Understanding Our Solar System

Observations from Hinode's X-Ray Telescope of the north pole of the sun. Image Credit: SAO/NASA/JAXA/NAOJ

Since the beginning of time, people have been watching the planets, moons, and stars as well as the comets as they move across the sky. In the next few decades, NASA intends to deepen our understanding of the solar system, with spacecraft fanning out to destinations from the innermost planet to the very edge of our sun's influence. Some will stay in Earth's orbit; others will follow looping one-way trajectories through the gravitational forces of the planets; and a few will come back carrying priceless samples from other worlds.

The space scientists and engineers at Marshall Space Flight Center are continually advancing our awareness and understanding of the sun-Earth planetary system. Marshall manages the Discovery and New Frontiers programs, which include lower-cost, highly focused planetary science investigations designed to increase our knowledge of the solar system. Marshall provides mission oversight, technology planning, systems assessment, flight assurance and public outreach.

The solar physics group at Marshall was formed in the early 1970s in conjunction with the Apollo Space Lab mission. The group seeks to understand how the sun works, why it changes, and how these changes affect space exploration and influence us on Earth. They use a variety of instruments, such as telescopes and probes, to study sun-influenced space weather and energetic particle emissions from solar flares and other solar eruptions. It is important to understand these phenomena because they can adversely affect satellites and pose a threat to astronauts. The effect on the Earth's magnetic field can also impact electrical systems, destroying equipment and knocking out power to large areas.

The expertise of this solar physics team plays a critical role in many NASA-led and international missions. One example is the Hinode mission, which seeks to explore the sun's magnetic fields to improve our understanding of the mechanisms that power the solar atmosphere and drive solar eruptions. Hinode is a collaborative mission led by the Japanese Aerospace Exploration Agency, NASA, the Science and Technology Facilities Council, and theEuropean Space Agency. Marshall managed the development of Hinode's scientific instrumentation and currently manages the U.S. portion of the science derived from the spacecraft’s three instruments.

NASA's New Eye on the Sun Delivers Stunning First Images

View related briefing materials here.

NASA's recently launched Solar Dynamics Observatory, or SDO, is returning early images that confirm an unprecedented new capability for scientists to better understand our sun’s dynamic processes. These solar activities affect everything on Earth.

Some of the images from the spacecraft show never-before-seen detail of material streaming outward and away from sunspots. Others show extreme close-ups of activity on the sun’s surface. The spacecraft also has made the first high-resolution measurements of solar flares in a broad range of extreme ultraviolet wavelengths.

"These initial images show a dynamic sun that I had never seen in more than 40 years of solar research,” said Richard Fisher, director of the Heliophysics Division at NASA Headquarters in Washington. "SDO will change our understanding of the sun and its processes, which affect our lives and society. This mission will have a huge impact on science, similar to the impact of the Hubble Space Telescope on modern astrophysics.”

A full-disk multiwavelength extreme ultraviolet image of the sun taken by SDO on March 30, 2010. False colors trace different gas temperatures. Reds are relatively cool (about 60,000 Kelvin, or 107,540 F); blues and greens are hotter (greater than 1 million Kelvin, or 1,799,540 F). Credit: NASA/Goddard/SDO AIA Team
› Larger image

Launched on Feb. 11, 2010, SDO is the most advanced spacecraft ever designed to study the sun. During its five-year mission, it will examine the sun's magnetic field and also provide a better understanding of the role the sun plays in Earth's atmospheric chemistry and climate. Since launch, engineers have been conducting testing and verification of the spacecraft’s components. Now fully operational, SDO will provide images with clarity 10 times better than high-definition television and will return more comprehensive science data faster than any other solar observing spacecraft.

A movie of the March 30, 2010, solar prominence eruption, as seen by SDO. Credit: NASA/Goddard

SDO will determine how the sun's magnetic field is generated, structured and converted into violent solar events such as turbulent solar wind, solar flares and coronal mass ejections. These immense clouds of material, when directed toward Earth, can cause large magnetic storms in our planet’s magnetosphere and upper atmosphere.

SDO will provide critical data that will improve the ability to predict these space weather events. NASA's Goddard Space Flight Center in Greenbelt, Md., built, operates and manages the SDO spacecraft for the agency’s Science Mission Directorate in Washington.

“I’m so proud of our brilliant work force at Goddard, which is rewriting science textbooks once again.” said Sen. Barbara Mikulski, D-Md., chairwoman of the Commerce, Justice and Science Appropriations Subcommittee that funds NASA. “This time Goddard is shedding new light on our closest star, the sun, discovering new information about powerful solar flares that affect us here on Earth by damaging communication satellites and temporarily knocking out power grids. Better data means more accurate solar storm warnings.”

