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8B- Astronomy- Annette Hong
Transcript of 8B- Astronomy- Annette Hong
& Electromagnetic Radiation Big Bang Theory Spiral Galaxies Elliptical Galaxies Irregular Galaxies Gas Clouds Star Clusters Quasars The theory that the universe began with a tremendous explosion .
13.7 billion years ago, all the content of the universe was compressed under extreme pressure, temperature, and density in a tiny spot.
Universe then rapidly expanded, matter began to come together and form galaxies. Cosmic Background Radiation Two scientists accidentally find out that there is radiation coming from space
Big Bang Theory: thermal energy from original explosion distributed in every direction as universe expanded; this cosmic background radiation now fills all of space One explanation: cosmic background radiation left over from the Big Bang Has a loose pattern. Every object in the universe is a part of something larger. (Cosmic Pattern) The Solar System
& the People of Astonomy. The Fomation of the Solar System The Sun Structure of the SUn Energy Production in the Sun solar Activity Colors of Stars Composition of Stars Classifying Stars How Bright is that Star? Distance to the Stars Motion of Stars The Beginning & End of Stars Different Types of Stars A Tool for Studying Stars When Stars Get Old The SOlar Nebula Upsetting the Balance How the Solar System was Formed The Earth Takes Shape Formation of the SOlid Earth How the Earth's Layers FOrmed FOrmation of the Earth's Atmosphere The Role of LIfe Formation of Oceans & Continents Optical Telescopes The Electromagnetic Spectrum Nonoptical Telescopes Can calculate age of universe from measuring distance from Earth to other galaxies; can predict rate of expansion Estimate age of universe by calculating old, nearby stars Universe must be as old as the oldest stars it contains How Old is our Universe? A Forever Expanding Universe As galaxies move apart, they age and stop forming stars Expansion depends on how much matter the universe contains If the universe stops expanding, it may go back to original state The universe will expand forever and as it gets colder after billions of years, it will be dark and continue to expand. Have a bulge in the center
Spiral arms Arms made up of gas, dust, and new stars New stars are formed in these denser regions of gas and dust Milky Way Hard to tell what type of galaxy we live in
Measurements made inside our galaxies+observing other galaxies
Milky Way- probably spiral galaxy. Elliptical- spheres & others are more stretched out.
Very little dust and gas
Mostly old stars
Some are huge ( giant elliptical galaxies )
Some are smaller ( dwarf elliptical galaxies )
So little flowing gas-- so few new stars form. Leftover galaxies
Galaxies that don't fit into a category
Large spiral galaxies may be distorting the shape of the irregular galaxies. Planetary Motion A Revolution in Astronomy Newton to the Rescue Nebulas (or nebulae) are large clouds of gas and dust
Some glow, some absorb light and hide stars
Some reflect sunlight
Some are regions in which new stars form
Spiral galaxies contain many.
Elliptical galaxies contain few. Globular clusters- groups of older stars; looks like a ball May be upto 1million stars in a globular cluster
Located in a spherical halo (surrounds spiral galaxies)
Also common near giant elliptical galaxies Open clusters- closely grouped stars Located along the spiral disk of a galaxy
Newly formed open clusters have many blue stars
Few hundred to few thousand. Star-like sources of light
Extremely far away
Among the most powerful energy sources in the universe
Caused by massive black holes Black holes located in the cores of galaxies. Red and yellow considered "cool colors"
Blue considered "warm color'
(ex. Bunsen Burner - blue fire is hotter than yellow fire)
(ex. Betelgeuse ~ [star name] is red, Rigel ~ [star name] is blue)
Can conclude that their different colors have different temperatures.
