Download Astronomy Power Point

Astronomy
-the study of stars
Stars
• Huge spheres of hot, glowing gas
– Example = sun
• Stars give off energy---how do we know
this?
Energy = waves
Electromagnetic spectrum
• Huge spheres of hot, glowing gas
– Example = sun
• Stars give off energy---how do we know
this?
– Visible light = we can see lots of stars in the
sky
– Radiant energy from the sun heats the earth
– Also, some stars give off radio waves
Telescopes
• Use lenses or mirrors to collect and focus
light from distant objects
• Three different types:
– Refracting telescope
– Reflecting telescope
– Radio telescope
Both of these are visible
light telescopes
Refracting telescope
• Consists of 2 convex lenses
– First lens (objective lens) gathers the light and
focuses it
– Second lens (eyepiece lens) magnifies it
Reflecting Telescope
• Uses a concave mirror to gather and focus
light
• A smaller mirror inside reflects this image
to the eyepiece lens which magnifies it
Radio Telescope
• Detects radio waves given off by objects in
space
• Most have curved reflecting surfaces that are
several hundred meters in diameter
• The bigger the radio telescope, the more radio
waves it can collect
Telescopes: Similarities and Differences
Traits which are
only true of
reflecting
telescopes
Traits which are
only true of
refracting
telescopes
Traits which are
only true of radio
telescopes
Spectroscopes
• Also called a spectrograph
– Breaks the light from an object into its
color spectrum
– Astronomers use this to get
information about stars including
their chemical compositions and
temperatures
Spectroscopes: star’s chemical
composition
• What elements is a star made up of?
• Astronomers compare the banding
patterns of known elements to those of the
stars.
What elements does this star
contain?
What makes up the universe?
• On the right side of your paper, list as
many things as you can come up with in
one minute.
• Stars, galaxies, star systems, nebulae,
etc.
• Universe = space and everything in it!
Review: What is a star?
• A star is a huge sphere of hot, glowing
gas.
• Can you think of any examples of stars?
– The sun is a star!
Stars
• What pieces of equipment can be used to
gain information about stars?
– Reflecting telescope
– Refracting telescope
– Radio telescope
– SPECTROSCOPE!!
What is a galaxy?
• A galaxy is a cluster of stars.
• Billions of stars make up a galaxy.
Can you think of the name of our galaxy?
– Milky Way galaxy
How do we measure distance to
stars and other galaxies?
• We have to use a unit called a light year.
• A light year is the distance light can travel
in one year….HUGE!
• light year is a unit of distance, not time!!!!
• 1 light year= ~9.5 million million kilometers
Parallax
• Parallax is the apparent change in position
of an object when you look at it from
different places.
What characteristics classify stars?
• All stars are huge spheres of glowing gas
(mostly hydrogen).
• Stars are classified based on 3 main
physical characteristics:
– Temperature
– Brightness
– size
LAB: Color vs. Temperature
• You will record the data for your lab in your
Cornell notes on the RIGHT side.
Summary of Lab Findings
• On the right side, place the order of star
color by increasing temperature
For example:
Coolest colornext colordsfsjsdhfjkhottest color
Temperature of stars
• Color of a star reveals its temperature.
• Remember the color vs. temperature lab?
– Red stars = relatively cool stars (still hot
~3200 degrees Celsius)
– Yellow- white = medium temperature (~5500
degrees Celsius)
– Blue-white stars = hottest stars (>10,000
degrees Celsius)
Brightness of stars
• Brightness = the amount of light stars give
off
– This depends on its size and temperature
– How bright it looks from Earth depends on
distance and actual brightness
• Apparent magnitude
• Absolute magnitude
Apparent Magnitude
• Brightness as seen from Earth
• Example: the sun looks very bright to us
on Earth, but it is not the brightest star
– It looks brighter because it is closer to earth
than other stars.
Absolute Magnitude
• Brightness of a star if it were a standard
distance from the earth
Review
• What characteristics are used to classify
stars?
• Now, we will look at graphs that show
these characteristics of stars…they are
called HR diagrams
Hertzsprung – Russell Diagram