Download Astronomy Webquest _2 STARS

9th Astronomy: Stellar Evolution and Star Brightness
Astronomy Webquest #2
From Earth, there are a number of things that we can observe about stars. One of the easiest
things to measure is the star's brightness, or magnitude. There are a number of things that
make stars appear brighter on Earth. One factor is the distance between Earth and the star.
Even though our sun is a fairly average star, because it is so close, it appears brighter on Earth
than even the brightest objects in the universe. The brightness of a star as seen from earth is
called its apparent magnitude. In order to learn more about a star, astronomers usually want to
determine its absolute magnitude, or how bright the star actually is. Another important attribute
of stars is their temperature. Astronomers can determine a star's temperature by looking at the
color of light that it emits. Hotter stars produce more blue light, while cooler stars produce
more red light.
To Do: Go to this Web Link
http://aspire.cosmic-ray.org/Labs/StarLife/studying.html
Click  Begin Observation  Find a Star  Analyze a Star
of Star for Several Stars That Appear on Our Star Chart
#
Star Name/Consetellation
1
Antares (Scorpio)
2
Spica (Virgo)
3
Our Sun
4
Procyon (Canis Minor)
5
Betelgeuse (Orion)
6
Bellatrix (Orion)
7
Vega (Lyra)
8
Rigel (Orion)
9
Altair (Aquila)
10
Polaris (Ursa Minor)
11
Pollux (Gemini)
12
Aldebaran (Taurus)
13
Arcturas (Bootes)
14
Sirius (Canis Major)
15
Deneb (Cygnus)
Star Type
Click and Record the Type and Color
Color
9th Astronomy: Stellar Evolution and Star Brightness
Astronomy Webquest #2
HERTZSPRUNG – RUSSELL DIAGRAM
Astronomers now know that these different patterns correspond to different types of stars in
different points in their life cycles. As a star ages, its temperature and luminosity will change
dramatically, moving it from one category of stars to another. It is important to remember that a
star's position on the HR diagram is not related to its position in the sky. The HertzsprungRussell diagram is a graph that plots the temperature of a star against its absolute magnitude or
luminosity. Most stars, including the Sun, can be found in the main sequence of stars - a
prominent band running from the top-left to the bottom-right of the diagram. In this main sequence
we find that the hotter a star is, the greater its absolute magnitude –(real brightness).
TO DO: Place the Number from the table (for example, Antares is #1) on the blank
Hertzsprung-Russell Diagram Below. Complete for all 15 Stars and Label the Type of Star
in the Appropriate Place on the Diagram.
BRIGHTEST
HOTTEST
What is Apparent Magnitude? ________________________________________________________
What is Absolute Magnitude? ________________________________________________________
What is a Main-Sequence Star? _____________________________________________
What Kind of Star is Our Sun? __________________________________________________________
9th Astronomy: Stellar Evolution and Star Brightness
Astronomy Webquest #2
Today You Will Learn About the Life Cycle of a Star—Called Stellar Evolution.
To Do: Click on This LINK 
http://www.schoolsobservatory.org.uk/astro/stars/lifecycle
Life Cycle of a Star
Stars are formed in clouds of gas and dust, known as ________________. _____________
_______________________ at the center (or core) of stars provides enough energy to
make them shine brightly for many years. The exact lifetime of a star depends very much
on its ______________. Very large, massive stars burn their fuel much faster 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 slowly.
Eventually, however, the ________________ 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 expand, cool and change color to become __________________________. The
path they follow beyond that depends on the mass of the star. Small stars, like our _____,
will undergo a relatively peaceful and beautiful death that sees them pass through a
planetary nebula phase to become a _______________________________ .
To Do: Click on Each Phase and Add Details Below – Begin By Clicking on Stellar Nebula
Stellar Nebula -- Star
Formation
Stars are formed, or are "born", in large clouds of ______________________________
called a nebula. The cloud slowly shrinks and then starts to collapse onto a number of
points (or cores) within the cloud, all due to the pull of _______________________ . Right
in the middle of these cores, it can get very hot and dense. When this happens,
________________________________ can start and a star is born. (CLICK SIMULATION)
Average Stars
Stars are massive, luminous balls of _________________ (plasma), which are held
together by gravity.
Stars exist because of A _________________________ between
gravity trying to make the star shrink and all the heat from the middle trying to make it
grow. Stars "live" for many millions of years, but they do not change much during most of
that time. However, amazing things can happen when they are "born" or when they run out
of nuclear fuel and "________________".
9th Astronomy: Stellar Evolution and Star Brightness
Astronomy Webquest #2
Red Giant Stars
When hydrogen fuel at the centre of a star is exhausted, nuclear reactions will start move
outwards into its atmosphere and burn the hydrogen that’s in a shell surrounding the core.
As a result, the outside of the star starts to expand and cool, turning much redder. Over
time, the star will change into a ___________________________ and grow to more than
400 times its original size. As they expand, red giants engulf some of their close-orbiting
planets. In the Sun's case, this will mean the fiery end of all the inner planets of our Solar
System, which might also include the Earth; but don't worry, this won't happen for another
5,000,000,000 years.
Planetary Nebula
Low-mass stars turn into planetary nebulae towards the _____________ of their red giant
phase. At that point the star becomes highly unstable and starts to pulsate. The outer
layers are ejected by the resulting stellar winds. Planetary nebula are relatively short-lived,
and last just a few tens of ________________________ of years. As the outer layers drift
away from the star, the remaining core shines brightly and is very hot (100,000°C+) - the
core is now a ______________________________________________________ .
White Dwarf
A white dwarf is the remaining compact core of a low-mass star that has come to the end of
its lifetime following a planetary nebula event. White dwarfs are made of highly
compressed ________________________________________ material, and are so dense
that their mass is comparable to that of the Sun, even though their size is similar to that of
the Earth's. A matchbox of white dwarf material would weigh the same as fifteen elephants.
Newly created white dwarfs have some of the hottest surface temperatures of any star, at
over 100,000°C, but because of their small size, they appear ________________________
from a distance.
As nuclear reactions no longer occur in white dwarfs, they have to rely on their thermal
store of energy for all heat and light. Over time this will gradually radiate away, allowing
them to cool down and change color. Eventually, they will disappear from sight to become
________________________________________________________________ .