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Setting the clock on a stellar explosion

Photo: NASA/CXC/GSFC/BJ Williams et al.; Optical: NASA/ESA/STScI

Although astronomers have seen the debris of dozens of exploded stars in the Milky Way and nearby galaxies, it is often difficult to determine the timeline of the star’s demise. By studying the spectacular remnants of a supernova in a neighboring galaxy with NASA telescopes, a team of astronomers has found enough clues to turn back the clock.

The supernova remnant, called SNR 0519-69.0 (SNR 0519 for short), is the debris from an explosion of a white dwarf star. After the star reached critical mass by pulling matter away from a companion star or merging with another white dwarf, it underwent a thermonuclear explosion and was destroyed. Scientists use this type of supernova, called a Type Ia, for a variety of scientific studies, ranging from studies of thermonuclear explosions to measuring distances to galaxies over billions of light years. SNR 0519 is located in the Large Magellanic Cloud, a small galaxy 160,000 light-years from Earth. This composite image shows X-ray data from NASA’s Chandra X-ray Observatory and optical data from NASA’s Hubble Space Telescope. The low, medium and high energy X-rays from SNR 0519 are shown in green, blue and purple, respectively, with some of these colors overlapping to appear white. Optical data shows the outline of the remnant in red and stars around the remnant in white.

Astronomers have combined the data from Chandra and Hubble with data from NASA’s retired Spitzer Space Telescope to determine how long ago the star exploded in SNR 0519 and to learn more about the environment in which the supernova occurred. This data offers scientists a chance to “rewind” the movie of the stellar evolution that has played out since then and determine when it started. The researchers compared Hubble images from 2010, 2011, and 2020 to measure the velocities of the material in the blast’s shock wave, which range from about 3.8 million to 5.5 million miles (9 million kilometers) per hour. If the speed is at the higher end of these estimated speeds, the astronomers have determined that the light from the explosion would have reached Earth about 670 years ago, or during the Hundred Years’ War between England and France and the height of the Ming dynasty in China.

However, it is likely that the material has slowed down since the first explosion and that the explosion occurred more recently than 670 years ago. The Chandra and Spitzer data indicate that this is the case. Astronomers found that the brightest X-ray regions of the remnant are where the slowest-moving material is, and that no X-rays are associated with the fastest-moving material. These results indicate that part of the blast wave struck dense gas around the remnant, slowing it down on its journey. Astronomers can use additional observations with Hubble to more accurately determine when the star’s time of demise should actually be determined.

An article on these results was published in the August issue of The Astrophysical Journal and a preprint is available here. The authors of the article are Brian Williams (NASA’s Goddard Space Flight Center (GSFC) in Greenbelt, Maryland); Parviz Ghavamian (Towson University, Towson, Maryland); Ivo Seitenzahl (University of New South Wales, Australian Defense Force Academy, Canberra, Australia); Stephen Reynolds (North Carolina State University (NCSU), Raleigh, NC); Kazimierz Borkowski (North Carolina State University, Raleigh, NC) and Robert Petre (GSFC). NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center manages science operations out of Cambridge, Massachusetts, and flight operations out of Burlington, Massachusetts.

Source: NASA

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