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In 1604, a white dwarf star became a supernova. This is completely normal behavior for a white dwarf star; but this one, at a distance of only 20,000 light years from Earth, was visible to the naked eye and documented by astronomers around the world, including German astronomer Johannes Kepler.
Kepler’s Supernova, as it has been known, is still expanding to this day, with the star’s guts exploding in space. And, according to new research, it’s not slowing down. The nodes of matter in the ejecta move at speeds of up to 8,700 kilometers per second (4,970 miles per hour) – more than 25,000 times faster than the speed of sound in Earth’s atmosphere.
You might be thinking “Duh, space is a frictionless vacuum, things will keep moving forever,” but a cloud of debris could slow down the movement of matter. And it was thought that this could be the case for Kepler’s Supernova.
This is because, as we now know, Kepler’s supernova was what is called a Type Ia supernova. These occur when a white dwarf star in a binary system cannibalizes its mate and accumulates so much mass that it is no longer stable – resulting in a cosmic kaboom.
But all the material removed from the companion star does not reach the white dwarf. Instead, it collects in a cloud surrounding the binary system, what we call the circumstellar medium. When the white dwarf becomes a supernova, it explodes in this environment.
Due to its proximity and relative recentness, Kepler’s supernova is today one of the most important objects in the Milky Way to study the evolution of type Ia supernovae. And a wealth of data dating back decades has helped reveal the speed at which the supernova ejecta is moving.
A team of astronomers led by Matthew Millard University of Texas in Arlington used images of the supernova obtained by the Chandra X-ray Observatory from 2000, 2004, 2006, 2014 and 2016 to track 15 nodes of material in the ‘ejected from supernova, observing their changes able to calculate their speed in three-dimensional space.
Some nodes appear to be decelerating, as expected due to the interaction with the circumstellar medium.
To the team’s surprise, their measurements show that other nodes extend almost freely, 400 years after the event – and that their speeds, at an average of 4,600 kilometers per second (2,860 mps), are similar to those observed in optical observations of supernovae. in other galaxies just days or weeks after the actual explosion.
This suggests that at least some of the supernova material can explode through the circumstellar medium, without being slowed down.
Interestingly, the directions of these nodes are not evenly distributed. Eight of the 15 nodes are moving away from Earth; only two are heading towards her (the direction of the other five could not be determined).
This asymmetry of direction suggests that the explosion itself may have been asymmetric; or, there is an asymmetry in the circumstellar medium along our line of sight. It is, however, impossible to know at this stage – further study is needed.
The asymmetry, however, can reveal information about the supernova explosion itself. Four of the fastest nodes are close together, moving in the same direction, and have similar elemental abundances. This, the researchers note, suggests they originate from the same region on the surface of the white dwarf ancestor.
In all, their findings suggest that the supernova itself might have been unusually energetic for a Type Ia. Measuring the speeds of more ejection nodes over the next few years could help confirm their measurements and calculations, build a more complete three-dimensional map of the material distribution, and put constraints on the energy degree of this explosion. .
The research was published in The astrophysical journal.
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