Interstellar matter

[x ī ng jì wù zhì]

The general term of matter and radiation fields between galaxies and stars

Interstellar matter (abbreviated as ISM ）， Is present in Galaxy And stars radiation field (ISRF). Interstellar matter in astrophysical accuracy It plays a key role because it is an intermediate role between galaxies and stars.

Stars form in molecular clouds with high interstellar material density, and pass through Planetary nebula , Constant Stellar wind and Supernova Get energy and materials replenished. From another perspective, the interaction between stars and interstellar matter can help measure the Consumption rate , that is Star formation The time of the living glory period.

Chinese name: Interstellar matter
Foreign name: ISM

Features: Nonuniformity
Form Shape: Planetary nebula and stellar wind

catalog

structure

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Matter between stars, including Interstellar gas ﹑ Interstellar dust And all kinds of Interstellar cloud , can also include the interstellar magnetic field and cosmic ray 。 Interstellar matter Total mass About Galaxy 5% of the total mass. The average density is 10/cm, equivalent to average The density is 1 per cubic centimeter hydrogen atom The density range is 10~10/cm. This density is far from being reached in laboratories on earth vacuum degree (At present, the maximum vacuum degree in the laboratory is 10 ^ - 7 Mm mercury column , equivalent to 32000 particles per cubic centimeter). The temperature of interstellar matter varies greatly, from several K to ten million K.

The distribution of interstellar matter in the Milky Way is characterized by: Nonuniformity The density of interstellar matter in different regions can vary greatly Interstellar gas And dust as particles Number density When it exceeds 10 to 10 particles per cubic centimeter, it becomes an interstellar cloud, and the density between clouds is as low as 0.1 particles per cubic centimeter. Interstellar matter and young stars are highly concentrated Galactic surface , especially in Swivel arm Medium.

Interstellar gas includes gaseous atoms, molecules, electrons and ions, and its chemical composition can pass through various electromagnetic waves Spectral line Is calculated. The results show that the Element abundance Compared with those derived from the sun, stars and meteorites Cosmic abundance Similarly, hydrogen is the most, followed by helium, and other elements are very low. The second row of the following table is the key Logarithmic scale The third row of the listed cosmic abundances is the sun and Ophiuchus ζ Star The fourth line is the difference between the abundance of interstellar gas elements. In interstellar gas, 90% is hydrogen, about 10% is helium, and other elements, such as lithium, nitrogen, oxygen, are less than 1% in total. The interstellar gas depends on the main elements - hydrogen atom Of Existing form It is divided into ionized hydrogen region and neutral hydrogen region.

Interstellar dust It is a solid particle with a diameter of about 10 (or 10) cm, dispersed in interstellar gas. The total mass of interstellar dust accounts for about 10% of the total mass of interstellar matter. Interstellar dust may be composed of the following substances:; Water, ammonia methane Waiting Ice ； silicon dioxide ﹑ Magnesium silicate ﹑ Ferric oxide Isominerals graphite Grain; A mixture of the above three substances. Interstellar dust scattering starlight , weakening the starlight; This phenomenon is called Interstellar extinction 。 The interstellar extinction increases with the increase of wavelength, and the color of starlight also turns red; this phenomenon is called Interstellar reddening 。 Interstellar dust Interstellar molecule Its formation and existence play an important role. On the one hand, dust can block starlight Ultraviolet radiation No interstellar molecules dissociation On the other hand, solid dust as a catalyst can accelerate the formation of interstellar molecules.

Interstellar matter (abbreviated as ISM ）Is the matter and radiation field (ISRF). Interstellar matter in astrophysical accuracy It plays a key role because it is an intermediate role between galaxies and stars. Stars form in molecular clouds with high interstellar material density, and pass through Planetary nebula , Constant Stellar wind , and Supernova Get energy and materials replenished. From another perspective, the interaction between stars and interstellar matter can help measure the Consumption rate , that is Star formation The time of the living glory period.

By Earth's standards, interstellar matter is extremely thin plasma , gas, and dust are ions, atoms, molecules, dust electromagnetic radiation 、 cosmic rays A mixture of,, and magnetic fields. The composition of matter is 99% gas and 1% dust, which are full of interstellar space. This extremely thin mixture has a typical density of only hundreds to hundreds of millions of particles per cubic meter. According to the results of early nuclear synthesis, the composition of gas should be 90% hydrogen and 10% helium in quantity, and other trace "metals" (in astronomical terms, elements other than hydrogen and helium are metals).

observation

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The observation of interstellar matter can be carried out in different electromagnetic wave bands. For example, in 1904, in the spectral binary Orion δ Of Visible spectrum The interstellar ions whose displacement does not change according to the orbital motion of binary stars are found in Absorption line The existence of interstellar ions is confirmed for the first time.

