This image from NASA's IRIS spacecraft shows the region around two sunspots - the
dark areas at upper left and lower right. It shows emission from ionized silicon (Si IV)
in the transition region at a temperature of about 116,000 degrees Fahrenheit, plus
ultraviolet continuum from the chromosphere at a temperature of about 17,000 °F.
The bright dots are short-lived, intense patches of Si IV emission. The role that
these dynamic events have in heating the solar atmosphere is currently unknown.
This image from NASA's Solar Dynamics Observatory shows a larger
area around the two sunspots that were photographed by IRIS.NASA's Interface Region Imaging Spectrograph (IRIS) observatory has produced its first images and spectra of a little understood region of the Sun through which the energy that supports the Sun's hot corona is transported. IRIS was launched on June 27, 2013, and the front cover of the IRIS telescope was opened on July 17.
"Already, we're finding that IRIS has the capability to reveal a very dynamic and highly structured chromosphere and transition region," says astrophysicist Hui Tian of the Harvard-Smithsonian Center for Astrophysics (CfA). "Thin and elongated structures are clearly present in these first-light images, and they evolve quickly in time."
Important goals of the IRIS mission are to understand how the Sun's million degree corona is heated and to reveal the genesis of the solar wind. By tracing the flow of energy and plasma through the transition region - between the solar surface and the solar corona - where most of the Sun's ultraviolet emissions are generated, IRIS data will allow scientists to study and model a region of the Sun that has yet to reveal its secrets. Ultimately, such understanding could enable scientists to provide forecasts for the Sun's destructive behavior, which can disable satellites, cause power grid failures and disrupt GPS services. IRIS will deliver near continuous solar observations throughout its two-year mission.
IRIS takes images with four different filters in the ultraviolet wavelength range. It is the first time that images in these wavelengths have been taken with very high resolution (~150 miles) and at a cadence that can capture the rapid evolution of the chromosphere (every 10 seconds).
IRIS also takes very high-resolution spectra in three ultraviolet wavelength ranges. The spectra are critical for providing physical measurements underlying the dynamics seen in the images. Through the analysis of high-spatial-resolution spectra, scientists can measure flow speeds, energy deposition, and wave properties and densities of the atmospheric plasma.
The IRIS science instrument and spacecraft were built at the Lockheed Martin Advanced Technology Center (ATC) Solar and Astrophysics Laboratory in Palo Alto, Calif. The IRIS solar telescope was built by the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., which also assists in science operations and data analysis.
"The IRIS mission has been from inception an enormous international collaborative development effort," says Dr. Alan Title, IRIS principal investigator and physicist at the Lockheed Martin ATC Solar and Astrophysics Laboratory. "Our IRIS team was formed to design the mission and prepare the initial proposal. We have worked together seamlessly ever since."
Image Credits: NASA/GSFC 
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