The Pencil Nebula: Remnants of an exploded star
Officially known as NGC 2736, the Pencil Nebula is part of the huge Vela supernova remnant, located in the southern constellation Vela. Discovered by Sir John Herschel in the 1840s, the nebula’s linear appearance triggered its popular name. The nebula’s shape suggests that it is part of the supernova shock wave that recently encountered a region of dense gas. It is this interaction that causes the nebula to glow, appearing like a rippled sheet.
The nebula’s luminous appearance comes from dense gas regions that have been struck by the supernova shock wave. As the shock wave travels through space, it rams into interstellar material. Initially the gas is heated to millions of degrees, but then subsequently cools down, emitting the optical light visible in the image.
The colors of the various regions in the nebula yield clues about this cooling process. Some regions are still so hot that the emission is dominated by ionized oxygen atoms, which glow blue in the picture. Other regions have cooled more and are seen emitting red in the image (cooler hydrogen atoms). In this situation, color shows the temperature of the gas. The nebula is visible in this image because it is glowing.
The supernova explosion left a spinning pulsar at the core of the Vela region. Based on the rate at which the pulsar is slowing down, astronomers estimate that the explosion may have occurred about 11,000 years ago. Although no historical records of the blast exist, the Vela supernova would have been 250 times brighter than Venus and would have been easily visible to southern observers in broad daylight. The age of the blast, if correct, would imply that the initial explosion pushed material from the star at nearly 22 million miles per hour. As the Vela supernova remnant expands, the speed of its moving filaments, such as the Pencil Nebula, decreases. The Pencil Nebula, for example, is moving at roughly 400,000 miles per hour.
Source: Hubblesite.org
This processing is part of a processing contest organized by Greg Turgeon, Deep Sky West and Tolga.
RA: 08h 59m 42.305s
DEC: -46° 02′ 01.736″
Size: 36.4 x 29.8 arcmin
Orientation: Up is 90 degrees E of N
Location: Vela
Distance: 815 ly
Magnitude: 12
Acquisition January 2021
Total acquisition time of 30 hours.
Technical Details
Data acquisition: Greg TURGEON
Processing: Nicolas ROLLAND
Location: Deep Sky West, Chile
L 24 x 600 sec
R 24 x 600 sec
G 24 x 600 sec
B 23 x 600 sec
Ha 22 x 1800 sec
OIII 17 x 1800 sec
Optics: Planewave 17“ CDK @ F6.8
Mount: 10Micron GM3000
CCD: FLI ML16803
Pre Processing: CCDstack & Pixinsight
Post Processing: Photoshop CC