In 1930, it was observed that the distant starlight turned red Color index Bigger (i.e. interstellar reddening), first confirmed Interstellar dust The exists of. In 1951, through observation Galaxy within Neutral hydrogen 21 cm spectral line , confirming the interstellar hydrogen atom A large number of. In 1975, using Artificial satellite Ultraviolet spectrometer Observing more than 100 stars Interstellar extinction Relation with wavelength, it is known that absorption peak 。 In 1977, the interstellar observation X-ray Band, finding ο Ⅶ 21.6 A (0.57 K Electron volt ）Of Spectral line Confirm that there is high-temperature gas with a temperature of 10~10K.

The relationship between interstellar matter and stellar matter, according to modern stars Evolutionary theory It is generally believed that the early stars were formed by the accumulation of interstellar matter, and the stars sent the matter back by various eruptions, ejections and losses Interstellar space 。

nature

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When we mention Cosmic space We often think that there is nothing there, dark and silent vacuum. In fact, this is not completely right. The vast space between stars may be silent, but far from being a real "vacuum", there are various substances. These substances include Interstellar gas , dust and particle flow, which are called "interstellar matter".

Interstellar matter is closely related to the evolution of celestial bodies. Observations have confirmed that interstellar gas is mainly composed of hydrogen and helium, which is the same as the composition of stars. People even suspect that stars are formed by "condensation" of interstellar gas. Interstellar dust They are small solid substances, including carbon compounds oxide Etc. The distribution of interstellar matter in space is uneven. Under the action of gravity, the gas and dust in some places may attract each other and become dense, forming a cloud. People call them "nebulae" figuratively. According to the form, Galaxy The nebula in can be divided into Diffuse nebula 、 Planetary nebula And so on.

Development history

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The term "interstellar" first appeared in 1626 Francis Bacon Used in his manuscripts. He wrote: "The Interstellar Skie.. Has.. So much Affinity with the Starre, that there is a Rotation of that, as well as of the Starre. "(Sylva § 354 – 5). The natural philosopher Robert Boyle mentioned in his discussion in 1674:" Space in the interstellar space hedonism The essence of interstellar matter was not noticed by astronomers and scientists until the 19th century.

In 1862, Paterson wrote: "The vibration or vibration caused by the air flow is ether It is caused by filling in the air. "(Ess. Hist.&Art 10) The concept of the ether continued into the 20th century, and some characteristics were described. In 1912, William Henry Pickering Write: "Cause interstellar absorption The medium of is simply ether, which will selectively absorb. As Kaptan pointed out, there are some gas characteristics, as well as some free gas molecules, which may be constantly released by the sun and stars "

In 1913, Norway "From our point of view, Hypothetical space The whole is full of electrons. The leap of various electrons and ions seems to be the result of nature, because we assume that Stellar system In the process of evolution, charged particles are constantly thrown into space. So everywhere in the universe, that is, in the "empty" space, we can find that there is a lot of matter, not only in the solar system And nebulae should be reasonable See "Polar Magnetic Phenomena and Terrella Experiments＂, in The Norwegian Aurora Polaris Expedition 1902-1903 (publ. 1913, p.720)〉.

In 1930, Samuel L. Thorndike wrote: "It is hard to believe that the huge space between stars will be completely empty, and the aurora of the earth may be from the sun charged particle , from solar radiation It is generated by the excitation of particles. If millions of other stars also emit ions, if there is no doubt, then Galaxy There can be no absolute vacuum between them. "

problem

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Due to the existence of a large amount of interstellar matter, the light emitted by the celestial body is absorbed and weakened, which is called Interstellar extinction 。 In addition, the light of celestial bodies is also scattered, making the light red, which is called Interstellar reddening 。 Interstellar reddening needs to be corrected in stellar research.

The interstellar world generally refers to the vast space between planets (including the Earth), stars and galaxies, from hundreds of millions of kilometers (between planets) to light years (between stars) to infinite distance. It is usually filled with innumerable interstellar materials, and the temperature is about 200 degrees below zero. Including multiple universes Parallel universe And high dimensional space and its infinite extension

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