Star made of different elements in gas form
- Star's inner layers very dense and hot
- Outer layers (star's atmosphere) made of cool gases
- Atmosphere's elements abosrb some light radiating from star
- Different elements absorb different wavelengths of light Therefore can tell what elements a star is made of from light observed from star Colors of Light - Spectrum - the band of colors produced when white light passes through a prism
- [Spectrum] consists of millions of colors
- Solid object gives off continuous spectrum
Spectrum that shows all colors - Star's spectrum is spectrograph Used to break star's light into a spectrum - Spectrum gives information about composition & temperature of a star. Making an ID - Neon signs seen when neon sign glows when electric current flows through gas.
- You would see emission lines instead of a continuous spectrum (in spectrograph) Lines made when certain wavelengths of light are given off by hot gases. - When element emits light, only some colors in spectrum show up ~ others are missing.
- Each element has different set of [bright] emission lines Trapping the Light - Cosmic Detective Work - Star produces a spectrum
- Star's spectrum made of dark emission lines
- Star's atmosphere absorbs certain colors of light in spectrum When planets are young and small-- irregular in shape.
Gains more matter-- gravitational force increases.
Rocky planet reaches diameter of about 350km-- force> strength of rock The Effects of Gravity The Effects of Heat
Earth grew- rock got crushed- became more round.
Changes shape- heating up.
Planetesimals continue to collide with
Energy of their motion heats up the earth.
Radioactive material, present at the time, also heated up the earth.
Earth reached a certain size= temperature rose faster than interior could cool.
The rocky material began to melt inside. Volcanoes, earthquakes, and hot springs. Denser materials sank to the center
Less dense-- floated to the surface
Crust- thin, outermost layer 5-100km thick.
Oxygen, Silicon, Aluminum Mantle Layer beneath crust
2,900km below surface
Magnesium, Iron, denser than crustal rock. Core Center of the Earth
Densest materials- Iron, Nickel
6,400km below surface.
Earth's Early Atmosphere Earth's Changing Atmosphere Mixture of gases released as Earth cooled
Molten rock released carbon dioxide & water vapor.
Steamy mixture of carbon dioxide & water vapor.
Earth cooled- atmosphere changed again.
Probably formed from volcanic gases.
Chlorine, nitrogen, and sulfur + carbon dioxide & water vapor
Water vapor may have condensed to form the first oceans.
Comets may have contributed Comets- planetesimals made of ice Comets crashed into Earth- brought a range of elements Carbon, hydrogen, oxygen, nitrogen. May have brought some water. Ultraviolet Radiation The Source of Oxygen The Growth of
Continents Oceans probably formed during Earth's 2nd atmosphere.
Millions of years of rainfall- water began to cover the Earth
4 billion years ago- global ocean covered the planet
First few hundred years- may not have been any continents
Rocks which formed continents- melted and cooled many times Each time it melted and cooled- lighter elements rise
Some rocks were light enough to pile up
These rocks- beginning of the earliest continents
Continents got thicker & rose above the ocean surface
Young continents didn't stay in one place
Slow transfer of thermal energy in mantle pushed them around
2.5 billion years ago- continents really started to grow
1.5 billion years ago-upper mantle- cooled and became denser and heavier cooler parts sank
made it easier for continents to move in the way they do today. 3.4 billion years ago- organisms that used photosynthesis appeared
Photosynthesis- process of using the sun and carbon dioxide from the atmosphere to produce food
Waste products- Oxygen Over the next hundreds of years- more and more oxygen
Carbon dioxide was removed at the same time
Oxygen formed a layer of ozone
Ozone blocked most of the UV May have helped produce conditions needed for life
UV light- lots of energy
Can break apart molecules in your skin & air.
Today- shielded from most UV due to ozone
Early atmosphere probably didn't contain ozone UV broke apart molecules in the air and surface
Material collected in waters
Water offered protection from UV radiation In water, chemicals may have combined to form life
First organisms- very simple, didn't need oxygen.
