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

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

So how far is it? Speed of light is about 186,000 miles/sec Speed of light is about 186,000 miles/sec That is about 671,000,000,000,000 miles per hour (671 Trillion mph) 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 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! 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) 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) 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. 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? 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! 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: All physical matter and energy that exist in space: Planets Planets Stars Stars Galaxies Galaxies All the contents of intergalactic space All the contents of intergalactic space

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

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

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

Galaxies Spiral = Milky Way Stars form “arms”, curve out from center, disk or pancake shaped Stars form “arms”, curve out from center, disk or pancake shaped Holds old & young stars, gas, & dust Holds old & young stars, gas, & dust

Galaxies Elliptical Stars form shape like a football Stars form shape like a football

Galaxies Irregular No special shape = blobs w/threads No special shape = blobs w/threads Holds large amount of gas and dust Holds large amount of gas and dust

Stars Large ball of gas that creates & emits its own radiation Variety of shapes, sizes, and colors Variety of shapes, sizes, and colors Nebula, Main Sequence, Red & Super Giants, White Dwarf, Brown Dwarf, & Supernova Nebula, Main Sequence, Red & Super Giants, White Dwarf, Brown Dwarf, & Supernova UM = M agnitude = degree of brightness UM = M agnitude = 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 nge.html A Star is born Protostar – critical temperature is reached – hydrogen begins fusing into helium Protostar – critical temperature is reached – hydrogen begins fusing into helium

Once a star is born it becomes a Main Sequence Star – shines as nuclear reactions inside produce light and heat Main Sequence Star – shines as nuclear reactions inside produce light and heat But if it doesn’t have enough mass to produce radiant heat it becomes a Brown Dwarf But if it doesn’t have enough mass to produce radiant heat it becomes a Brown Dwarf

At this point Stars can become a Super Giant or Red Giant Super Giant Star of greater mass Expands, cools, & turns red Star of greater mass Expands, cools, & turns red Super Giant EXPLODES blasting away outer layers becoming a Super Nova

Supernova can become either: Neutron Star – core collapses & becomes very dense Black Hole – core collapses completely & vanishes

If a Star becomes a Red Giant, then Red Giant – star of less mass expands, glows red as it cools, then Planetary Nebula – outer layer of gas puff off; hot core will be white dwarf space-uncovers-an-ancient-star/

Red Giant =Planetary Nebula = White Dwarf = White Dwarf Cooling White Dwarf – very dense, almost transparent White Dwarf Cooling – takes billions of years to cool then fades to black

Cooling White Dwarf = Black Dwarf Black Dwarf - A non-radiating ball of gas; star stops glowing