1 / 38

Properties of Sun

Properties of Sun. Goals. Summarize the overall properties of the Sun. What are the different parts of the Sun and how do we know this? Where does the light we see come from? Solar activity and magnetic fields. The Sun, Our Star. The Sun is an average star.

chassett
Download Presentation

Properties of Sun

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Properties of Sun www.assignmentpoint.com

  2. Goals • Summarize the overall properties of the Sun. • What are the different parts of the Sun and how do we know this? • Where does the light we see come from? • Solar activity and magnetic fields. www.assignmentpoint.com

  3. The Sun, Our Star • The Sun is an average star. • From the Sun, we base our understanding of all stars in the Universe. • Like Jovian Planets it’s a giant ball of gas. • No solid surface. www.assignmentpoint.com

  4. Vital Statistics • Radius = 100 x Earth (696,000 km) • Mass = 300,000 x Earth (1.99 x 1030 kg) • Surface temp = 5780 K • Core temp = 15,000,000 K • Luminosity = 4 x 1026 Watts • Solar “Day” = • 24.9 Earth days (equator) • 29.8 Earth days (poles) www.assignmentpoint.com

  5. Structure • ‘Surface’ • Photosphere • ‘Atmosphere’ • Chromosphere • Transistion zone • Corona • Solar wind • ‘Interior’ • Convection zone • Radiation zone • Core www.assignmentpoint.com

  6. The Solar Interior • How do we know what’s inside the Sun? • Observe the outside. • Theorize what happens on the inside. • Complex computer programs model the theory. • Model predicts what will happen on the outside. • Compare model prediction with observations of the outside. • Scientific Method! www.assignmentpoint.c om

  7. Helioseismology • Continuous monitoring of Sun. • Ground based observatories • One spacecraft (SOHO) • Surface of the Sun is ‘ringing’ • Sound waves cross the the solar interior and reflect off of the surface (photosphere). www.assignmentpoint.com

  8. Interior Properties • Core = 20 x density of iron • Surface = 10,000 x less dense than air • Average density = Jupiter • Core = 15,000,000 K • Surface = 5780 K www.assignmentpoint.com

  9. Do you see the light? • Everything in the solar system reflects light. • Everything also absorbs light and heats up producing blackbody radiation. • Q: Where does this light come from? • A: The Sun. • But where does the Sun’s light come from? www.assignmentpoint.com

  10. Our Journey through the Sun • Journey from the Sun’s core to the edge of its ‘atmosphere.’ • See where its light originates. • See what the different regions of the Sun are like. • See how energy in the core makes it to the light we see on Earth. www.assignmentpoint.com

  11. Density = 20 x density of Iron Temperature = 15,000,000 K Hydrogen atoms fuse together Create Helium atoms. In The Core www.assignmentpoint.com

  12. Nuclear Fusion • 4H  He • The mass of 4 H atoms: 4 x (1.674 x10-27 kg) = 6.694 x 10-27 kg • The mass of He atom: = 6.646 x 10-27 kg • Where does the extra 4.8 x 10-29 kg go? • ENERGY!  E = mc2 • E = (4.8 x 10-29 kg ) x (3.0 x 108 m/s)2 • E = hc/l l = 4.6 x 10-14 m (gamma rays) • So: 4H  He + light! www.assignmentpoint.com

  13. The Radiation Zone • This region is transparent to light. • Why? • At the temperatures near the core all atoms are ionized. • Electrons float freely from nuclei • If light wave hits atom, no electron to absorb it. • So: Light and atoms don’t interact. • Energy is passed from core, through this region, and towards surface by radiation. www.assignmentpoint.com

  14. The Convection Zone • This region is totally opaque to light. • Why? • Closer to surface, the temperature is cooler. • Atoms are no longer ionized. • Electrons around nuclei can absorb light from below. • No light from core ever reaches the surface! • But where does the energy in the light go? • Energy instead makes it to the surface by convection. www.assignmentpoint.com

  15. Convection • A pot of boiling water: • Hot material rises. • Cooler material sinks. • The energy from the pot’s hot bottom is physically carried by the convection cells in the water to the surface. • Same for the Sun. www.assignmentpoint.com

