Branches of Earth Science Chapter 21: Stars Notes Astronomy: The study of planets, stars, and other objects in space. Lithosphere: the land masses of earth o Litho means rock Hydrosphere: waters of the earth o Hydro means water Atmosphere: The envelope of gases that surround the Earth as well as space and stars. Tools Used to Study Stars Spectroscope: Breaks light from a distant star into its characteristic colors o SPECTRUM: the band of colors that forms as light passes through a prism o Used to see if galaxies are moving away or toward the earth Telescopes: device that makes distant objects appear closer Types of Telescopes o Optical o Radio o X-Ray o U-V o Infrared Constellations Constellations: group of stars that formed patterns Different cultures gave different names to the constellations o Greeks named constellations according to myths Greek Orion Ancient Sumerian Sheep China Three Importance of Constellations o Navigation Sailors use Polaris (North Star) Important in space navigation o Used to predict weather Best Known Constellations o Big Bear or Ursa Major Has pointer stars to Polaris o Little Bear or Ursa Minor Characteristics of Stars What are stars like? o Stars are made up of mostly hydrogen o Stars produce energy through nuclear fusion.
There are 4 characteristics of starts that scientists use to Classify stars o Color & Temperature o Size o Composition o Brightness Color and Temperature o A stars color reveals its surface temperature The surface temperature is lower than the core temperature due to nuclear fusion. o Stars are very Patriotic when it comes to color Coldest Red White Hottest Blue Size o 5 Types or Categories o Smallest Neutron (16-20 km diameter) White dwarf (size of Earth) Medium Size (the sun) *MOST STARS * Giant (10-1000 x s the sun) o Largest Super Giant (1000 x the diameter of the sun) o Betelgeus o Rigel o Antares Composition (Chemical Makeup) o Most stars have the same general composition 73% Hydrogen Most Common 25% Helium 2 nd most common 2% Other Elements o Scientists use a spectroscope to identify characteristics Characteristic: Something that identifies an object Elements have Fingerprint color characteristics They have a unique set of lines in the spectrum Brightness (Also called Magnitude) o Depends on Temperature Size Distance o Apparent Brightness: the brightness of a star as it appears on Earth. o Absolute Magnitude: The amount of light the star actually gives off Measuring Distance to Stars Light Year- Astronomers use light years to measure the distances between stars
o A light year is the distance that light travels in one year 9,460,730,472,580.8 km 5,878,630,000,000 miles Parallax- the apparent change in the position of a star in the sky. o The change is due to the change in the Earth position as the Earth revolves around the sun. Hertzsprung-Russell Diagram: (H-R Diagram) It is a scatter plot Shows the relationship between absolute brightness and surface temperature This is the single most important diagram that astronomers use Uses o Classify Stars o Understand how stars change over time Bright Absolute Magnitude Dim Hottest Surface Temp Main sequence: the area where the most stars are located o Extends from the upper left corner to the lower right corner o 90% of stars are located here. Coolest Lifecycle of Stars Nebula (large cloud of gas and dust) forms protostar with gravity o Nuclear Fusion (atoms combine to form heavier atoms) o Lower Mass Stars
Giant Star: outer layer expands White Dwarf: extremely dense Black Dwarf: dead o Higher Mass Stars Super Giant: Fusion continues until iron is formed EXPLOSION: No more nuclear fusion Super Nova: star breaks apart o Neutron Star o BLACK HOLE Life Cycle of a Star Average Star Red Giant Planetary Nebula White Dwarf Stellar Nebula Neutron Star Massive Star Red Super Giant Supernova Black Hole Deaths of Stars: when a star begins to run out of fuel, its core shrinks and its outer portion expands o White Dwarf o Neutron Star o Black Hole Multiple Star Systems Multi Star System: Star system with one or more companion stars Most stars have companions but not all stars o The sun does not have a companion The sun is the closest star to the earth Example of multi star system: ALPHA CENTAURI: a three star system that is the CLOSEST star to the sun. Binary Stars: Star systems with two stars o Bi = 2 (remember bicycle) Eclipsing Binary Star System
Star Clusters o The larger companion blocks the smaller companion Star Clusters: large groupings of stars o Open Cluster Loose and disorganized appearance Contain few hundred to 1000 stars Young stars o Globular Cluster more common round, densely packed stars 100,000 to 1,000,000 stars older stars Galaxies Galaxy is a huge collection of stars bound by gravity o Contain various star groups Billions of galaxies in the universe 3 types of galaxies o Spiral o Elliptical o Irregular The Milky Way The galaxy we live in Spiral shaped Looks like a milky or whitish band in the sky Sun is located in one of the spiral arms It has 400 billion stars It takes the sun and planets over 200 million years to move around the center of the milky way Big Bang Theory Theory is an idea that is supported by evidence The universe began to expand with the explosion of concentrated matter and energy and has been expanding ever since