Lesson 6 Flashcards
How do telescopes work like eyes?
Because they have areas that capture light, as well as focus the light to form images
What is refraction? What does it do to light?
The bending of light as it passes from one substance to another
- refraction changes the angle at which light travels
What is a focal plane?
Where light from different directions comes into focus
What is the focal point?
Where the light from different points can converge
What is angular resolution?
The smallest angle over which we can tell that two dots (or two stars) are distinct
What is a defraction limit?
The resolution of a telescope that has perfect resolution, save only for the interference of light waves
What are the two fundamental properties of telescopes?
- its light collecting area
2. its angular resolution
When a telescope’s light collecting area has a larger diameter, what is the effect produced?
It means that more light is being collected at one time = increases angular resolution
What is the angular resolution of the human eye?
approximately 1 degree
What is the angular resolution of the Hubble Space telescope?
approximately 0.05 arcseconds
What does angular separation depend on?
Actual separation, as well as the distance from us
What is the ultimate limit to a telescope’s resolution?
From the interference of light waves in a telescope
What does the defraction limit depend on?
The diameter of the telescope, its primary mirror, and the wavelength of light being observed
- larger telescopes have a smaller defraction limit
What are the two basic designs of telescopes?
- refracting telescopes
2. reflecting telescopes
Describe refracting telescopes?
They focus the light with lenses, and in order to get a clear picture, the lens needs to be very thick, and the telescope needs to be very long
What kind of telescopes are most today?
Reflecting telescopes
Describe reflecting telescopes?
They focus light using mirrors
- uses a secondary mirror to reflect light to focus point
What are the three subtypes of reflecting telescopes?
a) cassgrain design: light is focused through a hole in the primary mirror
b) newtonian focus: light is focused through a hole in the side of the telescope
c) nasmyth/coude focus- light is focused by a third mirror lower down in the telescope
What three things do we use telescopes for?
- imaging
- spectroscopy
- time monitoring (tracks how an object changes with time)
Why are most telescopes build at higher altitudes, where the air is thinner?
Because the motion of molecules in earth’s atmosphere distorts images taken by telescopes
Which location has one of the largest collections of research telescopes in the world?
Kitt Peak, Arizona
Which location is one of the best places for optical telescopes to be built?
Mauna Kea, Hawaii
Which location has the most optimal atmospheric conditions for reducing distortion of air particles?
The high deserts in Chile
What is another way we can reduce atmospheric distortion?
By putting telescopes in space
Why do we need to composite images taken from telescopes in space?
Because they have smaller diameters
Why do some telescopes only work in space?
Because certain wavelengths of light can’t penetrate Earth’s atmosphere (i.e. X-rays)
What is a radio telescope?
A telescope that reflects radio waves to a focus
What are grazing incidence mirrors?
Mirrors specially designed to deflect X-rays
What is interferometry?
Allows telescopes to work together, thus adding to their combined angular resolution
What two wavelengths most easily pass through Earths’s atmosphere?
- radio waves
- visible light
Why might we need more than one type of telescope?
- Because planets emit primarily infrared light
- Because hot stars emit ultraviolet light and X-rays
- Because astronomical events produce gamma rays
What is interference?
The place where waves meet
Can all telescopes capture light from the visible spectrum?
No
Name some non-visible light telescopes
- Radio telescopes
- X-ray telescopes
- gamma ray telescopes
Where do X-ray telescopes need to be placed?
Above Earth’s atmosphere, because this wavelength cannot penetrate the atmosphere
- X-ray telescopes need to be specially designed because the X-rays can damage other kinds of telescopes
Where do gamma ray telescopes need to be placed?
In space
What would happen if a gamma ray hit a regular telescope?
The telescope would be destroyed because of the power of the gamma rays
Which kind of telescope would make interferometry easiest to accomplish?
Radio waves;
it is possible to accomplish with with infrared and visible light telescopes as well
What are the four categories of robotic space exploration?
- flyby
- orbiter
- sample return mission
- lander/probe
Describe a flyby?
When a spacecraft flies by a planet just once before continuing on its way
What does an orbiter space mission accomplish?
It orbits the world it is studying
What is a sample return mission?
The robot comes back to Earth to return a sample it has collected
What does a lander/probe do?
It either lands on a planet to study it, or to probe an atmosphere
