Astronomy Unit Review 2016

The Life Cycle of a Star

  • stars begin in a stellar nebulae of gas and dust
  • pressure condenses the gas in dust in nebulae to form protostars
  • when a protostar actively begins fusing hydrogen into helium a star is born and becomes a main sequence star; this process is called fusion
  • when the core runs out of fuel, the outer layers expand, cool, and become less bright forming a red giant or a red super giant (depending on their initial mass)
  • the star will eventually collapse or explode and become either a white dwarf, neutron star, or black hole
  • neutron stars and black holes are remnants of once VERY large stars
  • the larger a star’s initial mass, the more compact and dense it is when it dies
  • our sun will turn into a red giant next, then a planetary nebula, then a white dwarf
  • the sun is a very AVERAGE sized main sequence star that gets its energy from fusion taking place in the core
  • hot stars are blue, colder stars are red

The H-R Diagram

  • this diagram plots the luminosity (also called

theabsolute magnitude) of a star versus the

surface temperature

  • also used to classify stars according to

where they are in their life cycle

  • upper left corner are hot, bright stars
  • upper right corner are cool, bright stars
  • lower left corner are warm, dim stars at

the end of their life

  • main sequence stars vary in size, color,

luminosity, and temperature but are all

actively fusing hydrogen into helium

  • the sun is a yellow main sequence star

marked by ‘x”

  • stars differ from planets in that they make their

own light while planets only reflect light

  • this is the electromagnetic spectrum which is a continuum of electromagnetic radiation
  • we can only see the visible light portion that is made from Red, Orange, Yellow, Green, Blue, Indigo, and Violet (ROYGBIV)
  • visible light travels to the Earth from the Sun in the form of radiant energy, which travels in transverse waves
  • the diagram below shows twotransverse waves
  • A has a long wavelength (crest to crest or

trough to trough) and a low frequency (# of

waves per second)

  • B has a shorter wavelength than a, and a higher

frequency, which means it has more energy

  • X-rays, UV rays, and Gamma Rays can destroy your

body’s cells and give you cancer

  • radio waves have the longest wavelength and the

lowest amount of energy; gamma rays have the

shortest wavelength and the highest frequency and

energy

-by looking at the spectrums of stars we can figureout their temperature, composition, and direction of movement

-Doppler Effect is whenever sound or light waves become compressed (closer together) or elongated (spread far apart)

-waves become compressed when the object is moving towards you

  • waves become elongated when the object is moving away from you
  • when objects in space like stars or galaxies are moving away from us, their light waves are elongated, this is called RED SHIFT; when objects in space move towards us, their waves are compressed which is called BLUE SHIFT
  • a spectroscope breaks visible light into ROYGBIV and produces emission spectra that we can use to analyze the composition of stars and Doppler Shift

Measurement in Space

  • 1 Astronomical Unit (AU)= 150 million kilometers or the average distance between the sun and Earth
  • Light year= the distance light travels in one year; used for measuring great distances outside the solar system
  • Parsec= “parallax second”= 3.26 light years

Telescopes

  • refracting uses lenses that bend light, reflecting uses mirrors that reflect light (Hubble Telescope), radio uses waves that are gathered and organized by a computer

Constellations

  • Circumpolar constellations can be seen year round and seem to rotate around the Earth’s poles; examples of these are Ursa Major, Ursa Minor, and Cassiopeia
  • The real name for the North Star is Polaris
  • Ursa Major (The Big Dipper) contains the two “pointer” stars used to locate Polaris
  • Ursa Minor (The Little Dipper) contains Polarisin its “handle”
  • Stars and constellations move from east to west across the night sky because the Earth is rotating on its axis
  • Certain stars and constellations can be seen during different season because the Earth orbits around the sun and is at different positions in its orbit at different times of the year

Astronomers

  • Ptolemy said everything in the universe revolved around the Earth; this is called the geocentric model
  • Copernicus was the astronomer that proposed the heliocentric model where everything revolves around the sun; this is the model of our solar system
  • Newton came up with 3 laws of gravity and the Universal Law of Gravitation
  • Kepler explained that our planets move in elliptical orbits and his 3 laws of planetary motion

accurately describe how the planets orbit the sun today

  • Galileo invented the first telescope, which was a refracting telescope, and used it to discover Jupiter’s four largest moons. This proved that not all heavenly bodies revolve around the Earth.

Galaxies

  • a galaxy is a group of stars held together by gravity; there are 3 types- elliptical, spiral, and irregular
  • Our galaxy is a spiral galaxy called the Milky Way Galaxy 100,000 light years across
  • The Andromeda galaxy is the nearest galaxy to our own about 1 million light years away; it is also a spiral galaxy
  • The Big Bang Theory is the current theory of the origin of our universe stating that everything was once a condensed ball of gas and dust until it exploded and expanded 10-20 billion years ago

Planets

  • List the terrestrial planets and describe what makes them “terrestrial”
  • List the Gas Giants describe what makes them “Gas Planets”
  • Be able to identify features unique to each planet
  • Be able to identify components of the planet atmospheres
  • List the Inner Planets in order to the Sun (closet to farthest)
  • List the Outer planets in order to the Sun (closet to farthest)
  • Know what retrograde rotation means. Illustrate the direction it moves.
  • Know which celestial object has an eccentric orbit and crosses over the orbit of the other planets
  • Know what a period of rotation is
  • Know what a period of revolution is
  • Know why planets in our solar system orbit the Sun
  • Know what the rings of Saturn are composed of

Solar System stuff

  • Know the definition of “satellite”
  • Know the parts of a comet
  • Know the difference in these two areas, and what can be found there
  1. Kuiper Belt
  2. Oort Cloud
  • Know the difference between meteors, meteorites, and meteoroids
  • Know where the asteroid belt is located
  • Know the position of the Earth during perihelion and aphelion
  • Know the approximate dates and seasons for solstices and equinoxes

The Moon

  • Know the phases of the moon, and the position of the moon, earth & sun for each phase.
  • Know the position of the moon, earth & sun for solar and lunar eclipses.
  • Know these terms: maria, highlands, craters, umbra, penumbra, apogee, perigee
  • Know the widely accepted theory for how the moon was created

The Sun

  • Define/describe the parts of the sun:

a. Corona

b. Chromosphere

c. Photosphere

d. Convective zone

e. radiative zone

f. core

  • Know the difference between solar flares, solar prominences, sunspots, and CMEs

Note: This guide is not all inclusive of what can be on the unit test. You should also review your notes, labs and other assignments that were completed during this unit.