SDO Recall column summary summary Recall column Comet ISON closest approach Dec 26 APOD: Solar Eclipse Flash spectrum summary Recall column
Diffraction grating spectrum Not absorption lines! Lower part of atmosphere blocked by moon. Chromosphere emission line individual images H_alpha on right. summary Phys 1830: Lecture 26 Recall column NASAs Solar Dynamics Observatory: Extreme UltraViolet wavelengths Image Workshop!
Dec 3 at 7-10pm Allen Building Take up test on Monday new password Previous Classes: The Sun This Class The Sun
Greenhouse Effect Stars Luminosity Upcoming Classes Stars Radii, Mass Lifetime
Stellar Populations The Sun summary Recall column Unexpectedly the atmospheric temperature increases with distance from the core! Probably caused by disturbances in the Suns magnetic field.
The photosphere is the visible "surface" of the Sun. Below it lie the convection zone, the radiation zone, and the core. Above the photosphere, the solar atmosphere consists of the chromosphere, the transition zone, and the corona Solar Flares and Coronal Mass Ejections summary Recall column
Green: solar flare -- can also be seen in X-ray (100 million K) Flash across region in minutes and blast into space. Red: coronal mass ejection Giant magnetic bubbles of ionized gas separating from the solar atmosphere. Occur weekly at sunspot mininum and a few times a day at maximum. Blue: proton shower recall fast moving particles are called cosmic rays. Solar Wind
summary Recall column Continous stream of electromagnetic radiation and cosmic rays. 1. from high in corona where gas is hot enough to escape. 2. From coronal holes regions where magnetic field loops snap and extend into space. summary SDO 2 instruments & many filters stellar components Recall column
The Realm of Belief: The World Will End 2012 Recall column summary SOHO/ESA/NASA Some 2012 fears are related to solar activity at the peak of sunspot activity. The peak is predicted to occur in 2013 (not 2012) by NOAAs SWPC. Earths Magnetosphere:
summary Illustration Recall column The Earth's magnetic field is complicated and will protect life even if a polarity shift was occurring. However solar activity does disrupt satellite communications and power networks. Influence of the Sun: The edge of the Solar System? (No)
summary Solar Wind: The sun exhales a thin, hot wind of electrically conducting gas, called plasma, into space at about 1.5 million km per hr. Recall column Heliosphere: The solar wind forms a large plasma bubble as the sun orbits in our Galaxy. The heliosphere has an inner and outer region. Termination Shock: The thin, invisible boundary of the inner, solar wind region. The solar wind abruptly drops in speed at the termination shock estimated between 80 100 AU (i.e. within the Kuiper Belt).
Voyagers 1 & 2 have crossed the termination shock. Heliopause: Termination of the heliosphere. Separates the solar material from the interstellar medium. Estimated between 120 to 150 AU IBEX is studying the heliosphere boundaries. Voyager 1 crossed boundary at 125 AU Bow Shock summary Suns Influence: On Earth Recall column
Recall Inverse Square Brightness Law Suns Influence: On Earth summary Recall column The suns luminosity is equivalent to the detonation of 10 billion 1-megaton nuclear bombs per second. When this energy reaches the earth 30% is intercepted by the atmosphere. 0-20% reflected by the clouds.
A sunbather receives the equivalent of 5 100-Watt light bulbs. Suns Influence: On Earth summary Recall column The relationship between earth and the sun is complex and is a frontier of research. Can this lead to climate change? The solar cycle leads to an increase in solar luminosity of 0.2-0.3 % during the peak. This cycle could lead to weather patterns, but
they are weaker than those caused by El Nino or volcanic dust. summary Suns Influence: On Earth Recall column Intergovernmental Panel on Climate Change. IPCC won Nobel Prize. Thousands of scientists from all over the world contribute to the work of the IPCC on a voluntary basis. See the IPCC summary and FAQ. http://www.ipcc.ch/report/ar5/wg1/#.UoZuz6
WLljE http://www.climatechange2013.org/images/u ploads/WGI_AR5_SPM_brochure.pdf Climate Skeptic now says there is global warming: http://online.wsj.com/article/SB1000142405297020442240 4576594872796327348.html Suns Influence: On Earth summary Recall column
Solar luminosity contribution to global warming (blue line above) is small. Note the increase in greenhouse gases (since the industrial revolution ~ 1750) Suns Influence: On Earth summary Recall column Details about these plots:
The black line is based on data i.e. what is measured. The temperature increase is happening. Recall that simulations use the laws of physics and assumptions. Therefore there are uncertainties. These uncertainties generate the width of the blue and pink regions. Modelling just the natural forces that can make the temperature change shows that the temperature would be rather stable the horizontal blue region. This includes the variation in luminosity of the sun. Modelling both the natural forces and the impact of human beings generates the pink region note how large the uncertainties are. The width of this
region shows uncertainties and variations between models are not being ignored. Note how the models with both natural forces and the impact of human beings are better at matching the observations. Suns Influence: On Earth summary Recall column These are measurements over time of the amount of each of these green house gases. Notice that there are error bars to
mark the uncertainty. Notice that the spike is much higher in value than the uncertainties in the measurement. That is, it is not an error. New IPCC report trends continue Recall column summary Suns Influence: On Earth Recall column Summary: The sun has influence
throughout the solar system and our distance from it allows liquid water. However the solar cycle and activity is not responsible for global warming. Human activity is a likely cause. Check the Kings Centre for Visualization in Science for interactives on climate change: http://www.kcvs.ca/site/projects /climate.html summary Stars: Their Characteristics
Recall column Luminosity: energy output Temperature Size summary summary Stars: Their Characteristics Recall column Recall Inverse Square Brightness Law
Luminosity, or absolute brightness, is a measure of the total power radiated by a star. Apparent brightness is how bright a star appears when viewed from Earth; it depends on the absolute brightness but also on the distance of the star. Luminosity and Apparent Brightness Therefore, two stars that appear equally bright might be a closer, dimmer star and a farther, brighter one: More Precisely 17-1: More on the Magnitude Scale Apparent brightness when measured using a logarithmic, magnitude scale, which is related to our perception is called
apparent magnitude. Absolute magnitude is the apparent magnitude that a star would have if it were placed 10 parsecs from Earth. A reduction of 5 in magnitude corresponds to an increase in a factor of 100 in luminosity. Magnitudes are inverted in scale, such that bright stars have low magnitudes. Converting from magnitude to luminosity in solar units: This graph allows us to perform this conversion simply by reading horizontally.
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