Stars, Galaxies, and the Universe

Stars, Galaxies, and the Universe

Stars, Galaxies, and the UniverseChapter 21How does distance affect an image?Telescope- device that makes an object in the sky appear closer.Revolutionized astronomy (study of space)- allowed them to see objects in space for first time.Galileo made telescope famous seeing sun spots, Saturns rings, and Jupiters moonsElectromagnetic RadiationThere are waves of energy and light moving around us in the form of TV and radio transmissions, gamma radiation from space, and heat in the atmosphere. The waves of energy are called electromagnetic (EM) because they have both electric and magnetic characteristics.

Electromagnetic RadiationThey are classified by the frequency of their wavelength, going from high to low frequency. When a wave has a lot of energy, it could be a gamma ray or x-ray, and has high frequency. If it has low frequency, it has less energy and could be a TV or radio wave.

http://video.pbs.org/video/2219781967/DETECTING ENERGYAll types of EM radiation are useful to the world of science. Radio waves for example, They are used to carry communications from one point to another. Astronomers listen to the radio waves of other galaxies to learn more about their stars. Stars give off large amounts of EM radiation across the entire spectrum and we can study that radiation to learn more about the universe. Space MeasurementParallax- the apparent shift in position of an object when viewed from 2 separate positionsSeen if you look at a star when Earth is at two different points during its orbit around the sunScientists can measure the parallax of relatively close stars to determine their distance from Earth.Knowing the angle that the stars position changes and the size of the Earths orbit, we can calculate the distance of the star from Earth.Classifying StarsColorTemperatureSize CompositionBrightnessStar PropertiesColor & temperaturewhite / Hot starsBlueYellow, orange, red / Cool stars

Star PropertiesSizeneutron- smallestwhite dwarfmediumlargegiant/ super giant

Star PropertiesCompositionUse a spectrograph (breaks light into colors and produces an image) to detect elementsGases in a stars atmosphere absorb some of the wavelength of the light it producesEach Chemical element absorbs light

BrightnessHow a star appears from Earth depends on the distance and the actual brightness of the starActual brightness depends on size and temperature (absolute)Distance depends on how bright it appears (apparent)Star Magnitude (Brightness)Two types of magnitudeAbsoluteApparentApparent magnitude brightnessMeasure of the amount of light received on Earth from a star.Brightness seen from EarthBoth apparent and received have a rAbsolute Magnitude BrightnessThe brightness the star would have at a standard distance from Earth.The total measure of the amount of light given off by a star. Total= absolute

Light-yearThe distance between stars and galaxies in the universe is so vast it would be too much to describe it in miles or kilometerslike measuring the distance from New York to Tokyo in inches! Instead, scientists use light-years to measure distances in space. Light-yearis actually a distance: the distance that light travels in one year.Light travels 186,000 miles per second which is equal to 300,000 km/s9.5 trillion km/yearScientists can measure the parallax of relatively close stars to determine their distance from Earth.Knowing the angle that the stars position changes and the size of the Earths orbit, we can calculate the distance of the star from Earth.Space MeasurementSpace MeasurementParallax- the apparent shift or change in position of an object when you look from 2 different positionsSeen if you look at a star when Earth is at two different points during its orbit around the sunif you stretch out your hand in front of you and look at your thumb while taking turns covering one eye and then the other, your thumb will appear to move back and forth. Stars do the same thing, but our eyes are much too close to see the difference. If we take a picture while on one side of Earth's orbit, and then take another when we get to the opposite side of the orbit, then we have a large enough distance that we can see the stars parallax, and determine how far away they really are.Parallax

Classifying StarsEjnar Hertzsprung and Henry Russell graphed stars by temperature and absolute magnitude in a H-R diagramMain SequenceDwarfsGiants(Pg 722)

Main sequence stars90% fall on the diagonal band of the H-R diagram

Stars in upper left of diagram graphs the hot, blue, bright stars

Stars in lower right are cool, red, dim stars

Stars in the middle are average, yellow stars like our sun

Dwarfs and giantsThe 10% that fall outside the diagonal of the main sequence stars are dwarfs and giants

FusionThe fusion of hydrogen in the core of star releases huge amounts of energy- atoms combine to form heavier atoms

(2) HYDROGEN ATOMS SMASH and FUSE into HELIUM with a RELEASE of ENERGY A Star is Born

