SunScapes: Our Magnetic Star main content.

SunScapes: Our Magnetic Star

Part of the Journey To The Stars exhibition.

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Solar Mosaic In this image, dozens of ultraviolet photographs of the Sun are stitched into a mosaic, with the coldest regions shaded blue and the hottest red and white.

More than simply beautiful, these photographs from the National Aeronautics and Space Administration (NASA) allow astronomers to study in further detail the Sun’s magnetic field.As the star at the center of our solar system, the Sun makes life on Earth possible. But not all of its effects on our lives are beneficial: the Sun sporadically disrupts our weather patterns and interrupts our communication and navigation systems. It generates radiation that may harm astronauts and airline passengers. It can even push power grids to failure. All of these and other phenomena, including the many spectacular solar events shown in the following photographs, are controlled by the Sun’s variable magnetic field.

On Earth, there is a magnetic field that remains relatively stable over time. Explorers, surveyors, pilots and ship captains use this field to orient their compasses and to find their way around the globe. Even animals, like some migratory birds, can use the Earth’s magnetic field to navigate with their own internal compasses. But on the Sun, the magnetic field is much more erratic; there are many magnetic poles whose positions and strengths constantly change. Indeed, a compass on the Sun would merely point to the pole closest and strongest at that moment.

As troublesome as it is for us, the Sun’s magnetic field is also useful, as it makes direct observations of the Sun possible. All elements caught in the Sun’s magnetic field emit extreme ultraviolet light, invisible and exceptionally dangerous. Orbiting telescopes can detect such light and represent it as safe, visible, recognizable colors. More than simply beautiful, these photographs from the National Aeronautics and Space Administration (NASA) allow astronomers to study in further detail the Sun’s magnetic field.

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Rotational Chaos From surface to core, the Sun is a star made of very hot gas that rotates around its axis. Astronomers detect sound waves on the Sun by measuring the minute variations in the surface brightness, and in turn use those sound waves to measure the Sun’s average rotational speed at any one interior or surface point. That speed is represented in this image by color, with the fast gas near the equator shown in red and slow gas near the poles in blue. This differential rotation wreaks havoc on the Sun’s magnetic field—literally twisting the field into knots—causing the disruptions and irregularities that affect life on Earth.
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Sunspot Connections Sprinkled across the solar surface are cold patches of intense magnetic field—called sunspots—which appear darker than surrounding, hotter areas. In this composite image, dark sunspots can be seen in each "layer" where the field is strong and coherent. The bottom green panel shows the visible surface at about 5,000 °C (9,000 °F). The blue image (not to scale) shows the emission up to some 6,500 kilometers (about 4,000 miles) above the solar surface. The yellow image shows the Sun in the light of hydrogen gas. The top image shows the highest domain of the solar atmosphere, called the corona, over 1.5 million km (roughly 1 million miles) above the solar surface, where the temperature exceeds 1 million °C (1.8 million °F).

The Yellow Sun?

The Sun’s magnetic field heats its atmospheric gases to millions of degrees Celsius. Paradoxically, the gasses closest to the Sun are the coolest and densest and the ones farther away are hotter and more diffuse. At these different temperatures, the Sun’s atmosphere glows at different wavelengths or colors, most of which are invisible to the human eye. Indeed, the Sun emits all the colors of the spectrum of light, but gives off more yellow light than any other. In fact, when we look up at the Sun, our “yellow light” sensitive eyes only see the coolest part of its atmosphere, the gas glowing at visible wavelengths, itsphotosphere, as seen in this photograph. The hotter parts of the atmosphere farther away from the surface glow at wavelengths visible only to special optical systems and detectors. The following photographs, all taken on February 8th, 2001 by telescopes outfitted with such systems, show the Sun at a variety of wavelengths ranging from the visible, through the ultraviolet to the X-ray part of the spectrum. False colors were used in those images that depict the Sun at wavelengths outside of the visible spectrum, giving visual form to things we could never see with our own eyes.

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The Yellow Sun? When we look up at the Sun, our “yellow light” sensitive eyes only see the coolest part of its atmosphere, the gas glowing at visible wavelengths, its photosphere, as seen in this photograph.
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Sunspotted Magnetic maps of the Sun, like this one created with polarized filters that are tuned to very narrow color ranges, show regions of north magnetic polarity as bright, and regions of south polarity as dark. Comparisons with images of the Sun taken in visible light show that sunspots correspond to compact, strong clusters of magnetic field.
The Sun glowing blue, in the light of calcium
In the Light of Calcium Within the first 6,500 km (about 4,000 miles) above the Sun's visible surface, the temperature within the magnetic field nearly doubles from 5,500 to 10,000 °C (about 10,000 to 18,000 °F) and the gas glows in the light of calcium (in blue).
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