Astronomers have discovered important new details about Kepler's supernova, more than 400 years after it was first seen in the night sky.
The famous explosion was first spotted by Johannes Kepler in 1604. Since the sighting took place before telescopes were used, the supernova was seen with the naked eye. It must have been quite a sight, given that the supernova derived from a thermonuclear explosion that warmed gas temperatures to millions of degrees.
Now astronomers are finding that the explosion was more powerful than originally thought and may have occurred further away in space. Using data from NASA's Chandra X-ray observatory, the astronomers found a disk-shaped structure near the center of the supernova's remnant along with a large amount of magnesium.
These discoveries have important implications for how this particular supernova formed, and for the study of supernovas in general. When most stars die they cast off their outer layers, leaving a concentrated core called a white dwarf. A white dwarf is usually the size of Earth but with a mass of our sun. This makes white dwarfs extremely dense (a teaspoon of material from a white dwarf would weigh 15 tons).
As a result of their density, white dwarfs can become unstable. If one acquires material, from another star for instance, and its mass increases to 1.4 times that of the sun, it will quickly collapse, warm and explode, forming a Type 1a supernova.
Scientists debate how exactly white dwarfs become Type 1a supernovas. It is possible that they are caused by two white dwarfs colliding. The new findings, however, suggest that Kepler's supernova resulted from a white dwarf taking material from a companion star. This is suggested by the presence of the disk-shaped structure in the supernova remnant's center, which gives the appearance of a ring of gas and dust forming as it was sucked from a star. The theory is also suggested by the strong presence of magnesium in the remnant, given that magnesium is not formed in large quantity in Type 1a supernovas.
The study is published in the "Astrophysical Journal."
