Stars, Galaxies, Stars, Galaxies, and Constellationsand Constellations

StarsStars Stars are born when Stars are born when

there is a large there is a large amount of gas and amount of gas and dust in a small area dust in a small area that becomes so hot that becomes so hot that nuclear fusion that nuclear fusion starts.starts.

The gas continues to The gas continues to burn until it runs out.burn until it runs out.

More burning gas = a More burning gas = a bigger and brighter bigger and brighter star!star!

Our Sun is a Our Sun is a starstar and is the largest and is the largest object in our object in our solar systemsolar system. It is the . It is the

onlyonly star in our solar systemstar in our solar system

Our SunOur Sun

Billions of years ago, things may have been differentBillions of years ago, things may have been different The Sun was cooler (by up to 30%!)The Sun was cooler (by up to 30%!) Earth’s atmosphere was different (thicker, carbon dioxide)Earth’s atmosphere was different (thicker, carbon dioxide)

Conditions will be different in the futureConditions will be different in the future By many accounts, increases in the Sun’s temperature will make Earth By many accounts, increases in the Sun’s temperature will make Earth

uninhabitable in 1 billion years or lessuninhabitable in 1 billion years or less

Our SunOur Sun

The Sun will spend most of its life in the The Sun will spend most of its life in the main sequence. main sequence.

It will expand into a red giantIt will expand into a red giant In about 5 billion years, it will turn into a In about 5 billion years, it will turn into a

white dwarf. white dwarf.

The Sun compared to other stars in The Sun compared to other stars in our galaxy…our galaxy…

And yet larger stars…And yet larger stars…

Temperature of a StarTemperature of a Star

3,000° – 6,000° Fahrenheit (1,649° – 3,316° Celsius): Red3,000° – 6,000° Fahrenheit (1,649° – 3,316° Celsius): Red 6,000° – 8,500° F (3,316° – 4,704° Celsius): Orange6,000° – 8,500° F (3,316° – 4,704° Celsius): Orange 8,500° - 10,500° F (4,704° – 5,816° Celsius): Yellow/ White 8,500° - 10,500° F (4,704° – 5,816° Celsius): Yellow/ White 10,500° – 13,000° F(5,816° – 7,204° Celsius): Type F -White 10,500° – 13,000° F(5,816° – 7,204° Celsius): Type F -White 13,000° - 17,500° F(7,204° – 9,704° Celsius): Type A -White13,000° - 17,500° F(7,204° – 9,704° Celsius): Type A -White 17,500° – 50,000° F (9,704° – 27,760° Celsius): Blue -White17,500° – 50,000° F (9,704° – 27,760° Celsius): Blue -White 50,000° - 100,000° F (27,760° – 55,538° Celsius): Blue50,000° - 100,000° F (27,760° – 55,538° Celsius): Blue

What is a Galaxy?What is a Galaxy?

A large group of stars outside of our own Milky A large group of stars outside of our own Milky WayWay

Made of billions to trillions of starsMade of billions to trillions of stars Also may have gas and dust Also may have gas and dust

Spiral, or elliptical, or irregular shapedSpiral, or elliptical, or irregular shaped

Types of GalaxiesTypes of GalaxiesSpiral GalaxiesSpiral Galaxies Have arms of stars, gas Have arms of stars, gas

and dust that curve away and dust that curve away from the center of the from the center of the galaxy in a spiral form.galaxy in a spiral form.

There is a central disk of There is a central disk of older stars at the center.older stars at the center.

The youngest stars are The youngest stars are on the outer armson the outer arms

There is a lot of dust and There is a lot of dust and gasgas

The Milky Way GalaxyThe Milky Way Galaxy We live in the Milky Way galaxy.We live in the Milky Way galaxy. The Milky Way is a spiral galaxy.The Milky Way is a spiral galaxy. It has about 200 billion stars, and

lots of gas and dust. All the stars in the Milky Way All the stars in the Milky Way

have their own motion, some have their own motion, some are moving towards the sun are moving towards the sun while others are moving away while others are moving away from our sun.from our sun.

