GAMMA-RAY EMISSION FROM THE SNR HB3

Image: At a distance of about 20,000 light years, G292.0+1.8 is one of only three supernova remnants in the Milky Way known to contain large amounts of oxygen. These oxygen-rich supernovas are of great interest to astronomers because they are one of the primary sources of the heavy elements (that is, everything other than hydrogen and helium) necessary to form planets and people. The X-ray image from Chandra shows a rapidly expanding, intricately structured, debris field that contains, along with oxygen (yellow and orange), other elements such as magnesium (green) and silicon and sulfur (blue) that were forged in the star before it exploded. Credit: NASA/CXC/SAO

The processes of particles acceleration to very high energies from the supernova shock region and diffusion in the interstellar medium of such particles has not been well understood so far. Gamma-ray observations in the GeV regime are a powerful probe of these mechanisms

In a recent paper (Katagiri et al. 2016, ApJ) the authors report the discovery of extended gamma-ray emission spatially correlated with the region of the supernova remnant (SNR) HB 3 (G132.7+1.3) and the W3 H II complex adjacent to the southeast of the remnant. W3 is a region rich of CO clouds.

Supernova remnant HB 3 (www.cfa.harvard.edu)

The authors find that the decay of neutral pions produced in nucleon-nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray emission from HB3. The cosmic rays accelerated in HB 3 irradiate the CO clouds and generate the emission from W3 region.

▪ Katagiri et al. 2016, ApJ - Fermi LAT Discovery of Extended Gamma-Ray Emissions in the Vicinity of the HB3 Supernova Remnant (arXiv)

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ORBITAL PERIODS OF THE PLANETS

For orbital period generally we refer to the sidereal period, that is the temporal cycle that it takes an object to make a full orbit, relative to the stars. This is the orbital period in an inertial (non-rotating) frame of reference (365,25 days for the earth).

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A composite image of the HD 142527 binary star system from data captured by ALMA shows a distinctive arc of dust (red) and a ring of carbon monoxide (blue and green). The red arc is free of gas, suggesting the carbon monoxide has "frozen out", forming a layer of frost on the dust grains in that region. Astronomers speculate this frost provides a boost to planet formation. The two dots in the center represent the two stars in the system. Credit: Andrea Isella/Rice University; B. Saxton (NRAO/AUI/NSF); ALMA (NRAO/ESO/NAOJ) The Atacama Large Millimeter/submillimeter Array (ALMA) has observed a new very early stage of planet formation around the binary star system HD 142527 (in the costellation of Lupus) and has provided fresh insights into the planet-forming potential of a binary system.

Fermi Bubbles

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