Nebula | One Of The Most Dazzling Objects In Space | ScienceMonk

Nebula is an interstellar cloud primarily consisting of dust, hydrogen, helium and some other ionized gases which serves as perfect ingredients for star formation, hence nebulae are often star-forming regions. In these regions, matter comes together to form a dense gas ball which after many stages like proto-star results into the formation of a Star.

On a starry night directing your telescope towards the south of Orion belt, will reveal a cloudy object which is nothing but a Nebula. Probably from its appearance only, nebula got its name as, ‘Nebula’ is Latin for word cloud or mist. It will not be an exaggeration if we call it one of the spectacular objects holding many secrets of the universe.

nebula
 Picture Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) – http://hubblesite.org/image/3471/news_release/2015-01

The NASA/ESA Hubble Space Telescope has revisited one of its most iconic and popular images: the Eagle Nebula’s Pillars of Creation. This image shows the pillars as seen in visible light, capturing the multi-colored glow of gas clouds, wispy tendrils of dark cosmic dust, and the rust-colored elephants’ trunks of the nebula’s famous pillars.

The dust and gas in the pillars are seared by the intense radiation from young stars and eroded by strong winds from massive nearby stars. With these new images come better contrast and a more precise view for astronomers to study how the structure of the pillars is changing over time.

By now, this description is just the surface of the ocean in understating the significance of their existence and importance. The discovery of Nebula traces back in the time of Ptolemy. The references of Nebula can be found in his literature.

Some references with the name of ‘a little cloud’ have also come forward which now is known to be directed towards what we know as Andromeda Galaxy. Astronomers from Arabic and Chinese civilization have also made observations of Crab Nebula in the around 11th century, and yet there are many more observations that can be listed.

The idea of Nebula may not be new, but still, astronomers are drawn towards the study of nebulae because of the enormous information that can be gathered from the study. Nebulae can help us to know about star formation, life cycle, evolution, and a lot more. Nebulae are waiting to unfold the answers to many questions we have been searching for.

Nebulae Are Classified Into Four Main Categories

H-II regions or diffuse Nebulae, Planetary Nebulae, Supernova remnant, and Dark nebula are four types of nebulae. These are further classified into subcategories. Before, when, their nature was not adequately understood, Galaxies and Star clusters were also classified as nebulae, but they are no longer part of the nebulae family.

The classification is based on various aspects such as shape, size, and what is it made up of. Many nebulae fall under the diffused nebulae category, it has a large size and no definite boundary. Some nebulae do not have the light of their own but reflect the light from other stars.

The remnant of lower-mass stars after stellar evolution forms planetary nebulae. The term planetary nebula is quite misleading. Initially, astronomers were not able to distinguish them from planets from which planetary nebulae got its name.

In a star, energy is produced by the nuclear fusion reaction. Nuclear fusion reaction expands a star and gravity contracts it. These two processes give stability to a star. When fusion reaction stops there is nothing to expand a star, and hence gravity is the only force left, due to which material gets attracted to the center.

This inward moving gas gets heated up resulting in the outward expansion from the core. And star explodes! Expanding a shell of gas forms a supernova remnant giving rise to nebulae.

nebula
M42 represents the location of Orion nebula in Orion constellation. Credit: Bob Moler’s Ephemeris Blog

Where To Look For Nebula In The Sky?

All these deep sky objects are cataloged, one of which is Messier Objects given by French astronomer Charles Messier. This catalog has 110 objects listed in it. Out of these many are Nebulae. Like M1 (Crab Nebula) in Taurus, M8 Lagoon Nebula in Sagittarius, and many more. However, most convenient of all to find is Orion Nebula (M42) in Orion constellation. You might be able to see it with naked eyes if you are fortunate.

Leave a comment