Starburst debris has not slowed down after 400 years

Astronomers used NASA’s Chandra X-ray Observatory to record material exploded far from the site of an exploded star at speeds over 20 million miles per hour. This is about 25,000 times faster than the speed of sound on Earth.

Kepler’s supernova remnants are the debris of a detonated star located about 20,000 light years from Earth in our Milky Way galaxy. In 1604, the first astronomers, including Johannes Kepler who became the namesake of the object, saw the explosion of the supernova which destroyed the star.

We now know that Kepler’s supernova remnant is the sequel to a so-called Type Ia supernova, where a small, dense star, known as the white dwarf, exceeds a critical mass limit after interacting with a star. companion and suffers a thermonuclear explosion that shatters the white dwarf and throws its remains outward.

The latest study tracked the speed of 15 small “knots” of debris in Kepler’s supernova remnants, all bright in x-rays, all bright in x-rays. The fastest node was measured to have a speed of 23 million miles per hour, the highest ever detected speed of supernova remnant debris in x-rays. The average knot speed is around 10 million miles per hour, and the blast wave extends at about 15 million miles per hour. These results independently confirm the discovery in 2017 of nodes traveling at speeds of over 20 million miles per hour in Kepler’s supernova remnant.

Researchers in the latest study estimated node speeds by analyzing Chandra X-ray spectra, which give the intensity of x-rays at different wavelengths, obtained in 2016. By comparing wavelengths of characteristics of the X-ray spectrum with lab values ​​and using the Doppler effect, they measured the speed of each node along Chandra’s line of sight to the rest. They also used Chandra images obtained in 2000, 2004, 2006 and 2014 to detect changes in node position and measure their speed perpendicular to our line of sight. These two measurements combined to give an estimate of the actual speed of each node in three-dimensional space. A graph gives a visual explanation of how the movements of the nodes in the images and the X-ray spectra were combined to estimate the total velocities.

The 2017 work applied the same general technique as the new study, but used x-ray spectra from a different instrument on Chandra. This meant that the new study had more accurate determinations of node velocities along the line of sight and, therefore, total velocities in all directions.

In this new sequence of four Chandra images of Kepler’s supernova remnant, red, green and blue reveal low, medium and high energy x-rays, respectively. The movie zooms in to show several of the faster knots.

Kepler’s high velocities are similar to those scientists saw in optical observations of supernova explosions in other galaxies just days or weeks after the explosion, long before any supernova remnants formed. decades later. This comparison implies that some nodes at Kepler have barely been slowed down by collisions with material surrounding the rest in the roughly 400 years since the explosion.

Based on the Chandra spectra, eight of the 15 nodes are definitely moving away from Earth, but only two are confirmed to be heading towards her. (The other five do not show a clear direction of movement along our line of sight.) This asymmetry in node movement implies that the debris may not be symmetrical along our line of sight, but more study is needed. of nodes to confirm this result.

The four nodes with the highest total velocities are all located along a horizontal band of bright X-ray emission. Three of them are labeled close-up. These four nodes all move in a similar direction and have similar amounts of elements such as silicon, suggesting that the material in all of these nodes came from the same layer of the exploded white dwarf.

One of the other fastest knots is in the ‘ear’ on the right side of the rest, supporting the intriguing idea that the three-dimensional shape of the debris looks more like a soccer ball than a uniform sphere. This node and two others are labeled with arrows in a close-up view.

The explanation of the material at high speed is unclear. Some scientists have suggested that Kepler’s supernova remnant came from an unusually powerful Type Ia, which may explain the fast-moving material. It’s also possible that the immediate environment around the residue itself is lumpy, which could allow some of the debris to tunnel through areas of low density and avoid slowing down too much.

The 2017 team also used their data to refine previous estimates of the location of the supernova explosion. This allowed them to search for a companion of the white dwarf who may have been left behind after the supernova and learn more about what triggered the explosion. They found a lack of bright stars near the center of the rest. This implied that a star like the Sun did not donate material to the white dwarf until it had reached critical mass. A fusion between two white dwarfs is rather favored.

The new findings were reported in an article edited by Matthew Millard, University of Texas at Arlington, and published in the April 20, 2020 issue of Astrophysics Journal.

An article by Toshiki Sato and Jack Hughes reported the discovery of fast nodes in Kepler’s supernova remnant and was published in the August 20, 2017 issue of The Astrophysics Journal.