This image compares the relative size of SDO's imagery to that of other missions. Credit: NASA
› Larger image

Space weather has been recognized as a cause of technological problems since the invention of the telegraph in the 19th century. These events produce disturbances in electromagnetic fields on Earth that can induce extreme currents in wires, disrupting power lines and causing widespread blackouts. These solar storms can interfere with communications between ground controllers, satellites and airplane pilots flying near Earth's poles. Radio noise from the storm also can disrupt cell phone service.

More "Hello, SDO!" videos from NASA Goddard's Scientific Visualization Studio. Credit: NASA/Goddard/Chris Smith

SDO will send 1.5 terabytes of data back to Earth each day, which is equivalent to a daily download of half a million songs onto an MP3 player. The observatory carries three state-of the-art instruments for conducting solar research.

The Helioseismic and Magnetic Imager maps solar magnetic fields and looks beneath the sun’s opaque surface. The experiment will decipher the physics of the sun’s activity, taking pictures in several very narrow bands of visible light. Scientists will be able to make ultrasound images of the sun and study active regions in a way similar to watching sand shift in a desert dune. The instrument’s principal investigator is Phil Scherrer of Stanford University. HMI was built by a collaboration of Stanford University and the Lockheed Martin Solar and Astrophysics Laboratory in Palo Alto, Calif.

The Atmospheric Imaging Assembly is a group of four telescopes designed to photograph the sun’s surface and atmosphere. The instrument covers 10 different wavelength bands, or colors, selected to reveal key aspects of solar activity. These types of images will show details never seen before by scientists. The principal investigator is Alan Title of the Lockheed Martin Solar and Astrophysics Laboratory, which built the instrument.

The Extreme Ultraviolet Variability Experiment measures fluctuations in the sun’s radiant emissions. These emissions have a direct and powerful effect on Earth’s upper atmosphere -- heating it, puffing it up, and breaking apart atoms and molecules. Researchers don’t know how fast the sun can vary at many of these wavelengths, so they expect to make discoveries about flare events. The principal investigator is Tom Woods of the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder. LASP built the instrument.

"These amazing images, which show our dynamic sun in a new level of detail, are only the beginning of SDO's contribution to our understanding of the sun," said SDO Project Scientist Dean Pesnell of Goddard.

SDO is the first mission of NASA's Living with a Star Program, or LWS, and the crown jewel in a fleet of NASA missions that study our sun and space environment. The goal of LWS is to develop the scientific understanding necessary to address those aspects of the connected sun-Earth system that directly affect our lives and society.

Hinode Discovers the Origin of White Light Flare

View large image
Fig. 1, above, White light images of solar surface observed by the Hinode Solar Optical Telescope at 22:07 UT, before the flare, and below, at 22:09 UT, during the flare on Dec. 14, 2006. Image Credit: NASA/JAXA
View large image

A joint Japan-United States research team has identified the origin of the white light emission in solar flares.

The team, led by Dr. Kyoko Watanabe, an aerospace project research associate at the Japan Aerospace Exploration Agency, made its discovery by quantitatively analyzing an X-class solar flare, which was observed by two successive, solar-observing satellites: Hinode and the NASA SMEX mission RHESSI. The origin of the white light emission had not been clarified since its first discovery about 150 years ago.

A solar flare is the most energetic explosion observed in the solar system. Different ways of viewing solar flares include X-rays, radio and chromospheric spectral lines. A large percentage of flares are recognized as a result of associated brightening in the visible light spectrum, and thus are called white light flares.

British astronomer Richard Carrington made the first observation of solar flares in 1859 by sketching details of sunspots, including bright features that at times corresponded to white light emissions. However, the occurrence of such emissions is infrequent, leaving the mechanism for their creation unclear.

The Solar Optical Telescope, aboard the solar observing satellite Hinode, provides the white light images, allowing scientists for the first time to accurately study the brightness and its time variations. The Hinode observations completed so far indicate that many solar flares are accompanied by white light emissions. Hinode was launched on Sept. 23, 2006 by JAXA, in partnership with NASA and in collaboration with space-agency partners in the United Kingdom, Norway, Europe and Japan's National Astronomical Observatory.

