A deep-sky masterpiece

It is one of the most fascinating celestial objects that adorn the sky. To observe this nebula in all its beauty, a good telescope is needed, but even with sufficiently powerful binoculars, under a dark sky and far from city lights, you can discern its faint glow. We are talking about the Eagle Nebula (M16), a nebula located about 7,000 light-years away, in the direction of the constellation Serpens, visible in the August and September sky during the early hours of the night, towards the southwest.

Naturally, photography reveals much more detail and color nuances, primarily due to the presence of hydrogen (red), which is especially abundant in emission nebulae where ultraviolet radiation from young stars excites the surrounding gas. The blue hue is produced by ionized oxygen, while the darker regions result from dense interstellar dust that absorbs and blocks the light from stars behind it.
The Eagle Nebula’s name comes from its distinctive symmetrical shape, resembling the silhouette of a bird of prey with outstretched wings and visible talons. These “claws,” which are the true masterpiece of the sky, are actually dense columns of gas and dust extending within the nebula and representing regions of intense star formation. These structures form through the combined effects of radiation and stellar winds from nearby massive stars, which erode the surrounding material, exposing the most compact and resistant regions. Because these columns are denser than their surroundings, they evaporate much more slowly than the diffuse gas around them and can therefore persist over time.

These columns, known as the “Pillars of Creation,” are vast structures of gas and dust shaped by the ultraviolet radiation from young stars. Within the pillars, potential star embryos, called Bok Globules, have been identified and may soon ignite.

Inside these interstellar columns, the gas density becomes so high that gravity takes over and causes the gas to collapse into ever smaller clumps. As more and more gas settles, the temperature inside them rises to millions of degrees, triggering nuclear fusion reactions in their nuclei and “igniting” as stars. *Photo G. Neccia*

These pillars represent a highly dynamic and active process. The gas is not merely heated and passively dispersed into space; it undergoes intense ionization by the ultraviolet radiation emitted by nearby massive stars. The material is then further shaped and eroded by the combined effects of radiation pressure and stellar winds, which consist of streams of high-energy charged particles that act like cosmic sandpaper on the tops of these structures.

In this extraordinary image, captured by the Hubble Space Telescope and showing a small section of the nebula, you can clearly see the shaping of these structures. It is in these regions that new stars are being born, which will contribute to shaping the surrounding environment with their energy and radiation.

The orange, which we see particularly in the upper part of the photograph, represents the starlight’s attempt to break through the dust wall: the blue light is absorbed, while the reddish light manages to make its way through the dust grains and reveal itself to Hubble’s sharp gaze.
The structures visible in these images correspond to regions with higher gas and dust density, capable of offering greater resistance to photoevaporation and radiative erosion than the less dense surrounding material.
*The image was obtained using new image processing techniques and is part of a series of images celebrating the 35th anniversary of the famous space telescope. Credits: ESA/Hubble & NASA, K. Nol*

In the long term, however, these structures too are destined to be progressively eroded and dispersed by the intense activity of the massive stars present in the Eagle Nebula region.

Measuring about 4-5 light-years tall, the Pillars of Creation are a fascinating but relatively small feature of the entire Eagle Nebula, which spans 70 light-years.

However, the spectacle of the Eagle Nebula does not end with the Pillars of Creation; within it lies the open cluster NGC 6611. This star cluster contains several thousand stars with an average age of about one million years, including approximately fifty stars with masses greater than ten times that of the Sun. The ultraviolet radiation emitted by these stars significantly impacts the residual molecular cloud from which they formed, contributing to its ionization, erosion, and gradual dispersion.

*Combining images from two cameras aboard the NASA/ESA/CSA James Webb Space Telescope, in the near-infrared and mid-infrared, we see this star-forming region blazing. Credits: ESA/NASA*

Today, M16 is one of the most intense spectacles in the entire galaxy, but it will not remain so forever. Within a few million years, star formation will have exhausted or dispersed the available raw material, and the massive stars that illuminate the Eagle Nebula will have ended their short lives, dying in spectacular supernova explosions. However, even if the nebula disappears, most of the stars that formed there will remain. The Eagle Nebula’s progeny will “take flight” among the hundreds of billions of stars that make up our galaxy.

The nebula was discovered in 1745 by the Swiss astronomer Jean-Philippe Loys de Chéseaux.

Credits

Author: Giancarlo Neccia is an amateur astronomer and astrophotographer of the “La via delle Stelle” association of which he is vice president. He is the technical manager of the “La via delle stelle” observatory in Montelanico (Rome) and the Maurizio Cassandra observatory in Carpineto Romano (Rome) equipped with a 400 mm Marcon telescope.

Translated by Maria Antonietta Sessa