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Flux Simulator Flux Simulator for Fluxiness we found
Engage: Flux Lab How can we use the inverse square law of light to find out how luminous the sun is? Think for a few minutes in groups. Brainstorming.
Flux Lab – groups of 3-4 • Demonstrate the concept in the room with 2 light bulbs. • Explain that there are 2 measurements to make • distance to bulb for equal brightness wax – each person decides • Color of wax on each side when equal brightness
Photometer Lab Equation One of these items is the light bulb One of these items is the Sun L is the power Not the same ‘bulb’ as in prior slide
Discussion % error Color – each person better have something written down Sources of error: Brainstorm
% error Used when know actual value and you are doing a verification lab. Provides a measure of the accuracy of your results (hint – see characteristics of science)
% difference Used when you don’t know the answer. Provides a measure of the precision of your results. Helps identify outliers.
Wien’s Law – Color and Temperature Wavelength in meters from this formula 1 nanometer = 10-9 meter 1 meter = 109 nanometer
Find Temperature of the Sun You need the radius of sun from the pinhole camera experiment. (Surface Area of a sphere… is) Use Stefan-Boltzmann (hyper-physics calculator for power/area - http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html) Or Wolfram Alpha calculator (http://www.wolframalpha.com/entities/calculators/stefan-boltzmann_law/mn/o0/q0/) Prize to the group with the closest measurement if your workshop facilitator thinks it is OK
Find color of the Sun http://science-edu.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.html Compare with what you saw.
Explain: Flux Lab We used inverse square law model & known source We assumed Sun was blackbody (known from other observations) We used Stefan-Boltzmann model and pinhole camera radius (from geometry and knowing distance) to get temperature of the sun as blackbody We used Wien’s Law model for peak wavelength of blackbody emitter using the temperature
Models Models (aka theories, math equations, previously tested ideas) help extend our knowledge of the world around us Why can’t we just go measure the temperature of the Sun? How do we measure anything in astronomy?
Sun Sun & Space Weather – if have DVDs available. Jhelioviewer Teaching EM Spectrum with the Sun – lesson plan presented at NSTA by Webster & Aguilar
Elaborate: Intrinsic Properties of Stars Let’s think back to initial categories made of star image Having made a few measurements now – let’s list the intrinsic properties of stars on the board together
Organizing Stars Astronomers want nothing more than to classify and categorize – just like every other scientist First thing we do is try to plot things on graphs to see if there is a pattern Let’s plot two intrinsic properties against one another.
This is on board – not in powerpoint Start with axes only Point out logarithmic scaling Point out backwards temperature Add main sequence – units of solar lum – what that mean Test for understanding – ask where blue stars Ask where red stars Ask where luminous, cold, hot, less luminous
Add white dwarfs Ask for understanding – hot cold dim not Add supergiants Add giants
Hey.. You know – dwarfs, giants.. Seems to imply something about radius Blackbodies follow Stefan-Boltzmann relation Luminosity and temperature and radius all related.
WOW! What a great diagram – 3 intrinsic properties in one graph!
Mass? Yes indeedy… mass for main sequence is on this diagram too. Luminosity – Mass Relation
Age on diagram? Sort of – if high mass main sequence star – know something. As they fuse such a short time If a high mass star is “on” main sequence – know it is young! But what about if it is a G star, like the Sun? Is it 2 billion years old? 1 billion? Need groups of stars and use a model
Composition? No… but hey Luminosity, Mass, temperature, radius, and age… on one graph! Models of blackbodies allow us to know more about stars than we can get from observations alone.
Elaborate more: Create a diagram • If time – if not, assign for HW. (11:30 data files – some are on usb key) • Nearby Stars • Bright Stars • Cluster 1 • Put all on same axes!
Your Graphs Did all the graphs look the same?
Misconceptions about HR Motion – actually a time evolution – for a single star – temperature
Stellar Evolution Engage: What are some questions you have about stars right now? Brainstorm a list on your whiteboards.
Explore: Stellar Evolution Simulators – as on agenda. Is the main sequence for stars on the L-T diagram a sequence of age?
