Stars, Galaxies, and Constellations

1
Stars, Galaxies, and Constellations
2
Stars

• Stars are born when there is a large amount of
  gas and dust in a small area that becomes so hot
  that nuclear fusion starts.
• The gas continues to burn until it runs out.
• More burning gas a bigger and brighter star!

3

• Our Sun is a star and is the largest object in
  our solar system. It is the only star in our
  solar system

4
Our Sun

• Billions of years ago, things may have been
  different
• The Sun was cooler (by up to 30!)
• Earths atmosphere was different (thicker, carbon
  dioxide)
• Conditions will be different in the future
• By many accounts, increases in the Suns
  temperature will make Earth uninhabitable in 1
  billion years or less

5
Our Sun

• The Sun will spend most of its life in the main
  sequence.
• It will expand into a red giant
• In about 5 billion years, it will turn into a
  white dwarf.

6
The Sun compared to other stars in our galaxy
7
And yet larger stars
8
Temperature of a Star

• 3,000 6,000 Fahrenheit (1,649 3,316
  Celsius) Red
• 6,000 8,500 F (3,316 4,704 Celsius)
  Orange
• 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
• 13,000 - 17,500 F(7,204 9,704 Celsius)
  Type A -White
• 17,500 50,000 F (9,704 27,760 Celsius)
  Blue -White
• 50,000 - 100,000 F (27,760 55,538 Celsius)
  Blue

9
What is a Galaxy?

• A large group of stars outside of our own Milky
  Way
• Made of billions to trillions of stars
• Also may have gas and dust
• Spiral, or elliptical, or irregular shaped

10
Types of Galaxies

• Spiral Galaxies
• Have arms of stars, gas and dust that curve away
  from the center of the galaxy in a spiral form.
• There is a central disk of older stars at the
  center.
• The youngest stars are on the outer arms
• There is a lot of dust and gas

11
The Milky Way Galaxy

• We live in the Milky Way 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 have their own
  motion, some are moving towards the sun while
  others are moving away 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

12
The Milky Way Galaxy

• The Milky Way has a diameter of about 100,000
  light years.
• The nucleus is 2000 light years thick.
• Our sun is located 30,000 light years from the
  nucleus.
• It takes the sun 200 million years to make one
  Revolution around the center.

13
The Milky Way Galaxy

• You can look outside on a clear dark night and
  see the Milky Way!!!
• In the night sky it will appear as a band of
  stars that stretches across the sky.
• It will appear milky in the sky.
• You are actually looking at one of the arms of
  the galaxy!

14
Types of Galaxies

• Elliptical Galaxies
• Elliptical galaxies contain many older stars, up
  to one trillion, but little dust and gas.
• They are typically larger galaxies.
• There are no young stars.

15
Types of Galaxies

• Irregular Galaxies
• They lack shape
• They are the smallest galaxies with the fewest
  stars.
• Could be formed from the collision of two
  different galaxies.
• Stars are of low mass and cannot organize into a
  pattern

16
The next closest galaxy to us is Andromeda,
which is also a spiral galaxy. Andromeda is about
2.5 million light years away.
There are an estimated 50 billion to 1 trillion
galaxies in the known universe!
17
What is a Nebula?

• A cloud in space
• Made of gas and dust
• Can have stars inside
• Most of the ones we see are inside our Milky Way
  Galaxy
• Young stars form
• in nebulae

18
WHAT ELSE IS IN A GALAXY?The Nebulas cometh

• Galaxies also contain gases and dust.
• There are two bright nebulas.
• One glows bright from the hot gases within.
• The other shines by reflecting light from nearby
  stars.

19
THE DARK SIDE OF THE NEBULA.The dark nebula.

• Other nebulas are dark in nature.
• Dark nebulas are visible as dark areas among the
  stars.
• Dark nebulas absorb light of more distant stars
  behind them.
• The Horsehead Nebula is an example of a dark
  nebula.

20
(No Transcript)
21
Leftovers from an Explosion

• Supernova- A Massive Star Explodes

22
Neutron Star or Pulsar
A neutron star is a type of stellar remnant that
can result from the gravitational collapse of a
massive star
23
Black 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

24
Light Years

• What is a Light Year?
• 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 far would it
  move in a year?
• About 10 trillion km (or about 6 trillion miles).

25
Parallax

• Parallax is a difference in the apparent position
  of an object viewed along two different lines of
  sight.
• Astronomers use the principle of parallax to
  measure distances to celestial objects including
  to the Moon, the Sun, and to stars beyond the
  Solar System.

26
Binary Star Systems

• A pair of stars that revolve around each other.
• Multiple star systems- have more than two stars.
  Two will orbit rapidly around one another while a
  third will move slowly at a greater distance
  away.

27
Constellations

• All the stars that we can see from Earth are in
  our galaxy.
• Constellations are patterns of stars in the sky.

28

• Ancient Greeks and Romans saw pictures in the
  stars of the night sky.
• These pictures were later associated with myths.

29
Astronomers recognize 88 constellations including

• 14 men and women
• 9 birds
• 2 insects
• 19 land animals
• 10 water creatures
• 2 centaurs

• A serpent
• A dragon
• A flying horse
• A river
• 1 head of hair
• 29 inanimate objects

30
Example Scorpius

• The scorpion is believed to be responsible for
  the death of the great hunter, Orion.
• Orion was stung and killed after he was boasting
  that he could defeat any beast.
• Scorpius was placed in the sky opposite from
  Orion to avoid any further contact.

31
Stars as Tools for Navigation

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

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

32
Stars as Tools for Navigation

• The North Star is called Polaris and located
  directly above the North Pole. This star appears
  in the same place every night all year long.
• In the Northern Hemisphere, if you find Polaris
  you will be able to tell which direction is north.

• The Southern Hemisphere does not have a star to
  help you find its pole. In stead it has what is
  known as the Southern Cross.
• The Southern Cross consists of 4 bright stars and
  some dimmer ones. All of these together point to
  the south pole.

33
Extra Info.

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