* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Ch 3 Sec 1 Tools of modern astronomy
History of Solar System formation and evolution hypotheses wikipedia , lookup
Aries (constellation) wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
Dialogue Concerning the Two Chief World Systems wikipedia , lookup
Space Interferometry Mission wikipedia , lookup
Spitzer Space Telescope wikipedia , lookup
Gamma-ray burst wikipedia , lookup
Outer space wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
Extraterrestrial life wikipedia , lookup
Corona Australis wikipedia , lookup
Cassiopeia (constellation) wikipedia , lookup
Perseus (constellation) wikipedia , lookup
Astrophotography wikipedia , lookup
Star catalogue wikipedia , lookup
Stellar classification wikipedia , lookup
Planetary system wikipedia , lookup
International Ultraviolet Explorer wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Planetary habitability wikipedia , lookup
Chronology of the universe wikipedia , lookup
Cygnus (constellation) wikipedia , lookup
Cosmic distance ladder wikipedia , lookup
Hubble Deep Field wikipedia , lookup
Stellar evolution wikipedia , lookup
Corvus (constellation) wikipedia , lookup
Stellar kinematics wikipedia , lookup
Star formation wikipedia , lookup
Ch 3 Sec 1 Tools of modern astronomy I. Constellations A. Stars that are in the same direction, and form the outline of a pattern B. May be very different distances from Earth II. Electromagnetic radiation A. Types of electromagnetic radiation 1. What you see is “visible light” 2. Electromagnetic radiation is energy traveling through space in the form of waves B. The electromagnetic spectrum 1. The distance between one wave and the next is the “wavelength” a) From as short as one millionth of a meter to as long as several meters 2. Light can be split into different colors, each with different wavelengths, called the spectrum a) Visible light spectrum is red, orange, yellow, green, blue, and violet 3. Electromagnetic spectrum, from longest to shortest, is radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. III. Telescopes A. Purpose is to collect and focus electromagnetic radiation, including visible light. B. Visible light telescopes 1. Refracting telescopes are straight through, usually with a convex lens at each end a) The length of the tube depends on the focal length of the objective lens 2. Reflecting telescopes use a mirror instead of an objective lens a) All the big telescopes now are reflecting C. Radio telescopes 1. Use radio waves the same way reflecting telescopes use visible light 2. The dish may be bigger than 3 football fields D. Other telescopes – there are instruments to capture all parts of the electromagnetic spectrum IV. V. Observatories A. Buildings housing one or more telescopes B. Visual light observatories are up on mountains 1. Atmosphere makes images blurry 2. City lights interfere with images C. Radio telescopes can be anywhere – light doesn’t matter to them Satellites A. Atmosphere blocks much UV, X-ray, & gamma ray radiation, so have to put telescopes above the atmosphere to study these parts of the electromagnetic spectrum B. Hubble Space Telescope uses a 2.4 m mirror 1. You’ve seen its images on NASA’s web site VI. Spectrographs A. Breaks light into a spectrum and records the colors. (“Spectrograph” means recording of the spectrum) B. Tells astronomers about chemical composition and temperature C. Chemical composition 1. Different elements absorb different parts of the spectrum 2. Where light is absorbed, there is a dark bar in the spectrum, so that element must be present in the star’s atmosphere D. Temperature 1. The strongest line for an element depends on temperature, so the presence or absence of a strong line tells something about temperature Ch. 3 Sec 2 Characteristics of stars I. Galaxies and universe E. A galaxy is a collection of stars – hundreds of billions of stars each F. There is lots of nearly empty space inside and between galaxies 1. Light takes 8 minutes to get here from the sun (so the sun is 8 light-minutes away) 2. Light from the nearest star takes 4.2 years (so distance is 4.2 light-years) 3. Light from the center of our galaxy takes 25,000 years to get here 4. Light from the next galaxy takes 2,000,000 years to get here G. The universe is all of space VII. Distances to stars A. Measured in “light-years” – how far light travels in one year (about 9,500,000,000,000,000 kilometers) VIII. Measuring distances to stars A. Astronomers use “parallax” to measure the distances B. Parallax is the apparent change in position of an object when looked at from two different places. C. Commonly done by measurements 6 months apart D. The further away, the smaller the parallax shift (the less it appears to move) E. Only good to about 1,000 light-years, before the shift gets too small to measure IX. Classifying stars A. Astronomers use size, temperature, and brightness to characterize stars B. Sizes range from supergiants, giants, medium (like our sun), to dwarves and neutron stars (20 km in diameter) C. Color tells you how hot a star is – cooler stars are red, middle are white, and hottest are blue-white D. Brightness depends on both size and temperature 1. A cool star won’t give off much light, but if it’s huge, will appear bright to us. 2. Apparent magnitude is how bright it appears from Earth a) Depends on how close it is to Earth b) A flashlight doesn’t change, but will look much brighter to you if it’s in your face than a block away 3. Absolute magnitude is how bright the star would be at a standard distance E. Hertzsprung-Russell diagrams 1. Graphs brightness against surface temperature a) Note that the X-axis is backwards – gets smaller as you go right. 