Sun Facts and Figures (DO NOT WRITE) Distance from Earth= 1 AU 1AU = 150,000,000 km (93 million miles) Diameter = 1.4 x 106 km (870000miles) 1 million Earth’s could fit inside the sun! Mass= 2 x 1030 kg (333333x Earth’s mass) 99.8% the mass of the Solar System Density = 1400 kg/m3

90% of the mass is found in interior half Color = yellow (due to surface temperature)

Definitions

Sun: Star at the center of our solar system. Also another name for any star.

Luminosity: measures how bright a star would be in relation to the sun if all stars were the same distance from the observer

Nuclear fusion: the combining of the nuclei of smaller elements to form the nuclei of larger elements with some mass being converted into energy- this is how the sun produces energy

Definitions

Sunspots: a darker region of the sun’s visible surface; increased number of sunspots are related to an increase in electromagnetic energy emitted from the sun

Galaxy: the large groupings of millions or billions of stars and other forms of mass held together by gravitation

Stefan-Boltzmann Law(Energy directly proportional to temperature)

As stars get hotter, their energy output increases quickly! (hot stars burn “fast”)

A star 10 x’s hotter than Sun has 10,000 times more energy output (will “die” quicker)

Our sun burns “slowly” 9 billion years total (4.5 billions years left to go!)

Info.

The sun is the nearest star to the Earth

The Hertzsprung-Russel diagram (H-R diagram) on page 15 of the ESRT arranges groups of stars by color and luminosity

Color is an indication of temperature The H-R diagram is basically the life

cycle of an average star, like our sun

Stars may follow different paths in this cycle

Life cycle may take billions of years Some stars created soon after the

Big Bang may still exist

Star Types- Main Sequence A broad band where 90% of studied

stars are located Majority of a star’s life span The luminosity increases from red to

blue-white, which is related to an increase in star size and higher temperatures

Our sun is a main sequence star of yellow color

Red Dwarf: smallest and coolest very common

Giant Stars

Rare red, orange, and yellow stars commonly seen at night because of their large size and high luminosity

Low temperature stars Represent the late stage in the

evolution of medium to small-size main sequence stars

Super Giants

Super giant stars can be up to 1000 times larger than the diameter of the sun

Late stage of evolution Usually explode in what is called a

supernova Blue super giants are the brightest

and exhibit the highest temperature

White Dwarfs Not always white Small (around the size of Earth) Hot on the surface, low in luminosity Represent last stage of low to

medium mass stars

Black Dwarf

When a white dwarf cools and no longer emits much electromagnetic energy

“Dead” star

Sunspot Cycle11 year cycle - not always consistent (2001 last maximum)

Temporary storms that are a little cooler and dimmer than the normal surface of the sun

Always appear within 30º of the solar equator

Possible link to Earth’s climate Rotation of the spots show that the

sun rotates on its axis every 27 days Often occur in pairs

Photosphere with Sun Spots

Underneath the Spot

Hot gas is prevented from entering region by twisted magnetic field lines, thus region becomes coolerhttp://umbra.nascom.nasa.gov

Little Ice Age

The Solar Atmosphere

The Chromosphere The middle layer (has red-ish

color) Temperatures average 28,000 °C (cooler than corona but hotter than photosphere)

Only visible during a total eclipse

Chromosphere

The Solar Atmosphere

Photosphere (sphere of light) Outer layer of interior/Lower layer of

atmosphere (the surface) Visible part of sun (what we see!) Looks boring! (But is boiling!) Closer look- granules Bubbles from convection zone Temperature about 6000° C

The edge of the Sun

Other activity about the Sun Prominences

Loops of ionized gas (plasma) bent by magnetic fields May last up to three months

Flares - much violent than prominences Eruptions on the lasting 5 to 10 min Includes coronal mass ejections (500 to 1000 km/s) Can disrupt communications and electricity Cause more aurorae and can disable satellites

All these phenomenon happen in active regions on the Sun, which vary in position.

We don’t understand the details for the formations of these structures

Prominences

Photosphere with ProminencePhotosphere with Prominence

Solar Flares

A continuous stream of high-energy A continuous stream of high-energy particles from the corona.particles from the corona.

Solar flares will sometimes increase Solar flares will sometimes increase the speed of the solar wind and the speed of the solar wind and cause interference with radio cause interference with radio communications here on Earth.communications here on Earth.

Solar WindSolar Wind

The Energy coming from the Sun is called Solar Wind. com comes out from the Sun is called the solar wind.

Movies

Birth of the Sun Life Cycle of Stars NASA

A star differs from a planet in that a star

a.Has a fixed orbitb.Is self-luminousc.Revolves about the sund.Shines by reflected light

Using page 15 of the ESRT… A main sequence star is 1000 times

more luminous than the sun. The temperature is likely to be most nearly

a.3000 degrees Celsiusb.5000 degrees Celsiusc.12000 degrees Celsiusd.25000 degrees Celsius

A giant star has a luminosity of 300. Its color is most likely to be

a.yellow-redb.Blackc.Whited.Blue-white

A white dwarf star has a temperature of 13000 degrees Celsius. What is the probably luminosity of the star?

a.100b.10c.0.1d.0.01