Cygnus Loop: 20 years of data from the Hubble telescope sees supernova bubble expand into space

Scientists have compiled 20 years of data from the Hubble Space Telescope to reveal how a supernova bubble expands into space.

The remains of the supernova led to the creation of a new nebula, known as the Cygnus Loop which formed a bubble-like shape around 120 light-years in diameter. The distance to its centre is approximately 2,600 light-years and the entire nebula has a width of six full Moons as seen in the sky.

The star died around 20,000 years ago, and the nebula was discovered in 1784, but the pictures were taken from 2001 to 2020 to show how the shock of the supernova develops over time.

Scientists say the Cygnus Loop looks like a wide cotton ball with a bright blobby centre and glowing cobweb shell. The researchers used the data from the Hubble to create a video on how the star still lives on.

"Hubble is the only way that we can actually watch what's happening at the edge of the bubble with such clarity," said Ravi Sankrit, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland. "The Hubble images are spectacular when you look at them in detail. They're telling us about the density differences encountered by the supernova shocks as they propagate through space, and the turbulence in the regions behind these shocks."

A close-up shows the filaments glowing hydrogen and ionized oxygen shows that they look like a wrinkled sheet seen from the side. "You're seeing ripples in the sheet that is being seen edge-on, so it looks like twisted ribbons of light," said William Blair of the Johns Hopkins University, Baltimore, Maryland. "Those wiggles arise as the shock wave encounters more or less dense material in the interstellar medium."

The time-lapse movie over nearly two decades shows the filaments moving against the background stars but keeping their shape.

Blair added: "When we pointed Hubble at the Cygnus Loop we knew that this was the leading edge of a shock front, which we wanted to study. When we got the initial picture and saw this incredible, delicate ribbon of light, well, that was a bonus. We didn't know it was going to resolve that kind of structure."

The filaments have not slowed down or changed shape in the last 20 years, thanks to the Loop's shock wave. In perspective, the Loop's wave is forcing filaments to zoom into interstellar space fast enough for humans to travel from the Earth to the moon in less than half an hour - if the velocity was matched.