Kepler's First Law of Motion Kepler's Second Law of Motion Kepler's Third Law of Motion Came from his careful study of Mars
Found out that Mars moves in an ellipse (elongated circle) Ellipse- closed curve in which the sum of the distances from the edge of the cure to two points inside the ellipse is always the same
maximum length - major axis half of this distance - semi-major axis (usually used to describe the size of an ellipse Semi-major axis of Earth's orbit (the maximum distance between Earth and the sun): about 150 million km Planets seem to move faster when they are close to the sun and slower when they are father away Planets that are more distant from the sun take longer to orbit the sun - explains relationship between the period of a planet's revolution and its semimajor axis
Kepler used this (how long each planet takes to orbit the sun) to calculate the planet's distance from the sun
Kepler wondered what caused the planets closest to the sun to move faster than the planets farther away
Newton finds out that this is because of gravity, however didn't know what caused gravity and why gravity worked The Law of Universal Gravity Orbits Falling Down & Around Newton reasoned that an object falls toward Earth because Earth and the object are attracted to each other by gravity
Newton's law of universal gravity states: force of gravity depends on the product of the masses of the objects over the square of the distance between the objects Larger the masses of two objects, the closer together they objects are, the greater the force of gravity between the objects are Inertia explains the reason why the moon doesn't come crashing to the Earth Inertia: an object's resistance in speed or direction until an outside force acts on the object In space, no air for resistance or slowing down the moon; so, it keeps moving but gravity keeps the moon orbiting
This principle explains why all bodies in orbit keep doing so (applies to all planets) Causes black lines to appear
- Star's atmosphere absorbs colors of light, not emitting.
- Absorption Spectrum is spectrum of a star
Identifying Elements Using Dark Lines Produced when light from hot solid/dense gas pass through less dense gas. - Cooler gas absorbs some portions of spectrum, so black lines of spectrum show portions of spectrum absorbed by atmosphere.
- Pattern of lines of star's absorption spectrum show some elments in star's atmosphere.
- Star is a mixture of elements
- All different sets of lines for star's element appear together in it's spectrum - In 1800s, astronomers started to collect and classify.
- At first, letters assigned to each type of spectra [of stars]
- Stars classified to elements they were made of.
- Scientists found classification is wrong. Differences in Temperature - Stars now classified by hotness.
- Temp. differences between stars result different colors Difference in Brightness - Early astronomers created system to classify stars based on brightness
- Brightest stars called first-magnitude stars.
- Dimmest stars called Sixth-magnitude stars.
- After telescopes were used, many stars too dim could be seen.
- Instead of replacing system, astronomers added.
- Positive numbers = dimmer stars, negative numbers = brighter stars
- ex. Using telescope, can see stars as dim as 29th magnitude. Apparent Magnitude - Brightness of a light/star is apparent magnitude
- If you measure brightness of street light with light meter, lights brightness depends on square of ratio between light and the light meter.
Absolute Magnitude - Astronomers use star's apparent magnitude and distance from Earth to calculate its absolute magnitude
- Absolute Magnitude - actual brightness of a star
- If all stars had same distances, their absolute magnitude would be same for apparent magnitude - Astronomers use light-years to measure distances from Earth to stars [because stars are far away]
- Light year - distance that light travels in one year.
- Stars near Earth seem to move
- Stars further away seem to stay the same as Earth revolves around the sun
- Parallax - a star's apparent shift in position
- Shift can only be seen through telescope
- Astronomers use parallax and simple trigonometry to find distances of stars close to Earth. - Earth's tilt and revolution around sun cause seasons.
- Daytime and nighttime are caused by Earth's rotation.
