Stars

A Star is an object that produces energy at its core! A mass of plasma held together by its own gravity;

Energy is released as electromagnetic radiation!Stars differ in size, age and temperature.

Star PowerStars are powered by nuclear fusion

•At 15 million degrees Celsius in the center of the star, fusion occurs.

•Very simplified: 4 Hydrogen 1 Helium + energy!

E = mc2

• Fusion makes LOTS of energy

• E = mc2What do E and M symbolize?

….and “c”….?

E = Energy and m = mass

c = the speed of light (300,000,000 m/s)c = the speed of light (300,000,000 m/s)

Nuclear fusion

• Astronomers learn about stars by studying their luminosity, spectrum, and motion

Life Cycle of the Stars

Stars are formed, changed, and recycled!

Stars• A celestial

body of hot gases that radiates

energy from nuclear fusion

occurring at the core.

http://news.nationalgeographic.com/news/2007/10/images/071002-star-picture_big.jpg

Milky Way, Nebula NGC 360320,000 light years away

_______ _____ is the distance light can travel in ONE YEAR. Light travels at a speed of 300,000,000 meters/second.

Light Year

9,400,000,000,000,000 meters

9 quadrillion (9 thousand billion)

http://www.nasa.gov/multimedia/imagegallery/image_feature_202.html

Milky Way, NGC 3949, 50 million light years

In one Second, light can travel

around the Earth 10 times, according to

one estimate.

Horesehead Nebula; 1500 light years distant

http://www.nasa.gov/multimedia/imagegallery/image_feature_73.htmlhttp://www.nasa.gov/mission_pages/spitzer/news/spitzer-20070212.html ____________:

A dense cloud of gas and dust; the birthplace of stars.

NEBULA

Bubble Nebula

Stingray Nebula

Horsehead Nebula

Red Square Nebula

Crab Nebula

Eye (of God) Nebula

Southern Crab Nebula

Eskimo Nebula

The nebula begins to contract due to __________. The pressure and temperature increase as a _____________ is formed.

GRAVITY

PROTOSTAR

When the temperature gets hot enough, _______________ begins and a _______ ____________ star is born.

FUSIONMAIN SEQUENCE

Nuclear Fusion: The process

of taking atom centers ( the nucleus) and fusing them together.

Throughout its life, these two forces determine the stages of a star’s life.

• Energy released from nuclear fusion counter-acts inward force of gravity.

A Balancing Act

A star loses ____________ during fusion as energy is released.

This decreases the star’s gravity. A star will expand, becoming a _______________.

Very massive stars become ________ _____ _________.

MASS

RED GIANT

http://www.universetoday.com/2008/01/31/will-earth-survive-when-the-sun-becomes-a-red-giant/http://www.daviddarling.info/images/red_giant.gif

SUPER RED GIANTS

As the fuel runs out in a average sized star, _________ slows down. The star will shrink in size, becoming a _________ _______.

fusion

A ____________ is a rotating white dwarf emitting radio waves.

PULSAR

White Dwarf

BLACK DWARVES

http://chandra.harvard.edu/photo/2004/rxj1242/index.html

http://www2.ph.ed.ac.uk/nuclear/photo/

A ___________________ is an _____________ that marks the end of a very massive star’s life. When it occurs, the exploding star can outshine all of the other stars in the galaxy in total for several days and may leave behind only a crushed core.

SUPERNOVA explosion

1987 SupernovaLarge Magellanic Cloud160,000 light years away

Discovered by 14 year old Catherine Moore, on Nov. 7 2008.

Larger stars supernovae and form __________________.

http://chandra.harvard.edu/photo/2004/rxj1242/index.html

http://www2.ph.ed.ac.uk/nuclear/photo/

The most massive stars supernovae and form _________________BLACK

HOLES

A black hole is an extremely massive remnant from which light

can not escape.“Black holes are where God divided by zero” Stephen Wright

The Largest stars are red supergiants, 1500 times our sun. The smallest are red dwarfs, not

much larger than Jupiter.

What makes some stars appear brighter?

• LUMINOSITY refers to the brightness of stars. Because some stars are CLOSER or BIGGER, they may seem more luminous.

What makes some stars appear different colors?

• The temperature affects the color. The hottest stars are blue, while the coolest stars are red.

Blue > 30,000 Kelvin Blue to blue white 10,000 -> 30,000

Kelvin White 7,500 -> 10,000 Kelvin

Yellowish White 6,000 -> 7,500 Kelvin Yellow 5,200 -> 6,000 Kelvin Orange 3,700 -> 5,200 Kelvin

Red 1,000 < 3,700 KelvinBrown < 1,000 Kelvin

Black 0 Kelvin

H-R

dia

gra

mhttp://www.cosmosportal.eu/cosmos/tr/node/56058

Large, more massive stars have much more _____________ than the sun. This greater internal pressure causes fusion reactions to occur __________. This causes the largest stars to burn their fuel, and eventually run out, much more ______________.

Larger stars live ___________ lives.

Bigger stars are brighter and hotter due to the rapid rate of __________.

Do larger stars or smaller stars last longer?

Do hot stars or cool stars last longer?Large, more massive stars have much

more _____________ than the sun. This greater internal pressure causes fusion reactions to occur __________. This causes the largest stars to burn their fuel, and eventually run out, much more ______________.

Larger stars live ___________ lives.

Bigger stars are brighter and hotter due to the rapid rate of __________.

gravity

quicklyquickly

fusion

shorter

All stars spend the majority of their lives fusing __________ into ________________: the main sequence.

When all of the _____________ in the central regions is converted to helium, the star will begin to “burn” helium into _______________. Stars heavier than about 5 times the mass of

the ______ can do this with no problem: they burn _____________, and then _______________, and then _____________, _______________, silicon, and so on…until Iron.

hydrogen helium

hydrogen

carbon

hydrogen heliumcarbo

noxygen

Iron is the lightest element that doesn’t release __________ when you attempt to fuse it together. You actually end up with less energy than you started with! So instead of generating pressure to hold up the outer layers, the iron fusion actually takes it out of the core. Thus, there is nothing left to combat ________________ from the outer layers. The result: ___________!

energy

gravitysupernova

Iron

This implosion (___________) happens very, very quickly: about 15 seconds. During the collapse, the nuclei in the outer parts of the star are pushed together, so close that elements heavier than __________ are formed.

collapse

Iron

Apparent Magnitude: How bright an object appears from Earth.

Absolute Magnitude: How bright an object would appear from 32.6 light years away.

Low numbers are brighter. Negative numbers are extremely bright.

The End.