© 2011 pearson education, inc. the sun: our star a glowing ball of gas held together by its own...

© 2011 Pearson Education, Inc.

The Sun: Our Star

A glowing ball of gas held together by its own gravity and powered by nuclear fusion


Interactive notes---I am supplying you with a set of notes to help you study. I have taken out some slides that are mostly pictures or instructions to the class.

Please refer to the online set of notes as you study. Use

these as a tool.

Our Star, the Sun


Radius: 700,000 km

Mass: 2.0 × 1030 kg

Density: 1400 kg/m3

about ¼ the earth’s density, similar to the Jovian planets

Rotation: We use sunspots to determine. Differential (faster at the equator (25 days), slower at the poles (31 days at 6o degree latitude); period about a month

Surface temperature: 5800 K (above melting point of any known material)

Apparent surface of Sun is photosphere –not a solid surface

Physical Properties ofthe Sun

The Sun is the Largest Object in the Solar System

• The Sun contains more than 99.85% of the total mass of the solar system

• If you put all the planets in the solar system, they would not fill up the volume of the Sun

• 110 Earths or 10 Jupiters fit across the diameter of the Sun

How big is the Sun?

Let’s take a look at the Sun sizeWith a Lecture Tutorial

Copyright © 2012 Pearson Education, Inc.

Let’s reduce the size of the solar system by a factor of 10 billion; the Sun is now the size of a large grapefruit (14 cm diameter).

How big is Earth on this scale?

A. an atom

B. the tip of a ballpoint pen

C. a marble

D. a golf ball


The scale of the solar system• On a 1-to-10 billion

scale:— Sun is the size of a

large grapefruit (14 centimeters).

— Earth is the size of a tip of a ballpoint pen, 15 meters away.

Relative Distance of the Nearest Star


Scales and Sizes In Astronomy

• Mercury’s distance from the Sun.• Is about half the Sun-Earth distance.• It is half an Astronomical Unit.

• The star Sirius is about twice as massive as the Sun• We say it has a mass of two solar masses.

• Sirius is about 25 times more luminous than the Sun.• We say it has a luminosity of twenty-five solar luminosities.

An X-ray look at the Sun.

http://bcs.whfreeman.com/universe6e/pages/bcs-main.asp?v=category&s=00110&n=01000&i=18110.07&o=|18000|01000|&ns=0

http://bcs.whfreeman.com/universe6e/pages/bcs-main.asp?v=category&s=00110&n=01000&i=18110.07&o=%7C18000%7C01000%7C&ns=0


SOHO: Eavesdropping on the Sun

SOHO: Solar and Heliospheric Observatory

Orbits at Earth’s L1 point, outside the magnetosphere

Multiple instruments measure magnetic field, corona, vibrations, and ultraviolet emissions

SunspotsSunspots

What are they?What are they?What do they do to us?What do they do to us?

Why should you even care?Why should you even care?

What is a sunspot

Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity that draws off the convection of heat to the surface, thus cooling the surface.

Sunspots are usually in pairs because of the magnetic activity causing North and South poles at either of the spots.

Pic on next slide

NASA Image of sunspots, September, 2011

What do sunspots do to us?

Sunspots are a main hotbed of solar flares and prominences from the sun.

These are in turn pushed by their energy into space as solar wind once they break free of the sun's gravity

These solar winds are comprised of highly charged particles hurtling towards Earth

Sunspot projecting a flare into space

What does that mean to you? All of those charged particles will wreak havoc with

electronics. A particularly large solar flare caused blackouts over a large portion of Canada.

The particles can also cause the Aurora Borealis over the northern latitudes, known as the Northern Lights.

On a darker note this can also cause massive disruptions to communications, GPS, and military satellites. So if a bad solar storm were to hit, it could potentially cut off your phone from Facebook, cause your car to get wrong directions, and make the Air Force shoot a missile at the wrong building.

What happens with a solar flare.

Watch Danger Solar Flare and information about the SDO

Answer the questions on the provided sheet --be ready to discuss your answers

Online Activity of Solar activity


Day 2 Notes



This is a filtered image of the Sun showing sunspots, the sharp edge of the Sun due to the thin photosphere, and the corona


SDO site a plethora of pictures and video

http://www.nasa.gov/mission_pages/sdo/main/index.html

http://sdo.gsfc.nasa.gov/



http://sdo.gsfc.nasa.gov/

The Active Sun

1. Sunspots appear dark because they are cooler areasthey have a regular 11 year cycle

2. ProminencesHuge cloudlike structures of chromatic gasestrapped by magnetic fields

3. Solar flaressudden brightening above a sunset cluster

Auroras-display of color near poles caused by solar flares

http://www.solarviews.com/cap/vss/VSS00032.htm


What is the Sun Made of?


Interior structure of the Sun: The core is where nuclear fusion takes place

The photosphere is the visible “surface” of the Sun. Below it lie the convection zone, the radiation zone, and the core. Solar atmosphere consists of the chromosphere, the transition zone (temperature rises dramatically), and the corona.

Convection zone and Radiation zone

• Convection

-Below photosphere where the material is in constant convective motion

• Radiation– Solar energy is transported due to radiation

Photosphere

• Grainy appearance to sun when look in a telescope caused by granules, areas of hotter gases rising—last 10 minutes and new ones arise causing a convection

• 90% of sun’s surface are hydrogen

• 10% helium

ChromosphereAbove the photosphere is a thin layer of hot

gases. It is viewed during an eclipse as a thin red rim

Corona

Outermost portion of the atmosphere

Visible only when photosphere is covered

Solar wind—ionized gases that escape the gravitational pull of the sun and bombard parts of solar system, it can effect our atmosphere.

