The Night Sky - Episode 8
THE EAGLE NEBULA
This is episode 8 in my series on our night sky.
The boundless canvas of our night sky holds numerous wonders. One such wonder that has enraptured the hearts and imaginations of astronomers and stargazers alike is the Eagle Nebula, officially designated M16.
An image of the Eagle Nebula (M16). Over 9.5 hours of faint light from deep space were captured to create this image.
Image by Achint Thomas
Nestled within the boundaries of the Serpens constellation, the Eagle Nebula (M16) is a sprawling region of space situated approximately 5,700 light-years from Earth. The nebula’s enigmatic name stems from its striking resemblance to a majestic eagle in flight, wings outstretched, as it basks in the radiance of fiery, newborn stars.
M16's colossal size is nothing short of awe-inspiring. Stretching across approximately 70 by 55 light-years, this expanse of space - while relatively young at only 55 million years - is a nurturing playground for budding stars, making it one of our galaxy’s most majestic stellar nurseries.
The Messier Catalog and Mapping the Night Sky
The history of M16's discovery can be traced back to the 18th century when it came under the discerning gaze of Charles Messier, a French astronomer. His catalogue, the Messier Catalogue, contains 110 deep-sky objects. M16 is the 16th entry in this catalogue. Born out of frustration with repeatedly mistaking non-cometary objects for comets, Messier created his catalogue to record deep-space objects and indexes a host of galaxies, nebulae, and star clusters.
In addition to the Messier Catalogue, there are dozens of other astronomical catalogues of deep-sky objects. They allow astronomers to collaborate on research and map out the universe. Some of the more well-known ones include:
The celestial targets contained in these catalogues act as kindling for amateur stargazers and professional researchers alike as they explore the night sky.
The Eagle Nebula’s Location in the Milky Way
In the northern hemisphere, the Eagle Nebula (M16) is visible only in the summer months when the core of the Milky Way rises above the horizon in the southern sky after sunset.
A panoramic image of the Milky Way galaxy in the northern hemisphere showing the approximate location of the Eagle Nebula.
Image by Achint Thomas
M16 is located in one of our galaxy's spiral arms, the Sagittarius Arm. This dense galactic neighbourhood is teeming with space dust, nebulosity, and regions of star formation. There are several other nebulae and star clouds in the visual proximity of M16.
A section of the Milky Way galaxy showing a magnified view of the visual region around the Eagle Nebula.
Image by Achint Thomas
The Pillars of Creation
When discussing the Eagle Nebula (M16), it's impossible not to evoke the iconic image of the "Pillars of Creation." Captured by the Hubble Space Telescope in 1995, this breathtaking photograph - arguably one the most recognized and celebrated astronomical images in history - unveils a mesmerizing scene of towering pillars of gas and dust, each hundreds of times the size of our solar system!
“Pillars of Creation“ image taken by the Hubble Space Telescope [image reference]
The Pillars of Creation offers a glimpse into a realm of intense star formation, where massive, hot stars irradiate their surroundings, shaping these colossal pillars. The pillars themselves are stellar nurseries, cradling numerous nascent stars within their shrouded embrace.
Hubble's image of the Pillars of Creation showcases the cosmos' breathtaking beauty and provides invaluable insights into the process of star formation. It deepens our comprehension of the physical mechanisms at play within these extensive clouds of gas and dust, illuminating the process of the gestation and birth of stars concealed within.
A magnified view of the core of the Eagle Nebula showing the region famously referred to as the Pillars of Creation. The structure of the “pillars” is clearly visible in this view. Image is at a 640mm equivalent field of view.
Image by Achint Thomas
Other Structures in the Eagle Nebula
While the Pillars of Creation undoubtedly constitute the most iconic feature of M16, this nebula also harbours other cosmic treasures. The region is adorned with clusters of young, scorching hot stars, some of which can be observed through amateur telescopes.
Annotated survey image of the region around M16. Yellow markers show Messier and NGC objects. Green markers show H-II regions. White markers show prominent stars.
Image by Achint Thomas
One such cluster within M16 is NGC 6611, a brilliant star cluster located at the heart of the nebula. This cluster houses a population of massive, luminous stars - the kind that exerts a significant influence on their immediate surroundings. The intense radiation emitted by these stars sculpts the nebula and triggers the formation of additional stars within the surrounding dusty clouds.
Why Astrophotographs Contain a Lot of Red
Astrophotography often displays a prevalence of red hues, a feature rooted in the composition of our cosmos. This reddish tinge is primarily attributed to the abundance of Hydrogen in the universe, resulting in the abundance of hydrogen-alpha (Hα) emissions. Hα emissions occur when hydrogen gas becomes ionized by the intense radiation from nearby stars and subsequently releases this acquired energy by emitting light in the red part of the spectrum (specifically - 656.46 nm). Consequently, objects like nebulae, star-forming regions, and even certain galaxies are often rich in Hα emissions, casting them in shades of red.
Astrophotographers use Hα filters to isolate this specific wavelength in the red portion of the spectrum.
The Eagle Nebula when viewed using an Hα filter. The image appears monochrome because it corresponds to a single wavelength of light.
Image by Achint Thomas
As we gaze upon celestial wonders like the Eagle Nebula, we witness the cosmic ballet of ionized Hydrogen gas, painted in radiant shades of red and tinged with the stories of stars being born.
The universe is a fascinating place filled with mesmerizing objects. Nebulae are some of the most expansive of these objects, spanning light-years across and containing intricate structures that inspire awe in the beholder. And the Eagle Nebula is definitely among the most interesting.
Check out some other nebulae I have captured.
Capture details
Camera: Astro-modified Canon 80D
Lens: Sigma 100-400mm f/5-6.3 DG OS HSM
Focal length: 400mm (equivalent to 640mm full-frame)
f-Ratio: 6.3
ISO: 800
Number of exposures: 197 total
- 62*300s with Astronomik Hα filter
- 135*120s with Optolong L-Enhance filter
Total integration time: 9.6 hours over 6 sessions
Calibration frames: 30 darks, 30 flats, 30 bias for each session
Mount: SkyWatcher Star Adventurer
Guide camera: ZWO 120mm mini
Guide scope: ZWO Mini Guide scope
Capture control: ZWO ASIAir Pro
Dew control: SvBony dew heater
Sky quality: Bortle 3 and Bortle 5
Moon phase: Various from 0% to 95%
Processing: PixInsight, Photoshop