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Name: Esmeralda
Status: other
Grade: other
Location: NV
Country: N/A
Date: N/A


Question:
Hello,
My name is Esmeralda and I work with children between 6 and 9 years at a Montessori school in Bangalore. I recently gave the children the Story of the universe, which is essentially the Big Bang and the formation of the earth. After this a lot of project work on Galaxies has taken off in class and the children are really exited. With this excitement, of course, come a lot of what, why and how's ? One question that I need help answering was asked by a 7 yr old - Are black holes stars?


Replies:
Esmeralda,

Black holes, while previously stars, are no longer stars. If you look at the definition of a star, one qualification is that it is a self-luminous body. It is not possible for light to escape/radiate from a black hole.

Matt Voss


Hi Esmeralda

Black holes used to be stars. When a star that is considerably bigger than the sun (around 10 - 20 times the mass) ends its life as a supernova, it can leave behind something that becomes a black hole. There are a number of very good web sites that cover this in detail, such as

http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html

and

http://cosmology.berkeley.edu/Education/BHfaq.html

If you have not already done so, you might want to introduce the kids to stellar evolution. Black holes would be the final chapter in the life of very big stars. Hope this helps!

Bob Froehlich


Esmeralda,

The way I would answer this is to have the children blow up a balloon and have them imagine it as a star and then have them discover how there are two opposing forces in that balloon. You can judge whether the students can make the discovery on their own, and make the conclusions as follows, with your guidance.

Like a star, there is a force that is pushing outward (the energy from the nuclear fusion reaction) just like the gas in the balloon is pushing outward. Also like a star, there is a force pulling things inward (the gravity of the star), which, just like the skin of the balloon, is try to shrink inward. Because the outward force and the inward force are balanced the star (and the balloon) maintains its shape. But let us say the outward force diminishes (as when you let air out of the balloon) as when the fuel in the star gets depleted, then the balloon shrinks. If this continues on and on, the star can shrink down to a black hole. So, what we believe is that a black hole may have started out as a star that kept shrinking down due to its own gravity.

The nice thing about this is that you can also lead them into thoughts about the other way that a star may die: a nova (or supernova) - when the outward forces win.

Greg (Roberto Gregorius)



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