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- Any object that exists in space.
- i.e.- the Sun, Stars, Planets, the Moon, etc.
- A scientist who studies astronomy.
- The Mesopotamians were the first astronomers as early as 6000 years ago.
- The time it takes for an object to orbit another object.
- i.e.- Earth's revolution around the Sun is 365.24 days
- The turning of an object around an imaginary axis running through it.
- i.e.- Earth's rotation around it's axis is 24 hours
- A group of stars that seem to form a distinctive pattern in the stars.
- Appear close to eachother and the same distance from Earth because they are on the same line of sight.
- i.e.- Cassiopeia, Orion, etc.
- Figure below shows how constellations are seen as patterns
- The DISTANCE that light travels in one year
- 9.5 trillion () km in one year
- The brightness of a star from equal distances.
- Measured on a stellar magnitude scale which opes from -26 (the Sun) to over 6 in Magnitude.
- A smaller group of stars that forms patterns within a constellation
- i.e.- Big Dipper, Summer Triangle
- Figure below shows the smaller pattern (big dipper) inside a larger constellation (Ursa Major).
- The big dipper's 2 end stars are called the pointer stars because they point toward polaris.
- Figure below shows the pointer stars and polaris, which they appear to point towards
- The rising and fallling of ocean water as a result of the Moon's gravity and Earth's gravity.
- Figure below shows how the Moon influences the tides, along with the caption below.
Phases of the Moon
- The monthly progression of changes in the appearance of the Moon that result from different portions of the Moon's sunlit side being visible from Earth.
- The image below shows the phases of the Moon and how they are seen from Earth.
- When the full Moon passes through the umbra position of Earth's shadow so the Earth is between the Sun and the Moon.
- Figure below (A) shows the Moon passing through Earth's shadow. The red Moon (B) beside it is an example of what the Moon would look like during a Lunar Eclipse.
- When the shadow of the Moon falls on Earth's surface.
- The moon is between the Sun and Earth during a new Moon.
- Happens twice a year and can usually only be seen from very specific, often remote places on Earth's surface.
- This is NOT safe to look at with the bare eye.
- Figure below (B) shows the Shadow of the Moon on Earth's surface. The Black Moon with the Sun behind it (A) is what a Solar eclipse would look like from Earth.
Why do we have seasons?
- On Earth, we have seasons because the Earth is on an axis. In Summer in North America, the Northern hemisphere is facing the Sun so it's rays are concentrated on the surface. In winter, the Northern hemisphere is not facing the sun so the light is spread out on the surface. Concentration of Sun's rays results in warmer weather, and when the rays are spread, it results in colder weather.
- Figures below show the Sun's rays on Earth in both a concentrated way and a 'spread' way.
- Figure below shows how the Earth is on an axis so the Northern hemispher ha summer solstace on June 21st.
- An object that orbits one of more stars in spherical, and does not share its orbit with another object.
- i.e.- Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
- Table below shows which planets are inner (Between the Sun and Mars)and which are outer (After Mars)
- Made up of the planets, the Sun, and other smallers objects which are kept in the solar system by the Sun's gravity.
- Figure below shows the planets, the Sun, and other small objects in the solar system
- The movement of an object in the sky, usually a planet, from East to West, rather that it's normal West to East
- Due to Earth moving faster than outer planets causing it to catch up and move between them
- Figure below shows what a planet in retrograde motion appears from Earth
The average distance between Earth and the Sun, about 150 million km or
- Average distance between the Sun and an object orbiting the Sun.
- This number is expressed in astronomical units.
- A model of the planets by Ptolemy stating that all planets and the Sun revolved around the Earth in perfect circles.
- Figure below is the geocentric model, with geo meaning Earth (the Earth is the center of the solar system)
- A model of the planets by Copernicus stating that all planets revolved around the Sun in perfect circles.
- It was later changed by a J. Kepler stating that the planets orbit are ellipses.
- Figure below shows the Heliocentric model with Helio meaning Sun (the Sun is the center of the solar system)
- An object composed of rocky material, ice, and gas; comes from the Kuiper Belt or Oort Cloud.
- Often refered to as shooting stars
- An object in space that ranges in size from from a tiny speck, like a grain o sand, to 500 km wide; most asteroids originate in the asteroid belt between Mars and Jupiter.
- Section circled in white below is the asteroid belt
A piece of rock moving through space
A meteoroid that hits Earth's atmosphere and burns up
A meteoroid that is large enough to pass through Earth's atmosphere and reach the ground, without being totally burned up
- An object that circles the Sun beyond the orbit of Neptune.
