Unit 3 Earth in the Universe

Origin and Age of Universe Celestial object- anything above Earth’s atmosphere. Universe- all the space, matter, and energy in existence. Universe is very vast and more than 10 billion years old.

Origin Most scientist believe in the Big Bang theory. All matter and energy started out concentrated in a small area, after a gigantic explosion, matter began to organize into subatomic particles and atoms.

Origin con’t.

More Origin Most early atoms where hydrogen and helium. Within a billion years the atoms began to form into celestial bodies. As the bodies got bigger they began to increase their gravitational forces. This resulted in the grouping of stars. Remember that the universe was expanding then and is still expanding today.

Evidence for the Bang! If the Big Bang did occur, the energy released would expand along with the matter. Radiation from the bang would be mixed with radiation given off from stars at later times. Recently, background radiation has been found to be coming from all directions in the universe. Other evidence lies in the spectrum of the radiation given off by stars.

Electromagnetic Spectrum What is it? Waves of energy transmitted through space. Each element has its own signature wavelength in the spectrum. Scientists compare the wavelengths seen from space to the wavelengths of known elements on Earth.

Blue Shift/Red Shift

Blue Shift/Red Shift con’t. Doppler effect- the shifting of wavelengths How else can you observe the Doppler effect? If an object is moving towards Earth there is a blue shift (shorter wavelength), if an object is moving away there is a red shift (longer wavelength).

More Evidence of the Bang The collective light from all the stars in all the galaxies, except for a few close to Earth, is shifted to the red end of the spectrum. This proves that the universe is indeed expanding in all directions.

Structure of Universe The basic structure of a unit of matter seems to be a galaxy. Galaxy- a collection of stars, gas, and dust held together by gravity. An average galaxy contains over 100 billion stars! There are more than 100 billion galaxies!

Galaxy Shapes 3 types: -Elliptical -Irregular -Spiral Milky Way Galaxy- our solar system is a part of this galaxy, and is spiral shaped.

Irregular

Elliptical

Spiral Shapes

Stars Make up the majority of known matter in the universe. Star- large ball of gas held together by gravity and produces a tremendous amount of energy.

Energy Production Result of nuclear fusion- combines the nuclei of smaller elements to make larger ones. Mass is converted into energy. The sun converts hydrogen into helium with 7% of the mass converted to energy. Nuclear fusion can only occur in extremely high temperature and pressure situations. Energy is released into space as electromagnetic energy.

Luminosity and Temperature Chart is used to classify stars based on their surface temperature and luminosity.

Luminosity Star’s brightness compared to the sun Stars change colors depending on their temperature.

Star Types Main sequence- 90 % of stars. Majority of stars life spent as a main sequence. These stars are the average size. As they grow their luminosity moves from red to blue-white. Growing results in a higher temperature.

Star Types Giant stars- red, orange, and yellow giant stars are rare, but are commonly seen because they are so large.

Star Types Super giants- 100 to 1000 times the diameter of the sun. Usually explode in a tremendous event known as a supernova. What stars are brightest and the hottest?

White dwarfs- not all are white, but they are all small (size of Earth). Hot on the surface, but low in luminosity. Star Types

Black dwarfs- when a white dwarf cools and no longer emits electromagnetic energy it is known as a “dead” star/black dwarf.

Star Origin and Evolution Start from clouds of gas and dust molecules. Clouds are the result of the Big Bang or from stars that have undergone a supernova. Gravity draws these clouds together, forming larger and larger clouds. This process continues until the mass of the cloud is slightly larger than Jupiter. This gives the “star” a high enough temperature and pressure to begin nuclear fusion.

Evolution Most of the life of this new born star is spent in the main sequence. What the star evolves to next depends on their original mass. Stars with masses similar to our sun expand to become red giants. When the red giant uses up its nuclear fuel it collapses into a white dwarf and then a black dwarf.

Evolution con’t. Any star whose mass is 1 ½ times the sun have much different paths of evolution. Exist as a main sequence for a much shorter time, about 100 million years. These stars still turn into super giants. They then undergo a supernova and quickly collapse forming a center that is so dense only neutrons can exist (neutron star) Even larger stars explode into a black hole- allows no visible light or any other form of energy to escape.

Solar System Any star or group of stars that have non-star objects orbiting it.

Parts of the Solar System Satellites- any object that orbits another object. Planets- 9 revolve around sun. 100 planets have been found revolving around stars other than our sun. Asteroids- solid rocky, or metallic body that independently orbits the sun. Irregular in shape and have no atmosphere. Smaller than planets.

More Parts Moons- anything that orbits a planet or an asteroid as those objects orbit the sun. Comets- compared to a dirty snowball. Composed of a mixture of ices of water and methane, and metallic solids. What happens when a comet gets too close to the sun? Meteoroids- small solid fragments that orbit the sun. Size of dimes or grains of sand. What is a meteor?

Evolution of Solar System About 5 billion years old. Started as a gas cloud many times the size of today’s solar system. Gravitation caused the cloud to condense, most of the mass was pulled to the center and formed our sun. After Earth and other planets were formed, their gravity pulled on other smaller objects causing them to collide with the planets. This is called an impact event. Where is there evidence for this?

Planet Characteristics A planet’s distance from the sun largely determines its characteristics. When the sun was still forming it was much hotter than today, forcing less dense elements towards the outer solar system. Planets can be divided into two types: terrestrial and Jovian.

Terrestrial Planets Close to the sun and mostly solid. Small diameters and high densities Surfaces have impact craters Have few or no moons and no rings Name the terrestrial planets.

Jovian Planets Far from the sun Largely gaseous Relatively large diameters and low densities No solid surface/could have solid core Many moons and have rings Name the Jovian planets.

Motions of the Planets Planet rotation- spins on an imaginary axis - determines a planet’s length of day - 7 of 9 planets rotate in same direction of the rotation around the sun. - periods of rotations can be found in Earth Science Reference Tables Planet revolution- the planet’s motion around the sun, called an orbit.

Motions of the Planets Ellipse- the shape of the orbits of all planets. Foci- see page 42 in review book. Eccentricity- the amount of difference between an ellipse and a circle. Eccentricity of ellipse= distance between foci length of major axis The closer the number is to zero the closer the orbit is to resembling a circle.

Varying Distance of Planets from the Sun The Earth is 147 million km away at its closest point to the sun and 152 million km away at its furthest point to the sun. This does not determine seasons! click here to see the solar system drawn to scale

Inertia, Gravitation, Orbital Velocity/Speed, and Planet Orbits Inertia- an object at rest will remain at rest, and an object in motion will maintain the speed and direction of that motion unless an opposing force acts upon it. Gravitation- the attractive force between any two objects. -The greater the mass of one or both of the objects, the greater the attraction. -The closer the two objects together the greater the attraction. -What causes a planet to maintain its orbit?

Inertia, Gravitation, Orbital Velocity/Speed, and Planet Orbits Keeping in mind that each planet’s orbit has some degree of eccentricity, is the orbital velocity the same all the time? When is it fastest? When is it slowest? Revolution- the time it takes a planet to go all the way around the sun. Explain how a planet’s distance from the sun determines the speed of a planets revolution.