A new method of measuring the temperature of atoms during the explosive death of a star helps scientists understand the shock wave that occurs as a result of this supernova explosion. An international research team, including a Penn State scientist, combined observations of a nearby supernova remnant ̵
The research team analyzed long-term observations of the nearby supernova remnant SN1987A using NASA's Chandra X-ray Observatory and created a model describing the supernova. The team confirmed that the temperature of even the heaviest atoms – which had not yet been investigated – is related to their atomic weight, answering a long-standing question about shockwaves and providing important information about their physical processes. A paper describing the results will be published on January 21, 2019 in the journal Nature Astronomy .
"Supernova explosions and their remains provide cosmic laboratories that allow us to study physics in extreme conditions that are not possible on Earth," said David Burrows, a professor of astronomy and astrophysics at Penn State University and author of the newspaper. "Modern astronomical telescopes and instruments, both on the ground and in space, have enabled us to conduct detailed investigations of supernova remnants in our galaxy and near galaxies, and we have regular observations of the supernova remnant SN1987A with the Chandra X. The World's Best X-ray Telescope, just after Chandra was launched in 1999, and used simulations to answer longstanding questions about shock waves. "
The explosive death of a massive star like SN1987A drives the material high Speeds outward one tenth of the speed of light pushes shock waves into the surrounding interstellar gas. The researchers are particularly interested in the shock front, the abrupt transition between the supersonic explosion and the relatively slow-moving gas surrounding the star. The shock front heats this cool, slow-moving gas to millions of degrees – temperatures that are high enough for the gas to send detectable X-rays from Earth.
"The transition is similar to that observed in a kitchen sink at high speed. The jet of water hits the sink and flows gently outward until it abruptly jumps up and becomes turbulent," Burrows said. "Shock fronts have been extensively studied in the Earth's atmosphere where they occur in an extremely narrow region, but in space shock transitions are gradual and can not affect atoms of all elements in the same way."
The research team led by Marco Miceli and Salvatore Orlando from the University of Palermo, Italy, have measured the temperatures of various elements behind the shock front, thereby improving the understanding of the physics of the shock process. These temperatures are expected to be proportional to the atomic weight of the elements, but the temperatures are difficult to accurately measure. Previous studies have led to contradictory results regarding this relationship and have failed to consider heavy elements with high atomic weights. The research team turned to the supernova SN1987A to solve this dilemma.
Supernova SN1987A, which is located in the nearby constellation Large Magellanic Cloud, was the first supernova visible since Kepler's supernova in 1604, the first to be studied in detail with modern astronomical instruments. The explosion light first reached Earth on February 23, 1987, and has since been observed at all wavelengths of light, from radio waves to X-rays and gamma waves. The research team used these observations to build a model to describe the supernova.
Models of SN1987A typically focused on single observations, but in this study, researchers used three-dimensional numerical simulations to record the evolution of the supernova from their observations beginning the current age. A comparison of the X-ray observations and the model allowed the researchers to accurately measure the atomic temperatures of various elements with a broad range of atomic weights and to confirm the relationship that predicts the temperature reached by each type of atom in the interstellar gas.
"We can now accurately measure the temperatures of elements such as silicon and iron and have shown that they actually follow the relationship that the temperature of each element is proportional to the atomic weight of that element," Burrows said. "This result is an important topic for understanding astrophysical shockwaves and improves the understanding of the shock process."
Image: Chandra's view of the remnant of the Tycho supernova
Collisionless shock heating of heavy ions in SN 1987A, Nature Astronomy (2019). 10.1038 / s41550-018-0677-8, www.nature.com/articles/s41550-018-0677-8