Impossibly close?Yes, but one never knows what the future holds.
Our Solar System The Sun is the center of our solar system. All the planets and comets, everything in the solar system revolves around it.
The Milky Way galaxy• Our galaxy, the Milky Way, is just one of perhaps billions of galaxies in the universe• The closest star to Earth is about four light years away• There are more stars than grains of sand on Earth Our Milky Way galaxy seen at night
The Dynamic SunThe Sun, like allstars, is adynamic star,always active,always changing.The more welearn about it, themore we learnabout all stars.
Where the action is• Nuclear fusion occurs in the Sun’s core• Hydrogen atoms combine to form helium and release huge amounts of energy, radiation and light• It takes over 10,000 years for the light to get to the Sun’s surface The Sun vibrates from material moving inside of it and we have translated those vibrations into sound. Click HERE and turn up your volume to hear it.
Solar influenceWe live in the atmosphere of the Sun, basking in its light and warmth, protected by our magnetic shield, themagnetosphere (green lines in the video clip). We are also struck constantly by the flow of its solar wind.
The Sun is also the source of radiation and storms that we callSPACE WEATHER! Credit: the SolarMax IMAX film
First recorded sunspotsGalileo in 1610, using one of the first (just invented) telescopes, was thefirst person to observe and record the path of sunspots across the Sun forseveral weeks.
Sunspots from down under• Sunspots are magnetic structures that emerge from beneath the surface• The white lines represent magnetic field lines• When the lines tangle and break apart, they are the creators of solar storms
A sunspot is a kind of whirlpool controlled by intense magnetic forces where hot gases from inside the Sun are blocked from reaching the surface. Therefore they are cooler than the rest of the Sun and appear darker.Sunspots The Sun as seen here rotates about every 27 days.
The average sunspot is about the size of Earth, though the largest can be 20 times the size of Earth.
Zooming in for a closer lookFrom far awaysunspots appear like darkblobs on the Sun, but upclose, they revealincredible complexity.In the most close-upview, each little cell-likegray area you see isabout the size of Texas. Credit: Swedish Solar Telescope
This close-up video shows how sunspots andthe Sun’s surface can change in just half an hour.
Solar CyclesSince about 1750, people have kept written records of sunspots, so that weknow of the solar cycle, which is the rise and fall of sunspot numbers (andsolar activity) about every 11 years. This is due to the Sun’s changingmagnetic structure.
Next solar cycle• Was near its peak level or “solar maximum” at late 2000 or early 2001.• Scientists predict that the next solar maximum period (around 2013) will be milder than usual.• Dotted lines show range of prediction; solid curve is the average; jagged lines are monthly counts
Solar Rotation• The Sun rotates every 27 days or so. This causes magnetic field lines to become twisted and stretched to the breaking point. These eventually break and reconnect, creating heat, intense active regions, and solar blasts of charged particles.
Different Solar RotationIt must be noted that since the Sun is made of a gaseous plasma and is not asolid body, it does not rotate at the same speed at all places. Specifically, nearthe poles the surface rotates in around 35 days, but near its equator the Sunrotates about every 25 days. This is called differential rotation. This processleads to stretching and stressing of the Sun’s magnetic field, which does causesolar storms.
Underlying magnetismSunspots are magneticfeatures of the Sun.Magnetic field lines gettangled up in sunspots,block energy, and makethe area cooler anddarker. When a surfaceimage of sunspots iscompared to a black andwhite image of theSun’s magnetic fieldstrength (see video clip),the features line upalmost exactly.
It’s all in the magnetism! The Sun is strongly affected by magnetic forces. Solar storms carrymagnetic fields with them into space. These can interact with Earth’s magnetic field and often cause aurora to appear in the night sky.
Storms at their sourceWhen the magnetic forces above sunspots become tangled and break apart, violent storms can burst from the Sun. This is the main source of our strongest space weather events, either coronal mass ejections or solar flares. The white specks near the end of the clips are protons from the blast hitting the spacecraft’s imager.
Coronal mass ejections (CMEs)• CMEs are large solar storms that can blast out a cloud of billions of tons of particles at over two million Km per hour. Smaller ones can occur almost any day.• The clouds reach Earth’s orbit in 1 to 3 days but only a few of them actually head our way.
Solar flares• Flares are quick, intense but smaller explosions than CMEs• They appear as bright flashes sometimes followed by a burst of high energy particles that can travel at half the speed of light. Large flares can occur several times a year when the Sun is near its peak activity. (Green tint has been added)
Loops after a stormThis close-up videoshows a whole paradeof bright magnetic loopforming as the magneticfield reorganizes after apowerful flare/CMEcombination.
Magnetic strugglesIn UV light, thearea above asunspot is seenfrom the side aswildly violent asmagnetic forcesfight for control.The video showsabout 2 days ofactivity.
Stormyweather In October 2003 the Sun produced a record series of strong storms. This UV light video (green color added) shows many bursts of solar storms.The largest are called coronal mass ejections. These occur almost daily,but the larger ones occur only a few times a year. The brightest flashes are solar flares. Sometimes these both occur together.
CME in a Coronagraph In this stop-motion clip with the Sun blocked (red disk) to reveal the faint corona, we see a coronal mass ejection (CME) bursting into space over a few hours. This instrument that produced this kind ofimage is a coronagraph. The white circle represents the covered Sun.
CME clouds heading into spaceWith the Sun blocked out, clouds of material blasting out into space at about 2 million MPH can be seen. This clip shows 5 days of powerful solar activity.