Our Sun is halfway to the edge of an arm, revolving at half a million miles per hour around the center of the galaxy

The Milky Way GalaxyThe Milky Way Galaxy The Milky Way has a The Milky Way has a

diameter of about diameter of about 100,000 light years.100,000 light years.

The nucleus is 2000 light The nucleus is 2000 light years thick.years thick.

Our sun is located Our sun is located 30,000 light years from 30,000 light years from the nucleus.the nucleus.

It takes the sun 200 It takes the sun 200 million years to make million years to make one Revolution around one Revolution around the center.the center.

The Milky Way GalaxyThe Milky Way Galaxy You can look outside on You can look outside on

a clear dark night and a clear dark night and see the Milky Way!!!see the Milky Way!!!

In the night sky it will In the night sky it will appear as a band of appear as a band of stars that stretches stars that stretches across the sky.across the sky.

It will appear “milky” in It will appear “milky” in the sky.the sky.

You are actually looking You are actually looking at one of the arms of the at one of the arms of the galaxy!galaxy!

Types of GalaxiesTypes of Galaxies

Elliptical GalaxiesElliptical Galaxies Elliptical galaxies contain Elliptical galaxies contain

many older stars, up to many older stars, up to one trillion, but little dust one trillion, but little dust and gas.and gas.

They are typically larger They are typically larger galaxies.galaxies.

There are no young There are no young stars.stars.

Types of GalaxiesTypes of Galaxies

Irregular GalaxiesIrregular Galaxies They lack shapeThey lack shape They are the smallest They are the smallest

galaxies with the fewest galaxies with the fewest stars.stars.

Could be formed from Could be formed from the collision of two the collision of two different galaxies.different galaxies.

Stars are of low mass Stars are of low mass and cannot organize into and cannot organize into a patterna pattern

The next closest galaxy to us is The next closest galaxy to us is Andromeda, which is also a spiral Andromeda, which is also a spiral galaxy. Andromeda is about 2.5 galaxy. Andromeda is about 2.5

million light years away.million light years away.

There are an estimated50 billion to 1 trillion galaxies in the known universe!

What is a Nebula?What is a Nebula?

A cloud in spaceA cloud in space Made of gas and dust Made of gas and dust

Can have stars inside

Most of the ones we see are inside our Milky Most of the ones we see are inside our Milky Way GalaxyWay Galaxy

Young stars form Young stars form

in nebulaein nebulae

WHAT ELSE IS IN A GALAXY?WHAT ELSE IS IN A GALAXY?The Nebula’s comethThe Nebula’s cometh

Galaxies also contain Galaxies also contain gases and dust.gases and dust.

There are two bright There are two bright nebulas.nebulas.

One glows bright from the One glows bright from the hot gases within.hot gases within.

The other shines by The other shines by reflecting light from reflecting light from nearby stars.nearby stars.

THE DARK SIDE OF THE NEBULA.THE DARK SIDE OF THE NEBULA.The dark nebula.The dark nebula.

Other nebula’s are dark in Other nebula’s are dark in nature.nature.

Dark nebulas are visible as Dark nebulas are visible as dark areas among the stars.dark areas among the stars.

Dark nebulas absorb light of Dark nebulas absorb light of more distant stars behind more distant stars behind them.them.

The Horsehead Nebula is an The Horsehead Nebula is an example of a dark nebula.example of a dark nebula.

Leftovers from an ExplosionLeftovers from an Explosion

Supernova- A Massive Star ExplodesSupernova- A Massive Star Explodes

Neutron Star or PulsarNeutron Star or PulsarA neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star

Black HolesBlack Holes•A black hole is a region of spacetime from which nothing, not even light, can escape.•Black holes of stellar mass are expected to form when very massive stars collapse at the end of their life cycle. •After a black hole has formed it can continue to grow by absorbing mass from its surroundings.•There is general consensus that supermassive black holes exist in the centers of most galaxies

Light YearsLight Years

What is a Light Year?What is a Light Year? A light year is the distance light travels in a year. Light moves at A light year is the distance light travels in a year. Light moves at

a velocity of about 300,000 kilometers (km) each second; how a velocity of about 300,000 kilometers (km) each second; how far would it move in a year?far would it move in a year?

