The Compton Spectrometer and Imager (COSI), jointly made by space science teams from Taiwan’s National Tsing Hua University (NTHU) and the University of California, Berkeley, in the US, was launched by balloon at the McMurdo station in Antarctica by NASA on Monday, to study astrophysical sources of nuclear line emission and gamma-ray polarization.
The device employs a compact Compton telescope design, utilizing 12 cross-strip germanium detectors to track the path of incident photons, where position and energy deposits from Compton interactions allow for a reconstruction of the source position in the sky, an inherent measure of the linear polarization and significant background reduction.
According to the science teams, the launch presents a significant milestone in terms of gamma ray detection in astrophysics.
Photo courtesy of National Tsing Hua University
COSI is a new generation of the Compton telescopes, smaller but more sensitive than previous generations, NTHU physics professor Chang Hsiang-kuang (張祥光) said.
The main purpose of the balloon launch is to monitor an event that is close to the center of the Milky Way galaxy, where there are strong emissions of annihilation radiation, Chang said.
The excess emission of energy in the form of gamma rays from the galactic center has been an unsolved phenomenon in astrophysics for the past half-century, and theories have been posited that the emissions come from high-density black holes, neutron stars and other black holes, or even low-density dark matter, he added.
Photo courtesy of National Tsing Hua University
Researchers are hoping that during flight COSI could capture a fleeting image of a gamma ray burst and provide data on photon polarization that could provide a possible answer to yet another unsolved astrophysics dilemma, Chang said.
The balloon-borne telescope was launched at the McMurdo station in Antarctica after two months of on-site equipment calibration and testing, as well as waiting for suitable weather, and is expected to remain airborne for 100 days, after which it may return with research data that could surprise the scientific community.
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