A strange "dandelion" in the universe? The mystery of the supernova remnant Pa30

Author: Duan Yuechu and Huang Xianghong

Deep in the vast universe, there is a mysterious treasure house, hiding countless celestial wonders, each of which is like a carefully crafted work of art, waiting for humans to uncover their mysterious veils like explorers. Today, we are going to visit a wonderful existence like a blooming "dandelion" in the universe - the supernova remnant Pa 30.

The October 31, 2024 issue of Scientific American is like a wise guide, bringing us this wonderful cosmic story. This is not an ordinary story, it carries the mysteries of the universe and takes us back to the distant year 1181.

That year, in the eyes of sky observers in China and Japan, an unprecedented "guest star" suddenly broke into their field of vision. This "guest star" was not simple, it was like the protagonist of a grand fireworks display in the universe - the product of a supernova explosion. What a shocking scene it was! Imagine that such a dazzling celestial body suddenly appeared in the originally peaceful starry sky. When it was brightest, its light could rival that of Saturn. Moreover, before it appeared, there were no visible stars in that position. It was like an uninvited guest, bringing the mysterious power of the universe, breaking into the sight of mankind.

This "guest star" remained visible for 185 days, but as its brilliant light gradually faded, it seemed to play hide-and-seek with humans again, and its exact location became a mystery that puzzled astronomers for centuries. But the secrets of the universe cannot be hidden after all, and after the unremitting efforts of countless scientists, in recent years, we have finally found it again and gradually unveiled its mysterious veil.

This supernova remnant is named Pa 30. When I first saw its artist's concept map, I was really shocked. It is like a dandelion blooming freely in the universe, beautiful and dreamy. It is composed of hundreds of gas and dust filaments, which seem to have been carefully arranged by a magical artist, surrounding a "zombie" white dwarf, just like dandelion seeds surrounding the pistil, forming a strange and spectacular picture.

Pa 30 is located about 8,000 light-years from our solar system, near the northern constellation of Cassiopeia. It is located in a planetary nebula, a unique piece of geometric art in the universe whose striking shape has fascinated scientists to this day. We still can't fully explain how it formed, but a new study has shone a light into the darkness, revealing some hidden details that give us hope of solving its mysteries.

At the center of Pa 30 is a special white dwarf called Parker's Star. Whenever I think of this star, I am filled with awe at the magical creativity of the universe. White dwarfs are the hot cores left behind when stars die, like the last afterglow of stellar life in the universe. But this "Parker's Star" is particularly special. It is a survivor of a supernova explosion, like a "zombie" that has stubbornly walked out of a cosmic disaster. This situation is extremely rare in the universe.

Generally speaking, supernovae are mostly caused by the explosion of massive stars after they run out of fuel and collapse under the relentless pull of their own gravity. Type Ia supernovae, on the other hand, are caused by the merger of a white dwarf with another white dwarf or the accretion of gas from a companion star. When the accretion exceeds a critical value, it will trigger a doomsday-like thermonuclear explosion, and the white dwarf will also be destroyed in this explosion.

But the supernova observed in 1181 was a much rarer type Iax supernova, in which the central white dwarf miraculously survived part of the cosmic carnival. On the vast stage of the universe, astronomers have discovered tens of thousands of "conventional" supernova remnants and more than a thousand type Ia supernova remnants, but there are very few type Iax supernova remnants, less than a hundred, and this "Parker Star" in our Milky Way is the only one. This is like discovering a unique gem in the vast universe, which is of immeasurable value for studying the evolution of the central star and ejected matter after the supernova explosion. It is like a precious sample of the universe placed on our doorstep, giving us the opportunity to peek into the mysteries of cosmic evolution up close.

To explore this strange supernova remnant in depth, scientists took out their "secret weapon" - the Keck Cosmic Web Imager (KCWI). This KCWI is not simple. It is installed on the WM Keck Observatory telescope near the top of Mauna Kea in Hawaii. It is a powerful spectrometer. In astronomical research, the spectrometer is like a magic key that can open the door to the chemical composition and structure of the universe. It can decompose light into different wavelengths, that is, different colors. In this wonderful way, the observer is like having a pair of perspective eyes, able to distinguish the chemical composition of the cosmic structure and even perceive their subtle movements.

