Stars, Galaxies, and Planets

What is a Star? Gigantic balls of very hot gases that give off electromagnetic radiation. The Sun is a star

The Sun The Sun gives off huge amounts of thermal (heat) energy, and light energy Energy comes from reactions with hydrogen and helium – When hydrogen atoms collide, they fuse together and make helium. This causes a huge amount of energy.

Brightness, Color, Temperature of Stars Brightest stars give off the most energy From Earth, a star’s size, distance, and temperature make stars look brighter or dimmer. Stars’ colors tell how bright they are – Red is coldest (4000 degrees F), orange and yellow are middle, and white or blue-white are hottest

Sun’s Layers Fiery ball of gas with no hard surfaces Photosphere: Innermost layer of the Sun, gives off light we see Chromosphere: Middle layer of the Sun Corona: Outermost layer of the Sun

Sun Spots Darks spots that move along the surface of the Sun. Part of the photosphere Look dark because not as hot as rest of Sun Indicate the Sun rotates more slowly at its poles than its equator 3bazto 3bazto

Solar Eruptions Prominences: Blazing gases that leap from the chromosphere to corona Solar Flare: Parts of the chromosphere erupt like a volcano. Causes temporary bright spot that may last for minutes or hours – Give off huge amounts of electromagnetic waves, protons, electrons – Can interrupt radio communication and cause damage to electrical systems.

Light-Year Light takes 8 minutes to reach Earth Light-year: The distance light travels in 1 year (about 9.4 trillion km) After the Sun, Alpha Centauri is the next closest and is 4 light-years away

Life of Stars Nebula: New stars formed in a cloud of gas and dust. Ways a star can die – 1. Uses up all its fuel – 2. Becomes a white dwarf, explodes and leaves behind a neutron star – 3. Becomes a black hole.

Supernova and Black hole Supernova: Giant explosion of a star Black hole: A point in space with such strong gravity that nothing within a certain distance can escape getting pulled in.

How Stars are Grouped Galaxy: A huge system of stars, dust, and gas held by gravity Types of galaxies – Spiral: ¾ of galaxies discovered. Look like pinwheels with bright bulging middles and wispy arms. Milky Way Galaxy – Elliptical: Round almost like a football. Largest galaxies – Irregular: No real shape. Young galaxies still forming

Constellation Constellation: A group of stars that form a pattern. People in the Northern and Southern Hemispheres see different constellations in the sky.