Chp 7 Astronomy Study Guide Constellations Patterns of

Chp. 7: Astronomy Study Guide

Constellations �Patterns of stars in the sky. �Ex. The Big Dipper

Astronomical Unit �Used to measure distances within our solar system. �Ex. The distance between Earth and the Sun

Light-Year �Used to measure large distances in our galaxy and universe. �Measured as the distance light travels in 1 year.

Apparent Magnitude �The measure of the amount of light or brightest of an object in space from here on Earth. �Ex. The apparent magnitude of our Sun is brighter than the star Sirius when looking at them from Earth.

Absolute Magnitude or Luminosity �The measure of the true brightness of light given off by an object in space. �Ex. The true brightness of Sirius is much brighter than the Sun.

Parallax � The apparent shift in position when viewed from two points. � This is another way to measure distances of objects in space. � Uses trigonometry and formulas to measure distances.

Electromagnetic Spectrum � The ES shows wavelengths of various waves ranging from radio to gamma rays. � The spectrum starts with longer, less frequent wavelength with low energy, and ends with shorter, high frequency wavelength with high energy. � Ex. As the wavelength of light increases, then it’s energy also increases.

Doppler Shift �The Doppler Shift is the shift of different wave lengths of light based on whether an object in space is moving towards you or away from you. �As light from an object moves away from you, its wavelength stretches out and shifts to the red end of the visual light portion of the Electromagnetic Spectrum. �The more distant a galaxy is, the faster it moves away from Earth, and is more redshifted.

Characteristics of the Sun �Sunspots are cooler areas on the Sun’s surface. �Solar Wind occurs when charged particles stream away from the sun. �Solar Flares are sudden increases in brightness of parts of the Sun that can last for minutes to hours.

Color and Temperature of Stars �The coolest stars in space are red. �The hottest stars in space are blue. �The order of the color of stars in regards to temperature from hottest to coolest are blue, yellow, orange, red.

Binary Star Systems �The most common star system where two stars orbit each other. �Astronomers can determine a star’s mass by studying binary star orbits. �The Sun is not in a binary system because the next closest star is 4. 2 light-years away.

Hertzsprung-Russell Diagram �A graph that plots luminosity (brightness) on the y-axis and temperature on the x-axis. � Most stars fall within the Main Sequence running diagonal on the graph. Our Sun is in the middle of the Main Sequence. � Super giants are very bright but cooler stars, while white dwarfs are not as bright but much hotter. � Also, the x-axis (temperature) is backwards compared to most graphs. It starts with the hottest temperatures and goes down to the cooler temperatures.

Hertzsprung-Russell Diagram Cont.

Star Cycle �All stars form in a large cloud of gas and dust called a nebula. After this the cycle changes based on the mass of the star. A massive star will begin as a Protostar after the nebula. �At the end of an average star’s life it becomes a planetary nebulae and condenses into a white dwarf. �At the end of a massive star’s life it becomes a supernova and either becomes a neutron star or a black hole based on how the supernova explodes/implodes.

Star Cycle Cont.

Black Holes �A region in space that is so dense that nothing, including light, can escape its gravity field.

Galaxies �Galaxies are groups of stars, gas, and dust held together by gravity. �There are 3 kind of galaxies: spiral, elliptical, and irregular.

Spiral Galaxy �A black hole is located at the center of spiral galaxies. �Earth is located in the disc of the Milky Way galaxy. The Milky Way is a spiral galaxy. �The Milky Way is part of a cluster of galaxies called a local group. It’s also 100, 000 light-years across and has about 200 billion stars.

Elliptical Galaxy �Elliptical galaxies are similar to a football shape. �These galaxies usually have a higher number of old red stars. �They also contain little or no gas and dust.

Irregular Galaxy �Irregular galaxies are oddly shaped. �Many form from the gravitational pull of a nearby galaxy. �They also contain many young stars.

Big Bang Theory �The Big Bang Theory states that between 15 and 20 billion years ago, the universe began expanding out of an enormous explosion.