An planetary nebula It is simply that solid emission nebula in a radiant envelope in scattering of plasma and ionized gas, fired during the stage of the large asymptotic branch crossed by the red giant stars in the last moments of their lives.
Origin Of The Name Of The Planetary Nebula
The name originates from the fact that its researchers, in the XNUMXth century, noticed that its appearance was similar to the gigantic planets seen through the visual telescopes of the station, although they certainly do not have any correlation with the planets.
It is a relatively brief phenomenon in knowledge astronomical, which persists on the order of tens of thousands of years (the lifetime of a star usual spans ten billion years).
Also, at the end of the life of the stars As they reach the red giant stage, the outer layers of the star are emitted due to throbbing and sharp space winds. After the exclusion of these layers, a small core of the star remains, which is very hot and glows penetratingly. In this sense, the ultraviolet illumination exposed by this axis ionizes the outer layers that the star had cast.
Likewise, planetary nebulae they are objects of great hierarchy in astronomy, due to the fact that they play a transcendental role in the chemical evolution of galaxies, restoring heavy metals and other products of star nucleosynthesis (such as carbon, nitrogen, oxygen and calcium). Furthermore, it has been proven that these processes are closely related to the dynamics of the galaxies and its evolution.
En galaxies distant, planetary nebulae are the ideal objects from which advantageous information about their chemical constitution can be obtained.
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In the same way, the images acquired by the telescope hubble space have shown that many planetary nebulae display highly complex morphologies. Only about a fifth of them exhibit more or less round shapes. The element causing this wide range of shapes is not yet well understood, however it is thought that central binary stars, stellar winds and magnetic fields could play a substantial role.
Stage of a Planetary Nebula
Once the Planetary Nebula stage has begun, the ejected gases travel at speeds of several kilometers per second in relation to the central star. It changes into the remnant (white dwarf) of the first red giant star, and is made up of carbon and oxygen with their electrons decayed, with insufficient hydrogen, since most of it was removed in the previous giant asymptotic branch stage. However, its evolution may make it interesting in the context of star formation.
As the gas diffuses, the center star appreciates an evolution in two stages: first, reducing as it heats up, carbonizing the hydrogen from the outer layer to the core.
In this phase, the central star maintains a constant brightness, finally reaching temperatures of around 100 K. In the second part, the star tolerates a freezing process when the outer hydrogen shell has been exhausted, wasting some mass at the same time.
The remainder diffuses its energy but the smelting reactions cease to take place, since a lot of mass has degenerated and what remains is not enough to reach the essential temperatures to release this type of process. The star freezes in such a way that the ultraviolet radiation diffused is not sharp enough to ionize the surrounding gas. Therefore, the study of these stages contributes to a better understanding of the life cycle of stars.
Finally, the Planetary Nebula stage expires when the gas cloud recombines, leaving the plasma state and becoming invisible. For an original Planetary Nebula, the tenure of this period is about 10 years. The stellar remnant, a white dwarf, it will persist without tolerating hardly any changes in its progress, freezing very gradually.
5 Physical Characteristics Of The Planetary Nebula
Some of the physical characteristics that this type of nebula, are:
1. Shapes
planetary nebulae they show widely disparate shapes, from anomalous and complex-looking to almost celestially round. However, the latter barely reach nearly 20% of its total.
2. They are classified according to their shapes
Most of the planetary nebulae can be classified according to their representation, that is, they can be spherical, elliptical, or bipolar (noted from the Earth, since the shape depends on the angle from which they are observed). However, to a lesser extent there are also others with different aspects, such as annular, quadrupolar, irregular, helical, and other physical shapes. This diversity in shapes also reflects the complex physics in the context of galactic formation.
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3. Diameter
An original Planetary Nebula has about a diameter of a light year, and is made up of highly dispersed gas, with a consistency of between 100 and 10 particles per cubic centimeter. Obviously, these characteristics vary considerably compared to those larger stars.
On balance, the Earth's atmosphere comprises 2,5 × 1019 particles per cm3. The nebulae younger they have higher consistencies, sometimes of the order of a million (106) particles per cm3. As the nebula decays, the density decreases due to its spreading out into space.
The radiation expressed by the central star ignites the gases to temperatures of about 10 K.000 In general, in the areas closest to the star, this gas can reach a much higher temperature, around 39-16 K. 000 The effective volume in the vicinity of the star central it is often filled with very hot gas, close to 1 K. This gas is caused on the surface of the star in the form of a very fast space wind.
4. Differences
Planetary nebulae can be uneven according to their limiting component, which can be matter or lighting. In the first case, there is not enough matter in the nebula to permeate all the ultraviolet photons expressed by the star, and the perceptible nebula comes across totally ionized.
In the latter, the star does not express enough ultraviolet photons to ionize all the gas near, spreading out from the star an ionization phase and leaving the outermost regions neutral, so not all the gas existing in the surroundings can be seen, since this gas is so cold that it pronounces illumination in the infrared range) .
5. Distribution
There are about 3000 known planetary nebulae in our galaxy. This is a small number compared to the total number of ; there is about one planetary nebula for every 60 million of them. This corresponds to their short lifetime in relation to the stars. It is observed that approximately three new planetary nebulae are formed each year. The distribution of these nebulae also allows us to study the history of the stars in our galaxy.
They are usually located in the plane of the Milky Way, being more exuberant next to the galactic center.
The study of the Planetary Nebula in open clusters allows us to determine with greater precision the mass limit between the ancestors of white dwarfs and neutron stars, located between 6-8 solar masses.
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On the other hand, when we mention this natural space phenomenon we must consider that it will always be related to the beginnings or beginnings of new stars and in this case, the Planetary Nebula has a lot to do with the origin of stars. stars red giants.
