Honors Astronomy Unit 24_25 PDF

Astronomy Intro & Waves Astronomy  Astronomy Unit Part 1: – Parts of a Wave – Electromagnetic Spectrum Part 2: Universe formation Part 3: Solar System Formation and Planetary Motion Part 4: Stars – Life Cycle – Classification  Terms we’ll use constantly…...

Astronomy Intro & Waves Astronomy  Astronomy Unit Part 1: – Parts of a Wave – Electromagnetic Spectrum Part 2: Universe formation Part 3: Solar System Formation and Planetary Motion Part 4: Stars – Life Cycle – Classification  Terms we’ll use constantly… ◻ Solar system: planets, moons, etc circling a star ◻ Galaxy: clusters of a few million to 400 billion stars ⬜ ex: Milky Way galaxy → ⬜ Small galaxies may orbit larger ones ⬜ Three shapes: Spiral galaxies: flattened disks with spiral or barred spiral arms Elliptical galaxies: spherical in shape with no spiral arms Irregular galaxies: no distinct shape ◻ Universe: enormous collection of all matter Click Here for an optional waves notesheet! PART 1: WAVES  Parts of a Wave Wave: a repeating disturbance that transfers energy through matter or space - Examples: ocean waves, sound waves, seismic waves, light waves Frequency: number of waves per unit of time  Study of Light Waves Newton (1666): Huygens (1670s): studied light traveling determined light through a prism & saw travels in waves; a spectrum of colors: shorter wavelengths ROYGBIV are refracted (bent) more than longer wavelengths This discovery led to the creation of spectroscopy- the study of the properties of light  Spectroscopy: Study of Light Radiation (light) released or reflected by distant objects allows scientists to study the universe. Electromagnetic Spectrum: the continuum of radiation released by celestial objects Long wavelength, low frequency Short wavelength, high frequency Types of Electromagnetic Radiation Electromagnetic waves – Travel at the speed of light—300,000 km/s – Transfer energy – Travel through space Include: – Gamma (CT scans) – X-Rays – UV light=sunburns – Infrared=heat – Microwaves & Radio waves The Electromagnetic Spectrum  What is the Speed of Light? Speed of light (c)- relationship between frequency and wavelength - 3 x 108 meters/sec (186,000 miles per sec!) Speed of light (m/s) wavelength (m) frequency (Hz)  Using the Speed of Light Equation This equation can be used to find wavelength or frequency of different types of light when we know the speed of light. Ex. Calculate the wavelength of violet light with a frequency of 750 x 1012 Hz. f = 750 x 1012 Hz λ=? 3 x 108 = 750 x 1012 λ c = 3 x 108 m/s 750 x 1012 750 x 1012 λ = 0.0000004 OR 4 x 10-7 m  Energy in types of EM radiation Which wave demonstrates more energy? → Energy is measured in Electron Volts (eV) Can solve using one of two formulas: E=hf or E= hc 𝛌 h is Planck’s Constant, f is the frequency, c is speed of light and 𝛌 is wavelength Planck’s Constant = 6.626 x 10-34 J s Energy of a photon (if you need extra help)  Let’s try it! Calculate the energy of a photon of radiation whose frequency is 5.00 x 1014 Hz Solve for wavelength first using c =(wavelength)(frequency) E= hc E = (6.626x10-34)(3x108) 𝛌 (0.0000006) E = 3.313x10-19 eV Calculate the energy of a photon of radiation with a wavelength of 3.3 µm. (3.3x10-6 m) E= hc E = (6.626x10-34)(3x108) 𝛌 (3.3x10-6 m) -20 E = 6.02x10 eV James Webb Space telescope Click here for a copy of the note sheet Part 2: Universe Formation  Big Bang Theory Theory that the universe began as a singularity and has been expanding ever since – Occurred about 14 (13.7) billion years ago Singularity- zone of infinite density What does this mean?? -all matter squished into a tiny amount of space  Expansion of the Universe Universe has two opposing forces: 1. Momentum of outward expansion 2. Gravity pushing inward to slow expansion Gravity Momentum Gravity Expansion  Outcome of Universe Depends on which opposing force is stronger Three possibilities: 1. Open – expansion will never stop 2. Closed – expansion stops and begins to contract 3. Flat – expansion slows to a halt, but does not contract Another View of the Universe’s