Astronomy 1021 Chapter Notes - Chapter 1: Interstellar Cloud, Star System, Observable Universe
28 May 2018
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Department
Course
Professor
Astronomy 1021
Chapter 1: A Modern View of the Universe
Definitions
•Star: spherical object that generates energy through nuclear fusion (ex. H to He); Sun is our
closest star; Next closest is Proxima Centauri; Stars twinkle, twinkling (scintillating) occurs b/c
starlight is being refracted into the Earth’s atmosphere and it shimmers, stars generate their own
light; 1000 stars visible in the sky
•Planet: spherical object that orbits a star; can see planets b/c reflects light, don’t generate their
own light; consist of rock, ice, gas, 8 planets in Solar System, 5 dwarf planets
οMust meet this criteria: orbits a star, large enough to be round using own gravity, free of
most other objects in its orbit; object meeting first 2 but not 3rd is called dwarf planet
(like Pluto)
ο5 Dwarf planets: Makemake, Eris, Haumea, Ceres, Pluto
•Moon (or satellite): object that orbits a planet; satellite refers to an object orbiting another
object; not big enough to pull itself into a sphere
•Solar System: region around a star that includes the Sun, material orbiting it, planets, dwarf
planets, countless small objects including asteroids, comets.
•Galaxy: very big collection of stars (and solar systems), gas, dust, and dark matter; held tog by
gravity and orbiting a common center; our galaxy is the Milky Way- contains more than 100 b
stars, orbited by planets
•Nebula: huge interstellar cloud of gas and dust; four main varieties; plural is nebulae
•Universe (Cosmos): sum total of all matter and energy- all galaxies and everything b/w them;
•Galaxy Clusters: collection of galaxies bound tog by gravity, small collections called groups,
larger called clusters
•Superclusters: large regions where many groups and clusters of galaxies are packed close tog.
•Asteroid: small, rocky object that orbits a star
•Comet: small and ice-rich object that orbits a star
•Small solar system body: an asteroid, comet, or other object that orbits a star but too small to
quantify as a planet/dwarf planet
•Star system: 1/more star and any planets and other materials that orbit it
•Observable universe: portion of the entire universe we can see from Earth
•Rotation: spinning of an object around its axis; ex. earth rotates once a day around its axis
•Orbit (revolution): orbital motion of one object around another due to gravity; ex. earth orbits
sun once a year
•Expansion (of the universe): increase in average distance b/ galaxies as time progresses
Document Summary
Chapter 1: a modern view of the universe. Star: spherical object that generates energy through nuclear fusion (ex. Must meet this criteria: orbits a star, large enough to be round using own gravity, free of most other objects in its orbit; object meeting first 2 but not 3rd is called dwarf planet (like pluto) 5 dwarf planets: makemake, eris, haumea, ceres, pluto: moon (or satellite): object that orbits a planet; satellite refers to an object orbiting another object; not big enough to pull itself into a sphere. Superclusters: large regions where many groups and clusters of galaxies are packed close tog: asteroid: small, rocky object that orbits a star, comet: small and ice-rich object that orbits a star. Small solar system body: an asteroid, comet, or other object that orbits a star but too small to quantify as a planet/dwarf planet.
