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Starts With A Bang

A Supernova Seen 1000 Years Ago Is Still Expanding Today

The Crab Nebula goes back to 1054, opening a window into our cosmic past.

On July 4, 1054, Chinese astronomers recorded a “guest star” in the Taurus constellation.

A ‘guest star’ identified as the supernova of 1054 in the pages of the Lidai mingchen zouyi (歷代名臣奏議), which dates to 1414. The highlighted passages refer to the supernova. The full (relevant) Chinese text reads: “宋仁宗至和二年。侍御史趙抃上言曰。臣伏見自去年五月巳来。妖星遂見。僅及周稔。至今光耀未退。此谷永所謂馳騁驟歩。芒炎長短。所厯奸犯。其為謫變。甚可畏也。⋯⋯ 不然。何以妖星謫變也。” (PANKENIER, DAVID W. 2006; JOURNAL OF ASTRONOMICAL HISTORY AND HERITAGE* 9(1): 77–82)

Later research uncovered contemporaneous sightings in Japan and the Middle East.

In 1054, a supernova went off in the constellation of Taurus. It was visible during the day for about 3 months, and finally faded from view in the night sky after a total of 2 years. Some ~700 years later, the remnant of this explosion was independently rediscovered, and the link between ancient and modern observations was established in 1921: 100 years ago. (JWNOCTIS / WIKIMEDIA COMMONS; STELLARIUM)

Temporarily outshining Venus, it faded after about two years: a common supernova.

When it was initially discovered in 1731, the remnant of the 1054 supernova would have been even less pronounced and identifiable than the “smudge” seen at the center-top of this image, which showcases the Crab Nebula through a small telescope with modern photography techniques. (STUB MANDREL; HTTP://WWW.STUBMANDREL.CO.UK/)

Hundreds of years later, its remnant was astronomically discovered.

The Crab Nebula, the remnant of a supernova from 1054, is currently 11 light-years across. The tendrils, filaments, gas and plasma surrounding the center have expanded at between 0.5% and 1% the speed of light for nearly 1000 years, and continue to expand today. (ZTF, GIUSEPPE DONATIELLO)

John Bevis found it in 1731, but it was a big source of confusion in 1758.

Through an 18th century-quality telescope, comets, nebulae, and other extended objects are not readily distinguishable from one another. It makes blindly hunting for a slow-moving comet very difficult, and the search for Halley’s Comet in 1758 sparked Charles Messier to develop his famous catalogue. (CHRIS BRANKIN’S DEEPSKY (MESSIER) OBJECTS; HTTP://WWW.STARGAZING.NET/)

Halley’s comet was due to return that year, also in Taurus.

Halley’s comet, which returns roughly every 76 years, passes through various portions of the sky on its periodic journey through the Solar System. Given that comets often look faint and fuzzy through small telescopes, similar to deep-sky objects, it makes sense to have a catalogue of deep-sky fixtures to avoid confusion. (F. Carter Smith/Sygma via Getty Images)

However, this faint, fuzzy, nebulous sight confounded many.

An optical composite/mosaic of the Crab Nebula as taken with the Hubble Space Telescope. The different colors correspond to different elements, and reveal the presence of hydrogen, oxygen, silicon and more, all segregated by mass. If the Earth were located within this nebula, which extends about 10 light-years across at present, it could cause an extinction-level event for humanity. (NASA, ESA, J. HESTER AND A. LOLL (ARIZONA STATE UNIVERSITY))

It wasn’t a comet, but a distant object ~6,500 light-years away.

The 110 objects on the Messier catalogue help skywatchers avoid confusion with permanent deep-sky objects while hunting for comets or other transient events. Today, more than 250 years after its creation, the Messier catalogue is an outstanding resource for amateur and professional astronomers to view the most prominent night sky objects. (MIKE KEITH)

Rediscovered independently by Charles Messier, it sparked the creation of astronomy’s most famous catalogue.

This blink animation shows the difference between the Crab Nebula from 2011 to 2021. The supernova remnant’s outskirts currently span a distance of 11 light-years, and are expanding outwards at about 0.5% the speed of light. (GIANLUCA MASI / VIRTUAL TELESCOPE PROJECT)

Nearly a millennium later, we actively see this remnant expanding.

This decade-long timelapse, from 2008 to 2017, shows incredibly detailed features in the gaseous and filamentary structures of the Crab Nebula expanding over time. Over the timescale this animation, the nebula has further increased in size by about a tenth of a light-year. (DETLEF HARTMANN; HTTPS://WWW.ASTROBIN.COM/FULL/327338/0/)

Its central engine is powered by a pulsing neutron star: the collapsed core of a very massive star.

A combination of X-ray, optical, and infrared data reveal the central pulsar at the core of the Crab Nebula, including the winds and outflows that the pulsars care in the surrounding matter. The central bright purplish-white spot is, indeed, the Crab pulsar, which itself spins at about 30 times per second. (X-RAY: NASA/CXC/SAO; OPTICAL: NASA/STSCI; INFRARED: NASA-JPL-CALTECH)

The former star’s outer layers, meanwhile, were ejected at tremendous speeds.

This five-panel composite shows the Crab Nebula as viewed in different wavelengths of light. Today we know it as the expanding gaseous remnant from a star that self-detonated as a supernova, briefly shining as brightly as 400 million suns. The explosion took place 6,500 light-years away. (G. DUBNER (IAFE, CONICET-UNIVERSITY OF BUENOS AIRES) ET AL.; NRAO/AUI/NSF; A. LOLL ET AL.; T. TEMIM ET AL.; F. SEWARD ET AL.; CHANDRA/CXC; SPITZER/JPL-CALTECH; XMM-NEWTON/ESA; AND HUBBLE/STSCI)

Smashing into previous ejecta and illuminated by radiation, they’re brilliantly visible today.

An infrared view of the Crab Nebula shows the filamentary structures (in red) are barely illuminated, while the diffuse gas surrounding the neutron star shines brightly due to the behavior of ionized electrons. This image was taken with NASA’s Spitzer Space Telescope. (NASA/JPL-CALTECH/R. GEHRZ (UNIVERSITY OF MINNESOTA))

After 967 years — nearly a full millennium — this supernova remnant spans 11 light-years across.

Based on its observed distance of ~6,500 light-years, the observed angular extent of the Crab Nebula allows us to calculate a diameter for this supernova remnant. Putting the math together gives us a diameter of about 11 light-years, with the nebula continuing to expand at about ~0.5% the speed of light. (JEFF STILLMAN)

Its outskirts are still expanding at ~0.5% the speed of light.

The elements found inside indicate these type II supernovae create the majority of many heavy elements.

The most current, up-to-date image showing the primary origin of each of the elements that occur naturally in the periodic table. Neutron star mergers, white dwarf collisions, and core-collapse supernovae may allow us to climb even higher than this table shows, but of the surviving elements, everything dominated by dark green comes from type II supernovae, like the event that created the Crab Nebula. (JENNIFER JOHNSON; ESA/NASA/AASNOVA)

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.

Starts With A Bang is written by Ethan Siegel, Ph.D., author of Beyond The Galaxy, and Treknology: The Science of Star Trek from Tricorders to Warp Drive.


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