- Earth faces a different part of the sky at night each season. 3 points = why you see different constellations
The Apparent Motion of the Stars - Sun appears to move across the sky because of Earth's rotation
- Earth's rotation causes all stars to make 1 complete circle around Polaris every day. The Actual Motion of the Stars - Hard to see actual motion because stars are distant
- First starts --> Ball of gas + Dust
- Nuclear Fusion :
a) Sphere becomes denser
b) It gets hotter
c) Hydrogen changes to helium
- As they get older, they lose material slowly
- Sometimes, they can lose material in big explosion
- When they die, material returns to space
- Some of material combine with gas + dust to form new stars - Classified: Size, mass, brightness, color, temperature, spectrum, age
- Types: Main sequence stars, giants, supergiants, white dwawrf stars
- They can be classified as a different star when they get older
- Final stage in life cycle :
a) Runs out of fuel
b) Central parts of star collapse inward - Ejnar Hertsprung
a) Compared brightness + temperature of stars on graph
- H - R Diagram : Shows relationship between star's surface temperature + magnitude
- Became a tool for studying lives of stars
- Shows classification
- Change over time - Scientists thought sun burned fuel to generate energy
- But amt of energy is released by burning wouldn't be enough to power sun
- Gravity --> Release enough energy to heat sun
- Release of gravitational energy --> More powerful than burning
- Scientists thought burning wouldn't last long enough to keep sun shining Burning or Shrinking? - Definition : 2 or more low - mass nuclei fuse to form another nucleus
- Four hydrogen nuclei can fuse to form 1 nucleus of helium
- Energy is produced
- Sun gets energy from NF
- Einstein showed matter + energy are interchangeable Nuclear Fusion - Nuclei of hydrogen atoms never get close enough to combine
- Positively charged Fusion in the Sun Sunspots Climate COnfusion SOlar Flares The Calendar The Universe Galaxies Stars & Solar Systems Planets, Planetesimals, etc H + H = He E=MC^2 Numbers can be used to classify color/temp. in addition to letters. Supernova - Definition : Gigantic explosion-->
Massive star collapses + Throws outer layers to space
- Massive stars use hydrogen faster
- Generate more energy
- Explosion --> Can be brighter than entire galaxy for several days
- Ringed Structure Neutron Stars & Pulsars - Neutron Star : Collapsed under gravity --> All of star's particles are neutrons
a) Center of collapsed star contracts to form new star
b) Particles inside star's core -> forced together - Pulsar = If neutron star is spinning
a) Sends out beam of radiation
b) Beam is detected on Earth by radio telescopes
Black Holes - Definition : Object --> So massive that light can't escape gravity
- Force of contraction crushes dense center of star
- Locating them is difficult (Don't give off light)
- If star is nearby, gas from star will spiral into black hole (give of X-rays)
- Allow astronomers to detect existence - Radiative Zone : Energy passed from core through very dense region
a) Matter is crowded (Light + energy = blocked)
b) They are sent in different directions - Convective Zone
a) Gas circulates
b) Energy is reached - Photosphere : Hot gases in convective zone carry energy
a) Visible surface of sun
b) Hot gases in convective zone carry energy -Core: Center of the Sun
a) Where all energy is produced. -Corona: Sun's outer atmosphere. -Chromosphere: 30,000km thick
a) Beneath Corona two positive nuclei fusing. - Definition : Cooler, dark spots of photosphere of sun
- Sun's magnetic fields slow down activity in convective zone
- Areas become cooler than surrounding areas
- # + Locations can change in regular circle - Scientists found sunspot activity can affect Earth
- Linked period of low sunspot activity with low temperatures
- More research is needed to fully understand possible connection between sunspots + climate
Cooler, dark spots of photosphere of sun
- Sun's magnetic fields slow down activity in convective zone
- Areas become cooler than surrounding areas
- # + Locations can change in regular circle -Definition: regions of extremely high brightness and temperature which occurs on the surface of the sun.
-Erupts--> sends huge streams of electrically charged particles out.
- In a minute, can reach out to several thousand km.
-Can interrupt radio communications. Year- The time required for the Earth to orbit once around the sun Month- Roughly the amount of time required for the moon to orbit once around the Earth (the word month originates from word moon) Day- Time required for the Earth to rotate once around its axis Ptolemy Earth-centered universe Copernicus Brahe Kepler Galileo Newton Hubble Sun-centered universe Sun & Moon revolved around the Earth;
Other planets revolved around the Sun. Theory was wrong, but made precise observations using special tools. Brahe's assistant;
Planetary Motion Used the telescope to observe space.
