Redshift in the spectra of stars. Expansion of the universe and redshift. Redshift and Doppler effect

For the first time, the phenomenon of a shift of spectral lines in the spectra of stars at spectral analysis was noticed by the Frenchman I. Fizeau in 1848 and he proposed to explain this phenomenon using. The essence of the phenomenon is simple: the greater the red shift in the spectrogram of an object, the faster the object moves away from us. In general, when moving away, the light from an object “reddens”, and when approaching, it “shifts” towards the violet side. Integers also have a red shift. Thanks to redshift, the rotation of galaxies was discovered. At one end, the light from the galaxy is red-shifted, and at the other, purple-shifted. Accordingly, it rotates! Distant galaxies have a larger displacement than nearby ones, and its magnitude increases in proportion to the distance. Consequently, the further away the galaxy, the faster it moves away from us.
Red shift, in accordance with the theory of relativity, is considered in the concept of space expansion. This displacement is also caused by expanding space and the proper motion of galaxies. The explanation is simple: while light travels through space from the source to us, space also expands. As a result, the wavelength from the source also expands during its journey. With a double expansion of space, the wavelength will also double.

Expansion of space

Redshift is an indicator of the expansion of the Universe. In the process of expanding space, galaxies increase the distances between them, but their coordinates remain the same. This process can be understood if we imagine that space is a rubber ball to which galaxies are “glued.” Given its spherical shape, the distances between objects will increase at all points when the balloon is inflated. Only there will be no center from which the removal occurs. But then the linear dimensions must also change inside solar system. It follows from this that the value of the standard length – the meter – should also change. Then it turns out that the number of meters to distant objects always remains the same, and there is no possibility of measuring the expansion of space.

Redshift and quasars

H. Arp, one of the discoverers, suggests that these objects have their own, internal, redshift. It does not depend on the object being deleted. Quasars are fairly small objects on a cosmic scale. But if the red shifts are correct in the light of Hubble’s law, then the distances to them, and their masses, and even the speed of their removal will have enormous values.

The speeds of quasars, billions of light years away from us, can reach tens of thousands of km/sec.

The redshift of object 3C48 shows that its speed is about half the speed of light, and its distance is 3.78 billion light years. And quasar 3C196 generally broke all records: its distance is 12 billion light years, and its speed is almost 200 thousand km/sec!

"Aging" of light

Some astronomers question the theory of redshift, or rather, the conclusion that its nature causes galaxies to necessarily scatter, and even at fantastic speeds. The idea was put forward that light, due to its extremely long journey through the tenuous gas of intergalactic space, turns red. This is due to the loss of short wavelengths in the spectrum, and the nebulae become redder, although the lines of the spectrum do not shift. But redshift implies precisely this process. Perhaps light, traveling endlessly in the Universe, loses some of its energy. Because of this, the waves lengthen, which generates a red shift, but is not associated with the retreat of galaxies. However, this theory has not yet been confirmed; no one has yet been able to prove that light can lose energy in any way. And where does this energy go is a big question. The example of quasars shows: the farther they are from us, the greater their redshift, and as mentioned, their removal speed is correspondingly greater.

redshift

an increase in the wavelengths of lines in the spectrum of the radiation source (shift of lines towards the red part of the spectrum) compared to the lines of the reference spectra. Redshift occurs when the distance between a radiation source and its receiver (observer) increases (see Doppler effect) or when the source is in a strong gravitational field (gravitational redshift). In astronomy, the greatest red shift is observed in the spectra of distant extragalactic objects (galaxies and quasars) and is considered as a consequence of the cosmological expansion of the Universe.

Redshift

frequency reduction electromagnetic radiation, one of the manifestations of the Doppler effect. The name "K. With." due to the fact that in the visible part of the spectrum, as a result of this phenomenon, the lines are shifted towards its red end; K. s. It is also observed in emissions of any other frequencies, for example in the radio range. The opposite effect, associated with higher frequencies, is called blue (or violet) shift. Most often the term "K. With." used to denote two phenomena ≈ cosmological cosmology. and gravitational K.s.