Explain Stars are simply balance (or imbalance) of forces – in vs. out. Formation – gravity stronger than gas pressure force Main sequence – gravity in balance with gas pressure force (btw – fusion!) Unbalance signals end of main sequence –exciting things happen Then back in balance for end state
Explain: Do all stars evolve the same way? Do all stars take the same amount of time to evolve? What is your evidence to support your claim? (from the simulators…)
Outcomes – from AstroGPS Identify end phases of stars like the sun Match evolutionary stages to initial mass ranges Relate atmospheric properties to astronomical equipment needed Relate mass of star to lifetime and power Correctly identify colors and luminosities of stars using an HR diagram
NASA’s Great Observatories http://coolcosmos.ipac.caltech.edu/cosmic_classroom/cosmic_reference/greatobs.html http://www.nasa.gov/audience/forstudents/postsecondary/features/F_NASA_Great_Observatories_PS.html Today we are going to look at some of the data from Chandra. The next 2 images are examples of what you can do with observations at multiple wavelengths of same part of sky
Summary: Really high mass High mass The Sun and the lower mass stars http://cheller.phy.georgiasouthern.edu/gears/Units/2-StellarEvolution/2Stars_7.html Compare main sequence lifetimes, end states.
End of Stars Main sequence is the stage of existence where stars are fusing hydrogen to helium Spend largest fraction of their existence doing this More massive stars – short lived Low mass stars – long lived Range – 100,000 years – 100 billion years!
Red Giant BP Psc is a star like our Sun, but one that is more evolved, about 1,000 light years away. New evidence from Chandra supports the case that BP Psc is not a very young star as previously thought. Rather, BP has spent its nuclear fuel and expanded into its "red giant" phase – likely consuming a star or planet in the process. Studying this type of stellar "cannibalism" may help astronomers better understand how stars and planets interact as they age. The composite image on the left shows X-ray and optical data for BP Piscium (BP Psc), a more evolved version of our Sun about 1,000 light years from Earth. Chandra X-ray Observatory data are colored in purple, and optical data from the 3-meter Shane telescope at Lick Observatory are shown in orange, green and blue. BP Psc is surrounded by a dusty and gaseous disk and has a pair of jets several light years long blasting out of the system. A close-up view is shown by the artist's impression on the right. For clarity a narrow jet is shown, but the actual jet is probably much wider, extending across the inner regions of the disk. Because of the dusty disk, the star's surface is obscured in optical and near-infrared light. Therefore, the Chandra observation is the first detection of this star in any wavelength.
White Dwarf An international team of astronomers, studying the left-over remnants of stars like our own Sun, have found a remarkable object where the nuclear reactor that once powered it has only just shut down. This star, the hottest known white dwarf, H1504+65, seems to have been stripped of its entire outer regions during its death throes leaving behind the core that formed its power plant. The Chandra X-ray data also reveal the signatures of neon, an expected by-product of helium fusion. However, a big surprise was the presence of magnesium in similar quantities. This result may provide a key to the unique composition of H1504+65 and validate theoretical predictions that, if massive enough, some stars can extend their lives by tapping yet another energy source: the fusion of carbon into magnesium. However, as magnesium can also be produced by helium fusion, proof of the theory is not yet ironclad. The final link in the puzzle would be the detection of sodium, which will require data from yet another observatory: the Hubble Space Telescope. The team has already been awarded time on the Hubble Space Telescope to search for sodium in H1504+65 next year, and will, hopefully, discover the final answer as to the origin of this unique star.
Star Death A composite image from NASA's Chandra (blue) and Spitzer (green and red-yellow) space telescopes shows the dusty remains of a collapsed star, a supernova remnant called G54.1+0.3. The white source at the center is a dead star called a pulsar, generating a wind of high-energy particles seen by Chandra in blue. The wind expands into the surrounding environment. The infrared shell that surrounds the pulsar wind, seen in red, is made up of gas and dust that condensed out of debris from the supernova explosion. A nearby cluster of stars is being engulfed by the dust. The nature and quantity of dust produced in supernova explosions is a long-standing mystery, and G54.1+0.3 supplies an important piece to the puzzle.
Black Holes http://hubblesite.org/explore_astronomy/black_holes/
Black Hole G1915+105. 14 solar masses.