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Light Year This is a DISTANCE not an amount of TIME EX: 3 Miles is a distance, 3 Years is a time Used to represent extremely LARGE distance in space Remember, Light is a Transverse Wave – and all waves travel, they don’t just appear So how far is it? distance is very large – it’s hard for the mind to understand how far this is Speed of Light = 300,000 km/sec That’s about 18,000,000 km/min This So how far is it? Speed of light is about 186,000 miles/sec That is about 671,000,000,000,000 miles per hour (671 Trillion mph) So how far is it? Now that you know how fast light travels it time think about distance If we look at how far light would travel for ONE full year – that distance is a Light Year! One Full Year The total distance light travels in one full year is about: 9,460,000,000,000 km (9.46 trillion km) In terms of miles that is about: 5,800,000,000,000 miles (5.80 trillion miles) An example close to home… So how far is that distance of a light year… really. EX: it is about 370,000 km from the Earth to the Moon. If you could walk from the Earth to the Moon, how many times would you have to go that distance to equal a light year? ANSWER: about 12 MILLION times back and forth from the Earth to the Moon! The Universe: Galaxies, Stars, and Nebulae March 3, 2011 The Universe All physical matter and energy that exist in space: Planets Stars Galaxies All the contents of intergalactic space A Planet Most scientist agree that a planet: a star – such as the Sun Is round - due to the strength of its own gravitational pull Orbits Galaxies single stars – includes: Stars, Gas, and Dust Variety of shapes, sizes, and colors Clustered in Groups Gravitationally attracted/held together NOT Galaxies Milky Way = part of Local Group 5 million light years across In 1999 HST est. 125 billion galaxies; HST found 3,000 visible galaxies in space (Hubble Space Telescope) Galaxies Spiral = Milky Way Stars form “arms”, curve out from center, disk or pancake shaped Holds old & young stars, gas, & dust http://www.hdwallpapers.com/photo/Space_pictures/Spiral_Galaxy_M81 Galaxies Elliptical Stars form shape like a football http://www.astronet.ru/db/xware/msg/1226180 Galaxies Irregular No special shape = blobs w/threads Holds large amount of gas and dust http://apod.nasa.gov/apod/ap081229.html Stars Large ball of gas that creates & emits its own radiation Variety of shapes, sizes, and colors Nebula, Main Sequence, Red & Super Giants, White Dwarf, Brown Dwarf, & Supernova UM = Magnitude = degree of brightness Lifecycle – NO star lives forever Born, Matures, Grows old, & Dies Nebula – dense region inside begins to shrink, warm up, becomes a protostar http://www.calvin.edu/academic/phys/observatory/images/Astr110.Fall2006/deLa nge.html A Star is born Protostar – critical temperature is reached – hydrogen begins fusing into helium http://photojournal.jpl.nasa.gov/ Once a star is born it becomes a Main Sequence Star – shines as nuclear reactions inside produce light and heat http://www.for68.com/new/2005/12/su86402129331912150024200-0.htm But if it doesn’t have enough mass to produce radiant heat it becomes a Brown Dwarf http://dsc.discovery.com/news/2009/04/20/brown-dwarf-cool.html At this point Stars can become a Super Giant or Red Giant Super Giant Star of greater mass Expands, cools, & turns red http://apod.nasa.gov/apod/ap001222.html Super Giant EXPLODES blasting away outer layers becoming a Super Nova http://news.discovery.com/space/beautiful-supernova-violence.html Supernova can become either: Neutron Star – core collapses & becomes very dense http://www.science.psu.edu/news-and-events/2007-news/Fox8-2007.htm Black Hole – core collapses completely & vanishes http://www.nasa.gov/mission_pages/chandra/multimedia/photo09-078.html If a Star becomes a Red Giant, then Red Giant – star of less mass expands, glows red as it cools, then http://smithsonianscience.org/2010/03/archaeological-%E2%80%9Cdig%E2%80%9D-in-outerspace-uncovers-an-ancient-star/ Planetary Nebula – outer layer of gas puff off; hot core will be white dwarf http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-astro-nebula.html Red Giant =Planetary Nebula = White Dwarf = White Dwarf Cooling White Dwarf – very dense, almost transparent http://www.jpl.nasa.gov/news/features.cfm?feature=576 White Dwarf Cooling – takes billions of years to cool then fades to black http://imagine.gsfc.nasa.gov/docs/science/know_l1/dwarfs.html Cooling White Dwarf = Black Dwarf Black Dwarf - A non-radiating ball of gas; star stops glowing http://news.discovery.com/space/intermediate-black-hole-implicated-in-stars-death.html