Maggie’s note: Please welcome a new guest blogger, astronomer Brian Williams!
Most of the stars in the universe will, like our Sun, live steadily for billions of years before ending in relative serenity. However, a select few will go out in a blaze of glory called a supernova, the explosion of an entire star. These cosmic blasts are among the most powerful events in the universe, and can be seen at distances of billions of light years; releasing, in a matter of seconds, an amount of energy equal to the Sun’s output over billions of years. In the past few decades, observations of distant supernovas helped astronomers pin down the expansion rate of the universe, allowing the determination that the universe is not, as was previously expected, slowing down in its expansion, but speeding up, due to the presence of a mysterious force known as “dark energy.”
Nearly all of the matter in the universe that we understand is made of hydrogen and helium, the simplest elements, created in the Big Bang. The rest, including the oxygen that we breath, the carbon, calcium, and iron in our bodies, sodium and choride on our dinner tables, and the silicon in our computer chips were forged in the cores of stars: hot and powerful element factories that convert lighter elements into heavier ones. The gravity that holds stars together generally keeps these elements locked deep inside their interiors, never to be spread throughout the universe. Luckily, supernova explosions provide a mechanism to do just this, liberating these fundamental building blocks of planetary systems and, indeed, life itself, throughout the universe. It is no exaggeration to say that we owe our entire existence to the life, and death, of stars that existed before our Sun and solar system were even created.
In my research at NASA’s Goddard Space Flight Center, the fading of a supernova from view marks only the beginning of my interests. I study the fiery aftermath of the explosion, which remains visible for thousands of years. An exploding star doesn’t simply dissipate into nothingness; rather, it forms a nebula known as a supernova remnant, a cloud of gas expanding at speeds of several million miles per hour. The gas cloud is made up of both material that has been ejected from the now exploded star and particles of gas and dust tenuously floating in the interstellar medium, the scientific name for the space between the stars. An example of a supernova remnant is shown below. This remnant, the remains of a star that exploded in 1604 A.D, is known as Kepler’s SNR, named for the famous German astronomer who kept detailed records of “De Stella Nova” (the New Star).
Kepler’s Supernova remnant, as seen by NASA’s Spitzer Space Telescope (red), Hubble Space Telescope (yellow), and Chandra X-ray Observatory (green and blue). Credit: NASA, R. Sankrit (NASA Ames) and W.P. Blair (Johns Hopkins Univ.)