New Study Sheds More Light on Origin of Kepler’s Supernova Remnant

An international team of astronomers using data from NASA’s Chandra X-ray Observatory has suggested that a stellar explosion known as the Kepler’s supernova was not only more powerful, but might have also occurred at a greater distance, than previously thought.

Composite image of the Kepler’s supernova remnant: Chandra X-ray data show different colors in a range from lower to higher energies: red, yellow, green, blue and purple; optical data – pale yellow and blue – from the Digitized Sky Survey shows stars in the field (X-ray: NASA / CXC / SAO / D.Patnaude, optical: DSS)

In 1604, a new star appeared in the night sky that was much brighter than Jupiter and dimmed over several weeks. This event was witnessed by sky watchers including the famous astronomer Johannes Kepler. Astronomers have long studied the Kepler supernova remnant and tried to determine exactly what happened when the star exploded to create it.

This image shows the Chandra data derived from more than 8 days worth of observing time. Previous analysis of the image has determined that the stellar explosion that created Kepler was what astronomers call a Type Ia supernova. This class of supernovas occurs when a white dwarf gains mass, either by pulling gas off a companion star or merging with another white dwarf, until it becomes unstable and is destroyed by a thermonuclear explosion.

Unlike other well-known Type Ia supernovas and their remnants, Kepler’s debris field is being strongly shaped by what it is running into. More specifically, most Type Ia supernova remnants are very symmetrical, but the Kepler remnant is asymmetrical with a bright arc of X-ray emission in its northern region. This indicates the expanding ball of debris from the supernova explosion is plowing into the gas and dust around the now-dead star.

The bright X-ray arc can be explained in two ways. In one model, the pre-supernova star and its companion were moving through the interstellar gas and losing mass at a significant rate via a wind, creating a bow shock wave similar to that of a boat moving through water.

Another possibility is that the X-ray arc is caused by debris from the supernova expanding into an interstellar cloud of gradually increasing density.

The wind and bow shock model described above requires that the Kepler’s supernova remnant is located at a distance of more than 23,000 light years. In the latter alternative, the gas into which the remnant is expanding has higher density than average, and the distance of the remnant from the earth is between about 16,000 and 20,000 light years.

Both alternatives give greater distances than the commonly used value of 13,000 light years.

The results were published in the recent issue of the Astrophysical Journal (arXiv.org version).

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Bibliographic information: Daniel J. Patnaude et al. 2012. The Origin of Kepler’s Supernova Remnant. ApJ 756, 6; doi: 10.1088/0004-637X/756/1/6