White light emissions were observed by the Solar Optical Telescope during an X-class flare that occurred at 22:09 UT on Dec. 14, 2006 (see Fig. 1). The RHESSI satellite simultaneously recorded hard X-ray emissions, an indicator of non-thermal electrons accelerated by solar flares. The team found that the spatial location and temporal change of white light emissions are correlated with those of hard X-ray emissions (see Fig. 2). Moreover, the energy of white light emissions is equivalent to the energy supplied by all the electrons accelerated to above 40 keV (~40 percent of the light speed). This finding strongly suggests that highly accelerated electrons are responsible for producing white light emissions.

Hard X-rays are emitted when accelerated electrons impact the dense atmosphere near the solar surface. Normally, white light emissions primarily come from the solar surface, whereas 40 keV electrons can penetrate into the atmosphere about 1,000 km above the solar surface, i.e., the chromosphere.

Fig.2: White light emission, left, taken by Hinode/SOT, and the difference image of white light emission and RHESSI hard X-ray contours at 22:09 UT. The background image is the differential white light image (the average of the images taken at 22:07 UT and 22:17 UT is subtracted). Blue contours show 40-100 keV emission. Image credit: NASA/JAXA
View large imageParticle acceleration is one of the many mysteries surrounding solar flares. Modeling energy transfer of high-energy particles in the solar atmosphere is an important subject for further improving human understanding of particle acceleration. Highly accelerated particles may travel toward the Earth and cause geomagnetic storms, resulting in impacts to Earth-orbiting hardware and human activity on the surface. Now, as solar activity gradually increases after a very long period of minimal high energy activity, solar physicists are hoping the increased solar activity will provide Hinode with additional opportunities to observe solar flares and extend its observations.

Hinode is a collaborative mission with NASA and the space agencies of Japan, the United Kingdom, Norway and Europe and Japan's National Astronomical Observatory. NASA's Marshall Space Flight Center in Huntsville, Ala., manages Hinode science operations and oversaw development of the scientific instrumentation provided for the mission by NASA, industry and other federal agencies. The Lockheed Martin Advanced Technology Center in Palo Alto, Calif., is the lead U.S. investigator for the Solar Optical Telescope. The Smithsonian Astrophysical Observatory in Cambridge, Mass., is the lead American investigator for the X-ray Telescope.

Why NASA Keeps a Close Eye on the Sun's Irradiance

05.25.10

For more than two centuries, scientists have wondered how much heat and light the sun expels, and whether this energy varies enough to change Earth’s climate. In the absence of a good method for measuring the sun's output, the scientific conversation was often heavy with speculation.

By 1976, that began to change when Jack Eddy, a solar astronomer from Boulder, Colo., examined historical records of sunspots and published aseminal paper that showed some century-long variations in solar activity are connected with major climatic shifts. Eddy helped show that an extended lull in solar activity during the 17th Century --called the Maunder Minimum -- was likely connected to a decades-long cold period on Earth called the "Little Ice Age."

Two years after Eddy published his paper, NASA launched the first in a series of satellite instruments called radiometers, which measure the amount of sunlight striking the top of Earth's atmosphere, or total solar irradiance. Radiometers have provided unparalleled details about how the sun's irradiance has varied in the decades since. Such measurements have helped validate and expand upon Eddy's findings. And they've led to a number of other discoveries—and questions—about the sun.

Without radiometers, scientists would probably still wonder how much energy the sun emits and whether it varies with the sunspot cycle. They wouldn't know of the competition between dark sunspots and bright spots called faculae that drives irradiance variations.

And they’d have little chance of answering a question that continues to perplex solar experts today: Has overall irradiance changed progressively throughout the past three 11-year cycles, or are variations in the sun's irradiance limited to a single cycle?

The answer has important implications for understanding climate change, as some scientists have suggested that trends in solar irradiance account for a significant portion of global warming.

The next space radiometer, slated for launch this November aboard NASA's Glory satellite, should help chip away at the uncertainty that surrounding the sun's role in climate change.

A Variable Sun

It's well known today that the sun's irradiance fluctuates constantly in conjunction with sunspots, which become more and less abundant every 11 years due to turbulent magnetic fields that course through the sun's interior and erupt onto its surface.

But as recently as the 1970s, scientists assumed that the sun’s irradiance was unchanging; the amount of energy it expels was even called the "solar constant."

It was data from radiometers aboard Nimbus 7, launched in 1978, and the Solar Maximum Mission, launched two years later, that were the death knell to the solar constant. Soon after launching, instruments aboard both satellites showed that solar irradiance changed significantly as patches of sunspots rotated around the sun's surface. Irradiance would fall, for example, when groups of sunspots faced Earth. And it would recover when the sunspots rotated to the far side of the sun.

