A team of international astronomers recently made a startling discovery- an “inside-out” nebula. How is that even possible? None of us are sure, but it’s pretty cool.
What is a nebula anyway?
A nebula is a cloud of gas and dust in space, an interstellar collection of particles and bits of stars. Nebulae (which is the plural), often come from the gas and dust thrown out by the explosion of a dying star, like a supernova. Nebulae can also, however, be made just when new baby stars are beginning to form.
We’ve been able to see nebulae from Earth through telescopes for a long time. Sometimes nebulae look like a bright patch against the dark of space or a dark silhouette against a sun.
What were scientists looking for this time?
You may have seen photos in the past from the Hubble telescope of nebulae: layers of gasses like helium and oxygen that stand out against the black starfield in a haze of color.
In nebulae, the layers usually start with the heaviest- ionized helium, which is followed by a layer of less-ionized oxygen. On the outside of the oxygen, then, is a layer that is usually barely ionized oxygen and nitrogen. We think this is because stars eject the mixture of dust and gas as they get old, and the heavier (more ionized) parts sink to the bottom.
This is the blueprint of all the nebulae that scientists have seen… up until now!
Why is this nebula so different?
The nebula that researchers found in August is inside out. The nebula has layers, just like they usually do, but they come in the opposite order. The heaviest and high-ionization gasses are on the outside!
How is that even possible? Well, until August, scientists didn’t think it was. They couldn’t imagine a way that this kind of nebula could have formed. The nebula, called “Hubi1” right now, seemed impossible.
So what could have happened?
As always with a new discovery, scientists are anxious and excited to figure out how this new kind of thing could have happened.
Scientists live to hypothesize, so that’s what they have done. The possible explanation that they have come up with is that as the star aged, shrinking down to a white dwarf star, it could have maybe had an explosion that was a final, “last gasp.”
This explosion could have sent a shock wave through the already building cloud of gas and dust, ionizing the gasses along the way. The more the shock wave cooled, the more ionization it would have been able to do, and that could explain why the outer layer has more ionization- the wave was cooler when it reached the outside, and could ionize more.
Some proof for this theory comes from the fact that when scientists looked back at old images of the star and the nebula, they see that it was brighter. The nebula has dimmed in the last 46 years. This fits with the theory that says the nebula is still volatile- and still changing as it reacts to the dimming of the star.
We don’t even know what we don’t know
This discovery and all the excitement around it show exactly how much we still don’t know about the universe and how it works. Things that researchers and scientists think are “impossible” one day turn out to be real possibilities the next day.
As the star connected to HuBi1 continues to die, and the dust settles, we will be able to see the nebula much more clearly and get even more answers about this new way that the universe can work.