AST 1002 Week 4 Lecture + Textbook Notes
AST 1002 Week 4 Lecture + Textbook Notes AST 1002-Section 1
Popular in Planets, Stars and Galaxies (AST 1002-Section 1, Mark Riley)
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This 5 page Class Notes was uploaded by Katherine Ruiz on Saturday October 1, 2016. The Class Notes belongs to AST 1002-Section 1 at Florida State University taught by Mark Riley in Fall 2016. Since its upload, it has received 23 views. For similar materials see Planets, Stars and Galaxies (AST 1002-Section 1, Mark Riley) in Science at Florida State University.
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Date Created: 10/01/16
ASTRONOMY AST 1001-0001 RILEY WEEK 4 WEEK FOUR LECTURE NOTES THE SOLAR SYSTEM • Terrestrial planets- 4 inner • Jovial planets- 4 outer • Our solar system is a very small part of the universe • Solar objects o Oort Cloud o Kulper Belt objects o Dwarf Planets (Pluto, Ceres, Eris) o 336 Moons (and counting) o 8 Planets o 1 Sun • Incline of Orbits o Except for Mercury, all orbits are on close to the same plane, the Eliptic o Mercury is 7° to the eliptic o Solar system-pretty much flat o Pluto is 37° at an incline • The ORBITAL PERIOD is how long it takes to go around the sun • You can measure the rotation period by direct observation • The solar system is 4.6 billion years old o How do we know this? o Radioactive Decay FORMATION OF THE SOLAR SYSTEM • Asteroids are very old and they have different properties from planets • KEPLER BELT- a collection of asteroid-size icy bodies orbiting Neptune • OORT CLOUD- comets in a distance far from the sun, icy fragments, do not orbit in the plane of the eliptic • Iron and heavier elements were created from dying stars in a process called NUCLEAR FUSION • Heavier elements make up the inner planets and lighter elements make up the outer planets • Cosmic recycling • Spectroscopy of distant stars • A cloud of interstellar gas and dust contracts because of its own gravity o Cloud flattens and begins to spin around axis o PROTOSTAR begins o Planets form out of the surrounding disk o Particle collision heats up the core o Gravitational energy creates thermal energy PROTOSTARS • Large, luminous • Infrared light emitted • Maintains ever-changing balance between pressure + energy • Collects material and compresses • Radiates thermal energy into space • The core temperature increases as the star shrinks • Hydrogen converts to helium in the core • Becomes a star! • Must reach 10 million Kelvin so the core is able to create nuclear reaction to turn H-He PROPLANETARY DISKS • Rapid rotation=nebula flattens that surrounds protostar • Approx. 100,000 years after contraction begins, a rotating, flattened disk surrounds the protosun ANGULAR MOMENTUM • The rotation rate depends on the radius • Angular momentum is CONSTANT at all times (Newton’s laws) TEMPERATURE IN A SOLAR NEBULA • Varies across solar nebula as planets form • Declines in temperature as the distance from the sun increases • Beyond 5 AU from the center of the nebula, the temperature is low enough to form ice • Beyond 30 AU, Methane can condense FORMATION OF THE SOLAR SYSTEM • Outer planet formation o Accreation of planetesimals forms core of outer planets o Ice+gas makes up planets due to the low temperature o The gravitational pull sweeps up surrounding gasses • Final Stages o Unstable young Sun ejects thin outermost layers out into space in a brief but intense burst of mass loss called T TAURI WIND o T Tauri Wind “cleaned out” the solar system • Gathering Atmospheres o Planets gather gasses from the disk o Increase of primary atmosphere o Asteroids hit OUR SOLAR SYSTEM IS NOT UNIQUE • The physical process is common • We can see young stars with disks • PLANET: a body that orbits a star and has a mass less than 13 Jupiters • Most solar systems aren’t like ours • Many have what are called “hot Jupiters” or Jupiter sized planets that are close to their sun KEPLER TELESCOPE • Detects Earth-like worlds • Kepler 62 system is multi-planet like our solar system • Two planets are most Earth-like o Kepler 62e o Kepler 62f DETECTING EXTRASOLAR PLANETS • 1. DIRECT OBSERVATION o Official count is over 837 o Detection in infrared o Star – brown dwarf o Mass of planet is about 5x Jupiter o Orbits 55 AU from star • 2. “WOBBLE” OF STAR o Jupiter orbiting the Sun causes the Sun to wobble o Radial velocity measured using the Doppler Effect • 3. TRANSIT METHOD o Periodic dimming of luminosity o Other planets discovered through the periodic dimming of their parent star’s luminosity o Kepler space telescope primarily designed to detect planets DOPPLER EFFECT • Object moving away from you is lower frequency- redshifted • Object moving towards you is a higher frequency- blueshifted • RECESSION- net velocity between source and observer • POSITIVE- source and observer moving apart • NEGATIVE- source and observer moving together CHAPTER FOUR NOTES SPEED OF LIGHT • Light travels at a finite speed • Original measurement by Romer was slightly slow • The speed of light moving through a medium is slower than moving through a vacuum • ENERGY- the ability to do work • KINETIC ENERGY- the energy of moving objects • THERMAL ENERGY- sum of all kinetic energy of moving bits of matter inside a substance LIGHT AS A WAVE • Light can act as both a wave and a particle • MEDIUM- a substance to travel through • Light waves don’t need a medium to travel • AMPLITUDE- the height of the wave above the undisturbed position • WAVELENGTH- the distance from one crest of a wave to the next • FREQUENCY- the number of wave crests passing a point in space each second • Frequency is measured by Hertz (Hz) LIGHT AS A PARTICLE • PHOTONS- massless particles that make up light and carry energy • Higher frequency = greater energy of photon • High energy light = blue • Low energy light = red THE ELECTROMAGNETIC SPECTRUM • The whole range of different wavelengths of light • Spread of colors is a SPECTRUM • Shortest waves are gamma rays-longest waves radio waves LIGHT AND MATTER • MOLECULES- a grouping of atoms by chemical bonds • Electrons that are torn apart and are floating on their own are called IONS THE EYE • INTEGRATION TIME- the time interval during which the eye can add up photons • QUANTUM EFFICIENCY- determines how many responses occur for each photon received • You need 10 photons in 100 milliseconds to activate a response from the eye • ANGULAR RESOLUTION-refers to how close two points of light can be to each other before you can’t distinguish them anymore SPECTRA AND SPECTROGRAPHS • EMISSION LINES- add light to the spectrum • ABSORBTION LINES- take light away • SPECTROGRAPHS- tools that take the spectrum of an object, split the light by the wavelength and then record it • SPECTROSCOPY-the study of an objects light in terms of its component wavelengths REFRACTORS AND REFLECTORS • REFRACTING TELESCOPES use lenses • REFLECTING TELESCOPES use mirrors • Large modern telescopes=all reflectors • Larger lens=more light gathering power RADIO TELESCOPES • Large steerable dishes typically tens of meters in diameter • Largest: Arecibo dish OBSERVING AT OTHER WAVELENGHTS • Images are distorted because of Earth’s atmosphere • You have to observe most light out of the visible light spectrum from space RESOLUTION AND THE ATOMOSPHERE • DIFFRACTION- the distortion that occurs as light passes the edge of an opaque object • DIFFRACTION LIMIT-the best resolution that a given telescope can achieve • Modern telescopes can adapt to the atmosphere’s distortion with adaptive optics