Astronomy unit one summative
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70 Terms
What is the brightest object in the night sky?
The moon
Why does the moon go through phases?
The moon orbits the earth
Five planets are visible from earth without needing a telescope
Mercury, Venus, Mars, Jupiter, and Saturn
The second brightest object in the night sky
Venus
Why do planets appear brighter than most stars?
They're closer
Why can't Uranus and Neptune be seen with a telescope?
They're too far away
Constellations
Patterns of stars in the sky
Milky Way Galaxy
Where we can see all the stars with our naked eyes
What affects how bright a star appears to us?
Intrinsic light and distance
Brightest star in the Earth's night sky
Sirius A
Canis Major
Constellation that has Sirius A
Star clusters
Groups of stars held together by gravity
Amount of stars in a star cluster
Ten or more
Nebula
Huge collection of gases and cosmic dust where stars form
Can be spotted without a telescope
Star clusters and nebulae
The Milky Way
Our galaxy
Why does the Milky Way galaxy look like a bright circle around Earth
We view from its inside
Comets
Icy objects from the outer solar system
What happens to comets as they approach the sun
They heat up and form two tails
The international space station
An orbiting space satellite for space research
Blinking lights are…
Planes
Why is it harder to see night sky objects in cities
Light pollution
How did people in the past observe stars for their advantage
Navigation, when to plant and harvest crops, and to tell stories
How many constellations are there
88
Asterism
Star grouping that is not an official constellation
Big Dipper
Asterism in the constellation Ursa Major
Orion's Belt
Asterism inside of the constellation Orion
What causes constellations to be visible or not
Your location on Earth and the time of year
Circumpolar constellations
Constellations that never appear to set
Circumpolar constellations for the northern hemisphere
Ursa Major, Ursa Minor, Draco
Circumpolar constellations for the southern hemisphere
Carina, Centaurus, Crux
Equator
The devision between the northern and southern hemispheres
Where to get the best view of all 88 constellations throughout the course of one year
The equator
Why can't we see all the constellations in one night?
Earth's revolution around the Sun
What dictates what constellations are visible during different times of the year
Earth and the Sun's relative position
Ecliptic
Path that the sun travels through
What are the ecliptic constellations more commonly known as?
Zodiac constellations
Polaris
Star located above the North Pole
How to find Polaris
Look for the Big Dipper, the stars on the side of it not facing the handle are south of Polaris
Why will Polaris not always be the North Star
The Earth's axis is wobbling
Precession
Wobble in Earth's rotational axis
Thuban
Star the North Pole pointed to 5000 years ago
Vega
Star the North Pole will point to in 13000 years
Amount of time it takes for the Earth's precession cycle to complete
26,000 years
Altitude
Height above the observer's horizon measured in degrees
How altitude is measured
Vertically starting from the horizon (0 degrees) and extending directly overhead (90 degrees)
Zenith
The point directly above you, has an altitude of 90 degrees
Max degrees an altitude can be
90 degrees
Azimuth
The horizontal direction of an object in the sky, measured in degrees clockwise from the north direction
How azimuth is measured
Along the horizon, starting from the north direction then sweeping clockwise
Degrees of azimuth at due north
0 degrees
Degrees of azimuth at due east
90 degrees
How are altitude and azimuth coordinates written
Altitude:Azimuth
Why do the positions of celestial objects in the night sky change with time
The earth rotating on its axis
How would the altitude of an object change during the course of the night
Appear higher in the sky as it moves the eastern horizon to its highest point in the sky and lower towards the western horizon
How do telescopes work
Collecting and focusing light
How do telescopes get better resolution
Larger area of a telescopes lens gives it more light to collect causing the resolution to improve
Two main types of telescopes
Refracting and reflecting
Refracting telescope
Uses lenses to gather light
Lens
Refracts (bends) light rays to bring them to a point called a focus
Focal length
Distance from the lens to the focus
Length of the telescope
Adding the focal lengths of the two lenses
What determines how much a refracting telescope magnifies an image
The ratio of the objective lens to the eyepiece lens
Why do some prefer refracting telescopes over reflecting
They are simple and low maintenance, great for backyard astronomy
Why do some prefer reflecting telescopes over refracting
Less expensive, less heavy, not as difficult to manufacture, bigger versions are better with these
Why are space telescopes good
Gives us much clearer images, no atmosphere in space
How do reflecting telescopes work
Uses mirrors to gather and focus light
Mirror
Reflects light rays, curved versions bring to a focus
Focal length
Distance from the mirror to the focus
Most popular space telescopes
Hubble space telescope, James Webb Space Telescope
Note 
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