The Solar Interior

Nuclear Fusion

-Converts four Hydrogen nuclei into one helium releasing energy

energy is released because some matter is converted to energy

Causes the core to grow in size

Sun can exist in its present state another 10 billion years

• Nuclear fusion in the sun is a process by which rapidly colliding nuclei, like those of hydrogen and helium, fuse together at very high temperatures, to form nuclei of higher atomic weight.

• Nuclear fusion in the sun is a merger of smaller nuclei into heavier ones, releasing a lot of energy in the process.

What is nuclear fusion in the sun?

How it works!

• In the process of the hydrogen and helium fusing together, some mass is lost and converted into energy.

• Nuclear fusion in the sun is only possible when the repulsion between protons is overcome. – For that to happen, energy and temperature

at the suns core has to be really high.

The Suns core

• The total radius of the sun is 6.955 x 10^5 km (about 109 times the radius of Earth) – Its core extends from the center to about 1.8

km, with a temperature of 14.5 million Kelvin.

• Consider that four hydrogen atoms have a combined atomic mass of 4.032 atomic mass units whereas the atomic mass of helium is 4.003 atomic mass units, or 0.029 less than the combined mass of hydrogen. The tiny missing mass is emitted as energy as according to Einstein's equation:

E=mc^2• E equals energy, m equals mass, and c equals the

speed of light. Because the speed of light if very great (300,000 km/s), the amount of energy released from even a small amount of mass is enormous.

• The conversion of just one pinheads worth of hydrogen to helium generates more energy than burning thousand of tons of coal.

• The sun is consuming an estimated 600 million tons of hydrogen each second; about 4 million tons are converted to energy. – Even at the enormous rate of consumption, the sun

has enough fuel to last easily another 100 billion years.

– However, evidence from other stars indicates that the sun will grow dramatically and engulf Earth long before all of its hydrogen is gone.

– It is thought that a star the size of the sun can exist in its present state for 10 billion years.

Today’s Lecture Tutorial

“ The Future of the Sun and the Earth”

You will need the internet to help you with the tutorial.

https://www.youtube.com/watch?v=3MmIDYRfr0o

https://www.youtube.com/watch?v=VCgi35M8qMU






Day 3 notes


Luminosity—total energy radiated by the Sun— can be calculated from the fraction of that energy that reaches Earth.

Solar constant—amount of Sun's energy reaching Earth—is 1400 W/m2. (W = watts)

Total luminosity is about 4 × 1026 W—the equivalent of 10 billion 1-megaton nuclear bombs per second.



We can draw an imaginary sphere around the Sun so that the sphere’s surface passes through Earth’s center. The radius of this imaginary sphere equals 1 AU. The “solar constant” is the amount of power striking a 1-m2 detector at Earth’s distance. By multiplying the sphere’s surface area by the solar constant, we can measure the Sun’s luminosity—the amount of energy it emits each second.

Solar Luminosity


Doppler shifts of solar spectral lines indicate a complex pattern of vibrations


Solar Oscillations (a) The Sun has been found to vibrate in a very

complex way. By observing the motion of the solar surface, scientists can determine the wavelength and the frequencies of the individual waves and deduce information about the solar interior not obtainable by other means. The alternating patches represent gas moving down (red) and up (blue).

(b) (b) Depending on their initial directions, the waves contributing to the observed oscillations may travel deep inside the Sun, providing vital information about the solar interior. (National Solar Observatory)


Solar density and temperature, according to the standard solar model


Sunspots come and go, typically in a few days.

Sunspots are linked by pairs of magnetic field lines.

Solar Magnetism


Solar MagnetismSunspots originate when magnetic field lines are distorted by Sun’s differential rotation


How fast does the Sun Spin Math sheet


The Sun has an 11-year sunspot cycle, during which sunspot numbers rise, fall, and then rise again

Solar Magnetism


This is really a 22-year cycle, because the spots switch polarities between the northern and southern hemispheres every 11 years

Maunder minimum: few, if any, sunspots

Solar Magnetism


Solar Convection Physical transport of energy in the Sun’s convection zone. We can visualize the upper interior as a boiling, seething sea of gas. Each convective loop is about 1000 km across. The convective cell sizes become progressively smaller closer to the surface.


Solar Granulation Typical solar granules are comparable in size to Earth’s continents. The bright portions of the image are regions where hot material is upwelling from below. The dark regions correspond to cooler gas that is sinking back down into the interior.


Solar Spectrum A detailed spectrum of our Sun shows thousands of Fraunhofer spectral lines which indicate the presence of some 67 different elements in various stages of excitation and ionization in the lower solar atmosphere. The numbers give wavelengths, in nanometers.(Palomar Observatory/Caltech)


Lab: Identifying Lines in the Solar Spectrum

solar spectrum


What are Neutrinos?

Neutrinos are subatomic particles produced by the decay of radioactive elements and are elementary particles that lack an electric charge

Neutrinos are emitted directly from the core of the Sun and escape, interacting with virtually nothing. Being able to observe these neutrinos would give us a direct picture of what is happening in the core. Unfortunately, they are no more likely to interact with Earth-based detectors than they are with the Sun;

Observations of Solar Neutrinos


16.7 Observations of Solar Neutrinos

Typical solar neutrino detectors; resolution is very poor


• Main interior regions of Sun: core, radiation zone, convection zone, photosphere, chromosphere, transition region, corona, solar wind

• Energy comes from nuclear fusion; produces neutrinos along with energy

•Study of solar oscillations leads to information about interior

•Absorption lines in spectrum tell composition and temperature

• Sunspots associated with intense magnetism

• Number of sunspots varies in an 11-year cycle

• Large solar ejection events: prominences, flares, and coronal ejections

Summary of the sun

© 2011 pearson education, inc. the sun: our star a glowing ball of gas held together by its own...

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