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Stratospheric Results from NASA's SOFIA Airborne Telescope

Press Release From: Universities Space Research Association
Posted: Tuesday, January 9, 2018

Scientists from the Universities Space Research Association (USRA), Columbia, Maryland, today announced a number of new astronomical findings at the 231st meeting of the American Astronomical Society in Washington, D.C.

The science results were obtained using NASA’s Stratospheric Observatory for Infrared Astronomy, SOFIA, a highly modified Boeing 747SP jetliner fitted with a 100-inch (2.5-meter) infrared telescope. SOFIA is an international partnership between NASA and the German Aerospace Center (DLR).

The flying observatory has a suite of seven different instruments -- cameras and spectrometers -- that are flown to altitudes as high as 45,000 feet (13.7 km) on missions up to 10 hours in duration. This altitude puts the observatory above more than 99 percent of the Earth’s water vapor that blocks infrared wavelengths from reaching the ground. SOFIA’s ability to study mid- and far-infrared wavelengths (28-320 microns) provides observations for the astronomical community any other current astronomical facility on the ground or in space.

“As an airborne platform that returns to base after each flight, SOFIA can bring the latest instruments to address the current questions about our universe,” said Dr. Nicholas White, USRA Senior Vice President, Science. USRA manages SOFIA’s science mission on behalf of NASA from the SOFIA Science Center at NASA Ames Research Center in Mountain View, California and NASA Armstrong Flight Research Center in Palmdale, California. Dr. White noted that “The observatory’s latest capabilities with the new High-resolution Airborne Wideband Camera (HAWC+), the upgraded German Receiver for Astronomy at Terahertz Frequencies (GREAT/upGREAT), and other instruments are opening our eyes as to the impact of magnetic fields and the major cooling lines of the interstellar medium, allowing stars and planets to form.”

Astronomers from the USRA SOFIA Science Mission Operations Center, Northwestern University, and the University of Maryland discussed new scientific results describing how their studies of dust grain polarization and celestial magnetic fields are leading to a better understanding of star formation, theories about how gas cools in the interstellar medium, and how magnetic fields are creating stellar winds around black holes:

B-G Andersson * USRA/SOFIA
SOFIA/HAWC+ Polarization in the Envelope IRC+10216
Astronomers assume that the polarization maps that we observe with instruments, such as HAWC+, trace the magnetic fields in space. To understand the polarization in detail, astronomers need to understand which grains contribute to the polarization, which do not, and under what conditions. One theory about how these grains behave is known as the Radiative Alignment Torque (RAT) theory.

Andersson presented the results of two recent tests supporting the RAT theory. The first set of observations show that the grain alignment in the wall of the Local Bubble (the low density cavity surrounding the Sun) is enhanced close to nearby star clusters. For these observations, Andersson’s team analyzed a large sample of visual light polarimetry, where the long direction of the grains block out more of the light from the background star than the short direction.

The second test showed that carbon grains in the envelope of the carbon-rich star CW Leo (IRC+10216) are aligned in a way consistent with RAT alignment. The CW Leo observations are of the heat radiation given off by the grains, where they emit more efficiently along their long axis than along the short one. Such observations have only recently been made possible with the HAWC+ camera on SOFIA.

Fabio Santos * Northwestern University
HAWC+/SOFIA Observations of Rho Oph A: Far-Infrared Polarization Spectrum
Scientists have observed one of the closest star-forming regions to our Solar System, known as Rho Ophiuchi, located approximately 424 light-years away. In the central parts of the cloud, known as Rho Oph A, several young stars are currently being formed, some of which will probably become stars with planetary systems much like our Sun.

With HAWC+, researchers at Northwestern University have observed for the first time that systematic variations of the far-infrared polarization spectrum exist within an interstellar cloud. More specifically, the observations show that moving from the more diffuse to the denser regions of Rho Oph A, the slope of the polarization spectrum smoothly changes from positive to negative. The observed change is consistent with the RAT theory. According to this theory, dust particles in the interstellar medium need to be exposed to light waves in order to become aligned. The change in the polarization spectrum can be predicted from the RAT theory, and these observations of Rho Oph A match the prediction.

Enrique Lopez-Rodriguez * USRA/SOFIA
A Far-Infrared View of Active Galactic Nuclei with SOFIA/HAWC+
HAWC+ has opened a new window to explore active galactic nuclei (AGN) and starburst galaxies, providing the best angular resolution and polarimetric capability within the 50-220 micron range.

Lopez-Rodriguez presented preliminary results of AGN and starburst galaxies observed with the far-infrared polarimeter HAWC+ onboard SOFIA. These observations of NGC 1068 at 53 microns have shown, for the first time, a magnetized arm along the spiral inner arm of the galaxy. Polarized flux observations of M82, in combination with previously published near infrared polarimetric observations, have shown evidence of a galactic magnetic wind at scales of few hundred parsecs.

Elizabeth Tarantino * University of Maryland, College Park
Characterizing the Multi-Phase Origin of the [CII] Emission in M101 and NGC 6946 with GREAT
The interstellar medium (ISM) found between stars is the building block from which future stars will form. A common mechanism to cool down the gas in the ISM is through radiation from singly ionized carbon. However, ionized carbon radiation can arise from three phases of the ISM: molecular gas, atomic gas, and ionized gas. Unraveling which phase the ionized carbon emission comes from and how it is dependent on environment is crucial for understanding the initial stages of star formation. This separation is better done with the GREAT instrument on SOFIA, which has the unique capability to measure the far-IR ionized carbon line at high spectral resolution. By comparing the velocity resolved spectra of gas tracing the different phases to the ionized carbon, we can infer the contribution of each phase to the ionized carbon emission. This has been studied in the Milky Way, but we present here some of the very few existing extragalactic observations, which allow us to study this process across different galaxies.

“SOFIA’s suite of new and upgraded instruments are now providing the astronomical community with both ultra-high spectral resolution at Terahertz frequencies as well as unprecedented sensitivity and spatial resolution of polarized radiation at far-infrared wavelengths,” said USRA’s Director of SOFIA Science Mission Operations Harold “Hal” Yorke. “We can now explore a wide range of science questions that cannot be examined anywhere else in the world.”

In addition to the results presented at the press conference, USRA-SOFIA senior science advisor and UCLA professor emeritus Eric Becklin, will present the Henry Norris Russell Lecture on Thursday, Jan. 11 at 4:30 p.m. Those in attendance will hear Becklin review his pioneering 54-year scientific career at the forefront of airborne infrared astronomy.

Founded in 1969, under the auspices of the National Academy of Sciences at the request of the U.S. Government, the Universities Space Research Association (USRA) is a nonprofit corporation chartered to advance space-related science, technology and engineering. USRA operates scientific institutes and facilities, and conducts other major research and educational programs, under Federal funding. USRA engages the university community and employs in-house scientific leadership, innovative research and development, and project management expertise. More information about USRA is available at http://www.usra.edu.

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