Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration
In about 1667, a star about 10,000 light years from Earth exploded in the constellation Cassiopeia but it wasn’t noticed by astronomers on Earth. Today, images from NASA’s Hubble Space Telescope show the remnants of this fireworks display. Cassiopeia A, or Cas A, is one of the youngest supernova in the Milky Way Galaxy. Huge swirls of star debris glow as it moves through space.
The supernova may have been observed by astronomer John Flamsteed in 1680. Astronomy historians have shown that Flamsteed cataloged a star near the supernova’s location. However, he did not recognize it as a “new star,” or supernova. In the 1940s, using new radio telescopes, astronomers found that Cas A was the strongest radio source in the sky beyond the solar system. Finding the dim remnants of this expanding shell of gas and dust didn’t occur until 1950.
Supernova result after a massive star, much larger and heavier than our Sun, collapses under its own weight due to gravity. As the material rapidly falls toward the center, the gas ignites once again blowing the outer layers into space in an explosion that not only destroys the star but also briefly outshines an entire galaxy. In the cores of stars hydrogen atoms are fused together to make heavier elements such as helium. The resulting light and heat from this nuclear fusion process power the star. But elements are only created up to a certain point. To make elements heavier and more complex than oxygen, we need a supernova. Inside a supernova, with it’s intense heat, the rest of the elements that make up the Earth and our bodies, such as gold, silver, carbon and uranium are created. We are made of star stuff. Without supernova explosions, we could not exist.
Cas A is only 340 years old. Hubble has been tasked repeatedly to image the supernova remnant to track changes in its rapidly expanding filaments. Already the leftover bubble is more than 10 light-years across. Some of the material on the upper edge is moving at more than 50 million kilometers per hour. That is fast enough to travel from Earth to the Moon in 30 seconds. Look for the different areas of color in the Hubble image. Bright green filaments are rich in oxygen, red and purple are sulfur, and blue of hydrogen and nitrogen.
Do you see any patterns left over in the expanding cloud of gas and dust?