Name: ______________________________________________
Date: ______________ Per: ________________
Astronomy: Life Cycle of a Star
Go to the following site: www.schoolsobservatory.org.uk/astro Click on Stars on the main menu.
Follow the section to answer complete the information below.
What is a Star?
All the energy in a star is produced by _________________________________. Stars exist because of
the balance between gravity trying to make the star shrink and ________________ from the core trying
to make it grow.
Why do Stars Shine?
The light and heat from stars such as the Sun, is made by a process known as
_________________________________. Fusion happens when two lightweight atoms are forced together to
form a heavier one, producing a lot of ________________. However, fusion can only occur at the
incredibly high __________________ and ______________________________ found at the center of stars.
Are Stars Different Colors?
Small stars are cool (less than 3000°C) with a ________________ appearance, whereas big, heavy
stars are hot (over 30,000°C) and have a ________________________ glow. The temperature of a star, and
therefore its color, actually depends on the amount of _________________ it has.
Although they are bigger, the hot, blue stars do not “live” as long as the smaller ones, because
they use up their fuel much more _______________________. The hottest stars live for a few
__________________________ years, whereas the smallest stars will live for hundreds of
__________________________ of years.
How Big are Stars?
Stars come in a huge range of sizes. _______________________________ can be just 20 to 40 km,
whereas ______________________________ can be very similar in size to ____________________. The largest
supergiants, on the other hand, can be more than __________________ times larger than our Sun.
Can we Classify Stars?
Different stars can be categorized into certain groups depending on their _____________ and
______________________________. These groups are known as O, B, A, F, G, K, M, whereas Stars classified in
the “O” group are the most ______________________________ and _____________________________ while those in
the “M” group are the _________________________________ and _______________________________.
The Life Cycle of a Star
Stars are formed in clouds of gas and dust, known as ____________________. The exact lifetime od
a star depends on its ____________. Very large, massive stars burn their fuel much __________________ than
smaller stars and may only last a few hundred thousand years. Smaller stars, however, will last for
several billion years, because they burn their fuel much more _____________________.
Eventually, however, the hydrogen fuel that powers the nuclear reactions within stars will
begin to run out, and they will enter the final phases of their lifetime. Over time, they will
_______________________, ____________ and change ______________________________ to become red giant stars.
The path they follow beyond that depends on the mass of the star.
Small stars, like the Sun, will undergo a relatively peaceful and beautiful death that sees them pass
through a planetary nebula phase to become a white dwarf. Massive stars, on the other hand, will
experience a most energetic and violent end, which will see their remains scattered about the
cosmos in an enormous explosion, called a supernova. Once the dust clears, the only thing
remaining will be a rapidly spinning neutron star, or possibly even a black hole for the most
massive stars.
An average star the size of our Sun will become a ___________________________________.
A star about 15 times as massive as our sun will become a ____________________________.
A star greater than 30 times the mass of our Sun will become a ________________________________.