Outcome  Contents of the Universe Universe expansion is accelerating (dark energy) Click here for a recap - Big Bang Explained Composition: – Dark energy (75%) (unknown) – Dark matter (21%) (unknown subatomic particles) – Luminous matter (4%)  Rubber Band Lab: Modeling Expansion Hubble’s Law explained  Support for Big Bang 1. Einstein’s Theory of Relativity & Quantum Physics: math based theory that proves objects are moving away from a “singularity” (and relative to each other) 2. Cosmic background radiation: Weak radiation left over from the early, hot stages of the Big Bang expansion  Cosmic Background Radiation Discovered in 1965 (background noise in radio antenna) Shorter wavelengths of light (when hot) that became longer (when cooled) The “leftovers” of the Big Bang  3. Doppler Effect- but first… Let’s review the properties of waves: Frequency: number of waves per unit of time Crest Trough THINK: What is the relationship between wavelength and frequency?  Support for Big Bang, cont. 3. Doppler Effect: an apparent change in the frequency of waves when the observer or the source of the waves is moving relative to each other. What does this mean??? Doppler Effect. Bazinga!  The Doppler Effect When objects are moving away from us, they show a red shift. When objects are moving towards us, they show a blue shift. Measuring Doppler Shift When an object in space is moving, its spectral lines will be shifted towards one end of the spectrum. We can use this shift to determine how fast a star is moving.  Measuring Doppler Shift Example: The spectral lines emitted from a distant star are analyzed. One of the lines for hydrogen has shifted from 450nm to 498nm. Is this star moving away from or toward earth? What is the speed of the star? Wavelengths became longer- indication of redshift- galaxy is Speed of Star = 3.2 x 107 m/sec moving away from Earth. Part 3: Our Solar System  Nebular Theory Page 953 in your book!- read this page!  1. Interstellar Cloud / Nebula clump of dust clouds mostly containing hydrogen and helium  2. Collapsing of Cloud (Contraction) Gravity (perhaps a nearby supernova explosion?) draws the matter together causing the cloud to collapse 3. Collapsed cloud spins faster pushing dense material to the center (will become SUN) 4. When temps reach 15 million degrees C, nuclear fusion begins → the Sun is born! 5. When spin slows the cloud will become a flat rotating disk (will become SOLAR SYSTEM)  Planets are Created: 6. Leftover matter clumps to form planetesimals (small, planet-like rocks). 7. Planetesimals smash together to form protoplanets (early planets). Distance from Sun Affected Distribution of Elements in Planets Resulted due to temperature differences - Inner planets – warmer region→ have elements with high melting points (reason why rocky and dense) – Outer planets – colder region → have more volatile elements (reason why they are mostly gas & ice)  What you’re left with: A Solar SYSTEM! ◻ A sun fusing hydrogen into helium and other heavy elements. ◻ Warm center ⬜ Heavy elements (high melting points) found here ⬜ Terrestrial planets: small & rocky, MVEM ◻ Cool edges ⬜ More volatile elements, explosive gases found here ⬜ Gas giants: solid, rocky cores w/liquid and gas atmospheres, rings & satellites: JSUN (J=beast, leftovers to SUN) ◻ Remnants of matter not in planets formed ⬜ Comets: frozen balls of ice and dust ⬜ Asteroids: dark, rocky planetesimals; many orbit sun in a belt btw Mars & Jupiter ⬜ Kuiper belt: zone of icy bodies left over from Big Bang ◻ Pluto?! Hold that thought! Review: Pages 950-954 in your textbook Video Review - click here  Planetary Motion Johannes Kepler- 17th Century- Developed 3 Laws of Planetary Motion 1. Each Planet orbits the Sun in an ellipse shape.  