Somewhere in deep space, a beautiful cosmic weed grows, scattering metaphorical pollen from its core at an incredible rate. For almost 900 years, the powerful cosmic explosion that caused this weed to bloom remained a mystery. Now, a state-of-the-art telescope is giving us a better look at the results.
The weed is actually a nebula called the Pa 30 nebula, and its shape has some eccentricities. In 2023, astronomers from Dartmouth College and Louisiana State University described the matter that flew out of the explosion as clumping together in filaments that sprouted from the center like a dandelion’s umbilical cord. Continuing this research, other astronomers mapped these filaments for the first time.
Humanity’s interest in this nebula can be traced back to 1181
Back then, astronomers in Japan and China recorded the appearance of a new star. Six months later, it disappeared, but was not forgotten. In 2013, an amateur astronomer named Dana Patchik was reviewing images taken by NASA’s Wide-field Infrared Survey Explorer space telescope, now decommissioned. He identified a nebula in a region of space where a star could be located, 7,500 light years from Earth, in the constellation Cassiopeia. Over the next decade, astronomers concluded that the Pa 30 nebula was likely the remnants of a supernova that ancient astronomers had observed many years earlier.
The birth of the Pa 30 nebula
Nebulae are often giant clusters of matter, such as ionized gas and cosmic dust, that swirl brightly. But not all nebulae are the same. Some of them are made up of the remnants of stars that die during powerful explosions. This is exactly what happened in the case of the Pa 30 nebula, and some of the results of the study are unique among known nebulae. In its core, the remnants of the star that gave birth to it have been preserved, with a surface temperature of 360,000 degrees Fahrenheit (200,000 Celsius). By comparison, our Sun has a surface temperature of about 10,000 degrees Fahrenheit (5,500 Celsius).
“We found that the material in the filaments is expanding ballistically,” said Tim Cunningham, a NASA research scientist at the Harvard and Smithsonian Centers for Astrophysics, “meaning that it has not slowed down or accelerated since the explosion. “This means that the material has not slowed down or accelerated after the explosion. Based on the measured velocities, looking back in time, we can accurately determine that the explosion occurred in about 1181.”
The nebula has a strange shape
Cunningham and his colleagues wanted to get a better idea of the shape of these filaments. They turned to a device in Hawaii called the Keck Cosmic Web Imager (KCWI), which detects light in the visible spectrum. Different colors travel with different amounts of energy. For example, blue has a relatively high energy level compared to red. The difference in energy allowed astronomers to determine which matter was moving toward the Earth and which was moving away. The result was a 3D map of the nebula’s filaments. The shape is asymmetrical, suggesting that the initial explosion was also asymmetrical. Between the star remnant in the center and the filaments is a strange cavity of nothingness up to 3 light-years wide, which is likely the result of an explosion that destroyed all matter that was too close to the center of the nebula.
“A standard image of a supernova remnant would be like a static photo of fireworks,” said Christopher Martin, a professor of physics at the California Institute of Technology who worked on the study published in The Astrophysical Journal Letters. “The KCWI gives us something more like a ‘movie’ because we can measure the motion of the explosion’s embers as they fly away from the central explosion.”
Why did this nebula take on this shape?
Cunningham believes that this could have happened because the shock wave condensed the dust, which was moving at speed, into bunches, but nothing can be said for sure. Even after almost a millennium, some mysteries remain.
