The Universe, Solar System, and Planets I

Questions:How do we know the Big Bang happened?

How do we know the Universe is expanding?

What is the timeframe of Universe evolution?

News Flash: NASA/CNN report first starsformed early than once thought

Edwin Hubble at Mt. Wilson

Hubble guiding the Hooker100 inch telescope in 1923. The Hooker 100 inch telescope atop Mt. Wilson

near Pasadena, CA. It was the largest telescope in the world from 1917-1947.

Hubble’s observations at the 100 inch during the1920’s led him to the conclusion that the universe is expanding, and that an object’s recession velocityis proportional to its distance from the observer.

A deep image of an “empty”portion of the sky with theHubble Space Telescopereveals that the universe isfilled with galaxies- many justlike our own. The lightwe see from the most distantgalaxies has traveled approx-imately 10 billion years to reach us.

Deep Hubble Space Telescope Image

Using the Doppler Effect to Measure Velocity

Blueshift Redshift

Calcium

Magnesium

Sodium

Galaxy Spectrum

Stellar Spectrum

Spectra of a nearby star and a distant galaxy

Star is nearby, approximately at rest Galaxy is distant, traveling away from

us at 12,000 km/s

Galaxy Spectroscopy

Origin of the Universe -Did It Begin with a Big Bang?

Penzias and Wilson, 1965 Arecibo Dish, Puerto Rico

Discovery of the Background Radiation from initial Big Bang-Long wavelength-came from all directions

Early History of the Universe

• Matter as we know it did not exist at the time of the Big Bang, only pure energy. Within one second, the 4 fundamental forces were separated– gravity - the attraction of one body toward another– electromagnetic force - binds atoms into molecules, can be

transmitted by photons– strong nuclear force - binds protons and neutrons together in the

nucleus– weak nuclear force - breaks down an atom’s nucleus, producing

radioactive decay

Early History of the Universe

• After 3 minutes, photons and neutrons began to fuse to form the nuclei of hydrogen and helium atoms

• About 300,000 years later, temperatures were cool enough for complete hydrogen and helium atoms to form

• Photons escaped from matter about the same time, and light existed for the first time

Changing Composition of the Universe

• 200 million years later, with expansion still occurring, stars and galaxies began forming from leftover matter - hydrogen and helium– nuclear fusion in stars has reduced the original composition of

100% H and He to 98%– when a dying star explodes, the heavier elements created by fusion

are blown into space to be recycled by newly forming stars– the overall composition of the galaxies is gradually changing to the

heavier elements

The Solar System - Its The Solar System - Its Origin and Early Origin and Early

DevelopmentDevelopment

Our solar Our solar system, part of system, part of the Milky Way the Milky Way galaxy, consists galaxy, consists of the Sun, nine of the Sun, nine planets, 64 planets, 64 known moons, known moons, many asteroids, many asteroids, millions of millions of comets and comets and meteorites, as meteorites, as well as well as interplanetary interplanetary dust and gasesdust and gases

The Solar System - Its The Solar System - Its Origin and Early Origin and Early

DevelopmentDevelopment

General Characteristics of the Solar System

• Planetary orbits and rotation– planet and satellite orbits are in a common plane– nearly all planet and satellite orbital and spin motions are

in the same direction– rotation axes of nearly all planets and satellites are

roughly perpendicular to the plane of the ecliptic

General Characteristics of the Solar System

• Chemical and physical properties of the planets– the terrestrial planets are small, have a high density, and are

composed of rock and metallic elements– the Jovian planets are large, have a low density, and are composed of

gases and frozen compounds

• Slow rotation of the Sun• Interplanetary material

– existence and location of asteroid belt

– distribution of interplanetary dust

Meteorites - Visitors from Outer Space

– Stones - composed of iron and magnesium silicates, about 93% of all meteorites

– Irons - composed of iron and nickel alloys– Stony-Irons - nearly equal amounts of iron and nickel

and silicate minerals

• Meteorites are believed to be pieces of material that originated in the formation of the Solar System about 4.6 billion years ago

*Prepared By: Sanyam Gandotra*Class: 6th BRoll No: 32

*Kendriya Vidyalaya Jyotipuram*Holiday Homework of Social Studies