Cosmological (metagalactic) K. s. call the decrease in radiation frequencies observed for all distant sources (galaxies, quasars), indicating the distance of these sources from each other and, in particular, from our Galaxy, i.e., the nonstationarity (expansion) of the Metagalaxy. K. s. for galaxies was discovered by the American astronomer W. Slifer in 1912–14; in 1929 E. Hubble discovered that K. s. for distant galaxies is greater than for nearby ones, and increases approximately in proportion to the distance (Ks.'s law, or Hubble's law). Various explanations have been proposed for the observed shifts in spectral lines. Such, for example, is the hypothesis about the decay of light quanta over a period of millions and billions of years, during which the light of distant sources reaches an earthly observer; According to this hypothesis, during decay the energy decreases, which is associated with a change in the frequency of the radiation. However, this hypothesis is not supported by observations. In particular, K. s. in different parts of the spectrum of the same source, within the framework of the hypothesis, should be different. Meanwhile, all observational data indicate that K. s. does not depend on frequency, the relative change in frequency z = (n0≈ n)/n0 is exactly the same for all radiation frequencies, not only in the optical, but also in the radio range of a given source (n0 ≈ frequency of a certain line of the source spectrum, n ≈ frequency of the same line, registered by the receiver;

In the relativity theory, Doppler cosmic s. is considered as a result of a slowdown in the flow of time in a moving frame of reference (the effect of the special theory of relativity). If the velocity of the source system relative to the receiver system is u (in the case of metagalactic cosmic rays, u ≈ is the radial velocity), then

═(c ≈ speed of light in vacuum) and according to the observed Q.s. it is easy to determine the radial velocity of the source: . From this equation it follows that when z ╝ ¥ the speed v approaches the speed of light, remaining always less than it (v< с). При скорости v, намного меньшей скорости света (u << с), формула упрощается: u » cz. Закон Хаббла в этом случае записывается в форме u = cz = Hr (r ≈ расстояние, Н ≈ постоянная Хаббла). Для определения расстояний до внегалактических объектов по этой формуле нужно знать численное значение постоянной Хаббла Н. Знание этой постоянной очень важно и для космологии: с ней связан т. н. возраст Вселенной.

Up to the 50s. 20th century extragalactic distances (the measurement of which is naturally associated with great difficulties) were greatly underestimated, and therefore the value of H determined from these distances turned out to be greatly overestimated. In the early 70s. 20th century for the Hubble constant, the value taken is H = 53 ╠ 5 (km/sec)/Mgpc, the reciprocal value T = 1/H = 18 billion years.

Photographing the spectra of weak (distant) sources to measure the cosmic effect, even when using the largest instruments and sensitive photographic plates, requires favorable observation conditions and long exposures. For galaxies, displacements z » 0.2 are confidently measured, corresponding to a speed u » 60,000 km/sec and a distance of over 1 billion pc. At such speeds and distances, Hubble's law is applicable in its simplest form (an error of the order of 10%, i.e., the same as the error in determining H). Quasars are on average a hundred times brighter than galaxies and, therefore, can be observed at distances ten times greater (if space is Euclidean). For quasars, z » 2 and more are actually recorded. At displacements z = 2, the speed is u » 0.8×s = 240,000 km/sec. At such speeds, specific cosmological effects are already evident - nonstationarity and curvature of space ≈ time; in particular, the concept of a single unambiguous distance becomes inapplicable (one of the distances ≈ the distance according to the K. s. ≈ is here, obviously, r = ulH = 4.5 billion ps). K. s. indicates the expansion of the entire observable part of the Universe; this phenomenon is usually called the expansion of the (astronomical) Universe.

Gravitational K. s. is a consequence of a slowdown in the rate of time and is caused by the gravitational field (the effect of general relativity). This phenomenon (also called the Einstein effect, the generalized Doppler effect) was predicted by A. Einstein in 1911, and has been observed since 1919, first in the radiation of the Sun, and then of some other stars. Gravitational K. s. It is customary to characterize it by the conditional velocity u, calculated formally using the same formulas as in cases of cosmological cosmology. Conditional speed values: for the Sun u = 0.6 km/sec, for the dense star Sirius B u = 20 km/sec. In 1959, for the first time, it was possible to measure the gravitational force caused by the Earth’s gravitational field, which is very small: u = 7.5 × 10-5 cm/sec (see Mössbauer effect). In some cases (for example, during gravitational collapse) CS should be observed. both types (as a total effect).

