Exam 1 Flashcards
What is an AU
average distance from the sun to the Earth
What is a light year
Distance light travels in one year
Put the following in order from smallest to largest:
human, universe, Galaxy, local group, Earth, Superclusters, and Solar system
Human, Earth, Solar system, Galaxy, Local group, Supercluster, and Universe
How did Aristotle know the Earth was round?
- Saw the shape of Earth’s shadow in the eclipse of the moon
- New stars become visible as you travel South
- Distant ships disappear at the bottom first
What is parallax?
An apparent shift of nearby stars with respect to distant stars as the Earth orbits the Sun
What is the “resolution” of a telescope
the smallest angular separation such that two points can be distinguished
What is the difference between heliocentric and geocentric thinking
heliocentric thinking is the thought that the planet orbits the sun while geocentric is the thought that the planets orbit Earth
What was Copernicus’ main contribution to astronomy
Challenged the Greek’s geocentric thinking
What were Galileo’s main contributions to astronomy
Discovered the 4 largest moons of Jupiter and the phases of Venus, further backing up Copernicus’ geocentric thinking
What was Tycho Brahe’s main contributions to astronomy
Collected data on the stars by making detailed, naked eye observations
What were Johannes Kepler’s contributions to astronomy
Using data collected by Brache, he came to 3 major conclusions
What is Kepler’s 1st Law?
Planets move in elliptical orbits with the Sun at one focus of the ellipse
What is Kepler’s 2nd law
The orbital speed of a planet varies so that a line joining the Sun and the planet will sweep out equal area in equal time intervals; the closer a planet is to the Sun during its orbit, the faster it moves
What is Kepler’s 3rd law
The amount of time a planet take to orbit the Sun is related to the size of its orbit; implies that a planet with a larger distance from the Sun, will take longer to orbit the Sun
What equation came out of Kepler’s 3rd law and what do the variables stand for
p^2 = a^3
a is the semimajor axis (half the diameter) and p is the time to complete orbit
What is Newton’s first law
Objects at rest tend to stay at rest while objects in motion tend to stay in motion
What are the vectors of velocity
Speed and direction
What is acceleration
speeding up/down or changing direction of velocity
What is force
anything that acts to change the velocity of an object
What is Newton’s second law
force = ma
What is Newton’s 3rd law
for any force, there is an equal and opposite reaction force
what is the equation for the momentum of an object
momentum (p) = M/v (mass divided by velocity)
How were Kepler’s 1st and 2nd law apply to orbiting objects
Found that both objects move in ellipses about a common center of mass that could be anywhere between the two objects
When an object is in orbit, what is the relationship between altitude and speed
When at higher altitude the object will slow down and vise versa
What is escape velocity
The needed velocity to escape an object’s orbit
What is gravitational potential energy
Stored energy when two objects are gravitationally attracted to each other
How would escape velocity for an object at the top of Mt. Everest compare to the escape velocity for the same object at sea level
Escape velocity would be lower at sea level since there is a larger radius making the denominator of the equation larger
How does the force of gravity from the moon affect the Earth
Water on the near side is pulled towards the Moon more than average while water on the far side is pulled towards the moon less than average
How does the Sun affect the tides on Earth
Sun also causes tides on Earth that can augment or partially cancel the tides from the Moon
What is a Roche limit
When an object get too close to its planet, the tidal forces will pull it apart
What is an eclipse
When a celestial body can occasionally be interrupted by another celestial body temorarily getting in the way
What is amplitude
magnitude of a wave
What is wavelength
distance from crest to crest of a wave
What is wave interference
When crests from one region combine with the crests of another to cause destructive or constructive interference
Is light a wave or particle
Both. light acts like a particle on microscopic scales while it acts like a wave on macroscopic scales
How does intensity of light change with distance
As you get farther out, the light spreads out into more area, so the amount per unit area decreases; gets less intense
What causes temperature
motion of atoms/molecules
Put the following in order of most hottest to least hottest: Orange, yellow, and red
Yellow, orange, red
What does a high temperature imply
Higher energy photons since they are moving more and shorter wavelength since wavelength and energy have an inverse relationship
Star Antares appears red while star spica is blue. Which star is hotter?
Star spica
What is power
energy given off per unit of time
What is luminosity
how many watts a star puts out
What is a blueshift
As wavelengths decrease, they shift towards the blue end of the spectrum
Waht is a redshift
When the source move away from you and the wavelength gets longer
A green laser has a wavelength of ~510.0 nm. If we see a green laser coming from the Andromeda galaxy, it would have a wavelength of 509.5 nm. How fast is Andromeda moving relative to us?
See slide for answer
What are the advantages and disadvantages of refractors
simple to construct and easy to clean but big lenses are hard to support, are expensive, can’t avoid defect in glass, and they absorb UV light
What are the types of radiation wavelenghts in order of lowest to highest frequency
Radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma ray
What are the benefits of using telescopes
Resolution (need an object to make a larger aperature), can only make so many observations with the naked eye, records what is being seen, humans are blind to most of the electromagnetic spectrum
Telescope A has a mirrir of a certain diameter. Telescope B has a mirror with a diameter 3 times larger. How many times bigger is the light-gathering capability of telescope B?
9 times larger since light gathering capability depends on the area which depends on the square of the size of the mirror
What is interferometry
Focusing individual mirrors on the same area to increase the aperature of the image
What is aperture
the diameter of the lens/mirrror the telescope uses to collect light
What is the use of infrared telescopes
anything that is colder than the sun emits a lot of IR radiation thus, allows us to see a lot more. Newly formed stars also emit in IR
What is a PSR
Pulsar; extremely hot star near the end of it life cycle
In 1996, astronomers discovered an icy object beyond Pluto, which was given the designation 1996 TL 66. It has a semimajor axis of 84 AU. What is its orbital period?
See study guide
Why might an astronomer decide to install a diffraction grating at the focus of an optical telescope
Diffraction grating acts like a prism, it splitsthe light up by wavelength. They are used to identify chemical elements in stars, determine stellar temperature, measure doppler shift…
What advantages are there to using a reflector telescope over refractor telescopes
no chromatic aberration, UV light is less absorbed in lenses, lenses are heavier than mirrors thus, harder to support since they have to be held by the edges
When looking for a photon with the greatest energy what shift do you look for? largest frequency? largest wavelenght?
highest to lowest level, largest energy, and wavelength and energy are inverse so lowest energy
How much energy an object emits is dependent on what
its size and temperature