All stars begin as a nebula (large cloud of gas and dust spread out in large volume)NebulaA nebula is a cloud of dust and gas, composed primarily of hydrogen (97%) and helium (3%). Within a nebula, there are varying regions when gravity causes this dust and gas to clump together. As these clumps gather more atoms (mass), their gravitational attraction to other atoms increases, pulling more atoms into the clump. Protostar

Protostar- a contracting cloud of dust with enough mass to start formation of a star- fusion has not begun

A star is born when the contracting gas and dust from a nebula become so dense and hot that nuclear fusion begins.The evolution of low mass starsHigh Mass Stars Recycling Matter Evolution quicker and more violentCore heats up quicklyCore collapses violently and outer portion of star explodesNeutrons stars are collapsed core of supernovas; only neutrons exist in neutron star. Spinning neutron stars are pulsars

Black hole form when supernova collapses to a point where no volume

Black Holes

http://coolcosmos.ipac.caltech.edu//cosmic_kids/AskKids/blackholes.shtmlGalaxies and the Universe

Clusters of starsOpenGlobular

Open- loose, disorganized appearance containing no more than 1000 stars

Globular- large groupings of older stars. Round and densely packed with stars. Some may contain more than a million stars

Galaxiesenormous swarms of stars, dust, gas, and dark matter held together by gravity. The sun is one of about 100 billion stars in our own galaxy, called the Milky Way. If you think thats incredible, imagine this: The Milky Way is just one of billions in the observable universe!

SpiralSpiral galaxies are shaped like disks and look like pinwheels from above. Young stars are found in the arms, and older stars are found in the central bulge, or nucleus

Elliptical galaxiesElliptical galaxies are the oldest and largest galaxies. They are smooth and oval and contain many old stars. There are many more elliptical galaxies in the universe than spiral galaxies

Irregular galaxiesIrregular galaxies dont have a distinct shape and are not symmetrical like spiral or elliptical galaxies. They may be young galaxies that have not yet formed a symmetrical shape, or their irregular shape may be caused by two galaxies colliding.

The Universe within 50000 Light YearsThe Milky Way Galaxy

Clusters of galaxies are often collected in super clusters. Our Milky Way is part of the Local Group and is part of the Virgo Super cluster, which contains several thousand galaxies. Milky Way GalaxyClassified as a normal spiral galaxyContains more than 200 billion stars

About 100,000 light years wideSun orbits galaxys core every 240 million yearsOther planets around other stars?http://www.nasa.gov/multimedia/videogallery/index.html?media_id=58885371Origin of the UniverseOrigins of the Universe

How did the Universe begin? Where did we all come from? Has the Universe always been the same? Does the Universe change?Steady State TheoryOne theory is the Steady State TheoryThe universe has always been the same and will always stay the sameEvidence suggests that this is not true though-indication are the universe was very different in the past.

Oscillating ModelA second idea is the Oscillating Model of the Universe. An expansion of the Universe began and everything moved outward.Over time, expansion slowed and the matter contracted back in. Process repeats itself over and overWorks like a slinkyBig Bang TheoryScientists accept this theory as more likely.We know the universe is expanding outwardsAbout 12-15 billion years ago a giant explosion occurred The universe began to expandBig Bang TheoryWithin a fraction of a second, the universe grew from the size of a pinhead to 2000 times the size of the sunBy the time the universe was one second old, it was a dense swirling mass of particles.Matter began to clump together, hydrogen and helium formedBig Bang TheoryMore than a billion years after the first explosion, the first stars were born.

Origin of UniverseSteady state theoryProposed the universe has always existed the same as it is nowOscillating modelUniverse began with expansion occurring in all areas of universe- expansion slowed, matter contracted, and process began again.Big Bang TheoryThe universe began with an enormous explosion.Our Expanding UniverseThe Doppler Shift explains how we know the Universe is expanding.If a star is moving towards Earth, the light wavelengths are compressed and you would see the spectrum in blueIf a star is moving away from Earth, the light wavelengths are stretched out and you see the spectrum in red.The Red Shift- Hubble LawIn 1929, Edwin Hubble published a paper about light from other galaxies.All galaxies beyond the Local Group (our group of galaxies) show a red shift in their spectrum, this shows they are moving away from us. The Universe is expanding.

Dark energyIn the late 1990s astronomers observed the expansion of the universe appeared to be accelerating.Galaxies seemed to be moving apart at a faster rate now than in the past. No know force to account for it which they now call dark energy.

http://hubblesite.org/hubble_discoveries/dark_energy/Looking Back in Time

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