KCWI's sharp spectroscopic observation capabilities gave the research team a magical paintbrush to draw an accurate three-dimensional map of this strange supernova remnant and its filaments. Now we know that these filaments are about three light years long, and they are like cosmic threads, dancing in the universe at a speed of about 1,000 kilometers per second. Moreover, since the supernova explosion more than 840 years ago, they seem to have maintained this speed, like a group of tireless dancers.

Normally, the gas and dust ejected by a supernova are much faster, reaching tens of thousands of kilometers per second, and the "zombie" white dwarf at the center of the nebula is also emitting a strong stellar wind. Surprisingly, these stellar winds do not seem to have any significant effect on the shape of the filaments, which is like a magical phenomenon in the universe, waiting for us to crack the mystery.

So how did these filaments form? This is really a question that makes people rack their brains. After repeated thinking and research, the researchers believe that they may be the result of the interaction between the ejected gas and dust and the "reverse shock wave" generated by the supernova explosion impacting the interstellar medium. This interaction is like a magic in the universe, which can not only explain the formation of filaments, but also may explain the sharp "inner edge" phenomenon of the Dandelion Nebula. This "inner edge" area is like a space full of mysterious atmosphere, filled with ejected gas and dust. They have not yet condensed into dense filaments. They are like a group of free elves in the universe, waiting for the right time to join this grand show.

In addition, the researchers also found some clues about the asymmetry of supernova explosions. From the observation, there are more filaments pointing away from the earth than pointing towards the earth. It's like the universe is showing us its subtle side. Although we are not sure whether this potential asymmetry will be confirmed in subsequent research, if it is real, it may help us solve the mystery of the central white dwarf's partial survival in the supernova explosion.

This strange object caught the attention of Quentin Parker, an astronomer and astrophysicist at the University of Hong Kong. Like an explorer attracted by treasure, he did not participate in the latest study, but he left his footprints in research papers on the star in 2021 and 2023. The 2021 paper was like a key, linking the nebula and relic to the supernova in 1181 for the first time and giving the star the unique name "Parker's Star". Parker has made extraordinary achievements in the discovery of planetary nebulae. He has discovered more than 1,000 planetary nebulae and is a well-deserved legend in this field. But before this, he had never given his name to any nebula, which shows how unique and fascinating this "Parker's Star" is, like a special gift prepared by the universe for him.

Parker spoke highly of the supernova remnant, saying, "This object will be a gold mine for research." I completely agree with him. This supernova remnant is like a magical Rubik's Cube in the universe. Every facet of it - from its strange shape, the special central white dwarf, to the possible asymmetric explosion - contains mysteries deep in the universe. It has attracted astronomical research teams from all over the world, like a huge magnet, and everyone is eager to dig out more treasures from this gold mine.

As research progresses, we hope to learn more about the mysterious thermonuclear processes through this relic. These thermonuclear processes not only play an important role in this supernova explosion, but also play a pivotal role in the broader evolution of celestial bodies in the universe. Every exploration of this relic is like finding a new piece in the grand puzzle of cosmic evolution, bringing us one step closer to a complete picture.

Astronomy is as dependent on the public as fish is on water. Media like Scientific American are a bridge to the knowledge of the universe, bringing the mysteries of the universe to everyone who is hungry for knowledge. If readers are as fascinated by the story of this supernova remnant as I am, please consider subscribing to the publication, which is like breathing new life into science journalism. By purchasing a subscription, we can ensure that the wonderful stories about the scientific discoveries and ideas that shape our world today can continue to be passed on, so that more people can feel the charm of the universe and inspire more people to love science.

The study of the Pa 30 supernova remnant is like opening a door to the mysterious world deep in the universe. From the "guest star" in historical records, to the strange "dandelion" shape presented by modern observation technology, to the mysterious "zombie" white dwarf in the center and the various physical phenomena and unsolved mysteries related to it, each link is like a story carefully woven by the universe, making us deeply feel the infinite charm and complexity of the universe. Scientists' research on it is like an endless adventure. In the future, we hope to have a deeper understanding of the cosmic mysteries contained in this unique celestial body through more observations and analysis, as well as the importance of these mysteries to our understanding of the evolution of the entire universe.

