Crab Nebula Has ‘Honeycomb Heart,’ Astronomers Say

New images captured by the SITELLE instrument on the Canada-France-Hawaii telescope (CFHT) in Mauna Kea, Hawaii, reveal an intricate honeycomb-like arrangement of gas filaments in the center of the Crab Nebula.

3D reconstruction of the Crab Nebula remnant as seen from Earth (left), and from another point of view showing its heart-shaped morphology (right). Image credit: Martin et al., doi: 10.1093/mnras/staa4046.

3D reconstruction of the Crab Nebula remnant as seen from Earth (left), and from another point of view showing its heart-shaped morphology (right). Image credit: Martin et al., doi: 10.1093/mnras/staa4046.

In the year 1054 CE, Chinese astronomers were startled by the appearance of a new star, so bright that it was the brightest object in the night sky, second only to the Moon, and was visible in broad daylight for 23 days. The stellar explosion was also recorded by Japanese, Arabic, and Native American stargazers.

Today, the Crab Nebula is visible at the site of that bright star. Also known as Messier 1 (M1), NGC 1952 and Taurus A, it lies approximately 6,500 light-years away in the constellation of Taurus.

The nebula was first identified in 1731 by English doctor, electrical researcher and astronomer John Bevis and was rediscovered in 1758 by French astronomer Charles Messier.

It derived its name from its appearance in a drawing made by Irish astronomer Lord Rosse in 1844.

Despite the rich history of investigation, many questions remain about what type of star was originally there and how the original explosion took place.

Université Laval astronomer Thomas Martin and colleagues aimed to answer these questions using a new 3D reconstruction of the nebula.

“Astronomers will now be able to move around and inside the Crab Nebula and study its filaments one by one,” Dr. Martin said.

The astronomers used the powerful SITELLE imaging spectrometer on CFHT to compare the 3D shape of the nebula to two other supernova remnants: 3C 58 and Cassiopeia A.

Remarkably, they found that all three remnants had ejecta arranged in large-scale rings, suggesting a history of turbulent mixing and radioactive plumes expanding from a collapsed iron core.

“The fascinating morphology of the Crab Nebula seems to go against the most popular explanation of the original explosion,” said Dr. Dan Milisavljevic, an astronomer at Purdue University.

“The Crab Nebula is often understood as being the result of an electron-capture supernova triggered by the collapse of an oxygen-neon-magnesium core, but the observed honeycomb structure may not be consistent with this scenario.”

“SITELLE was designed with objects like the Crab Nebula in mind; but its wide field of view and adaptability make it ideal to study nearby galaxies and even clusters of galaxies at large distances,” said Dr. Laurent Drissen, an astronomer at the Université Laval and the Université de Montréal.

“It is vital that we understand the fundamental processes in supernovae which make life possible. SITELLE will play a new and exciting role in this understanding,” Dr. Milisavljevic said.

The results were published in the Monthly Notices of the Royal Astronomical Society.

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T. Martin et al. 2021. 3D mapping of the Crab Nebula with SITELLE – I. Deconvolution and kinematic reconstruction. MNRAS 502 (2): 1864-1881; doi: 10.1093/mnras/staa4046

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