- A new image of SNR 0519-69.0 shows the debris of a star that exploded several hundred years ago in Earth’s timeframe.
- The explosion of a white dwarf star, after reaching a critical mass, created SNR 0519-69.0.
- This new image contains X-ray data (green, blue, and purple) from Chandra and optical data from Hubble (red and white).
- This is a special kind of supernova known as a “Type Ia” that astronomers use to measure distances across the Universe.
Although astronomers have seen the debris from numerous exploded stars in the Milky Way and nearby galaxies, it is often difficult to determine the timeline of the star’s demise. Using NASA telescopes to study the spectacular remains of a supernova in a neighboring galaxy, a team of astronomers has found enough clues to help wind back the clock.
Supernova remnant SNR 0519-69.0 (called SNR 0519 for short) is the debris from an explosion of a white dwarf star. After reaching a critical mass, either by merging with another white dwarf or pulling matter from a companion star, the star underwent a thermonuclear explosion and was destroyed. Scientists use this type of supernova, called a Type Ia, for a wide range of scientific studies ranging from studies of thermonuclear explosions to measuring distances to galaxies across billions of light-years.
SNR 0519 is in the Large Magellanic Cloud, a small galaxy located about 160,000 light-years from Earth. This composite image (top of the page) shows X-ray data from NASA’s Chandra X-ray Observatory and optical data from NASA’s Hubble Space Telescope. X-rays from SNR 0519 with low, medium, and high energies are shown in green, blue, and purple respectively, with some of these colors overlapping to appear white. Optical data shows the perimeter of the remnant in red and stars around the remnant in white.
Astronomers combined the data from Chandra and Hubble with data from NASA’s retired Spitzer Space telescope to determine how long ago the star in SNR 0519 exploded. They were also able to learn about the environment the supernova occurred in. This data provides scientists a chance to “rewind” the movie of the stellar evolution that has played out since and figure out when it got started.
The researchers compared Hubble images from 2010, 2011, and 2020 to measure the speeds of material in the blast wave from the explosion, which range from about 3.8 million (6 million kilometers) to 5.5 million miles (9 million kilometers) per hour. If the speed was toward the upper end of those estimated speeds, the astronomers determined that light from the explosion would have reached Earth about 670 years ago. This would have been during the Hundred Years’ War between England and France and the height of the Ming dynasty in China.
However, it’s likely that the material has slowed down since the initial explosion. There, the explosion would have happened more recently than 670 years ago. The Chandra and Spitzer data provide clues that this is the case. Astronomers found the brightest regions in X-rays of the remnant are where the slowest-moving material is located, and no X-ray emission is associated with the fastest-moving material.
These results imply that some of the blast wave has crashed into dense gas around the remnant, causing it to slow down as it traveled. Astronomers may use additional observations with Hubble to determine more precisely when the time of the star’s demise should truly be set.
Reference: “Evidence for a Dense, Inhomogeneous Circumstellar Medium in the Type Ia SNR 0519-69.0” by Brian J. Williams, Parviz Ghavamian, Ivo R. Seitenzahl, Stephen P. Reynolds, Kazimierz J. Borkowski and Robert Petre, 18 August 2022, The Astrophysical Journal.
A paper describing these results was published in the August issue of The Astrophysical Journal. The authors of the paper 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 Defence 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 controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
SNR 0519 is in the Large Magellanic Cloud, a small galaxy located about 160,000 light-years from Earth.
Everything we observe happened about 160,000 years ago, so how is it that they can claim that something happened only 670 years ago?
Your question suggests that you are thinking about time in a pre-relativity way. Einstein showed that the rate time flows is not absolute, the speed of light is constant, and time stops at that speed. In effect, a photon traveling from the supernova to Earth would experience no time (i.e. in its reference frame, it leaves the supernova and arrives on Earth in the same moment).
The end result is that the only way to have the universe make sense without contradictions is to adopt the photon’s reference frame. Thus, regardless of how long the light took to reach us in our reference frame (160,000 years), the supernova happened when its light reached us, 670 years ago. Einstein is saying “‘now’ is ‘when you see it happen’,” regardless of its distance.