  16. Solar Cross-Section • Progressively smaller convection cells carry the energy towards surface. • See tops of these cells as granules. www.assignmentpoint.com

  17. The Photosphere • This is the origin of the 5800 K blackbody radiation we see. • Why? • At the photosphere, the density is so low that the gas is again transparent to light. • The hot convection cell tops radiate energy as a function of their temperature (5800 K). l = k/T = k/(5800 K)  l = 480 nm (visible light) • This is the light we see. • That’s why we see this as the surface. www.assignmentpoint.com

  18. The Solar Atmosphere • Above the photosphere, transparent to light. • Unlike radiative zone, here atoms not totally ionized. • Therefore, there are electrons in atoms able to absorb light. • Absorption lines in solar spectrum are from these layers in the atmosphere. www.assignmentpoint.com

  19. Atmospheric Composition • Probably same as interior. • Same as seen on Jupiter. • Same as the rest of the Universe. www.assignmentpoint.com

  20. The Chromosphere • Very low density • But also very hot • Same as the gas tubes we saw in class and lab. • Energy from below excites the atoms and produces emission from this layer. • Predominant element – Hydrogen. • Brightest hydrogen line – Ha. • Chromosphere = color www.assignmentpoint.com

  21. Spicules and Prominences • Emission from the atmosphere is very faint relative to photosphere. • Violent storms in the Chromosphere. • Giant curved prominances • Long thin spicules. www.assignmentpoint.com

  22. Prominences www.assignmentpoint.com

  23. www.assignmentpoint.com

  24. Ha Sun www.assignmentpoint.com Photo by Robert Gendler

  25. Corona • Spicules and other magnetic activity carry energy up to the Transition Zone. • 10,000 km above photosphere. • Temperature climbs to 1,000,000 K • Remember photosphere is only 5800 K • The hot, low density, gas at this altitude emits the radiation we see as the Corona. www.assignmentpoint.com

  26. www.assignmentpoint.com

  27. The X-Ray Sun • Q: At 1,000,000 K where does a blackbody spectrum have its peak? • A: X-rays • Can monitor the Solar Coronasphere in the X-ray spectrum. • Monitor Coronal Holes www.assignmentpoint.com

  28. www.assignmentpoint.com

  29. Solar Wind • At and above the corona: • Gas is very hot • Very energetic • Like steam above our boiling pot of water, the gas ‘evaporates’. • Wind passes out through Coronal Holes • Solar Wind carries away a million tons of Sun’s mass each second! • Only 0.1% of total Sun’s mass in last 4.6 billion years. www.assignmentpoint.com

  30. The Aurora • The solar wind passes out through the Solar System. • Consists of electrons, protons and other charged particles stripped from the Sun’s surface. • Interaction with planetary magnetic fields gives rise to the aurora. www.assignmentpoint.com

  31. The Active Sun • Solar luminosity is nearly constant. • Very slight fluctuations. • 11-year cycle of activity. www.assignmentpoint.com

  32. Solar Cycle • Increase in Coronal holes • Increase in solar wind activity - Coronal Mass Ejections • Increase in Auroral displays on Earth • Increase in disruptions on and around Earth. www.assignmentpoint.com

  33. 11-year sunspot cycle. • Center – Umbra: 4500 K • Edge – Penumbra: 5500 K • Photosphere: 5800 K Sunspots www.assignmentpoint.com

  34. Can see that Sun doesn’t rotate as a solid body? • Equator rotates faster. • This differential rotation leads to complications in the Solar magnetic field. www.assignmentpoint.com

  35. Magnetic fields and Sunspots • At kinks, disruption in convection cells. • Sunspots form. www.assignmentpoint.com

  36. Magnetic fields and Sunspots • Sunspots come in pairs. • Opposite orientation in North and South. • Every other cycle the magnetic fields switch. www.assignmentpoint.com

  37. Sunspot Numbers www.assignmentpoint.com

  38. Active Regions • Areas around sunspots give rise to the prominences www.assignmentpoint.com

More Related