Shop Windows to the Universe

Ready, Set, SCIENCE!, by the National Research Council, focuses on K-8 science classsrooms. Check out the other publications in our online store, as well as classroom materials.
Sequence of the main phases of formation of a star: very slowly rotating cloud of gas, gravitational collapse, star formation by slow contraction and accretion with generation of intense stellar wind, collimation of the stellar wind into bipolar flow.
Click on image for full size
Image courtesy of the University of Oregon, Department of Physics, the Electronic Universe Project

The life cycle of the stars

A gas cloud, if big enough, starts to shrink. The density and temperature increase so nuclear fusion can start. This is when Hydrogen is turned into Helium. The "burning" of Hydrogen stops the gas cloud from shrinking. At this point, the gas cloud becomes a star. This is the current state of our Sun.

After billions of years, most of the Hydrogen fuel has been "burned", and the star begins to shrink again. The star has to use another source of fuel, Helium.

The next stage in the life of a star is called a red giant. The star here is much bigger than it was initially (that's why it's called a giant star!). When the red giant star runs out of fuel, the star begins to shrink again. This contraction heats up the core of the star enough so that elements like Iron can be made. When the star runs out of this last type of fuel, it has neared the end of its life.

The star begins to throw off layers because it can't support them anymore. This is called a planetary nebula. The core of the star becomes a white dwarf. This is an extremely dense star the size of a planet. Finally, when the white dwarf has used all its energy, it stops shining and becomes a "black dwarf", a dead star.

For stars with higher masses than the Sun (up to about 40 times greater), the outer layers of the star may be thrown off with much more force. This is a supernova. This type of star collapses down to a very compact size. This is what is called a "neutron star".

Stars bigger then 40 times the Sun may become a "black hole".


Last modified January 24, 2005 by Randy Russell.

Shop Windows to the Universe Science Store!

Cool It! is the new card game from the Union of Concerned Scientists that teaches kids about the choices we have when it comes to climate change—and how policy and technology decisions made today will matter. Cool It! is available in our online store.

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Fusion Reactions

The center of an atom is called the nucleus. Nuclei is the plural of nucleus. When two atoms come together, and their nuclei combine, you have fusion. Fusion releases energy. By using Einstein's famous...more

The Hydrogen Fusion Process

In the basic Hydrogen fusion cycle, four Hydrogen nuclei come together to make a Helium nucleus. This is the simple version of the story. There are actually electrons, neutrinos and photons involved in...more

The Supernova

A Supernova is a very massive star that explodes at the end of its life. The supernova is where the heavy elements (heavier than iron) are made. ...more

Fusion Inside the Stars

Fusion in the core of stars is reached when the density and temperature are high enough. There are different fusion cycles that happen in different phases of the life of a star. These different cycles...more

Diagnostics for the Solar Interior

The Sun releases energy. This energy is made in the center of the Sun. But we can't see past the surface of the Sun. So how do we know how this energy is made? Well, scientists use diagnostics to figure...more

The Neutron Capture Process

Neutron capture can occur when a neutron approaches a nucleus close enough for nuclear forces to be effective. The neutron is captured and forms a heavier isotope of the capturing element. When the new...more

IMF

The Sun acts like it has a big magnet in the middle of it. We call this the Sun's magnetic field. The Sun's magnetic field has a fancier name, the Interplanetary Magnetic Field (IMF). This just means that...more

The Cherenkov Effect

The theory of relativity states that no particle can travel at the speed of light in a vacuum. However, light travels at lower speeds in dense media, like water. A particle traveling in water must have...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF