An Emission Nebula is a nebula that shines brightly naturally as compared to that of a Reflection Nebula that is lit up by light from an external source. An emission nebula is lit up by an internal source. Emission Nebulas are also known as Diffuse Nebulas and H II Regions. Diffuse Nebula can also refer to Reflection Nebulae as well. Britannica.
The nebula lights up due to the ionisation of the atoms in the nebula. Ionisation is the process by which a molecule or atom receives a negative or positive charge by gaining or loosing an electron caused by an external source such as Ultra-Violet or UV Light. An Ion is charged when the number of electrons do not equal the number of protons. North Western University
Emission nebulae can be located in regions of star formation where the stars emit the necessary light. They can also occur in planetary nebula which is when the dying star has exposed its core and has lit up the surrounding clouds of dust and gas. Evant Horizon
Emission Nebulae are normally but not exclusively red. This is because they contain hydrogen as their most common element. Space.fm By studying the nebula's spectrum, scientists and astronomers are able to determine a number of different things about the Nebula such as colours.
The Great Orion Nebula is one of the closest star forming region to Earth. It was speculated that the Sun was born in this nebula some five billion years ago. Earth would have been born in a similar sort of nebula if this one wasn't it.
The nebula is visible with the naked eye on a clear night. You'd only be able to see a blur with a good pair of visual aids.
The first recorded observation of this nebula was on 26th November 1610 by Nicolas-Claude Fabri de Peiresc, a French astronomer. It had not been spotted or mentioned about by previous astronomers such as Ptolemy, the Ancient Greek astronomer who devised many of the constellations that we used today. It was also not spotted by Al Sufi, the Arab astronomer or Galileo Galilei. It is possible but unlikely that it was not as bright before the first recorded observation. South Astrodel
It was added to the Messier catalogue at entry M42 and M43. Charles Messier believed that the two parts of the nebula were separate entities hence why they had two separate ids.
At the centres of these nebulas are stars being formed which are ionizing the cloud therefore illuminating the surrounding gas clouds. The constellation of Orion is one of the easiest constellations in the star to spot given the three stars in formation.
The picture below shows you where the nebula can be seen. The picture was generated using Stellarium free astronomy application.
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