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Stars, Galaxies and the Universe PAGE 90 -121 How do we measure the distance between stars? • Parallax – an apparent shift in the position of an object when viewed from different locations. • Using parallax and trigonometry, astronomers can find distances to stars. • Closer stars seem to move more than distant stars as the earth revolves around the sun. What is the universe? All of space and everything in it! It’s enormous beyond imagination! • How do we Lights years measure Scientific notation things in the universe? It is a distance not a time What are used to measure things light years? that are very far apart. The distance that light travels in one year at 300,000,000 meters per second ( 186,000 miles per SECOND) – about 9.46 trillion kilometers! What is scientific notation? It uses powers of 10 to write very large or very small numbers in shorter form. Each number is written as a number between 1 and 10 and a power of 10. Ex. – 9,460,000,000,000,000 would be written as 9.5 x 10 15 What is a star? • A giant ball of gas, mostly hydrogen and helium that are undergoing nuclear fusion. • Our sun is an example of a star. What is a planet? • An object that orbits a star. • It must be large enough to have become rounded by it’s own gravity. • It must be the largest object in it’s orbit causing all particles to gravitate toward it. What is a solar system? • It contains a star and the planets and other objects that revolve around the star. • Our solar system contains the sun, and all the planets, moons, and objects that revolve around it. What is a star • Unlike our solar system, most stars are not found system? alone. If there are 2 stars, it’s called a binary star system – more than 2 stars, it’s called a star cluster. What is a galaxy? • A huge group of single stars, star systems, star clusters, dust and gas bound together by gravity. • Much larger than star systems or solar systems. • Spiral – like a pinwheel. What are the • Elliptical – round or flattened spheres. major types of galaxies? • Irregular – holds no regular shape • Quasars – active young galaxies with huge black holes at the center. What is… Gravity? • The force that attracts all objects toward each other. Mass • The amount of matter in an object. Weight • The measure of the force of gravity on an object. • The masses of the objects What and the distance between determines them. gravity? • The larger the mass and the closer they are, the greater the gravity. What is inertia? What is Newton’s 1st Law of Motion? • The tendency of an object to resist changes in motion. • An object at rest will stay at rest and an object in motion will stay in motion at a constant speed unless acted on by a force. What is accretion? • The process of gradually building something up by gathering together smaller pieces. • By color/temperature, size, chemical composition and How are stars brightness. classified? • Temperature – Hottest is blue, coolest red. • Blue, blue white, yellowwhite, yellow, orange, red. • Size – giant or super giantneutron • A device that breaks light What is a into colors. Astronomers spectrograph use it to determine the ? elements found in stars. Brightness • Brightness depends on size and temperature. • Apparent brightness – the brightness of the star as seen from earth. • Absolute brightness – the brightness the star would have if it were a standard • A tool that astromomers use to break a star’s light What is a spectograph? down into a spectrum. • From this spectrum, we can tell many things about the star • Composition • Temperature • A spectograph allows you to see the emission lines. Are there different types of spectrums? • Absorption spectrum – The spectrum of a star. Because a star’s atmosphere absorbs colors of light instead of emitting them – there are black lines. Continuous spectrum – A spectrum that shows all the colors. What so you call the black lines present in an absorption spectrum? • Emission Lines – lines made when certain wavelengths of light , or colors, are given off by hot gases • Each element has it’s own set of emission lines – We call this the elements “fingerprint” • (see page 112) • It is really the HertzsprungWhat’s an H-R Russell diagram, and it is Diagram? used to show the relationship between the surface temperature and the absolute brightness of stars. • (see page 114) What is the Main Sequence? • It’s a diagonal area on the H-R diagram that includes more than 90% of all stars. • These stars are in the middle of their lives. • Our sun is a main sequence star. How does a star form? • Nebula – a huge cloud of gas and dust spread out over an enormous area. • A nebula with enough mass to become a star is called a protostar. • As accretion takes place and the atoms are squeezed together nuclear fusion takes place – a star is born! How long does a star live? • This depends on the mass of the star – the larger the star, the shorter the life span. • Stars need a continuous source of hydrogen to continue to burn. Once the hydrogen supply is used up the star will die. Smaller stars need less, therefore live longer. • When a star runs out of fuel – it either becomes a What white dwarf, a neutron happens star, or a supernova. when a star • Small to medium sized dies? stars like our sun will burn out leaving only the bluewhite core called a white dwarf. When the white dwarf stops glowing it will become a black dwarf. What happens when a high-mass star dies? When it begins to die, it expands into a supergiant. When the supergiant runs out of fuel, it explodes! This explosion is called a supernova. Some of the material may become neutron stars – even smaller and denser than white dwarfs – only the size of a city!! lol What is a pulsar? What is a black hole? –A spinning neutron star –When the most massive stars die, they become black holes – an object with gravity so strong that not even light can escape. Review Review