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Solar spectrum

Solar spectrum

Before you is visible part of the solar spectrum in the range from 4000 to 7000 A (3𣛩29. Angstrom 3𣛩458. is an extra-systemic unit of length equal to 10 3𣛩299. 10 3𣛩300. m, i.e. 10 A = 1 nm). The image was created on the basis of digital atlas data obtained using Fourier transform spectrograph 3-3-3458. Observatory 3-3-3335. McMath-Pierce Solar Observatory located in the desert Sonora (state 3-3-3339. Arizona 3-3-3458., USA). This observatory is part of the Kitt Peak National Observatory complex ( Kitt Peak National Observatory ).

This is a continuous, continuous ribbon transition from red to purple, divided into 50 strips of 60 angstroms. The tape is dotted with vertical Fraunhofer lines - dark breaks in the rainbow of the solar spectrum, dividing the tape into separate "bricks". The presence of these lines is explained by the presence in the atmosphere of the Sun of elements whose atoms absorb light at certain frequencies. Therefore, in the places of the spectrum corresponding to these frequencies, dark dips are formed.

When looking at the Sun with the naked eye, we see it with a bright yellow or white hot disk. But another Isaac Newton by decomposing sunlight into the spectrum using a glass prisms 3-3-3458. , showed that in it are present, smoothly passing into each other, all the colors we see are from red to purple. In fact, the range of solar radiation, of course, is much wider. The visible light is Is the narrow part of electromagnetic spectrum extending from gamma radiation to multi-kilometer radio waves (More details can be found on our interactive 3-3-3361. Poster 3-3-3458.).

Solar spectrum

This diagram clearly shows how small a fragment of the entire variety of electromagnetic waves a person is able to see. Visible light lies between ultraviolet and infrared sections of the electromagnetic spectrum. Above is the frequency of hertz , that is, in fluctuations per second. For example, the frequency is 10 10 Hz corresponding to microwave range, means that the wave in one second manages to make 10 billion fluctuations. At the bottom of the gray ribbon are the wavelengths in meters. That is, the centimeter waves correspond to the same microwave range. Since the speed of light in vacuum is constant, the wavelength and its frequency are related: their product always gives the speed of light. In fact, light travels 300000000 m per second, and a wave makes 10 billion vibrations, which means that during one oscillation it travels 003 meters, or 3 centimeters, which corresponds to the range of centimeter waves. Image from ru.wikipedia.org

The sun shines without restricting itself to a narrow band of visible light: extra-atmospheric observations recorded radiation in the range from 0001 A to 1 km (the atmosphere absorbs part of the solar radiation). The Sun radiates both in X-ray, and in the infrared, and in the ultraviolet, and even in the region of 3-3-33101. radio waves .

Solar spectrum

Graph of solar radiation power (in watts per square meter) versus wavelength. External, translucent outline , demonstrates the spectrum of solar radiation in space, outside the earth's atmosphere. He leaves, gradually reducing the intensity, far to the right - to values of millions of nm. Almost all the energy emitted by the Sun is concentrated in this range. Further, to the kilometer-long radio waves mentioned above, the intensity decreases sharply. Internal circuit - this is a spectrum at sea level, taking into account the absorption of part of the radiation by the atmosphere. An iridescent vertical line corresponds to visible light. Image from fondriest.com

The solar spectrum, as seen in the main photo, is continuous, but overlaps with dark dips of the absorption lines. What does it mean? Any substance, as we know since the time of Democritus 3-3-3458. consists of atoms. The atoms themselves, which Democritus did not know, consist of a nucleus and electrons and have their own 3-3-3129. energy levels 3-3-3458. - fixed energy values that can be possessed by electrons located around the nucleus. The transition of an electron from level to level is accompanied by the emission (or absorption) of energy in the form of light.

Consider this process as an example of a hydrogen atom. Transitions can occur from the second level to the first, and from the fifth to the third. All possible transitions from overlying levels to any one are called spectral series . So, transitions to the first level are Lyman series , on the second - Balmer series etc. During these transitions, light quanta (3-3-3139. Photons 3-3-3458.) Of a certain frequency and wavelength are emitted.

