Team succeeded in precisely measuring expansion velocity of shockwave of supernova remnant W44
A research team led by Tomoro Sashida and Tomoharu Oka (Keio University) has succeeded in precisely measuring the expansion velocity of a shockwave of the supernova remnant W44. The remnant is located in the constellation of Aquila, approximately 10,000 light-years away from our solar system. The team observed the high-temperature and high-density molecular gas in the millimeter/submillimeter wave ranges. The analysis shows that the expansion velocity of the W44 shockwave is 12.9±0.2 km/sec. In addition, it became clear that the supernova explosion released kinetic energy of (1-3)×1050 erg into the interstellar medium. The energy emitted from the Sun is approximately 3.6 × 1033 ergs/sec. Can you image how enormous amount of energy is released from the supernova explosion? Furthermore, other molecular gas with an extremely high velocity of higher than 100 km/sec was also detected. The origin of this super-high-velocity molecular gas remains unclear at the present time.
A star with a mass of more than eight times of the Sun releases tremendous energy when it is dying and undergoes a supernova explosion. The shockwave caused by the supernova explosion expands, having a strong impact on the composition and physical state of surrounding interstellar materials. It also emits kinetic energy into interstellar space. “Galactic winds” blasting out a large amount of gas are often observed in galaxies where explosively active star formations take place. The energy source of such galactic wind is also thought to be many supernova explosions.
Thought to be about 20,000 years old — middle-aged for a such a structure — the W44 supernova remnant is located 9,800 light-years away in the constellation Aquila. The Fermi Large Area Telescope (LAT) not only detected W44, it actually revealed super-energetic gamma-rays coming from places where the remnant’s expanding shock wave is known to be interacting with cold, dense gas clouds, providing clues to the origin of cosmic rays, the particles, primarily protons, that move through space at nearly the speed of light. Magnetic fields deflect the particles as they race across the galaxy, and this interaction scrambles their path and masks their origins.
Scientists can’t say for sure where the highest-energy cosmic rays come from, but they regard supernova remnants as perhaps their likliest origin.
In 1949, the Fermi telescope’s namesake, physicist Enrico Fermi, suggested that the highest-energy cosmic rays were accelerated in the magnetic fields of gas clouds. In the decades that followed, astronomers showed that the magnetic fields in the expanding shock wave of a supernova remnant are just about the best location for this process to work.
So far, LAT observations of W44 and several other remnants strongly suggest that the gamma-ray emission arises from accelerated protons as they collide with gas atoms.
Supernova remnant W44 is the focus of this new image created by combining data from ESA’s Herschel and XMM-Newton space observatories. W44 is the vast purple sphere that dominates the left hand side of this image, and measures about 100 light-years across. XMM-Newton data reveal that the remnant is filled with X-ray emission from extremely hot gas. Herschel’s three-colour infrared view comprises PACS 70 and 160 micron and SPIRE 250 micron images. X-ray data from XMM-Newton’s EPIC instrument for W44 only has been added in light and dark blue to represent high- (2–8 keV) and low-energy (1.2–2 keV) X-ray emission, respectively. The field of view is about 1º across. North is towards the bottom left of the image; east is to the top right.
Herschel: Q. Nguyen Luong & F. Motte, HOBYS Key Program consortium, Herschel SPIRE/PACS/ESA consortia. XMM-Newton: ESA/XMM-Newton
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