Craters and mountains on Earth's moon.
Jupiter's four moons.
Sunspots on the sun.
Phases of Venus
Planets are actually physical bodies, like Earth.
All objects in the universe attract each other.
Force of gravity depends on mass of object and distance between planets.
Why all planets revolves around the sun. Other galaxies exist
Universe is much bigger than our galaxy What Determines whether a Galaxy will be a Spiral, Elliptical, or an Irregular Galaxy? Irregular Galaxies. When galaxies collide
Young galaxies that have not yet reached a shape. Spiral Galaxies Protogalactic cloud collapses
Bulge & halo form first
Remainder of cloud- rotating disk
Arms form later. Elliptical Galaxies Thought to be the result of two spiral galaxies colliding.
Gravity= Product of Masses
distance between objects ^2 Infrared Telescope Radio Telescope Gamma Ray Telescope X Ray Telescope - Ingredients for building planets, moons, stars found in empty space between stars
- Nebulas - mixture of gases (mainly hudrogen & helium) and dust made of elements (ex. carbon & iron)
=> nebulas are clouds made in space
- Can be seen when nearby stars illuminate them
- Usually invisible to optical telescopes Gravity pulls matter together. - There's a lot of space between the nebula particles
- Nebulas are less dense than air
- Gravitational attraction between nebula particles is very weak
- The force is enough to keep the nebula from drifting apart Pressure Pushes Matter Apart - Temperature - measure of average kinetic energy/energy of motion, of particles in an object
- If nebula has little kinetic energy, cloud temp is low. If nebula moves fast, cloud temp. is high.
- When particles move, sometimes crash into each other.
- These collisions cause particles to push away from each, creating pressure
- In nebulas, outward pressure balances inward gravitational pull & keeps cloud from collapsing
- Balance between gravity and pressure can be upset
- Upsets when 2 nebulas collide, or nearby star explodes
- These events compress small regions of a nebula (globules - gas cloulds)
- Globules can become dense that they contract under their own gravity
- Temperature increases & stars can form when globule collapses inward
- Solar nebula - cloud of gas and dust that formed our solar system (could have formed because of this) 1. Young solar nebula begins to collapse
2. Solar nebula rotates, flattens, & becomes warmer near its center.
3. Planetesimals begin to form within the swirling disk.
4. As the largest planetesimals grow in size, their gravity attracts more gas and dust.
5. Smaller planetesimals collide with the larger ones, and planets begin to grow.
6. A star is born, and remaining gas and dust are blown out of new solar system.
- After solar nebula began to collapse, it took 10 million years for solar system to form.
- As nebula collapsed, becameL
b) attraction between gas & dust particles increased
c) center of could became very dense & hot
- Over time, much of gas & dust began to rotate slowly around center of cloud
- Tremendous pressure at center of nebula:
a) not enough to keep cloud from collapsing
b) rotation helped balance the pull of gravity
- Over time, solar nebula flattened to rotating disk
- All planets still follow this rotation Spiral Galaxy Formation Simulation Bibliography http://docs.google.com/Doc?docid=0AXXks14epRdbZGc1cTc0dHFfM2R3dHFrdDc2&hl=en What are Telescopes? "An instrument that gathers electromagnetic radiation from objects in space and concentrates it for better observation." Astronomy black hole The Earth's First Oceans 2 Spiral galaxies combining/colliding Galaxies colliding Astronomy Astronomy Astronomy Astronomy Astronomy Astronomy Astronomy Astronomy Astrono my
Astronomy Astro nomy Astronomy Astronomy Astronomy Astronomy Astronomy Astronomy Astronomy Astronomy Annette Hong 8B Polaris