Planetary Motion Ellipse- oval shape centered around 2 points (foci) instead of a single point like a circle  Planetary Motion 2. A planet covers equal amounts of area in equal amounts of time. Planets move faster when close to the Sun Planets slow down when farther away from Sun  Planetary Motion 3. The relationship between the size of the planet’s orbit and its orbital period is p² = a³. In other words → the larger the size of the planet’s orbit, the longer its going to take to get around the Sun one time P = time in Earth years A = length of semi-major axis A dwarf planet discovered out beyond the orbit of pluto is known to have an orbital period of 619.36 years. What is the average distance from the sun? 72.7 AU Venus has an average distance of 0.7 AU from the Sun. What is Venus’s orbital period? 0.59 E years  Planetary Motion- Gravity Page 76-79 in book! Isaac Newton – Law of Universal Gravitation Gravity – Attraction force between two objects – Amount determined by: Mass of objects Distance between objects Explains planet movement (would move in straight line) What would happen if the Earth stopped its orbit? G= gravitational constant (6.67x10-11 Nm2kg2)  Example problem: Universal Gravitation - Two 3 kg masses are separated by 0.35m. Determine the force of gravitational attraction between them. (Answer= 5x10-9 N)  Challenge Solve for the Force of attraction between YOU and the Earth. 1kg= 2.2 lbs (to solve for your mass) mass of the Earth= 5.972 x 1024 kg radius of earth= 6.378 x 106 m  Back to Pluto… Why is Pluto no longer considered a planet?? Doesn’t meet one of these 3 planet criteria: – Must orbit the Sun → YES or NO – Must have enough gravitational force to draw matter together into a sphere → YES or NO – Must have cleared orbital neighborhood → YES or NO  Part 4: Stars Classification of Stars The Life Cycle of Stars Put it in perspective… Biggest Stars in the Universe How are distances to Stars Measured? Astronomical Units (AU): average distance from Sun→ Earth Light Year (ly) = 9.461x10¹²km- Pg 988 in book – DISTANCE light travels in a year Parsec (pc): 3.26 ly – 3.08x10¹³ km  Misconceptions Stars close to Earth aren’t always the brightest Bright stars in our sky could really be dim but close to Earth Dim stars could really be bright but far from Earth -Proxima Centauri: closest star to our Sun (4.2 ly) but dimmest in cluster -Alpha Centauri A&B: separated by a distance of Sun-Uranus (4.4 ly), brighter  What are Stars made of? Composition of most stars: 71.5% Hydrogen 27% Helium 1.4% Other heavy metals  Stellar Composition *Composition is similar to the gas giants- representative of the composition of stellar nebula and the galaxy as a whole.  Spectroscopy Spectroscopes (prism)- separates white light into all colors organized by wavelength- Pg 988 Produces a spectrum (plural: spectra) 3 types of spectra: – Continuous – Emission – Absorption  Spectroscopy Continuous Spectrum: produced when light from a highly compressed, glowing liquid passes through a prism No breaks- all wavelengths of visible light represented  Spectroscopy Emission Spectrum: produced when noncompressed, cool gas passes through a prism Contains bright lines at certain wavelengths Wavelengths visible depend on the elements present in the gas *By knowing the emission spectra of different gases, we can figure out what gases are present in distant stars by matching the star spectra with gases  Spectroscopy Absorption Spectrum: produced when light from a hot source (star) passes through a cool gas before a prism Produces a continuous spectrum with dark bands at certain wavelengths  Spectroscopy- Putting it all together! *Notice how the emission spectrum lines match the dark bands on the absorption spectrum  Spectroscopy *By knowing the emission spectra of different gases, we can figure out what gases are present in distant stars by matching the two spectra *This process also helps us see redshift/blueshift Lab Time: Introduction to Spectroscopy  Star Classification Basic Properties of Stars: – Mass: determines life span – Diameter – Temperature – Luminosity: power/energy released (Watts) – Magnitude: brightness Apparent magnitude: how bright it appears in sky *Based on this Absolute magnitude: how picture, we can see bright it WOULD be @ 10 luminosity depends parsecs on temperature and size  Star Classification- Spectral Class HR Diagram Spectral Class- A way of classing stars