THE LIFE CYCLE OF STARBy: Sethu

Stars

Stars can have different masses. Some have high masses, and some have low to medium masses.

Because of their different masses, they die in different ways.

A star is a sphere of gases . They are located in the outer space.

A star is a sphere of gases . They are located in the outer space.

They consist of hydrogen, some helium and other elements. Stars are grouped in galaxies.

Big stars have lots of energy, but use it up quickly. Small stars don’t have a lot of energy, but use it longer. Therefore, they live longer.

Low to Medium Mass Stars: Nebula All stars start out as a nebula, even if they may have different masses. A

nebula is made of gas (mostly hydrogen), plasma, and particles of dust.

While it collapses, it heats up. Nuclear fusion occurs once it is hot enough. Because of nuclear fusion, the star releases energy, making it glow. The star goes through the next phase and becomes a protostar.

The force of gravity starts to gather the particles of the nebula together. This forms a cloud. The cloud then collapses because of gravity. http://

www.godandscience.org/images/n44.jpg

Here is a nebula.

Low to Medium Mass Stars: Protostar to a failed star.

A protostar is a dense area of gasses. It is located in a nebula. It can possibly become a star.

It really depends on the mass of the protostar. If it doesn’t become bigger than 1/10 the mass of the sun, it will form into a brown dwarf.

http://www.astro.keele.ac.uk/workx/starlife/outflow1.gif

Here is a protostar.

Brown Dwarf

A brown dwarf is not a star. It is known to be a failed star. They are larger and different than our planets.

It doesn’t shine too bright, and eventually, it cools off slowly.

http://starchild.gsfc.nasa.gov/docs/StarChild/questions/brown_dwarf.html

Here is a brown dwarf.

Protostar to a star.

A protostar can become a star if it obtains enough mass.

Next, hydrogen begins to fuse in the star. It officially becomes a star once it begins fusion.

When it retains enough mass, the temperature increases and the pressure does, also.

http://aspire.cosmic-ray.org/labs/star_life/images/orion_protostar.gif

Here is another protostar.

Hydrogen Fusion

Hydrogen fusion occurs when 4 hydrogen nuclei and 2 electrons come together and make a helium nucleus.

Hydrogen fusion creates helium. Hydrogen fusion releases energy into

the core of the star. This energy helps the star stay hot and helps it shine.

Helium Fusion

Helium fusion occurs in red giants and supergiant. Helium fuses into beryllium and then into carbon.

Main Sequence Star

A main sequence star fuses hydrogen.

It eventually becomes a giant.

When this star runs out of hydrogen, it begins to fuse helium.

http://outreach.atnf.csiro.au/education/senior/astrophysics/images/stellarevolution/sun-nasa.jpg

Here is the sun. It is a main sequence star.

Red Giant A red giant can be colored red to yellow orange. They have a low mass that ranges from 0.5 to 10 solar masses.

The core gets hot, and the outer layers swell up. It then becomes giant. The outer layers of

the red giant are ejected outwards by gravity. It heats up. The star is shiny and extremely hot.

Solar masses are the standard way to express mass. Red giants do eventually stop the process of fusion.

http://imgsrc.hubblesite.org/hu/db/images/hs-1997-26-d-web.jpg

Here is a red giant.

Planetary Nebula

The outer layers of the red giant are viewed as a planetary nebula.

They aren’t very bright, but they do serve the purpose of helping make stars.

They can last for about 10,000.

http://www.noao.edu/image_gallery/images/d5/01g01rb.jpg

Here is a planetary nebula.

White Dwarf

A white dwarf is extremely hot. It shine a light that is white. It is the leftover heat of the collapsed star’s core.

For it to cool off, it takes almost trillions of years. It eventually becomes a black dwarf.

Although it’s the size of the earth, it has almost ½ the mass of the sun.

http://www.phy.mtu.edu/APOD/image/9711/m4wds_hst_big.jpg

Here is a white dwarf.

