Tour: Sagittarius A East

Astronomers may have found the first example of an unusual exploded star in our Galaxy. This discovery, made with NASA's Chandra X-ray Observatory, adds to the understanding of how some stars shatter and seed the Universe with elements critical for life on Earth.

This intriguing object lies near the center of the Milky Way in a supernova remnant called Sagittarius A East, or Sgr A East for short. Based on Chandra data, astronomers have previously classified the object as the remains of a massive star that exploded as a supernova, one of many kinds of exploded stars that scientists have catalogued.

Using longer Chandra observations, a team of astronomers has now instead concluded that a white dwarf exploded. These events are the results of thermonuclear reactions that travel quickly through a white dwarf star. This is a shrunken stellar ember from a fuel-depleted star like our Sun, after it pulls too much material from a companion star or merges with another white dwarf. The outcome is destruction of the white dwarf star and a stunning flash of light.

Astronomers use these so-called Type Ia supernovas as standard candles because most of them give off almost the same amount of light every time no matter where they are located in the Universe. This allows scientists to use them to accurately measure distances across space and study the expansion of the Universe.

Data from Chandra have revealed that Sgr A East, however, is no ordinary Type Ia. Instead, it appears that it belongs to a special group of these supernovas that produce different relative amounts of elements than traditional Type Ias do, and less powerful explosions. This subset is referred to as "Type Iax" supernovas, a potentially important member of the supernova family.

The explosion of white dwarfs in supernovas is one of the most important sources in the Universe of elements like iron, nickel, and chromium. The only place that scientists know these elements can be created is inside the nuclear furnace of stars or when they explode.

While astronomers have found Type Iax supernovas in other galaxies, they hadn't identified evidence for one in the Milky Way until now. This discovery is important for getting a handle of the different ways white dwarfs explode.