Supernova Starbursts

Teaching Pre K-8, Mar 2004 by Cowens, John

Colorful representations of the end of a star's life cycle (like the one shown below) are the focus for Youth Art Month

Stars are born, live their lifespans and die. The death of a star sometimes involves an explosion. If the energy from that explosion radiates in the form of waves, what might they look like? When stars explode, could there be rings of energy spreading outward at tremendous speeds? Here's an art activity in which students design and color a fictional version of a "starburst."

Materials: ,

12'' (30cm) diameter circle of white paper (one for each student) crayons pencil

Procedures:

1 Randomly place 8-10 pencil dots on the paper.

2 Start at one of the dots and use a bright crayon to draw 1/4'' marks outward and around the dot. Make the marks dark and even.

3 With another crayon, add another "ring" of marks around the first one.

4 Continue adding more layers of rings until you decide to stop.

5 Repeat the process on another dot. As you draw rings, consider the following: Should all the rings be the same size? Should the dot in the center of the piece of paper be expanded, causing the other dots to remain small?

6 As the rings expand and cover the paper, they may touch the rings that are around the other dots. Students can decide which sets of rings will overlap.

7 Keep adding rings until the sheet of paper is completely covered.

8 Mount the colorful "starbursts" on black paper.

Extensions

* Cut the finished "starburst" into pieces like those of a jigsaw puzzle and mount them on a larger piece of construction paper, leaving a 1/2'' space between pieces.

* Research the exciting mathematical and scientific world of fractals. Are the students' starbursts fractals? If not, can they be modified to become fractals?

Background

The life of a star is marked by an opposition between two kinds of pressure. One is the pressure from the star's core pushing outward and the other is gravity pulling the star's surface inward. When these forces are balanced, a star is stable and shines steadily. As a star's hydrogen fuel is depleted, however, the two forces are no longer balanced, and the star's core collapses. But, during the collapse, compression by gravity raises the temperature in the core and causes the star to expand to the point where it becomes what is known as a red giant.

The last sunset

During the final stage of a star's evolution, the star's mass determines its fate. Our sun, which is a medium-size star, will expand to 400 times its present diameter and engulf the inner planets - Mercury, Venus, Earth and Mars. In addition, a nebula will form and extend past the outer planets. After millions of years, its nuclear fuel will be depleted, and only a white dwarf star no larger than Earth will remain. As our sun slowly cools, it will become a black stellar corpse.

Finding a pulse

Stars that have more mass than giant stars will supernova, or explode, during their red giant stage. Gravity will then crush the core's residue, forming what's known as a neutron star. Neutron stars are only a few miles in diameter, but they're so dense that 10 billion tons of their matter would fit into a tablespoon! The crushing effect causes the neutron star to spin or "pulse" rapidly, and emit radio signals in its strong magnetic field. If we discover it, a star such as this becomes identified as a pulsar.

Into the abyss

Extremely massive stars have bizarre endings. According to the current laws of gravity, a star can collapse to the point of leaving what's known as a black hole. A black hole can't be seen by our eyes or with any instrument; its presence can be detected only by its influence on a visible companion star, which may look distorted by the black hole's gravitational attraction. No light or matter can ever leave the intense field of the black hole's cosmic abyss.

For further reading

* Nearest Star: The Surprising Science of Our Sun by Jay M. Pasachoff and Leon Golub (Harvard University Press, 2001, ISBN: 0-674-00467-1)

* The Sun: Our Nearest Star by Franklyn M. Branley (HarperCollins, 2002, ISBN: 0-064-45202-6)

* Our Star: The Sun by Robert Estalella and Marcel Socias (Barrons, 1993, ISBN: 0-812-01739-0)

Online explorations

* Spacelink - Our Sun: http://spacelink.nasa.gov/Instructional.Materials/Curriculum.Support/Space.Science/Our.Solar.System/Our.Sun/ Pictures, instructional materials and projects all related to our sun.

* Our Sun Does the Wave: http://sci.esa.int/science-e/www/object/mdex.cfm?fobjectid=32534 Information about the "supergranules" that move across the visible surface of the sun. Includes photos and video.

* Surfing for Sunbeams: www.lmsal.com/YPOP/Spotlight/Tour/ Take a virtual tour of our sun, with pictures, movies, diagrams and more. Includes links to other informative sites.

John Cowens teaches science at Fleming Middle School in Grants Pass, OR and is a Teaching Editor of Teaching K-8. E-mail: snewoc@yahoo.com