Our Star: The Sun Part I

Chapter 16

Sun Facts: (look up the facts) pg. 414

Diameter: Density: Rotation speed:

poles: equator: Surface Temp. Mass: Tilt: Gravity: Distance from Earth:

Our Star

It’s hard to see much similarity between the distant points of light we call stars and our sun.

Yet our Sun is a star, and it’s at the center of our solar system.

We are the leftovers of the formation of this star.

Our Star

Contains 99.9% of the mass of the solar system.

The Sun is the source of 99.9% of the energy and light here on Earth.

It is the gravitational anchor of the solar system.

Even still, our Sun is very ordinary.

The Solar “surface” Atmosphere

The Sun doesn’t have a solid surface. It’s “surface” is the gas layer that emits

the most light. We’ll start at the outer layers and work

our way in.

The Solar Atmosphere

When you look at the Sun during the day you are seeing at the photosphere.

This is the layer from which visible photons arise.

Temp = 6,000 K (10,340 °F) Lower layers are hidden, and

higher layers are so diffuse we can only see them during solar eclipses.

The PhotosphereThe PhotosphereThe “visible” surface of the sun.

Thin layer of gas (less than 500km deep) from which we receive the majority of the Sun’s light.

Average surface temperature ~ 6000K

Spectra? Gives off absorption spectra?!

Not That Kind of Chrome

The part right above the photosphere is the chromosphere.

It is normally hidden because the photosphere is far brighter.

During a total solar eclipse, the chromosphere is visible as a pinkish aura around the solar disk.

Hydrogen creates the pink hue.

The ChromosphereThe Chromosphere

The Chromosphere - “The Color Sphere.” irregular layer above the photosphere Inner or lower layer of the ‘atmosphere 10,000 km thick cannot normally be seen (photosphere is too

bright). gives off a reddish color (H-alpha emission).

Not That Kind of Chrome

The chromosphere is a storm-racked region, into which spicules, jets of expelled matter thousands of miles high, intrude.

Above the chromosphere is the transition zone.

Temperature rises sharply as we go out from the Sun. (??)

SpiculesSpicules

Spicules – •flame-like structures •100-1000m in diameter • extending up 10,000 km high• short durations of time (5 minutes or so). • appear near edges of large “supergranules” in the photosphere.• Result of magnetic disturbances

Chromosphere

Spicules

Convecting Granules

Not That Kind of Chrome

At about 6,000 miles above the photosphere, where the transition zone becomes the corona, temperatures exceed 1,000,000 K (1,799,540 °F)

How do we explain this?

A Luminous Crown

Corona is Latin for “crown”. It is the region beyond the transition

zone consisting of elements that have been highly ionized by the tremendous heat in the coronal region.

Normally invisible except in solar eclipses.

The CoronaThe Corona

· Also, only seen during eclipses· *can* extend as far as 12 times the Sun’s radius from the Sun!! Wow!· Very low density!! BUT very hot ~ 1,000,000K average temperature (varies from about 500,000K to nearly 2,000,000K)· Emisson Spectra· Why so hot??? Maybe the interaction with the Sun’s magnetic field. · The outer corona is so hot, Sun’s gravity can not hold onto the gas. A high velocity of gas atoms streams out from the Sun in all directions producing SOLAR WINDS

A Luminous Crown

The corona appears as a luminous crown surrounding the darkened disk of the Sun.

When the Sun is active, a cycle that peaks every 11 years, its surface becomes mottled with sunspots, solar flares, and prominences.

Solar Wind

This swiftly moving particle stream is known as the solar wind.

The solar wind blows past the earth at nearly 300-800km/sec (1000km/sec gusts)

Due to the incredible temperatures in the solar corona.

As a result, the gases are sufficiently hot to escape the tremendous gravitational pull of the Sun.

Sun is losing mass!! 2 million tons/sec.

(and yet only 0.1% in its 4.6 billion years)

Solar Wind

The surface of the Earth is protected from this wind by its magnetosphere.

This magnetic field either deflects or captures charged particles from the solar wind.

Some rain down at the poles creating aurora.

Prominent every 11 years.

ProminenceProminence

A prototypical prominence structure. The curved arch of solar material wraps around the magnetic field stretching between sunspots above the photosphere into higher layers. In chaotic areas these structures can be associated with solar flares.

Prominence

Sunspots

Photosphere

Solar FlareSolar Flare

Flare

photosphere

A “Solar Flare” can be a truly violent explosion from the solar surface reaching very far out from the Sun. Flares are much more violent than prominences. Flares often last from minutes to hours. A large flare can release the equivalent of nearly 2 billion megatons of TNT.

Hydrostatic Equilibrium

Sun’s Composition

What is the sun made of and how do scientists know??????

Spectral Analysis

ENERGY!

What’s It Made Of?

The Sun is mostly hydrogen (73%) and helium gas (25%).

Other elements are found in much smaller amounts, adding up to just under 2% of the Sun’s mass.

Include carbon, nitrogen, oxygen, neon, magnesium, silicon, sulfur, and iron.

A Spectacular, Mediocre Star

In terms of it size, mass, and energy released, the Sun is by far the most spectacular body in our solar system.

Radius = 6.96x108 m (100 times larger)

Mass = 1.99x1030 kg (300,000 times more massive)

Surface temp. = 5,780 K (~10,000 F)

Four Trillion Trillion Light Bulbs

Light bulbs are measured in wattage.

A watt is a measure of power, or how much energy is produced or consumed per second.

A 100-watt light bulb uses 100 joules of energy every second.

Four Trillion Trillion Light Bulbs

The Sun produces 4x1026 watts of power.

Solar constant That’s four trillion trillion 100-watt

light bulbs. Luminosity – rate of energy

production The Sun has an average luminosity.

Fun in the Sun

We will explore the interior parts of the Sun in the next presentation.

Bellwork: Sun’s Atmosphere Matching

1. Photosophere a. has pink color2. Chromosphere b. Seen during eclipse3. Transition zone c. the ‘visible layer4. Corona d. hottest temps.

e. solar winds

5. Spicules a. violent explosions6. Solar flares b. last 5 minutes7. Prominences c. arch between sunspots