With the rapid development of science and technology today, we are like standing on the shoulders of giants. New observation equipment and technologies are constantly emerging like mushrooms after rain, such as more advanced spectrometers, larger-caliber telescopes, etc. These new technologies are like new wings for cosmic exploration, which will provide us with clearer and more detailed images of the universe, allowing us to further explore celestial bodies like Pa 30 as if we had sharper eyes. Perhaps in the near future, we will be able to solve more mysteries of the Pa 30 supernova remnant, such as accurately figuring out the cause of its asymmetric explosion, gaining a deeper understanding of the physical properties of "zombie" white dwarfs in extreme environments, and more subtle physical mechanisms in the formation of nebula shapes.

International cooperation in astronomical research is like a grand concert, in which astronomers from every country and region are performers. The study of complex celestial bodies like Pa 30 requires everyone to play a harmonious movement together. Different research teams are like musicians with different instruments, each with its own advantages in observation methods, theoretical models, etc. Through cooperation, the wisdom of all parties can be gathered, just like different notes intertwined together to create beautiful music and accelerate the research process. Moreover, this kind of international cooperation is like a cradle for cultivating a new generation of astronomers, giving more young people the opportunity to participate in this fascinating research field and injecting new vitality into the cause of cosmic exploration.

From a broader scientific perspective, the study of the Pa 30 supernova remnant is like a huge spider web, inextricably linked to other disciplines. For example, the thermonuclear reaction process involved is related to nuclear physics in physics, like two intertwined silk threads. The study of its ejected matter may provide new clues to the evolution of matter in the universe for the chemical discipline, which is like opening a new window for the chemical discipline. The analysis of its historical observation data also requires the use of historical and archaeological methods, just like looking for traces of the universe in ancient documents and relics. This interdisciplinary research trend is becoming more and more obvious in modern science. It is like a beacon that allows us to understand the complex phenomena in the universe from multiple perspectives and provide a more comprehensive approach to solving scientific problems.

The public's interest and participation in astronomical research should not be limited to subscribing to scientific journals. There are now more and more popular science activities, astronomical exhibitions, online science platforms, etc., which are like treasure troves of cosmic knowledge, providing the public with opportunities to learn about astronomy. Through these channels, the public can feel the beauty and mystery of the universe more intuitively, just like walking into the picture scroll of the universe in person. They can learn scientific knowledge such as supernova remnants, which in turn inspires their support and participation in scientific research. Astronomy content can also be strengthened in school education, cultivating students' curiosity and desire to explore the universe from an early age, laying a solid foundation for the future reserve of scientific talents, just like sowing the seeds of hope for the cause of cosmic exploration.

In future studies, scientists may also compare the Pa 30 supernova remnant with other similar celestial bodies. There may be more types of supernova remnants in the universe, with different shapes, physical properties, and formation mechanisms, just like different flowers in the universe, each with its own beauty. Through comparative analysis, we can find out their commonalities and differences, just like looking for patterns in flowers, and further improve our understanding of supernova remnants as a class of celestial bodies. Moreover, with the deepening of research on dark matter, dark energy, etc. in the universe, we can also think about whether these cosmic components that have not yet been fully understood have played a role in the formation and evolution of supernova remnants. Perhaps this will bring new breakthroughs to our study of the basic composition and evolution laws of the universe, just like finding new light in the darkness.

In short, the Pa 30 supernova remnant is like a precious gift from the universe to us. It contains countless secrets waiting for us to unravel with scientific methods. Our exploration of it is not only a study of a celestial body, but also a microcosm of human pursuit of the mysteries of the universe. It will lead us to continue to move forward on the road of cosmic exploration, expand our cognitive boundaries of the universe, and let us have a deeper understanding of this magical universe we live in.

References:

What Made This Bizarre 'Dandelion' Supernova? | Scientific American