The Butterfly Nebula is the strangest of its kind, with an hourglass shape accurately resembling that of a butterfly. Most nebulae have an approximately circular shape, but NGC 6302, the original name of the nebula, is completely different from all others, although astronomers say that it is losing its wings.
Nebulae are incredible objects that spread throughout large portions of the star. They are the result of stellar explosions when giant gaseous stars run out of fuel and shed their layers into the cosmos, leaving a trail of dust and vibrant colors.
These bright clusters are often named after flowers or animals for quick identification. The NGC 6302 nebula is peculiar among all because it does not have a circular shape but instead has an hourglass shape, which is why it has been named the Butterfly Nebula.
It is located 4 billion years away from the Scorpius constellation, where our Solar System is located and is so large that its mantle covers about 3 light-years. Astronomers believe that at the center of the nebula, its dying star is still surviving, although it cannot be directly seen because it is hidden behind cosmic dust. Nevertheless, it is burning at 250,000°C, which is about 200 times hotter than our Sun, even though it is almost the size of our planet.
The Butterfly Is Losing its Wings
Researchers from the University of Washington, led by Bruce Balick, Emeritus Professor of Astronomy, have been closely monitoring the Butterfly Nebula to understand how it acquired its peculiar shape, but they have discovered that it is beginning to lose its wings. The team compared images from the Hubble Space Telescope taken over the last 11 years to trace velocities and growth patterns of features within the nebula’s wings.
Lars Borchert, the co-author of the research, discovered half a dozen ‘jets’ in the nebula that appear to have started 2,300 years ago and ended 900 years ago. The explosions have been ejecting material in a series of asymmetric outflows, as they move faster in the outer parts of the nebula, while the material near the hidden star expands much more slowly. It is then that the paths of the vibrant material intersect to form ‘disordered’ structures and the characteristic pattern of the wings.
However, they also found that something is amiss in the Butterfly Nebula. Hubble images show how between 2009 and 2020, there is a dramatic change in the material within the wings. The powerful winds are causing complex alterations in the wings, impoverishing their extension.
They believe that the hidden inner star may have merged with a companion star, or perhaps obtained material from a nearby star, which in turn generated complex magnetic fields that are responsible for the change in the butterfly’s wings. For now, Hubble cannot resolve the astronomers’ doubts about the Butterfly Nebula, but it is expected that in the future, the James Webb Space Telescope will be able to capture the central star’s infrared light with its powerful camera and finally solve the mystery.
Story originally published in Spanish in Ecoosfera.