based on temperature and luminosity – Stars are charted on the Hertzsprung-Russell Diagram X-axis: Temperature – Hottest→coolest – Blue→Red Y-axis: Luminosity compared to the Sun Main Sequence Star Life Cycle of Stars Main Sequence Star  Life Cycle of Stars: Page 989-993 It All Depends on Mass! Low mass stars: – Have longer life spans than high mass stars – Burn their fuel more slowly High mass stars – Have shorter life spans than low mass stars – Burn their fuel more quickly  Stellar Nebula Birthplace of stars, cloud of dust and gas – Stellar performance: star-like performance! – Nebular theory: creation of solar system Cloud condensed by passing stars or supernova (wait for it!) explosion Stars glow when hydrogen fuel is burned (aka nuclear fusion) As stars age, H fused to He, C, Fe & other heavier elements to increase star’s density  Main sequence/Massive Star Infancy Star begins process of nuclear fusion Longest stage of life cycle (~100,000 yrs) Star grows & becomes stable  Red Giant/Red Supergiant Hydrogen fuel begins to run out Temps cool as expansion occurs=red color Star expands in size  Death of a Low Mass Star Planetary nebula – Gas is used up – Star condenses & outer atmosphere blows off White Dwarf – Last of remaining fuel burns – Core of heavy elements shrinks in size Black Dwarf – No remaining fuel, stops burning – Just a core of leftover matter  Death of a High Mass Star Supernova – Gas used up, triggers violent collapse of RSG – Collapse triggers a huge explosion shockwaves can condense distant nebulae=new stars! Final fate of star determined by mass of star 1.4 X Sun’s mass: Neutron star Label arrow on top branch +3 X Sun’s mass: Black hole Label arrow on bottom branch  The end of a High Mass Star 1.4 X Sun’s mass: Neutron star (shell) Dense core can’t support self, collapses  +3 X Sun’s mass: Black hole Collapse so great all matter (even light!) is pulled in @ speed of light! THE SUN CH. 29.1  Sun Largest object in our Solar System – Mass = 99% of all mass in SS – Diameter = 109 Earth’s fit across Sun – Density = 13oo kg/m³ ~Jupiter Interior = plasma or ionized gases (only nuclei & electrons) Light produced each second = 4 trillion trillion 100-W lightbulbs  Layers of Sun’s Atmosphere Photosphere- – Innermost layer – Visible surface of Sun – Releases visible light – 400 km thick, 5800 K Chromosphere – 2500 km thick, 30,000 K – Strongest emissions = red λ – UV wavelenghts Corona – 7 million km thick, 1-2 mil K – X- rays emitted – Very dim, seen during eclipse  Solar Activity Solar Wind – Created by high speed gas flowing from corona – At 1 AU: 400km/sec wind of ions (charged particles) Deflected by Earth’s magnetic field Trapped in two huge rings called Van Allen Belts – High-energy particles collide with gases in Earth’s atmosphere to create an aurora  Solar Activity, cont. Sunspots – Dark spots on photosphere where pressure of Sun’s magnetic field pokes through – Appear darker in surrounding area because cooler in temp (but are bright) – Occur in pairs with a north & south pole like magnets Solar Activity, cont.  Solar Activity, cont. Sunspots: – Cycle through a maximum number of spots to a minimum number over the course of 11.2 years Because of a reversal in polarity of the Sun’s magnetic field (north pole become south pole, and vice versa) – 1645-1715: “Maunder Minimum”- period of time where the Sun had little solar activity and no sun spots “Little Ice Age”  Other Surface Features Solar Flares Prominences Violent eruptions of Arcs of gas ejected from particles and radiation chromosphere Can hit Earth and damage 50,000 K, hrs-months long atmosphere, disrupt long-range radios, satellites, and radar  Surface Features, cont. Space Weather: – www.spaceweather.com Classification of Solar Flares: – http://www.nasa.gov/mission_pages/sunearth/ne ws/X-class-flares.html  The Solar Interior Sun’s Core- energy is generated by fusion of hydrogen into helium Radiation Zone- energy travels through by radiation (atom to atom) Convection Zone- temperatures are cooler, so energy is transferred through gaseus convection currents