Did you know that the Sun’s outer atmosphere, or corona, is much hotter than its surface? Scientists have been quite curious about a mysterious interface region of the Sun’s atmosphere that amplifies energy from about 5,800 degrees Kelvin on the surface, or photosphere, to around 1,000,000 degrees Kelvin in the corona.
With Thursday’s launch of its Interface Region Imaging Spectrograph or IRIS spacecraft, NASA is planning to find out just how solar matter moves, gathers energy and heats up as it passes through the Sun’s chromosphere, it’s solar transition region, and into the corona that powers the solar wind.
According to NASA, most of the sun’s ultraviolet radiation, which they say has an impact on Earth’s climate, is also produced in this interface region.
“We are thrilled to add IRIS to the suite of NASA missions studying the sun,” said John Grunsfeld, NASA’s associate administrator for science in Washington. “IRIS will help scientists understand the mysterious and energetic interface between the surface and corona of the sun.”
At 6:30PM Thursday, an Orbital L-1011 carrier aircraft, with the Pegasus XL rocket and its IRIS spacecraft payload strapped beneath, it took off from California’s Vandenberg Air Force base to a release site over the Pacific Ocean.
Five seconds after being dropped by the plane, the first stage of the Pegasus XL ignited and carried IRIS into space. NASA officials said that the IRIS spacecraft successfully separated from its launch rocket’s third stage at 7:40 PM PDT. Twenty-five minutes later, at 8:05 PM PDT, the IRIS team received confirmation that the spacecraft successfully deployed its solar arrays (seen in the top photo), had power, acquired its target, the sun, and that all systems were operating as expected.
NASA Video of the release and launch of the Pegasus XL from its Orbital L-1011 carrier aircraft
NASA says the IRIS is now going through what it calls a 60-day commissioning phase to make sure the spacecraft and its onboard instruments are functioning properly.
Mission leaders say that they are centering IRIS’ science investigation on three main themes.
1. Which types of non-thermal energy dominate in the Sun’s chromosphere and beyond?
2. How does the chromosphere regulate mass and energy supply the corona and heliosphere, which NASA says is the giant magnetic bubble that extends way beyond the orbit of Pluto and contains our solar system, the solar wind, and the entire solar magnetic field?
3. How do magnetic flux, the flow of magnetic energy, and matter rise through the lower atmosphere, and what role does flux emergence play in flares and mass ejections?
According to NASA, the IRIS spacecraft, which weighs 167 Kilograms, is 2.1 meters long and 3.7 meters across, was designed by the Smithsonian Astrophysical Observatory headquartered at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.
After its launch, IRIS was placed in a sun-synchronous polar orbit where it will circle over the north and south poles and pass over the same part of Earth at about the same time of day. This unique orbit will allow the IRIS mission team to make almost continuous solar observations during its planned two-year mission.