Solar spectrum

Spectral series of hydrogen. The wavelength values corresponding to the photon emitted during the transitions between levels (3-3-33335. N 3-3-33336.) Are signed on the diagram. For example, in the Balmer series, when moving from the sixth level to the second, a photon with a wavelength of 410 nm will be emitted. Image from ru.wikipedia.org

Photons in the visible range are emitted only during transitions from upper levels to the second level. All transitions to the first level (Lyman series) are in the ultraviolet region, to the third and higher - in the infrared. The greater the photon energy, the greater its frequency and, accordingly, the shorter the wavelength. The transition from the third level to the second radiates the least energy, since the difference between such close levels is small. Therefore, the photon is the lowest energy for this series and with the longest wavelength - 6565 A (or 656.5 nm). It gives a red band in the hydrogen spectrum (since 6565 A is the red wavelength). 揊alls from higher levels will produce photons with an ever greater shift to the violet part of the spectrum.

Solar spectrum

The electrons inside the atom "jump" from the overlying levels to the second, radiating the energy difference in the form of a photon of a certain frequency. White arrows shows transitions from the third, fourth, fifth and sixth levels. Below the resulting spectrum of the hydrogen atom is shown, the wavelength (in angstroms) is indicated below it. The bottom image is from grotrian.nsu.ru

Emission spectra 3-3-3458. atoms therefore have distinct distinct luminous lines whose frequency corresponds to the frequencies of the emitted photons. This spectrum is called ruled . In 1859 the physicist 3-3-3191. Gustav Kirchhoff and chemist Robert Bunsen showed that emission spectra 3-3-3458. atoms of various substances correspond to different sets of lines in the spectra. In other words, the line spectrum of each element is unique, like a fingerprint, and by this fingerprint it can be identified. So appeared spectral analysis of 3-3-3458. .

Thanks to these unique portraits of atoms, it became possible to detect the presence of matter in any body, a mixture of liquids or gases, the spectrum of which we have received and can consider. But in order to have a linear spectrum, a substance must consist of such separate atoms, that is, be a rarefied atomic gas. For example, in chromosphere 3-3-3458. (parts 3-3-3203. atmosphere 3-3-3458.) The sun is present in the form of a very rarefied gas, ionized calcium.

Solar spectrum

Visible line spectrum of calcium radiation. Image from grotrian.nsu.ru

If a substance consists of molecules, and not of individual atoms, its spectra become more 搒meared, consisting of wide bands. Due to the interaction of atoms, new energy levels with close energies appear in the molecules, and the picture from them looks like wide bands. In the same case when a substance is in a solid or liquid state or is a gas under high pressure, its molecules constantly interact and no longer generate levels, but entire energy zones, the transitions between which and inside of them give 3𣛩225. continuous spectrum 3-3-3458. radiation.

Solar spectrum

Types of emission spectra: a) ruler, atomic : consists of individual narrow lines. b) molecular : molecular gas bands consist of many narrow bands, the same as in the line spectra, they are simply very densely arranged to each other. c) solid: radiation occurs at all frequencies 3-3-33463.

Here is the same continuous spectrum of the Sun. Dense, liquid or solid bodies possess a continuous spectrum, moreover, bodies are hot, heated enough so that the thermal interaction of their molecules creates multiple energy zones. To describe such thermal radiation, physicists (namely, the same Gustav Kirchhoff) introduced the concept of absolutely black body (ABP) - a kind of abstract ideal object that returns all the energy received only in the form of thermal radiation. A completely black body does not reflect anything from the radiation incident on it - not a single quantum in any range. Everything that falls on him goes to increase his internal energy. When heated, the blackbody begins to radiate itself, giving the very continuous spectrum of heated bodies. The color temperature indicated on some lighting fixtures, for example, on lamps (6000 K - 揷old white light, etc.) is the temperature of the blackbody at which it emits light of the same color (tone) as the marked instrument (K, 3-3-33257. kelvin 3-3-3458. - the temperature scale proposed by 3-3-33259. by Lord Kelvin 3-3-3458., the beginning of which coincides with 3-3-33261. absolute zero 3-3-3328., and the step is a degree on the Celsius scale).

In 2014 an artificial material made of carbon nanotubes was created, which is closest in its properties to a hypothetical blackbody - vantablack . In the visible range, it absorbs 99965% of the light incident on it (see the picture of the day 3-3-33267. The blackest material is 3-3-3458.). Last year, was created. an even blacker material with an absorption coefficient of 99995%, which is 10 times blacker than vantablack.