Lit.: Landau L.D., Lifshits E.M., Field Theory, 4th ed., M., 1962, ╖ 89, 107; Observational foundations of cosmology, trans. from English, M., 1965.

G.I. Naan.

Wikipedia

Redshift

Redshift- shift of spectral lines chemical elements to the red side. This phenomenon may be an expression of the Doppler effect or gravitational redshift, or a combination of both. The shift of spectral lines to the violet side is called blue shift. The shift of spectral lines in the spectra of stars was first described by the French physicist Hippolyte Fizeau in 1848, and proposed the Doppler effect caused by the radial velocity of the star to explain the shift.

The light emitted by a star, when viewed globally, is an electromagnetic vibration. When viewed locally, this radiation consists of light quanta - photons, which are carriers of energy in space. We now know that the emitted quantum of light excites the nearest elementary particle of space, which transfers the excitation to the neighboring particle. Based on the law of conservation of energy, in this case the speed of light should be limited. This shows the difference between the propagation of light and information, which (information) was considered in section 3.4. This idea of ​​light, space and the nature of interactions led to a change in the understanding of the universe. Therefore, the concept of red shift as an increase in wavelengths in the spectrum of a source (shift of lines towards the red part of the spectrum) compared to the lines of reference spectra should be reconsidered and the nature of the occurrence of this effect should be established (see Introduction, paragraph 7 and).

The red shift is due to two reasons. Firstly, it is known that the red shift due to the Doppler effect occurs when the movement of a light source relative to the observer leads to an increase in the distance between them.

Secondly, from the perspective of fractal physics, a red shift occurs when the emitter is placed in a region of a large electric field of a star. Then, in a new interpretation of this effect, light quanta - photons - will generate several

a different oscillation frequency compared to the earthly standard, whose electric field is insignificant. This influence of the star's electric field on the radiation leads to both a decrease in the energy of the nascent quantum and a decrease in the frequency that characterizes the quantum; accordingly, the radiation wavelength = C/ (C is the speed of light, approximately equal to 3 10 8 m/s). Since the star’s electric field also determines the star’s gravity, the effect of increasing the radiation wavelength will be called the old term “gravitational redshift.”

An example of gravitational redshift is the observed shift of lines in the spectra of the Sun and white dwarfs. It is the effect of gravitational red shift that has now been reliably established for white dwarfs and for the Sun. The gravitational redshift, equivalent to velocity, for white dwarfs is 30 km/s, and for the Sun - about 250 m/s. The difference in the redshifts of the Sun and white dwarfs by two orders of magnitude is due to the different electric fields of these physical objects. Let's consider this issue in more detail.

As stated above, a photon emitted in the electric field of a star will have a changed oscillation frequency. To derive the redshift formula, we use relation (3.7) for the photon mass: m ν = h /C 2 = E/C 2, where E is the photon energy, proportional to its frequency ν. From here we see that the relative changes in the mass and frequency of the photon are equal, so we present them in this form: m ν /m ν = / = E/C 2.

The change in energy AE of the nascent photon is caused by the electric potential of the star. The electric potential of the Earth, due to its smallness, is not taken into account in this case. Then the relative redshift of a photon emitted by a star with electric potential φ and radius R in the SI system is equal.

RED SHIFT

RED SHIFT

Increasing the wavelengths (l) of lines in the electric magnet. source spectrum (shift of lines towards the red part of the spectrum) compared to the lines of the reference spectra. Quantitatively K. s. characterized by the value z = (lprin-lexp)/lsp, where lsp and lprin are, respectively, the radiation emitted by the source and received by the observer (radiation receiver). Two mechanisms lead to the appearance of K. s.

