Although a doomed star exploded some 20,000 years ago, its mangled remnants are still hurtling toward space at breakneck speeds -- a scene captured by NASA's Hubble Space Telescope. Known as the Cygnus Ring Nebula, this nebula forms a bubble about 120 light-years across. The distance to its center is approximately 2,600 light-years. The entire nebula is as wide as six full moons in the sky.
Astronomers used Hubble to zoom in on a very small slice of the leading edge of this expanding supernova bubble, where the supernova explosion waves rush into surrounding material in space. Hubble images taken from 2001 to 2020 clearly show how the remnant's shock wave front expanded over time, and astronomers used these clear images to time its speed.
Astronomers used the Hubble Space Telescope to zoom in on a segment of the Cygnus Ring Nebula - a giant bubble of glowing gas. The Cygnus Ring Nebula is a giant glowing bubble. They found filaments like the lines in a wrinkled sheet, spanning two light-years. This region is located at the outer edge of the expanding bubble and was created by an exploding star 20,000 years ago. By analyzing the location of the shock waves, astronomers found that the filaments have not slowed down or changed shape at all during the past 20 years of Hubble observations. This material is hurtling toward interstellar space at more than 500,000 miles per hour—fast enough to travel from Earth to the moon in less than half an hour. Source: NASA, ESA, STScI
By analyzing the position of the shock wave, astronomers found that it had not slowed down at all over the past 20 years and was hurtling toward interstellar space at more than 500,000 miles per hour -- fast enough to travel from Earth to the moon in less than half an hour. While this seems incredibly fast, it's actually slow for the speed of a supernova shock wave. Researchers were able to assemble a "movie" from the Hubble images, giving a close look at how the broken star crashed into interstellar space.
Astronomers' insights
"Only Hubble gives us such a clear view of what's happening at the edge of the bubble," said astronomer Ravi Sankrit of the Space Telescope Science Institute in Baltimore, Maryland. "When you look closely at the Hubble images, they're spectacular. They tell us about the density differences that supernova shock waves encounter as they propagate through space, as well as the turbulence in the areas behind these shock waves."
Source: NASA, ESA, STScI: Thanks to: NSFNOIRLab, Akira Fujii, Jeff Hester, Davide DeMartin, Travis A. Rector, Ravi Sankrit (STScI), DSS
A close look at nearly two light-years of the glowing hydrogen filaments reveals that they look like a wrinkled sheet when viewed from the side. "What you see are ripples in the sheet when viewed from the side, so it looks like twisted ribbons of light," said William Blair of Johns Hopkins University in Baltimore, Maryland. "These wobbles occur when the shock wave encounters more or less dense material in the interstellar medium. Time-lapse movies from nearly two decades show that these filaments move against background stars but maintain their shape."
"When we pointed Hubble at the Cygnus rings, we knew this was the shock front and we wanted to study it. When we took the initial images and saw this incredibly delicate band of light, it was a real bonus," Blair said. "We had no idea it would resolve this structure."
Interaction of supernovae with the universe
Blair explained that the shock wave moved outward from the explosion site and then began to encounter the interstellar medium, the fragile region of gas and dust in interstellar space. This is a very brief stage in the supernova bubble's expansion in which invisible, neutral hydrogen is heated by the shock wave to 1 million degrees Fahrenheit or more. The gas then begins to glow as electrons are excited to higher energy states, emitting photons as they step back to lower energy states. Further behind the shock wave front, ionized oxygen atoms begin to cool, emitting a characteristic blue light.
The Cygnus Gyre was discovered by William Herschel in 1784 using a simple 18-inch reflecting telescope. He could never have imagined that more than two centuries later, we would have a telescope powerful enough to zoom in on a small part of the nebula and see this spectacular scene.