ASTRO101 MIDTERM 1 EXAM STUDY GUIDE Lecture Summary of 3 12 Completed Definitions Galileo orbiter Unmanned NASA spacecraft which studied the planet jupiter and its moons First spacecraft to orbit jupiter Cassini mission Robotic spacecraft sent to saturn to study the moons Roche Limit Distance which a celestial body held together only by its own gravity will disintegrate due to a second celestial bodies tidal forces exceeding the first body s self attraction Saturns rings lie within the roche limit Jupiter s Magnetic Field Thought to arise from electrical currents in the rapidly spinning metallic hydrogen interior Rapid rotation and large metallic interior o Note Magnetic fields for all jovian planets result from an interior region comprised of liquid metallic hydrogen Inside each of these planets is a rocky core Io Innermost of the four galilean moons of the planet jupiter Over 400 active volcanoes as a result from tidal heating v Also has more than 100 mountains and composed of silicate rock Tidal heating friction generated within a satellite s interior as it is pulled between other satellites For Io the planet is pulled between jupiter and other galilean satellites Titan Largest moon of saturn Only natural satellite known to have dense atmosphere and clear evidence of stable bodies of surface liquid Mainly composed of water ice and rocky material Dense atmosphere preventing understanding of titan s surface Europa Moon of jupiter composed of silicate rock and an iron core Atmosphere composed of oxygen and surface composed of ice Lots of cracks from melting and refreezing Europa is a water world Pluto Does not fit in with terrestrial or jovian planets Pluto would most likely be classified as a Kuiper Belt object rather than a planet and the international astronomical union voted to redefine the planets and pluto was reclassified as a dwarf planet along with Eris and Ceres Dwarf planet planetary mass object that is neither a planet nor a satellite Comets Coma sublimation fluorescence nucleus tail Oort Cloud Kuiper Belt meteor showers meteor meteorite impact iridium shocked quartz Chicxulub crater mass extinction Questions 1 How is Jupiter different from Earth 1 6x bigger lots of moons gas planet basically made from helium and hydrogen 2 extremely heavy Jupiter is more massive than the Earth while the Earth is much more dense What is the great red spot 1 persistent giant storm on Jupiter Why does jupiter have a magnetic field 1 Thought to arise from electrical currents in the rapidly spinning metallic hydrogen interior Rapid rotation and large metallic interior Why does a planet like Saturn have rings 2 2 2 Saturn has accumulated a great deal of dust and ice and these items are trapped by the gravitational pull 5 Why do Uranus and Neptune appear blue Both their atmospheres contain large quantities of methane gas which absorbs light in the red part of the spectrum and reflects back light in the blue part of the spectrum 6 What internal heat source powers Io s volcanoes Tidal heating 7 Why are Io Europa and Titan such interesting bodies 8 How would you classify Pluto Explain the new definition for a planet Pluto is a Kuiper Belt object The new definition is that a planet must orbit the sun independently be spherical and must clear its neighbouring region in other words became gravitationally dominant 9 Explain how and why a comet changes as it moves through one complete orbit Comets lose mass as they get closer to the sun from the ice sublimating 10 Compare the Kuiper Belt to the Oort Cloud Where comets come from Lecture Summary 3 26 Definitions exoplanet planets around other stars Doppler effect Helps us discover extrasolar planets change in frequency of a wave or other periodic event for an observer moving relative to its source Objects coming towards us are called blue shift and if the object is moving away it produces red shift Red has longer wavelengths With the Doppler technique we search for a star s orbital movement around the center of mass in a different way Astrometric method Very precise measurements of stellar positions in the sky astrometric means measurement of the stars the stars If a star wobbles gradually around its average position center of mass we must be observing the influence of unseen planets Transit Way of detecting distant planets based on slight changes in a star s brightness The planet appears to move across the face of the star causing a small temporary dip in the stars brightness Direct imaging migration electromagnetic radiation wavelength photon energy Angstrom electromagnetic spectrum gamma rays x rays ultraviolet light visible light infrared radiation radio waves transparent spectrum Bohr s atomic model energy levels ground state transitions ionization H alpha H beta H gamma photosphere solar core strong nuclear force electromagnetic force hydrogen fusion deuterium positron neutrino E mc2 Planet of the Day Questions March 12 1 How does Jupiter compare to the Earth Jupiter is way more massive than the Earth Jupiter is made of gases while the earth is a rock Earth is more dense than Jupiter and is a terrestrial planets while Jupiter is a Jovian planet Jupiter has a lot stronger gravity than the earth 2 Why does Saturn have rings Saturn has rings because of the Roche limit Saturns rings are made up of small rocks and particles that were shredded up when they entered Saturns Roche Limit The rings are thin because we can see stars through them Roche limit is where the rings are formed 3 In what ways are Io Europa Titan interesting IO Tidal heating Io is gravitationally tugged on one opposite sides by Jupiter and outer moons and has active volcanoes Europa Also has tidal heating due to it being tugged on by Jupiter and outer moons Is a water world Tidal heating allows water to stay liquid under the thin icy crust The icy crust looks cracked because parts of it melts and refreezes 4 Why is Pluto no longer considered a planet It does not clear its orbital neighborhood 5 What happens as a comet approaches the Sun The ices from the comet s nucleus sublimes This creates a coma The coma absorbs UV rays from the sun and re emits visible light It fluoresces so we can see the comet from the Earth The comet also loses mass as it gets closer to the sun due to sublimation 6 What is a meteor shower A meteor shower happens when the orbit of the Earth crosses the orbit of a comet Particles and debris from the comet s tail stays in the orbit of the comet and continues