- i.e.- PLuto, Sedna, Quaoar, etc.
- Radiation consisting of electromagnetic waves that travel at the speed of light
- i.e.- Visible light, radio waves, and X rays)
- A telescope that uses a lens to collect the light from an object
- A telescope that uses a mirror to collect light from an object
- An artificial (human made) object or vehicle that orbits Earth, the Moon, or other celestial bodies; also a celestial body that orbits another of fa larger size
- i.e.- the Moon is Earth's natural satellite
Observatories that orbit other celestial objects
Solar nebula theory
- The theory that described how stars and planets form from contracting, spinning disks of gas and dust. This is shown below.
A celestial object body made of hot gases, mainly hydrogen and some helium
A vast cloud of gas and dust, which may be the birthplace of stars and planets
Hot, condensed object at the center of a nebula
The process of energy production in which hydrogen nuclei combine to form helium nuclei
- The surface layer of the sun
- Shown on the right hand side below
- An area of strong magnestic fields on the photosphere
A stream of fastmoving charged particles ejected by the Sun into the solar system
- A solar flare is when complex groups of sun spots eject solar wind.
Importance of the Sun
- The Sun is needed for all life on Earth. Energy from the Sun drives most processes on Earth that support daily activities
- i.e.- Sun is necessary in finding sufficient food, and providing shelter. The Sun is also responsible of the natural heating and lighting of the Earth
A star's total energy output per second; its power in joules per second (j/s)
The magnitude of a star that we would observe if the stars were placed 32.6 light years from Earth
An optical instrument that produces a spectrum from a narrow beam of light, and usually projects the spectrum onto a photographic plate of a digital detector
Certain specific wavelengths within a spectrum characterized by lines; spectral lines identify specific chemical elements
Hertzsprung-Russell (H-R) diagram
A graph that compares the properties of stars
- A narrow band of stars on the H-R diagram that runs diagonally from the upper left (bright, hot stars) to the bottom right (dim, cool stars)
- About 90% of stars including hte Sun are in the main sequence
A small, dim, hot star
A massive explosion on which the entire outer portion of a star is blown off
A star so dense that only neutrons can exiat in the core
How low-mass stars evolve
Low-mass stars consume their hydrogen slowly over a time frame that may be up to 100 billion years. As they age they loose mass, become white dwarfs.
How intermediate-mass stars evolve
They consume hydrogen faster than low-mass stars. When their hydrogen is used up the core collapse. The layers begin to expand and the temperature rises. It now appears red and is called a red giant.
How high-mass stars evolve
These consume fuel faster than the other 2 and die quickly and violently. The stars expand into supergiants and heavy elements form by fusion. The outer part of the star creates a supernova, which can be billions of times brighter than the original star. A supernova ejects elements into the universe becoming new planets, stars, etc.
- A tiny patch of space that has no volume, but has mass and gravity
- Extremely strong gravitational pull means nothing can escape, not even light
- The galaxy that includes the solar system
- Appears as a hazy white band in the night sky
- A huge collection of stars, planets, gas, and dust that is held together by gravity
- A collection of stars held together by gravity
- The picture below shows the two types of cluster
- A collection of 50 to 1 000 stars
- Open clusters appear along the main band of the Milky Way
- A collection of 100 000 to 1 000 000 stars, which are arranged in a distinctive spherical shape
- They appear around the center of the Milky Way
- The small group of galaxies that includes the Milky Way
A gigantic cluster of 4 to 25 cluster of galaxies, which is hundreds of millions of light-years in size
Shapes of galaxies
- There are 3 shapes of galaxies.
- 1. Spiral Galaxy- looks like a pinwhell from above
- 2. Elliptical Galaxy- looks like a stretched out sphere into an ellipse
- 3. Irregular Galaxy- do not have a regular shape.
The study of the universe
- The change in frequency of a light source due to its motion relative to the observer
- The change in pitch is due to the motion of the source relative to an observer
- The effect in which objects moving away from an observer have their wavelengths lenghtened, toward the red end of the visible spectrum
- The third spectra above is redshifted
- The effect in which objects moving toward an observer have their wavelengths shortened, toward the blue end of the visible spectrum
- The second spectra above is blueshifted
The event that may have triggered the expansion of thte universe 14 billion years ago
Cosmic microwave background (CMB) radiation
- The radiation left over from the big bang, which fills the universe
- The most abundant form of matter in the universe
- It is invisible to telescopes
- A form of energy that makes up nearly three quarters of the universe, which has the effect of increasing the expanding of the universe