Fire and Stars

There are two types of light, incandescent light (white) and light that has color.  Light that has color comes from gas excitations.  For example, sparks, neon lights and mercury vapor lamps emit colored light. Incandescent light emits only a white light.  Gas excitations have an original type of line emission spectrum, which can be detected from a flame test.

 

When the atoms of a gas or vapor are excited, by heat or electricity, their electrons move from a ground state to a higher energy level.

 

When they return to the original ground state, they emit photons that have specific energy making them easily identifiable.

The energy corresponds to specific wavelengths of light, and thus makes the specific colors of light.

 

Each element has a specific line emission spectrum that allows scientists to identify the element by the color of flame

Copper: blue flame

Lithium: red

Strontium: red

Calcium: orange

Sodium: yellow

Barium: green

 

The hottest part of a flame, core, is light blue with a temperature of 1400 °C

Outside the flame are yellow, orange, and red (the furthest part from the core)

The farther from the flame’s core the warmer the flame is.

The red portion is about 800 °C

 

Exploding fireworks produce gas, which excites the electrons.

As they return to their ground state, they emit colored light according to the chemicals used:

Copper compounds: blue

Sulfur: yellow

Barium: green

 

Light that is moving has a changing frequency that is proportional to the wavelength.  When the frequency decreases, the wavelength increases.

Visible light moves towards the red part of the spectrum that is known as the red shift. A light source moving towards the observer increases in wavelength.

 

 

By analyzing the type of light from an object and how it has changed from the red shift, scientists can see how far light has traveled.  This is called Hubble’s Law.

 

Big Bang theory: The universe is expanding and must have started as one point.  Proof: signature radiation left over.

 

The color of a star is used to identify the star because the color corresponds to the star’s surface temperature, measured in the black body radiation scale.

 

The sun and yellow stars have a temperature of 5,500 K

Red stars are 3,500 K, which is cooler then the sun.

Dark red stars 2,500 K

Blue stars 10,000-50,000K, the hottest

 

A star does not stay the same color throughout its lifecycle, because its temperature changes