The Stingray Nebula is the youngest known planetary nebula. For half a century astronomers have watched its formation, and now they have noticed something strange: it is fading away.
“It’s very, very dramatic, and very strange,” said Martín A. Guerrero of the Instituto de Astrofísica de Andalucía in Granada, Spain, one of the co-authors a new study of the Stingray Nebula. “What we are seeing is the real-time evolution of the nebula. Over the span of a few years, we’ve seen variations in the nebula. We’ve never seen that before with the clarity we get with this display. “
Between 1996 and 2016, Hubble’s images of the Stingray Nebula respectively reveal that the Stingray Nebula is getting weaker, dimmer, and less prominent. It was a reflection of her old self, and was getting weaker by the day. For example, the brightness due to the presence of ionized oxygen fell by an unprecedented factor of 1,000 in the twenty years between observations.
What is going on?
Astronomer Karl Gordon Henize was the first to categorize the central star of the Stingray Nebula, known as SAO 244567, in 1967 as a bright blue giant. Just four years later, astronomers realized that the late-stage star was surrounded by a faint nebula, which they quickly identified as the start of a nebula planet. The stingray has the official designation Hen 3-1357, and is a type of nebula formed by such a star. nearing the end of his life and begins to expel its outer layer into the surrounding system.
Starting in 1971, the temperature of SAO 244567 began to skyrocket, rising from 40,000 to 108,000 degrees Fahrenheit at the turn of the millennium. And then it reverses direction, cools and fades in the process.
As the intensity of the central star decreases, the amount of radiation hitting the nebula decreases. Like dimming the lights in your room to make it more moody, the Stingray Nebula slowly turns off.
Astronomers suspect that the sudden spike in temperature was caused flash helium, the critical state inside a giant star where unburned helium shells melted in just a day, releasing a huge amount of pent up energy. But because stars are so large, it can take years to feel the changes on the surface.
But now that the star is back to normal, the brilliance of the stingray is fading. Presumably this happens all the time in the entire universe, but this time the astronomers were lucky enough to capture the process in progress.
