Average Star (Low Mass Star) Sun

Science.8
Hubble Space Pictures / Name ______
Date ______
Essential Questions
1. How do stars change over time?
2. How are stars classified on a Herztsprung-Russell Diagram? / Vocabulary
stars, galaxy, nebulae, red giant, white dwarfs, neutron stars, black holes, supernova, magnitude / Objectives
1. Describe objects in space such as stars (in all life stages) and galaxies.
2. Describe the life cycle of a star and correlate a star’s life stage to its placement on the HR-Diagram.

Stellar

Nebula

http://windows2universe.org/cool_stuff/tourstars_25.html

Average Star (Low Mass Star) Sun

http://images.mirror.co.uk/upl/m4/may2009/1/2/space-shuttle-atlantis-pic-nasa-image-1-312212999.jpg

A star's life begins when nuclear reactions start deep in the core. Hydrogen nuclei are fused to form a helium nucleus. Each helium nucleus has slightly less mass than the hydrogen nuclei that formed it. The missing mass is converted into energy. This energy released in the core creates high temperatures and pressures. The high internal pressure would blow the star apart if not for the weight of the outer layers pressing down upon the core.

The star spends almost all of its life on the main sequence as a very average star.

http://windows2universe.org/cool_stuff/tourstars_25.html

Red Giant (Arcturus)

http://maxatma.com/wp-content/uploads/2010/07/Arcturus_rel_size782.jpg

http://www.romesg.com/wp-content/uploads/arcturus-star.jpg

When the star uses up its hydrogen fuel in the core, it can no longer hold up its outer layers. They fall inward. The center gets hotter. The hot temperatures cause the outer layers of the star to expand. As a result, the star gets bigger and the surface cools. The star is now a red giant.

While the outer atmosphere is expanding, the core inside collapses to about the size of the Earth.

The temperature again increases, reaching about 100 million degrees. Suddenly, helium in the core begins to fuse to carbon and oxygen at a very rapid rate. Within a short time the helium is gone and gravitational collapse continues.

http://windows2universe.org/cool_stuff/tourstars_25.html

Planetary Nebula (Cat’s Eye Nebula)

http://imgsrc.hubblesite.org/hu/db/images/hs-1995-01-a-full_jpg.jpg

As the star expands, the outer layers blow off at an incredible rate. A star can lose more than half of its mass during this stage.

The gas cloud surrounding the star is called a planetary nebula.

The exposed inner part of the star remains as the central star in the planetary nebula. These central stars are the hottest stars known. They are not very luminous because they are extremely small -- about the size of the Earth.

http://windows2universe.org/cool_stuff/tourstars_25.html

White Dwarf (Procyon B)

When the fuel is used up, there is nothing to hold the star's layers up against gravity and the star begins to collapse. Gravity squeezes the star down into a very small size.

As you might imagine, the matter that makes up a white dwarf is like nothing you've ever seen before. It's as if the mass of an elephant were compressed into the space of a marble. A 70 kg (154 lbs) person would weigh about 600,000 kg (600 metric tons) standing on the surface of a white dwarf.

http://windows2universe.org/cool_stuff/tourstars_25.html

Stellar

Nebula

http://windows2universe.org/cool_stuff/tourstars_25.html

Science.8
Hubble Space Pictures / Name ______
Date ______
Essential Questions
1. How do stars change over time?
2. How are stars classified on a Herztsprung-Russell Diagram? / Vocabulary
Stars, galaxy, nebulae, red giant, white dwarfs, neutron stars, black holes, supernova, magnitude / Objectives
1. Describe objects in space such as stars (in all life stages) and galaxies.
2. Describe the life cycle of a star and correlate a star’s life stage to its placement on the HR-Diagram.

Massive Star (High Mass Star)

EX: Sp

http://imgsrc.hubblesite.org/hu/db/images/hs-1995-01-a-full_jpg.jpg http://www.bramboroson.com/astro/images/starsize_compare.gif

Stars that are much heavier than the sun start off as hot white, blue-white or blue stars, rather than yellow stars like our sun.

They last only a short time compared to the sun. A star 20 times heavier than the sun will use up its fuel in about 8 million years. The sun takes 1000 times longer.

