The first celebration of knowledge Flashcards
what is 100 billion in scientific notation?
1*10^11
how many kilometers is one AU (Astronomical unit)
1.496*10^8 km
what is an AU
Astronomical Unit; the distance between the earth and the sun
if it takes light 8 minutes to reach earth from the sun, how long does it take for light to reach pluto, at a distance of 40 times greater than
about 5 hours
what is the big bang
the “birth” of the universe about 13.7 years ago
what was probably the most abundant element at the big bang
hydrogen (75%) (and helium (25%))
formula for wave velocity
velocity = frequency * wavelength
if a frequency of a wave were to double, how would a wavelength change if the wave velocity remains constant?
it would decrease by 2x
the bigger the ______, the better
light gathering power (LGP)
the smaller the ______, the better
Resolving Power (RP)
bigger is SOMETIMES better with ______.
Magnification Power (MP)
why do radio radio telescopes need to be built larger than other telescopes?
the larger they are built, the better resolution they have
formula for LGP
pi(D/2)^2
formula for RP
2.5 * 10^5 (wavelength/Diameter)
formula for MP
focal point objective / focal point eyepiece
why are telescopes built on remote mountaintops?
- dark – far away from lights of civilization
- dry – limits cloud cover and precipitation
- calm – limits the the turbulence in the atmosphere
- high – above the densest part of earth’s atmosphere
what’s so important about LGP?
larger mirror = fainter objects
The primary mirror of the Keck I telescope is about 10 meters in diameter. It is comprised of 36 smaller hexagonal mirrors that are each about 1.7 meters in diameter. How much LGP does the entire mirror have compared to a single hexagon?
36 times greater
why can a telescope on the ground never reach its full resolution?
atmospheric turbulence can cause small deflections in light as it passes through atmosphere
What is adaptive optics?
a method to compensate for the blurring effects of the atmosphere
how can ground based telescopes achieve their maximum resolution
with adaptive optics
What type of telescope can be used on the ground
radio telescopes; clouds don’t block radio waves.
what is photometry?
measuring the brightness of objects at different wavelengths using different filters
What is the focal length
the distance from the lens to where the light rays achieve a focus
what does a refracting telescope do?
uses the lens as objective to collect and focus incoming light