Our sun in its spectrum is very close to the radiation of the blackbody heated to a temperature of 6000 K. However, the nature of its radiation is completely different than that of a solid heated body. Responsibility for the image of the Sun, as we see it, bears photosphere - part of the atmosphere of the Sun, where a continuous spectrum of solar radiation is formed. This is a small layer with a depth of about 300-400 km. The photosphere is not a solid at all - it is a gas, hot and very rarefied (the density of the photosphere is 3-3-33275. It is 3-3-3328. On average 10 3-3-33299. -9 3-3-33300 g /cm 3-3-33299. 3 3-3-33300. - One billionth of a cubic centimeter, in million times less than air density). This gas consists of hydrogen (74%), helium (25%), as well as oxygen and other elements (iron, carbon, magnesium, sulfur and others) that are in a gaseous state, which account for about 1% of the total mass. Nevertheless, the spectrum of its radiation is not at all linear.

Solar spectrum

The radiation spectrum of the Sun and the spectrum of a completely black body. Solid lines 3-3-33462. shows the observed data, hatched - spectrum of the blackbody at the indicated temperature. In the region of visible and infrared radiation, the experimental data are in good agreement with the blackbody line at a temperature of 6000 K (in the long-wavelength region, the temperature is 10 3𣛩299. 4 3𣛩300. K and 10 3𣛩299. 5 3𣛩300. K). Image from astronet.ru

In the photosphere there are metals that are very easily 3-3-3309. 3𣛩458 are ionized. that is, they lose electrons from the outer shells, weakly connected with the nucleus. The temperature of the photosphere is not enough to ionize helium or hydrogen, but the electrons of metals, 搘arming up, get enough energy to leave the metal atom and go into free flight. Crashing into the hydrogen atoms, they 搒tay there, giving rise to a very curious phenomenon - negative hydrogen ions (see 3-3-33311. Hydrogen anion 3-3-3458.). When 搒ettling into free energy levels, electrons emit the difference between their former energy and the energy of their newfound level in the hydrogen atom in the form of a quantum of light.

This process is similar to the radiation described above during transitions between levels, however, since an electron arrives from the outside and can have absolutely any energy, and not just strictly equal to the energy of the overlying layers, the radiation does not occur in narrow linear ranges corresponding to differences in the values of the transition energy, but in any range. In other words, if the transitions inside the same hydrogen atom give, as we saw in the image of its spectrum, a set of emissions at the same set of frequencies, then the quantum radiation from the 搇anded external electron can be anything and give a line in any part of the spectrum .

However, the atom remains in this state for long. A hundred million times per second, it emits photons, transferring electrons to lower energy levels, collides with new electrons, absorbs photons, and so on. Life is in full swing: a hydrogen atom constantly emits and absorbs photons, loses electrons, collides with new ones, radiates again, but in a different place in the spectrum. Due to the abundance of such radiation events, as well as due to the huge number of atoms, all wavelengths in the radiation spectrum are occupied. The photosphere emits over the entire range, thus forming a continuous spectrum.

As we have already said, an atom can not only emit photons, but also absorb. And besides the emission spectra there are also absorption spectra of that look like dark dips (stripes) in a solid beautiful spectrum. They arise when the same atoms themselves find themselves in a stream of light. Then flying photons excite electrons and 搕hrow them up, to high-energy levels. The electrons stay there for a short time and jump down again, but they re-radiate in all possible directions indiscriminately, which is why much less rays will travel in the direction of the original light beam with this wavelength, and the spectrum will fail at this point.

Solar spectrum

The spectrum of sodium. (a) - emission, or radiative: two bright bands against a black background, 589.0 nm and 58959 nm (the so-called "sodium doublet"); (b) - absorption (absorption): the same two bands at the exact same frequencies, but these are already black bands of the absence of light against the background of a continuous spectrum. Image from the website of the University of Wisconsin astro.wisc.edu

It is such dips in the main image that divide the continuous colorful stripes of the solar spectrum into separate "bricks". Discovered them in 1802 the English chemist William Woolaston , though not giving it any meaning. And here is the German physicist Joseph Fraunhofer gave and took in 1814 for their study. He described more than five hundred such dark 揹ips in the solar spectrum, and they are now called Fraunhofer lines.