About 10 trillion km (or about 6 trillion miles).About 10 trillion km (or about 6 trillion miles).

ParallaxParallax

ParallaxParallax is a difference in the apparent is a difference in the apparent position of an object viewed along two position of an object viewed along two different lines of sight.different lines of sight.[[

Astronomers use the principle of parallax Astronomers use the principle of parallax to measure distances to celestial objects to measure distances to celestial objects including to the Moon, the Sun, and to including to the Moon, the Sun, and to stars beyond the Solar System. stars beyond the Solar System.

Binary Star SystemsBinary Star Systems

A pair of stars that revolve around A pair of stars that revolve around each other.each other.

Multiple star systems-Multiple star systems- have more have more than two stars. Two will orbit rapidly than two stars. Two will orbit rapidly around one another while a third will around one another while a third will move slowly at a greater distance move slowly at a greater distance away.away.

ConstellationsConstellations

All the stars that we All the stars that we can see from Earth can see from Earth are in our galaxy.are in our galaxy.

Constellations are Constellations are patterns of stars in patterns of stars in the sky.the sky.

Ancient Greeks and Romans saw pictures Ancient Greeks and Romans saw pictures in the stars of the night sky.in the stars of the night sky.

These pictures were later associated with These pictures were later associated with myths.myths.

Astronomers recognize 88 Astronomers recognize 88 constellations including…constellations including…

14 men and women14 men and women 9 birds9 birds 2 insects2 insects 19 land animals19 land animals 10 water creatures10 water creatures 2 centaurs2 centaurs

A serpentA serpent A dragonA dragon A flying horseA flying horse A riverA river 1 head of hair1 head of hair 29 inanimate 29 inanimate

objectsobjects

Example: ScorpiusExample: Scorpius The scorpion is believed The scorpion is believed

to be responsible for the to be responsible for the death of the great hunter, death of the great hunter, Orion.Orion.

Orion was stung and Orion was stung and killed after he was killed after he was boasting that he could boasting that he could defeat any beast.defeat any beast.

Scorpius was placed in Scorpius was placed in the sky opposite from the sky opposite from Orion to avoid any further Orion to avoid any further contact.contact.

Stars as Tools for Stars as Tools for NavigationNavigation

Earth rotates on its Earth rotates on its axis, this makes axis, this makes most constellations most constellations appear to rise in appear to rise in the east and set in the east and set in the west during the the west during the night.night.

There is a group of There is a group of stars that appear in stars that appear in the sky all night long the sky all night long and all year long. It and all year long. It seems that these stars seems that these stars do not rise and set, but do not rise and set, but circle the Earth’s north circle the Earth’s north pole each night. pole each night. These stars are called These stars are called circumpolar.circumpolar.

Stars as Tools for Stars as Tools for NavigationNavigation

The North Star is called The North Star is called Polaris and located Polaris and located directly above the North directly above the North Pole. This star appears Pole. This star appears in the same place every in the same place every night all year long.night all year long.

In the Northern In the Northern Hemisphere, if you find Hemisphere, if you find Polaris you will be able to Polaris you will be able to tell which direction is tell which direction is north.north.

The Southern The Southern Hemisphere does not Hemisphere does not have a star to help you have a star to help you find its pole. In stead it find its pole. In stead it has what is known as the has what is known as the Southern Cross.Southern Cross.

The Southern Cross The Southern Cross consists of 4 bright stars consists of 4 bright stars and some dimmer ones. and some dimmer ones. All of these together point All of these together point to the south pole.to the south pole.

Extra Info.Extra Info.

The brightest constellation is Crux The brightest constellation is Crux (the Southern Cross). The (the Southern Cross). The constellation with the greatest constellation with the greatest number of visible stars in it is number of visible stars in it is Centaurus (the Centaur - with 101 Centaurus (the Centaur - with 101 stars). The largest constellation is stars). The largest constellation is Hydra (The Water Snake) which Hydra (The Water Snake) which extends over 3.158% of the sky. extends over 3.158% of the sky.