Black Dwarf

Black dwarves don’t emit any light whatsoever. They are the end of the death of stars.

http://www.daviddarling.info/images/black_dwarf.jpg

Here is a black dwarf.

High Mass Stars

Like the low to medium mass stars, high mass stars start off as a nebula.

Then, it goes into the main sequence star, only because of the bigger mass, it is a massive main sequence star.

Next, they go into the protostar phase.

Next is when it goes through a different stage.

Red Supergiant When the main sequence star

runs out of hydrogen, it becomes a red supergiant.

They only live for a few million years.

When it runs out of energy to create heat and light, gravity begins to take over. The heat from the center pushes outward.

Gravity presses at the center, and the energy is used up quickly. The star makes enough energy to push mass outward against gravity’s force.

http://www.nasa.gov/images/content/199918main_rs_image_feature_784_946x710.jpg

Here is a red supergiant.

Supernova

A supernova occurs when gravity pulls the center of the red supergiant inward quickly. It collapses into a ball.

Shock waves cause the rest of the star to explode outward. This collapses to a neutron star.

This collapse is fast and dangerous. The core is compressed.

http://www.oberlin.edu/physics/dstyer/Astronomy/Supernovae/Tycho.gif

Here is a supernova.

Neutron Stars

A neutron star is the remaining thing of a supernova. It is very small and made up of only nuclei. The large nucleus is held up by gravity. If the mass is 25 to 50 times of the sun’s, it forms

into a black hole.

http://sciencenow.sciencemag.org/content/vol2008/issue221/images/200822111.jpg

Black Hole

A black hole has a strong pull of gravity. It is formed from a neutron star that has a mass 25 to 50 times of the sun.

The black hole is so powerful, light cannot escape. This is really the death of a high mass star.

http://z.about.com/d/space/1/0/A/9/1/stsci1997028a.jpg

Here is a black hole.

Citations

http://simple.wikipedia.org/wiki/Star http://simple.wikipedia.org/wiki/Stellar_evolution http://simple.wikipedia.org/wiki/Nebula http://simple.wikipedia.org/wiki/Plasma_(physics) http://simple.wikipedia.org/wiki/Red_giant http://simple.wikipedia.org/wiki/Brown_dwarf http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question62.html http://starchild.gsfc.nasa.gov/docs/StarChild/questions/brown_dwarf.html http://www.windows.ucar.edu/tour/link=/sun/Solar_interior/Nuclear_Reactions/Fusion/Fusion_in_stars/H_fu

sion.html&edu=high http://www.windows.ucar.edu/tour/link=/sun/Solar_interior/Nuclear_Reactions/Fusion/Fusion_in_stars/H_fu

sion.html&edu=elem http://en.wikipedia.org/wiki/Helium_fusion http://www.bookrags.com/wiki/Helium_fusion http://www.ask.com/bar?q=What+is+helium+fusion+in+stars

%3F&page=1&adt=0&qsrc=0&ab=0&title=The Astrophysics Spectator: The Fusion of Helium in Stars=http%3A%2F%2Fwww.astrophysicsspectator.com%2Ftopics%2Fstars%2FFusionHelium.html

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/helfus.html#c1 http://wiki.answers.com/Q/Why_low-mass_high-mass_stars_take_different_paths_at_the_end_of_their_life http://www.historyoftheuniverse.com/starold.html http://cseligman.com/text/stars/starevol2b.htm http://www.windows.ucar.edu/tour/link=/sun/Solar_interior/Nuclear_Reactions/Fusion/Fusion_in_stars/H_fu

sion.html&edu=high http://www.windows.ucar.edu/tour/link=/sun/Solar_interior/Nuclear_Reactions/Fusion/Fusion_in_stars/H_fu

sion.html http://www.factmonster.com/ipka/A0004429.html http://nasascience.nasa.gov/astrophysics/how-do-stars-form-and-evolve http://www.where-what-how-why.com/?p=131 http://www.enchantedlearning.com/subjects/astronomy/stars/lifecycle/