The Sun

Earth Science - Mr. Gallagher

The Sun is the Earth's nearest star. Similar to most typical stars, it is a large ball of hot electrically charged gas which obtains its energy from nuclear reactions in its core This

energy release is similar to the energy expected from a countless number of hydrogen bombs exploding.

•Size comparison: 109 Earths lined up edge to edge to fit across the sun.

•330,000 times as massive as Earth

•99% of all the mass in the solar system

•As a result of it’s size the Sun controls the motion of the planets in our solar system

•The Sun is an average size star

•Diameter 1,390,000 km (863,706 miles)

• Mean Distance from Earth 149,597,890 km or 1 astronomical unit

•Age of Sun 4.5 - 4.7 x 109 years or ~4.5 billion years

•Volume (Earth=1) 1.412 x 1033 cm3

•Mass 1.99 x 1030 kg or 332,830 x more than the Earth

•Density 1.41 gm/cm3

•Length of day or Differential Rotation 25.38 Earth days. At the equator the surface rotates once every 25.38 Earth days; near the poles it's as much as 36 Earth days.

•Temperature core 5800 degrees Kelvin or 29 million degrees F surface 9935.930F

Factoids about the Sun

Structure of the Sun

Structure of the Sun

The Sun

Core

The outward flow of photons exerts a radiation pressure which balances the force of gravity and stops the collapse

The Sun

Core

The sun’s radius remains stable as long as the nuclear reactions continue in the core

The Sun

Core

The condition where the outward pressure counteracts the inward pull of gravity is called the hydrostatic equilibrium

Structure of the Sun

• Core – the center of the sun; makes up 10 percent of the sun’s total diameter of 1,300,000 km.

• The core is made up entirely of gas.• The most common nuclear reaction

occurring inside the sun is the fusion of hydrogen into helium.

Radiative zones

• Radiative zone – surrounds the core; energy moves from atom to atom in the form of electromagnetic waves, or radiation. (temp around 2,500,0000C)

Convective zones

• Around the radiative zone; energy is produced by convection, the transfer of energy by moving liquids or gases. (temp around 1,000,0000C)

Sun

Convection

Convection – the transfer of heat from one location to another by the flow of material.

Hot material

Cool material

Sun

Convection

Convection – the transfer of heat from one location to another by the flow of material.

Hot material rises

Cool material

Sun

Convection

Convection – the transfer of heat from one location to another by the flow of material.

Hot material rises

Cool material sinks

Sun

Convection

Convection current – the flow of material resulting from convection.

Hot material rises

Cool material sinks

Photosphere

• The innermost layer of the solar atmosphere; made of gases bubbling up from the convective zone. Much of the energy given off from the photosphere is in the form of visible light, seen from the earth. Therefore, the photosphere is considered the surface of the sun. (temp around 6,0000C)

Chromosphere

• Above the photosphere lies the chromosphere, or color sphere, a thin layer of gases that seems to glow with reddish light. (temp. ranges from 4,0000C - 50,0000C)

Corona

• The outermost layer of the sun’s atmosphere. A huge cloud of gas heated by the sun’s magnetic field to a temperature of about 2,000,0000C. Although the corona is relatively thin, it prevents most of the atomic particles from the sun’s surface from escaping into space.

The Sun

Outside of the visible portion of the sun is the corona, which cannot be seen because of the brightness of the sun. The corona can be observed during an eclipse

Total eclipse March 29, 2006

Solar Activity

• Sunspots – cool dark areas of gas within the photosphere that are caused by powerful magnetic fields.

Sun Spots

•Violent magnetic storms on the surface of the sun.

•Send high speed particles toward the Earth which can affect our communications systems and satellites

Sun spot cycles

Cyclic Change!

Prominences

• Great clouds of glowing gases that form huge arches that reach high above the sun’s surface.

• Each solar prominence follows curved lines of magnetic force from one sunspot area to another.

Solar Flare

• A sudden outward eruption of electrically charged atomic particles.

• Usually occur near sunspots.

• During a peak in a sunspot cycle, five to ten solar flares may be visible each day.

Sunspot and Solar Flare

Auroras

• When the electrically charged particles of the solar wind strike the gas molecules in the upper atmosphere, thereby producing green, red, blue, or violet sheets of light.

Aurora borealis, the “northern lights”

This slide shows the sun on two different days of the year. Each day is 6 months apart (January 3 and July 4). What do you notice about the Sun’s diameter from January to July?

What would cause the sun to appear to change its diameter cyclically over the course of each year?

Could the planets be orbiting the sun in a perfect circle or was it some other shape?

See the next slide to learn who was responsible for this new radical way of thinking.

Be sure you check out the definitions of these two new words. (http://epod.usra.edu/archive/images/animated.gif)

Definitions of Perihelion and Aphelion

ROTATION OF THE SUN

STARS ROTATE. WE USE SURFACE FEATURES LIKE

SUNSPOTS TO MEASURE THE RATE.