Earth Science: The Universe and the Solar System & Expanding Universe & Origin of the Universe

The Main Sequence

• About 90 percent of all stars fall along a sinuous band. All main-sequence stars are composed primarily of hydrogen and helium and are fueled by hydrogen fusion.

• More composition, means more pressure and higher.

Lifecycle of an Average-Mass Stars

Stars form from condensing nebulae of gas and dust, initiating fusion when temperatures rise. As hydrogen fusion ends, gravity compresses the core, raising temperature. Following helium fusion, the star expels a planetary nebula and contracts into a white dwarf.

Lifecycle of a Massive Star

A massive star generates sufficient heat to fuse heavier elements, leading to a supernova explosion. The remnant can form a neutron star or, if massive enough, collapse into a black hole.

• Higher mass, higher gravitational pull.

Galaxies

A large volume of space containing many billions of stars, held together by mutual gravitational attraction. Ex. Spiral, Barred Spiral, Elliptical.

The Milky Way

The Milky Way is a barred spiral galaxy containing our Sun, stars in its disk, captured dwarf galaxies, gas and dust clouds, and a halo of globular star clusters.

Dark Matter

Up to 96 percent of the Universe is invisible and is called dark matter.

Ordinary Matter

Comprises everything that you see and is 4% of the universe.

Dark Mass

Which makes up 23% of the universe is a form of matter that does not interact with light.

Dark Energy

Which makes up 73% of the universe is a repulsive force that pushes matter outward, causing the expansion of the universe to speed up.

Closed Universe Hypothesis

If the gravitational force of the universe is sufficient, all the galaxies will eventually slow down, reverse direction, fall back to the center, collapse and then explode again to form a new universe.

Open Universe Hypothesis

If the gravitational force of the universe is not sufficient to stop the expansion, then the galaxies will continue to fly apart forever. As the stars fade and cool, the galaxies will continue to separate into the cold void.

Waves

Are disturbances that transmit energy from one point to another in the form of periodic motions.

Crest

The highest point of a wave.

Throughs

The lowest point of a wave.

Wavelengths

Refer to the distance between successive waves.

Frequency

Refers to the number of waves that pass a point in a given time interval.

Red Shift

• If a light source moves away from you, the light you see becomes redder as the light shifts to longer wavelengths or lower frequencies.

• Scientists use this phenomenon to observe the expansion of the universe.

Blue Shift

If the source moves toward you, the light you see becomes more blue as the light shifts to higher frequencies.

Hubble’s Law

Galaxies recede at speeds proportional to their distances from the observer.

The Big Bang Theory

• About 13.7 billion years ago, the universe began with a massive and rapid expansion.

• Prior to this expansion, there was no space or time.

• Matter and energy were contained in a compact point called singularity.