chapter 31 Stars and Galaxies
Day 1:Technology and the Big Bang Studying the Stars A. Telescopes - Electromagnetic radiation emitted by stars and other objects include light, radio, and X-ray Space telescopes can collect information from all of these sources Space telescopes avoid the blurring effects of Earth's atmosphere
B. computers are used to manage data C. space probes send back materials and data from space D. accelerators provide subatomic particle energies that simulate conditions in the stars and in the early history of the universe before stars were born
E. Spectroscopes - visible light from stars can provide information about the stars composition, its surface temperature, and even how fast it is moving toward or away from Earth. light is composed of different wavelengths that can be separated prism or diffration grating separates light spectrum of the star
Big Bang Model is a broadly accepted theory for the origin and evolution of our universe l 12 to 14 billion years ago the universe was only a few millimeters across l the universe expanded explosively into existence and has been expanding ever since l as it cooled, atoms formed, and gravity pulled these atoms together into gas clouds that eventually became stars, which comprise young galaxies
Supporting evidence of "Big Bang" includes: A. Cosmic microwave background radiation; left-over radiation from the earliest light in the universe B. Hubble's Law and red shift; galaxies farther away have a greater red shift is the speed at which a galaxy is moving away is proportional to its distance from the Earth
Red Shift is the apparent shift of light to the red end of the spectrum due to the objects motion away from one another Red shift is due to the wavelengths being pulled apart because one object is moving away from another Blue shift would occur if the objects were moving toward each other
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Day 2: Evolution of Stars Stars are classified by their color, size, luminosity and mass Stars form from a large cloud of gas, ice, and dust called a nebula Gravational forces causes cloud to contract, and temperature to increase Protostar forms at center When temperature is high enough, nuclear fusion of hydrogen and helium begins
H-R diagram is the relationship between the brightness and temperature of stars brightness (luminosity) is on the Y axis, brighter stars at the top temperature (color) is on the X axis with the hottest stars (blue) toward the left and cooler stars (red) toward the right The H-R diagram shows the star's life cycle https://youtu.be/i7cfvjrktic
Main sequence stars as long as the star is fusing hydrogen into helium, the star remains as a main sequence; a broad band of stars they range from the hot bright stars in the upper left corner of the diagram to the cool dim stars in the lower right corner Our sun has been a main sequence star for about 5 billion years and will for about another 5 billion
Equilibrium ends what happens to a star when it uses up all its hydrogen core, depends upon its mass average mass star, like our Sun will become a red giant, then a white dwarf and finally a black dwaft more massive stars become a supergiants and eventually neutron stars or black holes stars of lower mass could remain on the main sequence as a red dwaft for up to 16 trillion years
90% of the star's life is in the main sequence with the rest of their time as a white dwarf, giant or supergiant As stars age they change color from blue to white then yellow and finally red All elements heavier than hydrogen or helium have been formed in stars
Day 3: Galaxies and the Milky Way Galaxy; large group of stars, dust, and gas held together by gravity The billions of galaxies are classified by size and shape; 3 shapes; spiral, elliptical, and irregular
Our solar system is part of the Milky Way Galaxy, a spiral galaxy Milky Way has more than 100 billion stars and a diameter of more than 100,000 light years (a light year is the distance light travels in a year) Spiral galaxies have spiral arms of gas, dust, and most of the younger stars around a disk of stars in the center
Elliptical galaxies range from nearly spherical in shape to football shaped they contain less ice, dust, and gas than spiral galaxies and therefore less stars they contain mostly older stars
Irregular galaxies smaller than spiral galaxies most common type of galaxy is the dwarf irregular; they contain high percentages of young stars and large amounts of ice, dust and gas