Very big stars that were born when dinosaurs lived on Earth have already used up their fuel and exploded. The sun has been around since long before the dinosaurs and its still here today

http://windows2universe.org/cool_stuff/tourstars_25.html

Science.8
Hubble Space Pictures / Name ______
Date ______
Essential Questions
1. How do stars change over time?
2. How are stars classified on a Herztsprung-Russell Diagram? / Vocabulary
stars, galaxy, nebulae, red giant, white dwarfs, neutron stars, black holes, supernova, magnitude / Objectives
1. Describe objects in space such as stars (in all life stages) and galaxies.
2. Describe the life cycle of a star and correlate a star’s life stage to its placement on the HR-Diagram.

Red Supergiant (Betelgeuse)

http://maxatma.com/wp-content/uploads/2010/07/Arcturus_rel_size782.jpg

After the star depletes the hydrogen in its core and moves off the main sequence, the core contracts and heats causing the outer layers to expand. The expansion of the outer layers results in a cooling of the surface temperature. The star gets redder.

Meanwhile, the core is getting hotter reaching 150 million K. At this temperature, helium (He) fuses explosively into carbon (C) and oxygen (O).

Gravitational collapse continues to raise the temperature of the core. When the core reaches an amazing 1 billion K, carbon fuses to produce neon (Ne), magnesium (Mg) and oxgyen (O). These elements fuse to produce even heavier elements.

At each stage, less total energy is released and thus the stages get progressively more short-lived.

Finally, an iron core is produced. Since no energy can be gained by fusing iron to make higher mass elements, the core collapses at blinding speeds.

http://windows2universe.org/cool_stuff/tourstars_25.html

Science.8
Hubble Space Pictures / Name ______
Date ______
Essential Questions
1. How do stars change over time?
2. How are stars classified on a Herztsprung-Russell Diagram? / Vocabulary
stars, galaxy, nebulae, red giant, white dwarfs, neutron stars, black holes, supernova, magnitude / Objectives
1. Describe objects in space such as stars (in all life stages) and galaxies.
2. Describe the life cycle of a star and correlate a star’s life stage to its placement on the HR-Diagram.

Supernova

http://imgsrc.hubblesite.org/hu/db/images/hs-1995-01-a-full_jpg.jpg

In the final moments of the star's life, nuclear fusion produces an iron core. No energy can be gained by fusing iron into heavier elements. There is now no energy source to sustain the intense internal pressures holding off gravitational collapse. The core collapses catastrophically inward at 1/4 of the speed of light.

In less than 1/10 of a second the core of the star is crushed into a sphere only 100 km across. The gravitational energy released in this fraction of a second is 100 times greater than the sun releases in its entire 10 billion-year lifetime.

http://windows2universe.org/cool_stuff/tourstars_25.html

Science.8
Hubble Space Pictures / Name ______
Date ______
Essential Questions
1. How do stars change over time?
2. How are stars classified on a Herztsprung-Russell Diagram? / Vocabulary
stars, galaxy, nebulae, red giant, white dwarfs, neutron stars, black holes, supernova, magnitude / Objectives
1. Describe objects in space such as stars (in all life stages) and galaxies.
2. Describe the life cycle of a star and correlate a star’s life stage to its placement on the HR-Diagram.

Neutron Star

http://scienceblogs.com/startswithabang/upload/2009/11/a_black_hole_without_a_singula/xray_neutronstar.jpg

After the supernova blast blows off the outer layers of the star, all that is left is the central core. The core now contains a mass between 1.4 and 3.0 times the sun's mass but condensed into a volume 10- to 20- km across - roughly the size of a small town on Earth.

The matter in a neutron star would be incredible to behold. It is thought to be no longer gaseous. The surface may be crystalline.

Densities are a trillion times greater than those in a white dwarf. In fact, it is so dense that one teaspoonful would outweigh the Empire State Building.

http://windows2universe.org/cool_stuff/tourstars_25.html

Black Hole

http://imgsrc.hubblesite.org/hu/db/images/hs-1995-01-a-full_jpg.jpg

http://www.starteachastronomy.com/pictures/black_hole.jpg

If the central core that remains after the supernova blast is greater than 3 times the sun's mass, the internal pressure cannot halt the gravitational collapse. The core will continue to collapse to form a black hole.

In a black hole, there is so much mass compressed into such a small volume that gravity prevents even light from escaping. Since no light can ever reach your eyes from the collapsed core, it appears black, hence the name.

The apparent surface of the black hole is the radius at which light just manages to escape. It is called the event horizon.

For example, a black hole with 3 times the solar mass would have a circumference of 55.5 kilometers (the size of a town). The Earth as a black hole would only be a couple of centimeters in diameter (about the size of a marble)!

http://windows2universe.org/cool_stuff/tourstars_25.html