K.s., caused by the Doppler effect, occurs when the light source relative to the observer leads to an increase in the distance between them (see DOPPLER EFFECT). In relative case when the motion of the source v relative to the receiver is comparable to the speed of light (c), K.s. can also occur if the distance between the source and receiver does not increase (the so-called transverse Doppler effect). The KS that arises in this case can be interpreted as a result of the relative. time dilation at the source relative to the observer (see RELATIVITY THEORY). Cosmological The cosmic effect observed in distant galaxies and quasars is interpreted on the basis of the general theory of relativity (GR) as the effect of the expansion of the metagalaxy (the mutual removal of galaxies from each other; (see COSMOLOGY)). The expansion of the Metagalaxy leads to an increase in the wavelengths of the CMB radiation and a decrease in the energy of its quanta (i.e., to the cooling of the CMB radiation).

Gravity K. s. occurs when the light receiver is in an area with lower gravity. potential (fi2) than the source (fi1). In this case, the cosmic effect is a consequence of a slowdown in the rate of time near the gravitating mass and a decrease in the frequency of emitted light quanta (general relativity effect): n=(1+(fi2-fi1)/c2), An example of gravitational K. s. may serve as a line shift in the spectra of dense stars - white dwarfs. Using the Mössbauer effect, in 1959 it was possible to measure K. s. in gravity Earth.

Physical encyclopedic dictionary. - M.: Soviet Encyclopedia. . 1983 .

RED SHIFT

Increasing the length of monochromatic component of the spectrum of the radiation source in the observer's frame of reference compared to the wavelength of this component in its own. reference system. The term "K.s." arose during the study of optical spectral lines. range, shifted towards the long-wave (red) end of the spectrum. The cause of K. s. movement of the source relative to the observer may appear - Doppler effect and/or difference in field strength gravity at the points of emission and registration of radiation - gravitational coherence. In both cases, the displacement parameter does not depend on the wavelength, so the radiation energy distribution density f 0 () is associated with a similar density in the proper. reference system f e(). ratio

Doppler shift of wavelength in the spectrum of a source moving with radial velocity and full speed is equal to

For purely radial motion, the redshift ( z D >>0) corresponds to an increase in the distance to the source (>0), however, with a non-zero tangential component of the velocity, the values Z D >O can also be observed at<0.

Gravity K. s. was predicted by A. Einstein (A. Einstein, 1911) when developing the general theory of relativity (GTR). In an approximation linear with respect to the Newtonian potential (see. Law of gravity) , Where accordingly the gravitational values. potential at the points of emission and registration of radiation ( z g>0 in the case when the modulus at the point of emission is greater). For massive compact objects with a strong gravitational field (e.g. neutron stars And black holes)should be used exact words. In particular, gravitational K. s. in the spectrum of spherical body mass M and radius (r g - gravitational radius, G - gravitational constant) is determined by the expression

Initially for experiment. To test the Einstein effect, the spectra of the Sun and other asters were studied. objects. For the Sun z g 2*10 -6 , which is too small for reliable measurement of the effect, but in the spectra white dwarfs (r 10 3 -10 4 km, r g 1-3 km, z g 10 -4 - 10 -5) the effect was discovered. In 1960, R. Pound and G. Rebka, using Mossbauer effect, measured gravity K. s. during the propagation of gamma radiation in terrestrial conditions ( z g 10 -15).

The idea of ​​cosmology. K. s. arose as a result of the work (1910-29) of V. Slipher, K. Wirtz, K. Lundmark and E. Hubble. The latter established the so-called in 1929. Hubble's law - approximately linear dependence z,. from distance D to distant galaxies and their clusters: z c(H 0 /c)D, Where H 0 - so-called Hubble parameter [modern grade H 0 75 km/(s*Mpc) with uncertainty up to a factor of 1.5].

Cosmological K. s. is associated with the general expansion of the Universe and is due to joint action Doppler and Einstein effects (for relatively close galaxies, with D<10 3 Мпк, осп. роль играет эффект Доплера). В спектрах галактик зарегистрировано макс. значение z c 3, in the spectra of quasars z c 4.5(1988). In 1965, A. Penzias and R. Wilson discovered microwave background with temperature of 2.7 K, interpreted as a relic of the early stage of expansion of the Universe. For cosmic microwave background radiation z from 1500.

