Bruce Balick/UW/Joel Kastner/Paula Baez Moraga/RIT/STSI
The color appearance of NGC 6302, the Butterfly Nebula, is created from black-and-white exposures taken by the Hubble Space Telescope in 2019 and 2020. In the purple region, strong stellar winds have actively reshaped the nebula’s wings over the last 900 years. Other features range in age from 1200 to 2300 years.
Nationalgeographic.co.id—Nebula planet formed when a red giant star ejects its outer layers because it runs out of helium fuel. It then becomes a hot, dense white dwarf that is about the size of Earth. The material that is spilled, enriched with carbon, forms dazzling patterns as it is gently blown into the interstellar medium.
Most planetary nebulae are roughly circular in shape, but some have an hourglass shape or wings, for which they are named “Kupu-Kupu Nebula.”
These shapes were most likely formed by the gravitational pull of a second star orbiting the nebula’s “parent” star, causing matter to expand into a pair of nebula lobes, or “wings”. Like an expanding balloon, its wings grow over time without changing their original shape.
But new research suggests that something is wrong in the Butterfly Nebula. When a team led by astronomers at the University of Washington compared two views of the Butterfly Nebula taken by the Hubble Space Telescope in 2009 and 2020, they saw dramatic changes in the material within the wings.
They reported these findings on January 12 at the 241st meeting of the American Astronomical Society in Seattle. According to them, strong winds prompted intricate material changes within nebula wings. They wanted to understand how such activity was possible from what should be a “star that is moribund and with no remaining fuel”.
“The Butterfly Nebula is extreme for its mass, speed and complexity of ejection from its central star, which is 200 times hotter than the sun but only slightly bigger than Earth,” said team leader Bruce Balick, a UW professor emeritus of astronomy. “I’ve been comparing Hubble images over the years and I’ve never seen anything like it.”
Lars Borchert and Bruce Balick/UW
Structural changes in the Butterfly Nebula between 2009 and 2020. Features have moved from black to white regions over 11 year intervals. The image reveals a surprisingly complex growth pattern caused by multiple ejections from the nebu’s central star
The team then compared high-quality Hubble images taken 11 years apart to map the speed and pattern of growth of features within the nebula’s wings. Most of the analysis was carried out by Lars Borchert, a graduate student at Aarhus University in Denmark who participated in the study.
Borchert discovered roughly half a dozen “jets” – starting about 2,300 years ago and ending 900 years ago. That pushes the material out in a series of asymmetric outflows. Matter in the outer nebula moves quickly, at about 804 kilometers per second, while matter closer to the hidden central star expands much more slowly, at about a tenth of that speed. The jet paths crisscross, forming a “messy” structure and growth pattern within the wing.
The nebula’s multi-polar, rapidly changing interior structure is not easy to explain using existing models of how planetary nebulae form and evolve, according to Balick. The star at the center of the nebula, hidden by dust and debris, could either merge with a companion star or pull material from a nearby star. This would create a complex magnetic field and produce a glow.
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“At this point, everything is just a hypothesis,” said Balick. “This shows us that we do not fully understand the various formation processes that were at work when planetary nebulae formed. The next step is to image the center of the nebula using the James Webb Space Telescope, because infrared light from stars can penetrate through dust.”
Stars like our sun will swell into red giants and form planetary nebulae one day. It will eject carbon and other relatively heavy elements into the interstellar medium to form star systems and planets in the distant future.
This new research, and other “time-lapse” analyzes of planetary nebulae, can help describe not only how the materials for future star systems will form, but also how the building blocks of our oases were produced and collected billions of years ago.
“This is a creation story that happens again and again in our universe,” said Balick. “The formation process provides key insights into the history and effects of stellar activity.”
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