The nebula understands simply the clouds of gas and dust in space. Since astronomical telescopes were previously poor, astronomers have identified and named a number of nebulae that are in fact not dust clouds but an entire galaxy. So how is the nebula understood in detail today? How many types of nebulae are known?
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For example, the M31 nebula is often called the nymph (Andromeda), which is essentially not a nebula as defined above but a galaxy, the Andromeda galaxy is the largest galaxy in their local galaxy cluster. me. Our Milkyway galaxy is only the second and third largest, a galaxy also misunderstood as nebula - M33.
According to the new concept, the nebula may be clumps of dust gathered together by gravity (mass is not enough to form a star or a large object) as mentioned above, it may be matter. released by the end of a star (nova and supernova).
Diffuse nebula (Diffuse nebula)
This is the most common nebula. Diffuse nebulae are dust clouds with no clear boundaries, they are usually divided into two types: emission nebula and reflection nebula.
- Emission nebula: the type of nebula whose gas and dust constituents near large, strongly excited stars lead to ionization and light emission. The temperature at the center of these nebula can be up to 8000 - 10000K, diameter of several tens to several hundred LY (Light Year - light year). Some of these nebulae are relatively well known as the Orion Nebula (M42), the Eagle Nebula (Eagle Nebula - M16).
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Eagle Nebula / M16.
- The reflection nebula: is the nebula that gets light compared to the surrounding due to reflections of light coming from nearby stars. This nebula consists of gases and dust that reflect light well. The light of this nebula is not as strong as that of emitted nebulae. However, this nebula has persistent photoluminescence (because light is reflected light) while the nebula is emitted, the spectrum has emission lines (due to stimulated emission).
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Pleiades / M45 Nebula.
Some nebulae are so transparent and dense that they can obscure the light from background radiation or reflective nebulae (such as the Horse Head Nebula) or prevent background stars (like Bao Than nebula in the constellation Southern Cross). In the sky, they appeared as black shadows due to the light from the stars being absorbed by most of the gas. The nebula is then called the dark nebula.
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The Horsehead Nebula in the constellation Orion is a dark nebula.
Planetary Nebula (Planetary Nebula) and supernova
Planetary nebulae or planetary cloud is a type of photoluminescent nebula containing the glowing ionized shells generated by red giants in their final stages. This is a relatively short-lived phenomenon, which takes only a few tens of thousands of years, compared with the normal life of billions of years of a star.
Supernova , or supernovae , are some kind of stellar explosions that make very bright objects mainly composed of plasma that flares up for a short time, apparent star levels that increase dramatically billions of times, then decrease. gradually over a few weeks or months. The total energy output reaches 1044J. Absolute star level can reach -20m.
The sa os exist by consuming the fusion energy source inside it to create a balanced force with gravity. When there is nothing left to consume, gravity will pull every material into the mind causing the star to collapse and end with a supernova explosion . The explosion had a tremendous amount of heat, igniting all matter and creating ultra-hot and brilliant plasma. Based on the luminous intensity they are recorded as a supernova or supernova.
With massive stars, the part thrown into this space is scattered and forms a large cloud of dust and gas surrounding the star, emitting radiation in strong X and radio bands, called remnants of a supernova explosion.
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Super Crab / M1 Nebula.
The Sun Nebula is a gaseous cloud from which our Solar System is thought to have formed. This Sun Nebula hypothesis was first introduced in 1734 by Emanuel Swedenborg. Another similar model was developed by Pierre-Simon Laplace in 1796.
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The formation of the Solar System.
With the help of amateur telescopes or a binoculars, it is possible to observe some nebulae already located.
Some nebula images
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Man Khoi Nebula has a nearly circular shape located at the edge of a giant molecular cloud in the constellation of the Unicorn.The nebula is located about 5200 light-years from the Sun.
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The Witch Nebula is located in the constellation Cepheus about 7000 light years from the earth.This nebula was discovered by Caroline Herschel in 1787. Her brother, William Herschel, discovered infrared light in 1800.
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Nebula Sand Clock is a young planetary nebula located in the constellation of Shangshan, 8000 light-years from Earth.
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Tarantula Spider Nebula lies in the galaxy of the Large Magellanic Cloud.This nebula is about 180,000 light-years away.Suppose the Tarantula Spider Nebula is about 1500 light-years away (like the Orion Nebula), it will cover about half of the Earth's sky.
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The Boomerang Nebula is the coldest place in the universe.In 1995, using large Swedish telescopes in Chile, astronomers discovered it had a negative temperature of 272 degrees Celsius, and was only 1 degree warmer than absolute zero (the lowest limit). of temperature).
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The reason is that the nebula is named California because this cosmic cloud coincides with the shape of California state map on the west coast of the United States and about 1,000 light-years from Earth.
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The Heart Nebula is in the constellation of the Earth and about 7500 light-years from Earth.
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The Boomerang Nebula is the coldest place in the universe and the Jellyfish Nebula is 10,000 times hotter than the sun and 5000 light years away.According to scientists, this is what remains from the fireballs released by a shooting star thousands of years ago.
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The Crescent Nebula is made up of a layer of dust gas surrounding a very bright star in the center.One theory is that the nebula was formed 250,000 years ago.