To refer to the Crab Nebula , it is important to know what a nebula is . This type of structure is a giant cloud of dust and gas found in space. Some nebulae come from gas and dust expelled by the explosion of a dying star , such as a supernova . Other nebulae are regions where new stars begin to form, which is why some nebulae are called ” stellar nurseries .”
What is the Crab Nebula?
The Crab Nebula is the remains of a supernova explosion , it is one of the most studied and observed space objects as it represents a very useful source of radiation for studying the different celestial bodies that exist in outer space .
Nebulae are made primarily of hydrogen and helium . The dust and gases in a nebula are widely dispersed, but gravity can slowly begin to gather together clumps of dust and gas. As these groups get bigger and bigger, their gravity gets stronger and stronger.
History of the Crab Nebula
This nebula was first observed by the Englishman John Bevis in 1793, who is considered to be its discoverer, despite the fact that it had already been seen and recorded by Chinese and Arab astrologers , who had said that it was like a star that could be to observe during the day, and that it could be seen for a continuous period of 22 months , day and night.
William Parsons , 3rd Earl of Rosse, observed it in 1840 and gave it the name of the Crab Nebula, since when he made a drawing of the nebula, it looked like a crab. At the beginning of the 20th century, several photographs of the nebula indicated that it was expanding and it was determined that it had formed some 900 years ago . Analysis of historical documents proves that the supernova that created the Crab Nebula occurred in April or early May 1054 , reaching its maximum brightness in July, being brighter than any other celestial object at night with the exception of the moon.
The Crab Nebula was first observed by John Bevis in 1731 and was rediscovered in 1758 by Charles Messier while observing the passing of a bright comet. It is believed according to various studies, that it originated 900 years ago.
The main characteristics of the nebula are as follows:
- It is a glowing mass of gas and dust.
- It is oval in shape that measures approximately 6 arc minutes in length and is 4 arc minutes wide.
- It has a density of around 1,300 particles per cm³.
- The filaments that form it are remnants of the atmosphere of the progenitor star, and are composed of helium and ionized hydrogen, carbon, oxygen, nitrogen, iron, neon and sulfur.
- It expands at a speed of 1 800 km / sec.
- The temperature of the filaments that make it up is approximately 11,000 and 18,000 K.
- Its center has a diffuse blue region.
- It is a nebula of the plerionic type, this means that it obtains its energy from the rotation of the pulsar and not from the material that has been thrown into the interstellar medium during the supernova explosion.
- In the center of the Nebula two stars can be observed, and it is thought that one of them was the one that caused the nebula.
- It is approximately 6 light years in radius.
- It is also known as the M1, NGC 1952, Taurus A, and Taurus X-1.
Where is the Crab Nebula?
The Crab Nebula is located in the constellation of Taurus , which means that it is about 6,500 light years from Earth.
Among the known objects in this nebula, we know that the core of a star died so violently that it became a pulsar. A pulsar is a neutron star that is rotating at great speed. It has a mass very similar to that of the Sun, with the difference that its radius is a few kilometers. The Crab pulsar rotates on its axis at a tremendous speed of 30 revolutions per second and also has a magnetic field of 100 million teslas. By having a very intense magnetosphere , it is capable of converting the object into an emitter of electromagnetic radiation, which, due to the rotation of the star on its axis, can be seen from our planet as brief periodic pulses, and this is the reason. for which it is given this name.
It is important to know that many of the observations that have been made in the nebula suggest that the Crab pulsar has a very complex magnetic field and that it has four poles instead of two, like other nebulae. It is also believed that the main radio pulse is emitted from a plasma cloud that is located on the surface of the star.
It is widely used by astronomers to calibrate x-rays and flux density, as it provides a fairly strong signal that is used to check the timing of X-ray detectors.
In the center of the Crab Nebula is located the core of the star that exploded and that gave rise to the nebula, which is a body that rotates at great speed. Perhaps one of the things that has been observed and that is the most surprising is that the neutron star emits a flash of radio waves that go in the direction of the Earth with each rotation , like a maritime lighthouse, 30 times per second.