosphere Characterized by 2 main features Colored bands zones and belts and the Great Red Spot Atmospheric content Molecular Hydrogen H2 86 Helium He 14 Small amounts of Methane CH4 ammonia NH3 and water The Great Red Spot seems to be a hurricane that has lasted for 400 years The bands are caused by convections and high wind velocity at the top of the clouds Darker BELTS lie atop the downward moving connective cells Lighter ZONES are above upward moving cells Belts are low pressure zones high pressures Jupiter has wind patterns moving EastWest Haze lies at the upper edge of the troposphere Below the layer of haze a thin layer of white ammonia clouds temp 12550K Colored clouds below that layer Thursday October 15 2015 Warmer temperatures 200 K Clouds are mostly droplets or crystals of ammonium hydrosulfide NH4NH At deeper levels clouds of water ice or water vapor The Galileo probe survived for about an hour before being crushed at this altitude The electronics failed due to high temperatures The presence as about 22 times the sealevel pressure Weather on Jupiter Main feature Great Red Spot Swirling hurricane winds They have lasted for almost 350 years Diameter twice the size of Earth s Rotates with the planet s interior The spot appears to be confined and powered by the zonal flow There are smaller storms that look like white ovals Why do the storms last so long Saturn s Atmosphere Molecular Hydrogen 924 Helium 74 traces of methane and ammonia A layer of haze at the tope of the atmosphere Troposphere contains 3 cloud layers Ammonia ice Ammonium hydrosulfide ice Water ice Overall temperature is cooler than Jupiter Thursday October 15 2015 Total cloud later thickness is about 3 times larger than Jupiter due to lower surface gravity on Saturn Thicker clouds result in less varied colors The atmospheres of Uranus and Neptune Molecular hydrogen 84 Helium 14 Methane 2 Uranus 3 Neptune Abundance of methane gives these planets their blue color Methane absorbs longer wavelength light red and reflects short wavelength light blue Weather on Uranus and Neptune Uranus few clouds in the coldupper atmosphere featureless Upper layer of haze blocks out the lower warmer clouds Neptune Upper atmosphere is slightly warmer than Uranus despite its further distance from the Sun More visible features Internal Structure of the Jovian Planets The metallic hydrogen is a superconductor A superconductor conducts electricity with minimum or no resistance Increasing temperature and pressure deeper in one Jupiter shape is distorted about 7 larger at the equator Caused by fast rotation large radius Saturn less asymmetriclarger core same basic overall structure UranusNeptune have a high density slush below cloud level compressed thick layers of water clouds with ammonia Thursday October 15 2015 Jupiter Internal Heating Some of the Jovian Planets have higher temperatures than expected from the Sun s heating alone This suggests an internal source of production of heat The heat may come from stored thermal energy Or it may come from heat being produced in the interior Primordial Heat Jupiter is slowly leaking heat that was produced during its formation by the heavy collapse of material onto the core It was expected to have a temperature about 105 K Instead of using radio and IR observations it was determine to be about 125 K According to Stefan s Law the energy being radiated should be about twice as much as the energy received by the Sun change in energy Delta E 125105 4 2 Saturn generates some heat due to the gravitational heating of liquid helium droplets falling into the liquid hydrogen This may account for the depletion of the outer layers of Helium Helium is about 7 if the composition of Saturn 14 in Jupiter Uranus no source of internal heating Neptune there is internal heating An explanation for the source is not yet clear Possibly heat trapped from formation which is slowly leaking due to its isolation of methane The axis tilt and magnetic fields Jupiter rotational axis is perpendicular and the magnetic field is tiled about 10 degrees Saturn magnetic field seems to be a line through the rotational axis The magnetic fields of the Jovian Planets and Earth are caused by the rapid rotation and the liquid cores or mantles All the Jovian planets and Earth emit low frequency radio emission The emission is caused by the interaction of electrons with the magnetic field Thursday October 15 2015 Jupiter has the strongest magnetic field of all the planets about 14 times that of Earth s magnetic field at clouds top Jupiter is the only low frequency planetary emission that can be received from ground baed radio telescopes It can be detected at frequencies less than 39 MHz short wavelength range Jupiter s radio emission is generated by electrons accelerated by the interaction f lo with the magnetic field Electrons spiral along magnetic field lines connecting lo and Jupiter This radio emission can be received with a simple antenna just a couple of dipoles The radio JOVE educational project is involved in detecting this emission 2 types of radio emission are common L long bursts and S Short bursts These examples of the radio were recorded at UF Radio Observatory The 1994 Collision of the Comet ShoemakerLevy 9 with Jupiter in 1993 the comet SL 9 made a close pas near Jupiter and broke into 23 pieces Strong tidal forces caused the comet to break apart Collided with Jupiter between July 16 and 22 1194 Another collision of a comet or asteroid with Jupiter in 2009 Jovian Planets Summary Most of their mass is hydrogen and helium light elements and low densities high surface gravity allows their atmospheres to retain these light elements dense compact core at the center no SOLID surface the gaseous atmosphere becomes denser eventually liquid at the core Differential rotation outer regions rotate at a different rate than thinner regions