Likewise, in 2003, a radiometer aboard NASA's Solar Radiation and Climate Experiment (SORCE) satellite observed large sunspot patches that caused irradiance to drop by as much 0.34 percent, the largest short-term decrease ever recorded.

"When you look at longer scales on the sun, it's the opposite," said Lean, a solar scientist at the U.S. Naval Research Laboratory in Washington, D.C., and a member of Glory's science team. "Overall, irradiance actually increases when the sun is more active even though sunspots are more common."

How can increases in dark, cool sunspots yield increases in irradiance? "It didn't make much sense until we were able to show that sunspots are just half of the story," said Lean.

Measurements collected during the 1980s and 1990s gave scientists the evidence they needed to prove that irradiance is actually a balance between darkening from sunspots and brightening from accompanying hot regions called faculae, a word meaning "bright torch" in Latin.

When solar activity increases, as it does every 11 years or so, both sunspots and faculae become more numerous. But during the peak of a cycle, the faculae brighten the sun more than sunspots dim it.

Overall, radiometers show that the sun’s irradiance changes by about 0.1 percent as the number of sunspots varies from about 20 sunspots or less per year during periods of low activity (solar minimum) to between 100 and 150 during periods of high activity (solar maximum).

“That may seem like a tiny amount, but it’s critical we understand even these small changes if we want to understand whether the sun's output is trending up or down and affecting climate,” said Greg Kopp, a principal investigator for Glory and scientist at the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

Though most scientists believe the 0.1 percent variation is too subtle to explain all of the recent warming, it's not impossible that long-term patterns -- proceeding over hundreds or thousands of years -- could cause more severe swings that could have profound impacts on climate.

Searching for a Trend Line

A total of 10 radiometers have monitored the sun since Nimbus 7, and by patching all of the measurements together into one data stream, scientists have tried to identify whether the sun’s irradiance has increased or decreased over the last three cycles.

However, melding the results from different instruments has proven complicated because many of the radiometers record slightly different absolute measurements. And the areas of overlap between instruments in the long-term record aren't as robust as scientists would like.

As a result, questions remain about how the sun's irradiance has changed. Richard Willson, principal investigator for NASA's Active Cavity Radiometer Irradiance Monitor (ACRIM), reported in a 2003 paper that the overall brightness of the sun was increasing by 0.05 percent per decade.

Subsequent assessments of the same data have come to a different conclusion. Other groups of scientists have shown that the apparent upward trend is actually an artifact of the radiometers and how they degrade in orbit. Complicating the issue further, an instrument aboard NASA's Solar and Heliospheric Observatory (SOHO) measured irradiance levels during a solar minimum in 2008 that were actually lower than the previous solar minimum.

Which measurements are right? Has the sun experienced subtle brightening or dimming during the last few solar cycles? Such questions remain controversial, but the radiometer aboard Glory, called the Total Irradiance Monitor (TIM), is ready to provide answers. The Glory TIM will be more accurate and stable than previous instruments because of unique optical and electrical advances. And each of its components has undergone a rigorous regime of calibrations at a newly-built facility at the University of Colorado.

“It’s a very exciting time to be studying the sun,” said Lean. “Every day there's something new, and we’re on the verge of answering some very important questions.”

Sunspots are darker areas of the Sun that have lower solar irradiance than other areas. A large sunspot group in 2003, observed by the Total Irradiance Monitor (TIM) radiometer, caused irradiance to decrease by 0.34 percent. Credit:University of Colorado/Laboratory for Atmospheric and Space Physics/Greg Kopp

› Larger image

› Click for video

Although sunspots cause a decrease in irradiance they're accompanied by bright white blotches called faculae that cause an overall increase in solar irradiance.Credit: NASA/Goddard/SORCE

› Larger image

Like sunspots, solar prominences are more likely to occur during the most active part of the solar cycle. Yet despite their striking appearance, they have little impact on the sun's total solar irradiance.Credit: NASA/GSFC/Solar Dynamics Observatory's AIA Instrument

› Larger image

Spacecraft Reveals Small Solar Events Have Large Scale Effects

Related briefing materials can be found here.

NASA's Solar Dynamics Observatory, or SDO, has allowed scientists for the first time to comprehensively view the dynamic nature of storms on the sun. Solar storms have been recognized as a cause of technological problems on Earth since the invention of the telegraph in the 19th century.

