NASA is now gearing up for the launch of a new Sun-monitoring satellite that will greatly improve our observation abilities with regards to the Sun’s lower atmosphere — a region that plays an important role in the behavior of the Sun’s atmosphere.
IRIS — the Interface Region Imaging Spectrograph — is currently expected to launch at the end of June. The IRIS mission will give us our best yet view of the very-active lower atmosphere, which experiences some of the widest ranges of temperatures observed on the Sun, and has until now been difficult to study.
“This region is crucial for understanding how the corona gets so hot,” said Joe Davila, IRIS project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “For the first time, we will have the capability to observe it at fundamental physical scale sizes and see details that have previously been hidden.”
The mission’s capabilities were designed specifically with the intention of “unraveling the interface region” — providing very high-resolution images as well as a type of data referred to as spectra. With regards to the high-resolution images, “IRIS will capture data on about one percent of the sun at a time. While these are relatively small snapshots, IRIS will be able to see very fine features, as small as 150 miles across.”
“We have some great space observatories currently looking at the sun,” said Bart DePontieu, the IRIS science lead at Lockheed Martin in Palo Alto, Calif. “But when it comes to the interface region, we’ve never been able to resolve individual structures. We have been able only to see conglomerates of various structures. Now we will finally be able to observe the details.”
Apparently IRIS’s images will be — impressively — 3-4 times more detailed than the images provided by NASA’s Solar Dynamics Observatory. SDO though, of course, can image all of the Sun at once. “SDO’s wavelengths are not tailored, however, to see the interface region. Scientists can use IRIS observations to hone in on smaller details while working with the larger instruments, such as SDO or the Japan Aerospace Exploration Agency’s Hinode, to capture images of the entire sun. Together, the observatories will explore how the corona works and impacts Earth — SDO and Hinode monitoring the solar surface and outer atmosphere, with IRIS watching the region in between.”
Ultraviolet images look at only one wavelength of light at a time, but IRIS will also provide spectra, a kind of data that can show information about many wavelengths of light at once. Spectrographs split the sun’s light into its various wavelengths and measure how much of any given wavelength is present. This is then portrayed on a graph showing spectral “lines” — taller lines correspond to wavelengths in which the sun emits relatively more radiation.
Each spectral line also corresponds to a given temperature, so this provides information about how much material of a particular temperature is present. The images from IRIS’ telescope will record observations of material at specific temperatures, ranging from 5,000 kelvins to 65,000 kelvins (8,540 F to 116,540 F) — and up to 10 million kelvins (about 18 million F) during solar flares — a range best suited to observe material on the sun’s surface and in the interface region.
“By looking at spectra of material in these temperature ranges, we can also diagnose velocity and perhaps density of the material, too,” said De Pontieu. “The IRIS instrument will capture a new image every five to 10 seconds, and spectra about once every two seconds. These unique capabilities will be coupled with state-of-the-art 3-D numerical modeling sophisticated enough to deal with the complexity of this region. The modeling makes use of supercomputers at NASA’s Ames Research Center, Moffet Field, California.”
When all of IRIS’ capabilities are taken together — high resolution, fast rate of imaging, wide temperature coverage — and combined with computer modeling, researchers will be able to, for the first time, track the journey of solar material as it’s heated and accelerated in the interface region. This new ability will help to accurately identify the “where and how the plasma gains energy and heat along its travels through the lower levels of the solar atmosphere.”