These lines give the elements that make up the photosphere, and it is curious that those whose presence is very small, for example, the same metals, make a big contribution. This is due to low ionization potentials metals: their external electrons, weakly bonded to the nucleus, require a few times less energy than hydrogen to transfer to another energy level and, accordingly, to absorb a quantum of light. To absorb hydrogen in the visible spectrum, it is necessary to have an electron not at the ground level, but at the second. As we said, electrons, descending from higher levels to the second, emit photons in the visible range. This is a series of Balmer. And vice versa, in order to absorb a photon in the visible spectrum, an atom must have an electron at this second level so that the photon energy is even enough to 搕hrow the electron at one of the 搖pper bounds. But in order to have an electron on the "second floor", the hydrogen atom must be excited which is difficult to achieve in the photosphere: the temperature is too low. Therefore, the number of such excited and therefore absorbing hydrogen atoms is extremely small - relative to their total number, of course.

Thus, at the temperature of the photosphere, hydrogen remains neutral (with the exception of the negative ions described above, but only one hydrogen atom per hundred million becomes such, and they contribute to the radiation spectrum of the photosphere, not absorption), and metals and other elements of the photosphere are ionized, absorbing photons for this, and almost all of their atoms participate in the creation of dark bands of the absorption spectrum (for a more detailed conclusion, see news 3𣛩357. Cecilia Payne is the mistress of the stellar kitchen 3𣛩458. in the section 揟he Sun: Calcium and Hydrogen, 揈lements, 2705 .2020).

Solar spectrum

A simplified version of the main image: absorption lines in the solar spectrum. Each of these dark stripes corresponds to an element. In the center is visible lines doublet sodium. Right - H-? - the hydrogen line dominating in the visible part of the spectrum (the same transition from the second energy level to the third with the absorption of a photon with a wavelength of 656 nm). Left leave a trace of calcium atoms that have lost one electron (Ca II ions); they emit and absorb light at several wavelengths, in particular, at 396.8 nm and 393.3 nm in the violet region of the spectrum. These are the Ca-H and Ca-K lines (stronger, that is, more intense, lines denoted by letters from A to K) of once-ionized calcium. Other black lines correspond to the absorption spectra of other elements; to establish which, according to letter designations, corresponding to Fraunhofer lines. Image from ru.wikipedia.org

Since the time of Fraunhofer, who discovered and described over 500 absorption lines, their number has grown to more than 25000 - this, of course, is already in the whole spectrum, not only in the visible part. Based on these spectral dips, conclusions can be drawn about the structure and composition of the Sun (for example, helium was discovered, named after the Sun).

Solar spectrum

Enlarged portion of the main image. This is what the familiar doublet of sodium looks like. The wavelength (in angstroms) is signed under the spectral tape. The name of the element to which the line belongs is above it. You can view the entire spectrum of the Sun in detail, where each absorption line is signed by downloading a file of 3-3-33401. reference

Studying the Sun in various electromagnetic ranges allows us to draw conclusions about its activity and the processes occurring there; in fact, this is the main way to obtain information about the energy transformations taking place in our star. For example, in the ultraviolet, 3𣛩409 motion patterns were obtained. plasma accompanying reconnection of magnetic lines in the atmosphere - the main candidate for an explanation of the elevated temperature solar corona (see problem 3-3-33415. Magnetic reconnection 3-3-3458.).

Solar spectrum

[i] Left - frame from movie shooting. The sun in the x-ray range, made by the Japanese satellite Hinode in January 2012. The surface of the Sun in X-rays almost does not radiate, so it looks like a black sphere in the picture. X-ray radiation is produced by the solar corona, heated to millions of degrees (red 揻og), and 3-3-33441. solar flares (small bright spots). Right - image in ultraviolet at a wavelength of 171 A, obtained Observatory of Solar Dynamics also in 2012. The active regions flashes and plasma loops along the lines of magnetic fields look bright. Photo from the site nasaviz.gsfc.nasa.gov . Both frames are initially monochrome and colorized. It is believed that the human eye perceives better the contrast between differently colored objects 3-3-33463.

Absorption lines help to obtain information about the solar structure from different layers. The physical characteristics of the solar atmosphere and, accordingly, the state of the elements change with height, which affects their spectra. The absorption lines allow us to consider the Sun without blinding exposure of the photosphere - for this we need to use a filter that has a narrow passband precisely at the frequency of the absorption line. So consider the light coming from the chromosphere, usually invisible in the bright light of the photospheric layer.

Image from noao.edu .

Vasily Derevyanko

20 棹睃 2020 /
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