Earth’s magnetic shieldThe Earth has a magnetic field with north and south poles. TheEarths magnetic field reaches 36,000 miles (57,000 km) into space.Earth is surrounded by aregion called themagnetosphere. Thisprevents most of theparticles from the Sun,carried in solar wind andstorms, from hitting theEarth. Some particles canenter the magnetosphere.Particles that enter fromthe tail end travel towardthe Earth and create theaurora light shows.
A solar storm heads our wayA CME hits Earth’s magnetic shield and flows to the back side, where magnetic energy builds up. Earth’s magnetic field thensnaps back, sending material back into our atmosphere near the poles along the magnetic field lines.
Polar auroral ovals Actual aurora footage shown on a model EarthIf a storm cloud of charged particles is headed towards Earth, we will experience space weather first-hand in one to three days. Our magnetic field (magnetosphere) shields us, but energized particles can spiral down our magnetic field lines and glow as oval aurora near the Earth’s Poles.
AuroraAurora, often called the Northern and Southern Lights, are visible signs of the Sun’s electrical connection to the Earth. The video clip shows aurora in real time as it changes -- not speeded up. Video credit: Aurora Experience
Space weather upsetsThere are less pleasant space weather effects. Energy pumped into our atmosphere upsets modern technology. Radio signals and communications become disrupted. Satellites orbiting around Earth can suffer damage. On the ground, magnetic field changes can damage electrical equipment on Earth.
Astronaut safetyAstronauts can get high doses of radiation from solar storms and cosmic radiation when out in space. For humans to travel to the Moon and Mars, better storm forecasting and shielding will be needed.
Global Warming?It is important to understand the long-term changes in the Sun and theirpotential effects onclimate. Thesechanges includegeneral activity level(see chart), UVradiation, and totalenergy output. Solargeneral activity mayinfluence cloudformation which can,in turn, trap heat inEarth’s atmosphere.Man-made factorsseem to play animportant role inglobal warming.
The Sun’s roleIs the Suns variability tied to Earths climate? Some scientists cite acorrelation with droughts, small ice ages, and large-scale weatherpatterns on Earth. Many scientists are researching this topic today.The latest research suggests that a small variability of the Sun candrive large-scale changes in weather. The small increase in solarradiation over the past 200 years may account for a part of ourglobal warming. The general consensus is that man-made causesare the major driving force in global warming. During the “Little Ice Age” in the 17th Century, Holland’s canals often froze in winters, a very rare event that does not occur anymore. This coincided with a period of very few sunspots and much lower than normal solar activity.
Solar exploration in spaceNASA is activelyinvolved inexploration of theSun and spaceweather. SOHO (theSolar andHeliosphericObservatory) hasbeen the main solarwatchdog for over 11years. Another,TRACE, is learningmore about solarstorms. And there areothers too!
SOHO (Solar and Heliospheric Observatory)• a joint mission of NASA and the European Space Agency (ESA) studying the Sun since 1996• 12 instruments to study the Sun’s interior, atmosphere, and solar wind all day every day• a major tool for monitoring space weather• weighs 2 tons; its solar panels span 25 feet• SOHO is 1 million miles (1.6 million Km) towards the Sun
SOHO science• Discover the source of high speed solar wind• Learn more about the structure inside the Sun• Find the causes of solar storms• Monitor space weather for the world
TRACE• Studies the Sun and solar events at a much smaller scale than SOHO• Launched in 1999• Works closely with SOHO
Some TRACE Images• Close-ups of flares and loops Video credit: SolarMax IMAX film
A recent solar mission, STEREO , launched in Oct. 2006, is unique.A pair of nearly identical NASA spacecraft are studying the Sun frompositions ahead of and trailing Earth. They are collecting data and providing3-D views of solar storms for the first time ever.
First image of the Sun from STEREO Dr. Lika Guhathakurta, STEREO Program Scientist, NASA This looks a lot like a SOHO image, doesn’t it? Thedifference is in the level of details that the STEREO imager can capture -- two times as much!
Detailed STEREO images• New coronagraph and ultraviolet images provide sharper details than ever before (2007) Solar loops arcing above active regions in extreme UV light
STEREO sees erupting prominence• With images taken every 10 minutes in four wavelengths of light, STEREO captures more events like this than SOHO can.
3-D SunScientists have waited for years to view the first ever 3-D views of the Sun from STEREO and at a level of detail never seen before! (You need 3D glasses to see this in 3D.) This image is a composite made from three wavelengths of light captured by each of the two STEREO spacecraft
More Sun-Earth missionsMissions from NASA and other U.S. and TIMEDforeign agencies exist or are planned forlaunch to study and monitor spaceweather. These will create a way to THEMISobserve the Sun-Earth connections as aninteractive system. Hinode Solar Dynamics Observatory Magnetospheric Multi-Scale Solar Sentinels
Solar Dynamics Observatory (SDO)• A “supercharged” SOHO on steroids• To launch in 2009• With images 4 times more detailed and 10 times more often than SOHO
Monitoring the SunSolar activity is being monitored around the clock. If there is a possible impact predicted from a solar storm, alerts are sent out from NOAA’s Space Environment Center to the rest of the world.
NASA will continue to explore the Sun-Earth connection over the next solar cycleand beyond. The more dependent we become on technology, the more we need to understand space weather and how it can affect our lives. Video clip: SolarMax, Chicago Museum of Science & Industry