Light Year l This is a DISTANCE not

Light Year l. This is a DISTANCE not an amount of TIME l. EX: 3 Miles is a distance, 3 Years is a time l. Used to represent extremely LARGE distance in space l. Remember, Light is a Transverse Wave – and all waves travel, they don’t just appear

So how far is it? l This distance is very large – it’s hard for the mind to understand how far this is l Speed of Light = 300, 000 km/sec l That’s about 18, 000 km/min

So how far is it? l Speed of light is about 186, 000 miles/sec l That is about 671, 000, 000 miles per hour (671 Trillion mph)

So how far is it? l Now that you know how fast light travels it time think about distance l If we look at how far light would travel for ONE full year – that distance is a Light Year!

One Full Year l The total distance light travels in one full year is about: 9, 460, 000, 000 km (9. 46 trillion km) l In terms of miles that is about: 5, 800, 000, 000 miles (5. 80 trillion miles)

An example close to home… l So how far is that distance of a light year… really. l 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? l 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 l All physical matter and energy that exist in space: l Planets l Stars l Galaxies l All the contents of intergalactic space

A Planet l Most scientist agree that a planet: l Orbits a star – such as the Sun l Is round - due to the strength of its own gravitational pull

Galaxies l NOT single stars – includes: Stars, Gas, and Dust l. Variety of shapes, sizes, and colors l. Clustered in Groups l. Gravitationally attracted/held together

Galaxies l. Milky Way = part of Local Group l 5 million light years across l. In 1999 HST est. 125 billion galaxies; HST found 3, 000 visible galaxies in space (Hubble Space Telescope)

Galaxies Spiral = Milky Way l Stars form “arms”, curve out from center, disk or pancake shaped l Holds old & young stars, gas, & dust http: //www. hdwallpapers. com/photo/Space_pictures/Spiral_Galaxy_M 81

Galaxies Elliptical l Stars form shape like a football http: //www. astronet. ru/db/xware/msg/1226180

Galaxies Irregular l No special shape = blobs w/threads l Holds large amount of gas and dust http: //apod. nasa. gov/apod/ap 081229. html

Stars Large ball of gas that creates & emits own radiation l Variety of shapes, sizes, and colors l Nebula, Main Sequence, Red & Super Giants, White Dwarf, Brown Dwarf, & Supernova l UM = Magnitude = degree of brightness Lifecycle – NO star lives forever l 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/Astr 110. Fall 2006/de. La nge. html A Star is born l Protostar – critical temperature is reached – hydrogen begins fusing into helium http: //photojournal. jpl. nasa. gov/

Once a star is born it becomes a l Main Sequence Star – shines as nuclear reactions inside produce light and heat l But if it doesn’t have enough mass to produce radiant heat it becomes a Brown Dwarf http: //www. for 68. com/new/2005/12/su 86402129331912150024200 -0. htm 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 l Star of greater mass Expands, cools, & turns red http: //apod. nasa. gov/apod/ap 001222. 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/Fox 8 -2007. htm Black Hole – core collapses completely & vanishes http: //www. nasa. gov/mission_pages/chandra/multimedia/photo 09 -078. html

If a Star becomes a Red Giant, then Red Giant – star of Planetary Nebula – less mass expands, glows red as it cools, then http: //smithsonianscience. org/2010/03/archaeological-%E 2%80%9 Cdig%E 2%80%9 D-in-outerspace-uncovers-an-ancient-star/ 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 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_l 1/dwarfs. html

Cooling White 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