Lec 1 Flashcards
(26 cards)
Milky Way Galaxy
the huge, disk-shaped collection of stars that our solar system belongs to
-galaxy is a great island of stars in space, all held together by gravity and orbit a common center
-groups of galaxies with more large members called GALAXY CLUSTERS
superclusters
regions in which galaxies and galaxy clusters are most tightly packaged
1 astronomical unit (AU)
Earth’s average distance from the Sun, which’s about 150 million km
1 light year (ly)
the distance that light can travel in 1 yr, which’s about 10 trillion km
-use light yrs to describe the distances of stars and galaxies
(**unit of distance and not time)
star
large, glowing ball of gas that generates heat and light through nuclear fusion in its core
-sun is a star
planet
large object that orbits a star and shines primarily by reflecting light from its star
Object can only be considered a planet if it:
1) orbits a star
2) is large enough for gravity to make it round
3) has cleared most other objects from its orbital path
Object that meets first 2 but not 3rd is called a DWARF planet
exoplanet
planet orbiting a star other than Sun
moon
object that orbits a planet
asteroid vs comet
asteroid–> small and rocky object that orbits star
comet–> small and ice-rich object that orbits star
universe (or cosmos)
the sum total of all matter and energy (all galaxies and everything between them)
rotation
the spinning of an object around its axis
orbit (or revolution)
the orbital motion of one object around another due to gravity
expansion (of the universe)
the increase in the average distance between galaxies as time progresses
nuclear fusion
process where atomic nuclei smash together and stick (or fuse) to make heavier nuclei
-the star “lives” as long as it can shine with energy from fusion, and “dies” when it exhausts its usable fuel
supernovae
a titanic explosion that causes most massive stars to die
Earth’s rotation
Earth rotates once each day around its axis, which’s the imaginary line connecting the North Pole to the South Pole
-earth rotates from west to east CCW, which’s why the Sun and stars appear to RISE in the east and SET in the west
Ecliptic plane
the flat plane that defines Earth’s orbital path
Earth’s axis tilt
Earth’s axis is tilted by 23.4 deg from a line perpendicular to the ecliptic plane
-this axis tilt is oriented so that the axis points almost directly at a star called Polaris, or the North Star
How do galaxies move within the universe?
-move relative to one another
-within the Local Group, some of the galaxies move twd us, some away and numerous orbit the Milky Way Galaxy
Virtually every galaxy OUTSIDE the Local Group is moving ______ from us
away
The more DISTANT the galaxy, the _____ it appears to be racing away.
faster
how did we come to be?
the universe began in the Big Bang and has been expanding ever since, except in localized regions where gravity has caused matter to collapse into galaxies and stars
-big bang produced hydrogen and helium
order of our cosmic address, from smallest to largest
Earth, Solar System, Milky Way Galaxy, Local Group (a small group of nearby galaxies), Local Supercluster (specifically the Laniakea Supercluster), Universe
Birth of the universe
Expansion of the universe began with the big bang
-Universe continues to expand, but on smaller scales gravity has pulled matter together to make galaxies
