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SwRI instruments aboard Rosetta help detect an unexpected ultraviolet aurora on a comet
Press release from: Southwest Research Institute
Published: Tuesday, September 22, 2020
Data from instruments run by the Southwest Research Institute aboard ESA’s Rosetta spacecraft have helped reveal auroral emissions in the far ultraviolet around a comet for the first time.
On Earth, auroras are formed when charged particles from the Sun follow the lines of our planet’s magnetic field toward the north and south poles. There, solar particles strike atoms and molecules in Earth’s atmosphere, creating shimmering shades of colorful light in high-latitude skies. Similar phenomena have been observed on various planets and moons in our solar system and even around a distant star. SwRI’s instruments, the Alice Far Ultraviolet Spectrograph (FUV) and the Ion Electron Sensor (IES), helped detect these new phenomena on Comet 67P / Churyumov-Gerasimenko (67P / CG).
“Charged particles from the Sun flowing toward the comet in the solar wind interact with the gas surrounding the comet’s icy, dusty nucleus and create the auroras,” said Dr. Jim Burch, vice president of SwRI, who leads IES. “The IES instrument detected the electrons that caused the aurora.”
The gas envelope around 67P / CG, called a “coma,” is excited by solar particles and glows with ultraviolet light, an interaction detected by the Alice FUV instrument.
“Initially, we thought that the ultraviolet emissions from Comet 67P were a phenomenon known as ‘daytime glow’, a process caused by solar photons interacting with cometary gas,” said Dr. Joel Parker of SwRI, who heads Spectrograph Alice . “We were surprised to find that UV emissions are auroras, driven not by photons, but by electrons in the solar wind that break up water and other molecules in the coma and have been accelerated in the comet’s close environment. The resulting excited atoms create this distinctive light. “
Dr Marina Galand of Imperial College London led a team that used a physics-based model to integrate measurements made by various instruments aboard Rosetta.
“By doing this, we didn’t have to rely on a single data set from one instrument,” said Galand, who is the lead author of a Nature Astronomy paper describing this discovery. Instead, we could gather a large data set from multiple instruments to get a better picture of what was happening. This allowed us to unambiguously identify how 67P / CG ultraviolet atomic emissions are formed and reveal their auroral nature. “
“I’ve been studying Earth’s auroras for five decades,” Burch said. “Finding auroras around 67P, which lacks a magnetic field, is surprising and fascinating.”
Following its encounter with 67P / CG in 2014-2016, Rosetta has provided a wealth of data revealing how the Sun and the solar wind interact with comets. In addition to discovering these cometary auroras, the spacecraft was the first to orbit a comet’s nucleus, the first to fly alongside a comet on its journey into the inner Solar System, and the first to send a lander to the surface. of a comet.
Additional instruments that contributed to this research were the Rosetta Langmuir Probe (LAP), the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA), the Rosetta Orbiter Microwave Instrument (MIRO), and the Infrared Thermal Imaging Spectrometer. and visible (VIRTIS).
Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta’s Philae lander is provided by a consortium led by DLR, MPS, CNES, and ASI. Airbus Defense and Space built the Rosetta spacecraft. NASA’s Jet Propulsion Laboratory (JPL) manages the US contribution from the Rosetta mission to NASA’s Science Mission Directorate in Washington, under a contract with the California Institute of Technology (Caltech). JPL also built the Microwave Instrument for the Rosetta Orbiter and houses its principal investigator, Dr. Mark Hofstadter. SwRI (San Antonio and Boulder, Colorado) developed the Rosetta Orbiter’s ion and electron sensor and Alice instrument and houses its principal investigators.
For more information visit https://www.swri.org/
About SwRI:
SwRI is an independent, non-profit, applied research and development organization based in San Antonio, Texas, with approximately 3,000 employees and an annual research volume of nearly $ 674 million. Southwest Research Institute and SwRI are registered trademarks in the US Patent and Trademark Office.For more information please visit newsroom.swri.org or www.swri.org.
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