Hubble captures the unprecedented fading of the Stingray Nebula

Great things take time. This is true when it comes to many processes in the universe. For example, it takes millions of years for stars, the building blocks of the universe, to form. Hence, many stars last for billions of years before they die and begin to emit shells of gas that glow against the vastness of space, what we call nebulae. It can be extremely rare to capture some of these processes in real time.

Fortunately for us, it appears that the Stingray Nebula, Hen 3-1357, was destined to stand out from the crowd since its inception. It was dubbed the youngest known planetary nebula in 1998 after Hubble caught a rare glimpse into the final stages of the central star’s life. Now, twenty years after its first snapshot, the Stingray Nebula is again catching the attention of astronomers for a very different reason.

Images from 2016 show a nebula that has drastically vanished over the past two decades. Additionally, the shells of gas surrounding the central star have changed, not as sharp as they once were. Changes like this have never been captured with this clarity before.

Astronomers have caught a rare glimpse of a rapidly dissolving veil of gas around an aging star. Archival data from NASA’s Hubble Space Telescope reveals that the Hen Nebula 3-1357, nicknamed the Stingray Nebula, has faded precipitously over the past two decades. Seeing such a rapid rate of change in a planetary nebula is extremely rare, the researchers say.

The images captured by Hubble in 2016, compared to the Hubble images taken in 1996, show a nebula that has drastically reduced in brightness and changed shape. The bright blue fluorescent tendrils and gas strands towards the center of the nebula have all but disappeared, and the wavy edges that earned this nebula its aquatic-themed name have virtually disappeared. The young nebula no longer appears against the black velvet background of the vast universe.

“This is very, very dramatic and very strange,” said team member Martín A. Guerrero from the Instituto de Astrofísica de Andalucía in Granada, Spain. “What we are seeing is the evolution of a nebula in real time. Over a span of years, we see variations in the nebula. We have never seen it before with the clarity we get with this vision.”

The researchers found unprecedented changes in the light emitted by the glowing nitrogen, hydrogen and oxygen ejected by the dying star at the center of the nebula. Oxygen emission, in particular, decreased in brightness by a factor of nearly 1,000 between 1996 and 2016.

“The changes in the nebulae have been seen before, but what we have here are changes in the nebula’s fundamental structure,” said Bruce Balick of the University of Washington Seattle, head of the new research. “In most studies, the nebula usually gets bigger. Here, it’s radically changing its shape and getting fainter, and it does so on an unprecedented time scale. Plus, to our surprise, it’s not growing any further. effects, the once bright interior the elliptical ring seems to shrink as it fades. “

Earth-based observations of other planetary nebulae have shown hints of changes in brightness over time, but those speculations have not been confirmed until now. Only Hubble can resolve the changes in the structure in this tiny nebula. The new article examines every image of the Stingray Nebula from the Hubble Archives.

“Due to the optical stability of Hubble, we are very, very confident that this nebula is changing in brightness with time,” added Guerrero. “This is something that can only be confirmed with Hubble’s visual acuity.”

The researchers note that the nebula’s rapid changes are a response to its central star, SAO 244567, which expands due to a drop in temperature and, in turn, emits less ionizing radiation.

A 2016 study by Nicole Reindl, now from the University of Potsdam, Germany, and a team of international researchers, also using Hubble data, noted that the star at the center of the Stingray Nebula, SAO 244567, is special in itself. standing.

Observations from 1971 to 2002 showed the star’s temperature soaring from less than 40,000 to 108,000 degrees Fahrenheit, more than ten times hotter than the surface of our Sun. Now, Reindl and his research team have shown that SAO 245567 is it’s cooling down. Reindl speculates that the temperature jump was caused by a brief flash of helium melting that occurred in a shell around the central star’s core. Recently, the star appears to have gone back to its early stage of stellar evolution.

“We are very lucky to be watching it right then,” Reindl said. “During such a helium burst, it evolves very rapidly and that implies short evolutionary times, so we usually can’t see how these stars evolve. We happened to be there at the right time to catch it.”

The team studying the rapid dissolution of the Stingray nebula can only speculate right now what is in store for the future of this young nebula. At its current rate of fading, the nebula is estimated to be barely detectable in 20 to 30 years.