Wanderers in Space, Key Terminology Flashcards

fundamental questions about the universe and our place within it

basic content and scale of the universe

ages of Earth and the universe

size and extent of the universe

- includes basic content and structure

development and changes in universe from its beginning to the present

a large, glowing ball of charged gas that generates heat and light through nuclear fusion in its core

"nuclear furnace"

a star and all the materials that orbit it -- including planets and moons

- our galaxy

- the band of light we see in the sky when we look into the plane of our galaxy

- great "island" of stars in space

- all held together by gravity

- orbit a common center

group of about 40 galaxies to which Milky Way galaxy belongs

- one of the two largest among them is Milky Way

collection of a few dozen or more galaxies bound together by gravity

- smaller collections called groups

clusters of galaxy clusters

largest known structures in the universe

local supercluster

translates to "immense heaven"

1 light-year = 9.46 trillion km

average distance (semimajor axis) from Earth to the Sun

~93 million miles (150 million kilometers)

distance that light can travel in one year

approx. 10 trillion kilometers

the further back we look in time

arranged in giant chains and sheets with huge voids between them

- moderately large object that orbits a star

- shines primarily by reflected light (from its star)

may be rocky, icy, or gaseous in composition

object that orbits a planet

any object orbiting another object

relatively small & rocky object that orbits a star

relatively small & ice rich object that orbits a star

asteroid, comet, or other object that orbits a star

too small to qualify as a planet or dwarf planet

sum total of all matter and energy

- all galaxies and everything in between them

portion of the entire universe that can be seen from Earth

planets in other solar systems around other stars

interstellar cloud of gas and dust

how stars and stellar systems are formed

dwarf planets

trans-neptunian objects

spinning of an object around its axis

orbital motion of one object around another due to gravity

14 billion years

boundary of our observable universe

increase in average distance between galaxies as time progresses

earth -> inner solar system -> outer solar system -> closest stars -> Milky Way -> local group -> laniakea -> local superclusters -> observable universe

time for the sun to return to the meridian

avg. 24 hours

time for a distant star to return to the meridian after a rotation

23 hours, 56 minutes, 4 seconds

*Earth's TRUE rotation rate*

Earth also has to revolve around the Sun in our orbit and have to turn a tiny bit more to face the sun again

directly above Earth's North Pole

the Sun's apparent annual path around the celestial sphere

ancient belief that universe is "Earth-centered"

ie. Earth is center of universe and all other celestial bodies orbit around Earth

Earth's orbital path

puts stars and constellations onto an imaginary sphere around us

*not realistic, just how it appears to us from Earth

west -> east

east -> west

counterclockwise (when viewed from above the North Pole)

23.5 degrees (from a line perpendicular to the ecliptic plane)

in the same direction in space throughout the year

in the same counterclockwise direction as its rotation

Polaris

- the North Star, always found in a direction of due north

varies slightly over the course of the each year

it rotates on its axis

region of the Sun and nearby stars

matter inferred to exist from gravitational effects, but no light has been detected

- dominates total mass of the universe

energy that could be causing the expansion of the universe to accelerate

away from us

the faster it appears to be racing away

analogy to explain expansion of universe

expansion of cake causes raisins to move away from local raisin -- more distant raisins move away faster

indicating that we live in an expanding universe

faster the rate of expansion, the more quickly galaxies reach their current position -- therefore the younger the universe must be

- cake has center and edges; same may not be true for the universe ( no place is more central than any other place)

-can't see galaxies moving apart with time

way of measuring speeds of galaxies via spreading their light into these spectra

region of the night sky with well-defined borders

familiar star patterns help us find them

point directly over Earth's South Pole

projection of Earth's equator into space

- makes a complete circle around the celestial sphere

band of light that circles around celestial sphere

- traces our galaxy's disk of stars-- the galactic plane-- as it appears from our location within the galaxy

sky as seen from wherever you happen to be standing

boundary between earth and sky

point directly overhead (in sky)

imaginary half-circle stretching from horizon due south, through the zenith, to the horizon due north

one of two coordinates needed to pinpoint an object in the local sky

(above horizon) the angular distance between the horizon and an object in the sky

north-south location on sky (like latitude)

(degrees, arcminutes, arcseconds)

east-west location on sky (like longitude)

hours, minutes, seconds

(of an object) the angle it appears to span in your field of view

- also depends on distance

(between objects) angle that appears to separate them

east to west

star that always remains above the horizon for a particular latitude

never rise above horizon at all

where the sun crosses the celestial equator on the march equinox

the smaller its angular size

circumpolar, meaning that they remain perpetually above the horizon, circling (counterclockwise) around the north celestial pole each day

never rise above the horizon at all

partly above the horizon & partly below

why they appear to rise in the east and set in the west

north of the equator

south of the equator

angular size/360 degrees = physical size / 2pi x distance

latitude

your latitude

change as we orbit the Sun

its orientation relative to the Sun changes as Earth orbits the Sun

we would NOT have seasons

occurs around June 21st

moment when the Northern Hemisphere is tipped most directly toward the Sun

- receives the most direct sunlight

occurs around December 21st

the moment when the Northern Hemisphere receives the least direct sunlight

Northern Hemisphere goes from being tipped slightly away from the Sun to being tipped slightly toward the sun

moment when the Northern Hemisphere first starts to be tipped away from the sun

the progression of the seasons

sun rises precisely due east and sets precisely due west

Sun rises and sets farthest to the north of due east and due west

more extreme seasons

gradual wobble that alters the orientation of Earth's axis in space

the direction the axis points in space changes slowly with the 26,000-year cycle of precession

gravity's effect on a tilted, rotating object

Moon's appearance in the sky changes as its position relative to the sun changes

all along the Moon's orbit

- we always see the same side of the moon facing Earth

- as moon orbits Earth, we see different combinations of its bright and dark faces

its position relative to the Sun as it orbits Earth

its rise and set times

rises and sets with sun

rise: before dawn

highest: mid-morning

set: mid-afternoon

rise: midnight