Chapter 4.1-Telescopes
Electromagnetic radiation is the light that can travel through space in the form
of waves.
There are many types of electromagnetic radiation:
1. visible light-light you can see with the naked eye;medium wavelength
2. radio waves-longest wavelength;need to be large ;invisible ; made of sound
3. infrared radiation-non visible light ; long wavelength measured UV
spectrum
http://www.jwst.nasa.gov/
http://www.youtube.com/watch?v=KrUGWMFM2U4
http://www.youtube.com/watch?v=L2d7joOgVLg
*4. ultraviolet radiation-non visible light often seen by insects
*5. x rays-non visible light given off by very hot objects short wavelengths
http://chandra.harvard.edu/about/
*6. gamma rays-have the shortest wavelengths and the most energy of any
wave in the electromagnetic spectrum
http://www.history.com/shows/armageddon/videos/gamma-rayburst#humanitys-f
*can be seen from space only due to atmospheric interference
Telescopes are instruments that collect and focus light and other forms of
electromagnetic radiation.
2 main types: (list and describe what they use to collect and focus light)
a. optical-uses lenses and mirrors to collect and focus visible light
b. non optical-collect and focus different types of electromagnetic radiation
(ie: x ray, infrared, uv)
Two main types of optical telescopes are: (list and describe what they use to
gather and focus light)
1.refracting telescopes-uses convex lenses(curved pieces of glass) smaller;less
light collection;objective-lens
2.reflecting telescopes-uses curved mirror to collect and focus light; larger ;
more light collection; objective-mirror (Hubble is an example)
Why are the largest optical telescopes usually reflecting telescopes? because
the mirror can be supported from below .Largest telescope in US in in Hawaii
...has a 10m mirror
Where are observatories and why are they often used to house telescopes?
building that contains one or more telescopes, usually found on mountain
tops to reduce atmospheric/light interference
Name some other types of telescopes & describe what they use to “see”:
Chandra- x ray (space)
Sofia-visible light
Hubble-visible, uv and infrared (space)
VLT-visible light
James Webb- (future space)
Spitzer-infrared(space)
Alma-uv, x ray , visible, infrared
Arecibo-radio
Chapter 4.2- The Scale of the Universe
Astronomers use parallax to measure the distance to nearby stars.
(to determine their distance)
Define: parallax-apparent change in position of an object when you look at it
from different places (measurable)
Define: universe-all space and everything in it.
Scientists frequently use scientific notation to describe the sizes and distances
in the universe. They use a unit called a light year to measure these distances.
Is a light year a measure of time or distance? distance
Practice Using scientific notation: scientific notation uses powers of ten to
write either very large or small #s.
How far away is the sun from Earth? 150,000,000,000 meters
Now write it out using scientific notation: 1.5 x 10 to the 11 meters
How far away is the next nearest star, Alpha Centauri from Sun?
42,000,000,000,00,000 meters
Now write it out using scientific notation: 4,2 x 10 to the 16 meters
What is the name of the nearest galaxy to the Milky Way and how far away is
it?
Andromeda galaxy 2.4 x 10 to the 22 meters
Practice:
Proxima Centauri is 39,700,000,000,000,000 meters away...write it in scientific
notation=______________________
Deneb(distant star) is 3.23 light years away =_______________________
Sun takes 220,000,000 to revolve around the galaxy=__________________
Chapter 4.3- Characteristics of Stars
What is a black hole? An object that has a gravity so strong that not even
light can escape it. Scientists believe stars become black holes when they die
How did scientists prove they existed? launched a rocket to record the x-rays
given off from high temperature heat released by matter being pulled into
black hole
Define: star-huge spheres of glowing gas
How do stars produce energy? nuclear fusion
Astronomers classify stars based on their physical characteristics
These 5 characteristics are:
1. color
2. temperature
3. size
4. composition
5. brightness
How are the color and temperature of stars related?
Color reveals stars surface temperature. Coolest stars appear red and hottest
blue
Compare the following sizes of the stars to the sun:
Giant or Supergiant stars- larger than the sun
White dwarf stars-smaller than the sun (~size of Earth)
Neutron stars-much smaller than (only 20km)
Most stars are composed of:
73% Hydrogen
25% Helium
2% other elements
Explain what a spectrograph is and describe how scientists use them to analyze
light: a device that breaks light into colors and produces an image of resulting
spectrum; used to determine the elements found in stars. (see ex: p.138)
The brightness of a star depends on two things:
1. size
2. temperature
Name/describe two ways to describe a star’s brightness:
1. apparent brightness- stars brightness as seen from Earth
2. absolute brightness- brightness a star would have if it were a standard
distance from Earth
What information would you need to determine a star’s absolute brightness?
The apparent brightness and distance are needed to calculate absolute
brightness of a star.