The Atmospheric Imaging Assembly (AIA), one of three instruments aboard SDO, allowed scientists to discover that even minor solar events are never truly small scale. Shortly after AIA opened its doors on March 30, scientists observed a large eruptive prominence on the sun's edge, followed by a filament eruption a third of the way across the star's disk from the eruption.

"Even small events restructure large regions of the solar surface," said Alan Title, AIA principal investigator at Lockheed Martin Advanced Technology Center in Palo Alto, Calif. "It's been possible to recognize the size of these regions because of the combination of spatial, temporal and area coverage provided by AIA."

The AIA instrument also has observed a number of very small flares that have generated magnetic instabilities and waves with clearly-observed effects over a substantial fraction of the solar surface. The instrument is capturing full-disk images in eight different temperature bands that span 10,000 to 36-million degrees Fahrenheit. This allows scientists to observe entire events that are very difficult to discern by looking in a single temperature band, at a slower rate, or over a more limited field of view.

The data from SDO is providing a torrent of new information and spectacular images to be studied and interpreted. Using AIA's high-resolution and nearly continuous full-disk images of the sun, scientists have a better understanding of how even small events on our nearest star can significantly impact technological infrastructure on Earth.

Solar storms produce disturbances in electromagnetic fields that can induce large currents in wires, disrupting power lines and causing widespread blackouts. The storms can interfere with global positioning systems, cable television, and communications between ground controllers and satellites and airplane pilots flying near Earth's poles. Radio noise from solar storms also can disrupt cell phone service.

Launched in Feb. 2010, the spacecraft's commissioning May 14 confirmed all three of its instruments successfully passed an on-orbit checkout, were calibrated and are collecting science data.

"We're already at five million images and counting," said Dean Pesnell, the SDO project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "With data and images pouring in from SDO, solar scientists are poised to make discoveries that will rewrite the books on how changes in solar activity have a direct effect on Earth. The observatory is working great, and it's just going to get better."

Goddard built, operates and manages the SDO spacecraft for NASA's Science Mission Directorate in Washington. SDO is the first mission of NASA's Living with a Star Program. The program's goal is to develop the scientific understanding necessary to address those aspects of the sun-Earth system that directly affect our lives and society.

As the Sun Awakens, NASA Keeps a Wary Eye on Space Weather

June 4, 2010: Earth and space are about to come into contact in a way that's new to human history. To make preparations, authorities in Washington DC are holding a meeting: The Space Weather Enterprise Forum at the National Press Club on June 8th.

Many technologies of the 21st century are vulnerable to solar storms. [more]

Richard Fisher, head of NASA's Heliophysics Division, explains what it's all about:

"The sun is waking up from a deep slumber, and in the next few years we expect to see much higher levels of solar activity. At the same time, our technological society has developed an unprecedented sensitivity to solar storms. The intersection of these two issues is what we're getting together to discuss."

The National Academy of Sciences framed the problem two years ago in a landmark report entitled "Severe Space Weather Events—Societal and Economic Impacts." It noted how people of the 21st-century rely on high-tech systems for the basics of daily life. Smart power grids, GPS navigation, air travel, financial services and emergency radio communications can all be knocked out by intense solar activity. A century-class solar storm, the Academy warned, could cause twenty times more economic damage than Hurricane Katrina.

Much of the damage can be mitigated if managers know a storm is coming. Putting satellites in 'safe mode' and disconnecting transformers can protect these assets from damaging electrical surges. Preventative action, however, requires accurate forecasting—a job that has been assigned to NOAA.

"Space weather forecasting is still in its infancy, but we're making rapid progress," says Thomas Bogdan, director of NOAA's Space Weather Prediction Center in Boulder, Colorado.

Bogdan sees the collaboration between NASA and NOAA as key. "NASA's fleet of heliophysics research spacecraft provides us with up-to-the-minute information about what's happening on the sun. They are an important complement to our own GOES and POES satellites, which focus more on the near-Earth environment."

Heliophysics

Understanding the Sun and its interactions with Earth and the solar system

An overview for NASA's Heliophysics division explains how NASA studies the sun--and more importantly--how it affects our daily lives. > Download Video

Mission Statement

At the center of our solar system there is a magnetic variable star, our Sun, that affects the planets, including the Earth, and sculptures the flows of interplanetary space itself. Heliophysics is the study of the Sun's influence throughout the solar system and, in particular, its connection to the Earth and the Earth’s extended space environment. The science of Heliophysics provides not only cultural and intellectual benefits to society, research results have direct economic and political impact in modern society.