Effect of K. s. in the spectra of distant galaxies (the effect of “scattering” galaxies) was explained within the framework of non-stationary cosmological model, based on general relativity (A. A. Friedman, 1922). For a nonstationary isotropic and homogeneous Universe (see. Cosmology)value z c associated with scale factor R(t)in emission t e and registration t 0 light ratio

The expansion of the Universe is answered here z c >0. Hubble's law is considered to be linear to the last relation with . Specific view functions R(t) is determined by the gravitational equations. Fields of Oto. V. Yu. Terebizh.

Physical encyclopedia. In 5 volumes. - M.: Soviet Encyclopedia. Editor-in-Chief A. M. Prokhorov. 1988 .

See what "RED SHIFT" is in other dictionaries:

Red shift is a shift in the spectral lines of chemical elements to the red (long wavelength) side. This phenomenon may be an expression of the Doppler effect or gravitational redshift, or a combination of both. Spectrum shift... Wikipedia

Modern encyclopedia

An increase in the wavelengths of lines in the spectrum of the radiation source (shift of lines towards the red part of the spectrum) compared to the lines of the reference spectra. red shift occurs when the distance between a radiation source and its receiver... ... Big Encyclopedic Dictionary

Redshift- RED SHIFT, an increase in the wavelengths of lines in the spectrum of the radiation source (shift of lines towards the red part of the spectrum) compared to the lines of the reference spectra. Red shift occurs when the distance between the radiation source and... ... Illustrated Encyclopedic Dictionary

- (symbol z), an increase in the wavelength of visible light or in another range of ELECTROMAGNETIC RADIATION, caused either by the removal of a source (DOPPLER effect) or by the expansion of the Universe (see EXPANDING UNIVERSE). Defined as a change... ... Scientific and technical encyclopedic dictionary

An increase in the wavelengths of lines in the spectrum of the radiation source (shift of lines towards the red part of the spectrum) compared to the lines of the reference spectra. Red shift occurs when the distance between a radiation source and its receiver... ... Encyclopedic Dictionary

RED SHIFT

The optical spectrum of a star or galaxy is a continuous band intersected by dark vertical lines corresponding to wavelengths characteristic of elements in the outer layers of the star. The lines of the spectrum shift due to the movement of the star as it approaches us or moves away from us. This is an example of the Doppler effect, which involves a change in the observed wavelength emitted by a source in motion relative to the observer. Spectral lines shift to longer wavelengths (redshifted) if the light source moves away, or to shorter wavelengths if the light source gets closer (blueshifted).

For light emitted by a monochromatic source with frequency f, which moves with speed u, it can be proven that the wavelength shift?? = ?/f = (?/s) ?, where c represents the speed of light, and? - wavelength. Thus, the speed of a distant star or galaxy can be measured based on the wavelength shift??, using the equation? =c? ?/?.

In 1917, while observing the spectra of various galaxies using the sixty-centimeter telescope at the Lowell Observatory in Arizona, Vesto Slipher discovered that individual spiral galaxies were moving away from us at speeds of more than 500 km/s - much faster than any object in our Galaxy. The term "redshift" was coined as a measure of the ratio of the change in wavelength to the emitted wavelength. So, a redshift of 0.1 means that the source is moving away from us at a speed of 0.1 the speed of light. Edwin Hubble continued Slipher's work by estimating the distances of up to two dozen galaxies with known redshifts. This is how Hubble's law was formulated, which states that the speed of a galaxy's retreat is proportional to its distance.

In 1963, Martin Schmidt discovered the first quasar as a result of the discovery that the spectral lines of the star-like object 3C 273 are redshifted by about 15%. He concluded that this object was moving away at the speed of 0.15 light years and should be more than 2 billion light years away, and therefore much more powerful than an ordinary star. Since then, many other quasars have been discovered.

See also the articles "Hubble's Law", "Quasar", "Optical Spectrum".