2. 90% of all stars are main sequence, which line up diagonally on an H-R diagram Ch. 3 Sec 3 Lives of stars I. Pulsars are neutron stars which are pulsating radio sources X. Star is born A. The earliest stage starts with a bunch of gas and dust gathered together, called a nebula B. As gravity starts to pull the gas/dust together, it is called a protostar C. The star is born when the gas/dust becomes so compacted and hot that nuclear fusion starts XI. Lifetime of stars A. Depends on how massive the star is B. The more mass, the shorter its life. 1. Smallest 200 billion years; sun-sized 10 billion years; largest only 10 million 2. Smaller stars don’t burn up their fuel as rapidly XII. Deaths of stars A. As they die, all stars become red giants or supergiants 1. The core is being used up, so gravity is not strong enough to hold the outer part, so it expands. B. Small and medium stars lose the outer part (it drifts away eventually) leaving only a core about the size of Earth, called a white dwarf 1. Even though it is very small, the white dwarf still has about as much mass as the sun (meaning density is quite high) 2. When the leftover energy is gone, the light goes out and it is a black dwarf C. Giants and supergiants may explode, called a supernova – is millions of times brighter, for a short period 1. The outer layer drifts away and may form a new nebula, and eventually be part of a new star 2. What’s left is smaller and denser than a dwarf. It’s called a neutron star. May be 3X as massive as our sum, but only 20 km across D. The biggest stars, more than 40X the sun, leave behind a black hole 1. There is no hole – it just looks like one 2. The star is so massive that its gravity is extremely high and nothing, not even light, can escape the gravity. 3. Commonly detected by finding X-rays emitted from gas being sucked into a black hole a) Also, can measure its effect on a nearby star E. Quasars are extremely bright but extremely far away. Astronomers think they are galaxies with huge black holes in the center, which are sucking in huge amounts of space gas. Ch. 3 Sec 4 Star systems and galaxies I. Star systems and planets A. More than 1/2 of all stars are in star systems – groups of 2 or more stars 1. Systems with 2 stars are binary stars a) A dark star may show itself by passing in front of the brighter star – called an eclipsing binary b) Or, the brighter star may appear to wobble, as the 2 stars pull on each other 2. Planets have been found around other stars a) Same techniques as used for binary star systems b) Means that can’t find planets as small as Earth – ones found so far are at least 1/2 the size of Jupiter XIII. Galaxies A. Milky Way looks milky because the stars are too close together to been seen individually 1. Our sun is far out on one arm of the Milky Way B. Spiral galaxies are relatively flat, with arms going out like pinwheels 1. These have lots of gas and dust in the center, so they are still making new stars C. Elliptical galaxies look like flattened balls 1. There is little gas and dust, so no new stars – only old stars D. Irregular galaxies are those with no regular shape Ch. 3 Sec 5 History of the universe I. Moving galaxies A. They are all moving. A few close ones are coming closer, but most moving away from us B. The further out a galaxy is, the faster it is moving away from us 1. Means that the universe is expanding II. Big bang theory A. If you could run time backwards, galaxies would all be moving closer together, until they were all at a single point. B. The explosion that started the outward motion happened about 10-15 million years ago 1. Knowing how fast it is expanding allows you to calculate how long it has been expanding III. Formation of the solar system A. About 5 billion years ago, a nebula started to collapse to form the solar system B. Started forming a spinning disk C. Gas in the center condensed into the sun D. Other bits of gas and dust gathered into the planets E. The inner planets lost their gases to the sun’s gravitational pull IV. Future of the universe A. Could continue to expand until the stars all use up their fuel and the universe goes dark and cold. B. Another possibility is that gravity will eventually stop the expansion and start sucking everything back to the center – could be the “big crunch”, the opposite of and beginning of the big bang C. Which will happen depends on how much matter there is in the universe (because more mass means more gravity), so astronomers are looking for dark matter between stars systems. They are finding quite a bit of it.