SOLAR PHYSICS Advanced Space Academy U.S. Space & Rocket Center

SOLAR PHYSICS  Why the Sun?  The Ozone Hole  Solar Structure  Solar Features  Solar Missions

Why The Sun? Clues to our origins Curiosity Energy Source Predict communication problems Avoid endangering astronauts and spacecraft

The Ozone Hole  16,000,000 square miles (26,000,000 square km) in size  Mainly located over Antarctica; however, its boundaries can extend upward uncovering portions of Australia, South America, and South Africa  Exacerbated by CFC’s

Solar Structure  Early Life –Gas & dust –Shock waves & gravity –Contraction increased pressure and temperature –Fusion at 15 million degrees F (8.3 million degrees C) –Electromagnetic radiation

Sun Facts  Mass - 1 billion trillion trillion tons  330,000 times the Earth’s mass  Diameter - 864,000 miles (1,390,000 km)  75% Hydrogen and 25% Helium by mass  93,000,000 miles (150,000,000 km) from Earth  The sun is an average G2 star (classification on next slide)

Sun Facts: Classification G2

Solar Structure  4 layers: –Core –Photosphere –Chromosphere –Corona  Radiation Travel Times: –millions of years from core to chromosphere –8 minutes to Earth  Striated rotation  Midlife Our Sun contains 99.9% of the matter in our solar system

The Solar Cycle  The Sun goes through a cycle every 11 years  Solar Minimum  Solar Maximum  The 11 year sunspot cycle is actually related to a 22 year cycle for the reversal of the Sun's magnetic field.

Our Sun is an Active Star

Solar Midlife - Core  Temperature – 27,000,000°F (15,000,000 °C)  Pressure billion atmospheres  The Radiative Zone  The Interface Layer  The Convection Zone

Solar Midlife - Core  MAGNETISM – the key to understanding the Sun  The magnetic field is produced in the Sun by the flow of electrically charged ions and electrons most likely in the interface layer

Solar Midlife - Photosphere  Temperature - 10,500°F (5,800ºC)  The sun’s lower atmosphere  62 miles (100 km) thick  It gives off most of its energy as visible light and heat  Sunspots originate on this layer

Photospheric Features  SUNSPOTS  appear as dark spots on the sun  They are really several spots clustered together  They originate at the poles  They are magnetic  Sunspots are “cool” regions - 6,800°F (3,800ºC) compared to their surroundings

Photospheric Features  SUNSPOTS –Observing sunspots “moving” across the Sun was how scientists figured out that the Sun actually rotated

Photospheric Features  FACULAE –Bright areas seen near the edge of the solar disk –These are magnetic areas but the magnetic field is in smaller bundles than in sunspots

Photospheric Features  GRANULES –Small cellular features that cover the entire Sun except for those areas covered by sunspots –Individual granules last for only about 20 minutes –The flow within the granules can reach supersonic speeds and produce sonic “booms” that generate waves on the Sun’s surface

Photospheric Features  SUPERGRANULES –Much larger versions of granules –The fluid flows observed in supergranules carry magnetic field bundles to the edges of the cells where they produce the chromospheric network

Solar Midlife - Chromosphere  Faint and red - seen only briefly during an eclipse  Temperature rises from 10,800°F (6,000ºC) to 36,000°F (20,000ºC)

Chromospheric Features  CHROMOSPHERIC NETWORK –Web-like pattern –Outlines the supergranule cells seen on the photosphere

Chromospheric Features  FILAMENTS –dense, somewhat cooler, clouds of material suspended above the chromosphere by loops of magnetic field  PLAGE –bright patches above sunspots

Chromospheric Features  PROMINENCES –dense clouds of material suspended above the surface of the Sun by loops of magnetic field

Chromospheric Features  SPICULES –Small jet-like eruptions seen throughout the chromospheric network

Chromospheric Features  SOLAR FLARES – can release as much energy as a billion megatons of TNT

Transition Region  A very thin, irregular layer of the Sun that separates the chromosphere from the corona  Temperature changes very rapidly in this region and causes hydrogen to become stripped of its electrons.  The light emitted by the transition region is dominated by ions illustrated in the pictures

Solar Midlife - Corona  The Sun’s outermost atmosphere  Temperature is 1,800,000°F (1,000,000°C)  The Solar Corona –The White-Light Corona –The Emission Line Corona –The X-Ray Corona

Solar Midlife - Corona  EMISSION LINE CORONA  Since hydrogen atoms have been ionized only the heavier trace elements like iron and calcium are able to retain a few of their electrons in this intense heat  It is emission from these elements that produce the color associated with the emission line corona

Solar Midlife - Corona  X-RAY CORONA  The corona shines brightly in x-rays because of its high temperature while other layers of the Sun do not emit x-rays  This allows us to view the corona across the disk of the Sun when we use an X-Ray telescope

Coronal Features  HELMET STREAMERS  Large cap-like coronal structures with long pointed peaks that usually overlie sunspots and active regions formed by a network of magnetic loops

Coronal Features  POLAR PLUMES  Long thin streamers that project outward from the Sun’s north and south poles  They are associated with the “open” magnetic field lines at the Sun’s poles

Coronal Features  CORONAL LOOPS  Found around sunspots and in active regions  Associated with the closed magnetic field lines that connect magnetic regions on the solar surface  Some loops appear after solar flares

Coronal Features  CORONAL HOLES  Regions where the corona is dark  Associated with “open” magnetic field lines and are often found at the poles  The solar wind originates in coronal holes

Coronal Features  CORONAL MASS EJECTIONS (CMEs)  huge bubbles of gas threaded with magnetic field lines that are ejected from the Sun over the course of several hours.  CMEs can disrupt the flow of the solar wind  CMEs are often associated with solar flares and prominence eruptions but they can also occur in the absence of either of these processes.

The Solar Wind  The solar wind streams off of the Sun in all directions at speeds of about 1 million miles per hour  The source of the solar wind is the Sun's hot Corona  The temperature of the corona is so high that the Sun's gravity cannot hold on to it

The Solar and Heliospheric Observatory (SOHO)  The SOHO spacecraft is a joint effort between NASA and ESA  It was launched on December 2, 1995  SOHO will take measurements of the solar interior, the solar atmosphere, and the solar wind

SOHO Images  Composite picture of 3 images taken by the EIT instrument on board SOHO  Each individual image shows a different temperature in the upper solar atmosphere and was assigned a specific color  Red at 2 million degrees F  Green at 1.5 million degrees F  Blue at 1 million degrees F

Transition Region and Coronal Explorer (TRACE)  TRACE will explore the magnetic field in the solar atmosphere  TRACE will work in conjunction with SOHO for part of its mission  It was launched by a Pegasus rocket in April 1998

TRACE Images  Solar flare observed on May 19,1998  A solar flare is a rapid release of energy from a localized region on the Sun in the form of electromagnetic radiation, energetic particles, and mass motions

GENESIS – Search for Origins  What is the Sun made of?  Launched August 8, 2001  Genesis will collect solar wind samples for 2 years  Libration points  22.3 ft (6.8m) solar panel length  1402 lbs (636 kg) at launch

Solar Structure The End Hydrogen depletion Red giant Fusion stops, outward pressure decreases Collapse Planetary Nebula White Dwarf