Astronomers Capture Rare Image of Supernova Remnant Observed in the Year 185

As long as humans have walked the Earth, we’ve gazed at the vast night skies, but our ancestors didn’t start making meticulous notes on what they saw until relatively recently. In the year 185 CE, Chinese astronomers created what is believed to be the first record of a supernova. Now, astronomers from the National Science Foundation’s NOIRLab have imaged the remnant of that event, providing a rare image of the full extent of this ancient structure.

While astronomy was more advanced in China than in the rest of the world in the year 185, these early scientists didn’t have any concept of stellar evolution or supernovae. They called the mysterious point of light a “guest star” due to its temporary nature. Modern astronomers have long suspected this event, now known as SN 185, was a supernova, and more recent analysis has supported the hypothesis. Based on those early records, we’ve identified a wispy cloud called RCW 86 as the remnant of that blast, and the NSF have just imaged the entire structure.

The image above covers 45 arcminutes (the full moon covers 31 arcminutes), an impressively wide field of view made possible by the US Department of Energy-built Dark Energy Camera (DECam), which is mounted on the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile. The darker section in the middle of the image (see top) is the interior of the “shell,” with the lighter halo and wispy tendrils marking the border of RCW 86.

The Dark Energy Camera on the Víctor M. Blanco 4-meter Telescope. Credit: Dark Energy Survey

For decades, astronomers were uncertain that RCW 86 was related to SN 185. It appeared much larger and therefore older than something connected to the 185 event. However, X-ray analysis has more recently spotted high iron content in the clouds, which is a telltale sign of a Type Ia supernova. So, about 11,000 years ago, a pair of stars were orbiting where RCW 86 sits today. One was a white dwarf stellar remnant, and the other was a larger main sequence star that had not yet exhausted its nuclear fuel. The white dwarf slowly pulled material away from its companion star until it reached critical mass and exploded in a Type Ia supernova. The white dwarf was annihilated, and the other star was ejected into space.

In the 1,800+ years since the light from that event reached Earth, the shell of dust and gas from the event has expanded considerably, covering more of the sky than the full moon, but it’s extremely dim. The unique design of the DECam, which has a massive array of 570 megapixels, each measuring 15 micrometers across (i.e. very large). This new view of RCW 86 provides astronomers with even more information about this important astronomical event. It’s not every day that a supernova explodes in our own backyard, after all.

Now read:

• Astronomers Shocked By Powerful Gamma-Ray Burst From Colliding Neutron Stars
• Breathtaking New 544MP Image of a Supernova Remnant Revealed
• Astronomers Track Down Mysterious ‘Guest Star’