Note key, please leave in binder. Our Sun 1/24/11 Understanding Stars Our Sun Shooting stars movie opener.

Note key, please leave in binder. 1/24/11 Our Sun What is the structure of our sun? What makes the sun shine? How do we know? What tools do we use to study our nearest star?

Note key, please leave in binder. 1/24/11 What tools do we use? Refracting telescopes- light passes through a lens to the eye Good clarity, good power, good magnification, High quality lenses needed, chromatic aberration Reflecting telescopes- uses a mirror to focus light Good clarity, good power, good magnification, glass not as high quality Secondary mirror blocks some light Radio Telescopes-focus incoming radio waves on an antenna, can be arranged in arrays X-Ray telescopes- detect incoming X-rays, space telescopes, focus on learning about black holes Gamma Ray telescopes - space telescopes to study visible light and gamma rays. And others. . .

Note key, please leave in binder. 1/24/11 How do we know? Spectroscopy - the study of the properties of light Detailed study of this in physics Depends on the wavelength Think a rainbow = continuous spectrum

Note key, please leave in binder. 1/24/11 How do we know? Absorption spectrum - when light is passed through cool gas under low pressure the gas will absorb some light and leave dark bands on the spectrum.

Note key, please leave in binder. 1/24/11 How do we know? Emission Spectrum - when light is passed through HOT gas under low pressure the gas will emit some light and these appear as bright bands on a dark spectrum. These act as finger prints to stars and tell us the chemical composition of stars.

Note key, please leave in binder. 1/24/11 Structure of the Sun Photosphere = visible surface Interior Atmospheric layers (2) Chromosphere Corona

Note key, please leave in binder. 1/24/11 Photosphere Visible surface of the sun Appears to have a grainy texture. Called granules size of TX last 10-20 min Due to convection within the sun Composed of 90% hydrogen, and <10% helium.

Note key, please leave in binder. 1/24/11 Sunspots Dark areas on surface (photosphere) Dark due to lower temperature Show sun activity and rotation of sun More spots = higher solar activity, 11 year cycle

Note key, please leave in binder. 1/24/11 Chromosphere Layer of atmosphere, thin (few thousand km) Visible during an eclipse Magnetic field evidence of the sun present in this layer. Dark webbed lines = magnetic fields Image courtesy University of Michigan

Note key, please leave in binder. 1/24/11 Prominences Arches or loops of chromospheric gases Extend into corona Ionized gases that are trapped by magnetic fields. Show areas of intense activity

Note key, please leave in binder. 1/24/11 Corona Outermost portion of solar atmosphere Origin of solar wind, aka space weather Energy travels at speeds up to 800km/sec. Solar flares Image by SOHO

Note key, please leave in binder. 1/24/11 Solar Flares Explosive solar events Release enormous amounts of energy in form of UV, radio, and X-rays Cause an increase in intensity of solar wind due to atomic particles that are ejected

Note key, please leave in binder. 1/24/11 NASA SDO example SDO = Solar Dynamics Observatory; Recorded in extreme UV range (gives purple/green color); X-class flares are big; they are major events that can trigger planet-wide radio blackouts and long-lasting radiation storms. M-class flares are medium-sized; they can cause brief radio blackouts that affect Earth's polar regions. Minor radiation storms sometimes follow an M-class flare. Compared to X- and M-class events, C-class flares are small with few noticeable consequences here on Earth. SDO = Solar Dynamics Observatory M5.6 class solar flare (Almost X class) 7/2/2012

Note key, please leave in binder. 1/24/11 Why does the sun shine? Nuclear fusion (opposite of fission) in the interior or core. Stars use nuclear fusion to combine light/low mass elements into heavier/higher mass elements. Matter is converted to energy 4 hydrogen combine to form one helium. One proton in each hydrogen atom, atomic mass = 4.032 atomic mass units One helium atom, atomic mass = 4.003 atomic mass units

Note key, please leave in binder. 1/24/11 Why does the sun shine? Stars use nuclear fusion to combine light/low mass elements into heavier/higher mass elements. Results in a small loss of mass as the mass is converted into energy Difference in atomic masses = 0.029 atomic mass units. Energy! E = mc2