Presentation on the topic "double stars". Double stars Download presentation on double stars
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Types of double stars First, let's find out which stars are called so. Let's immediately discard the type of double stars that are called "optical double stars." These are pairs of stars that happen to be nearby in the sky, that is, in the same direction, but in space, in fact, they are separated by large distances. We will not consider this type of double. We will be interested in the class of physically binary stars, that is, stars truly bound by gravitational interaction.
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Position of the center of mass Physically, double stars rotate in ellipses around a common center of mass. However, if you measure the coordinates of one star relative to another, it turns out that the stars move relative to each other also in ellipses. In this figure, we took the more massive blue star as our origin. In such a system, the center of mass (green dot) describes an ellipse around the blue star. I would like to warn the reader against the common misconception that it is often believed that a more massive star attracts a low-mass star more strongly than vice versa. Any two objects attract each other equally. But an object with a large mass is more difficult to move. And although a stone falling on the Earth attracts the Earth with the same force as its Earth, it is impossible to disturb our planet with this force, and we see how the stone moves.
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Often, however, there are so-called multiple systems, with three or more components. However, the motion of three or more interacting bodies is unstable. In a system of, say, three stars, one can always distinguish a double subsystem and a third star revolving around this pair. In a four-star system, there may be two binary subsystems orbiting a common center of mass. In other words, in nature, stable multiple systems always reduce to systems of two terms. The system of three stars includes the well-known Alpha Centauri, considered by many to be the closest star to us, but in fact, the third weak component of this system - Proxima Centauri, a red dwarf - is closer. All three stars of the system are visible separately due to their proximity. Indeed, sometimes the fact that a star is double is visible through a telescope. Such doubles are called visual doubles (not to be confused with optical doubles!). As a rule, these are not close pairs; the distances between the stars in them are large, much larger than their own sizes.
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The brilliance of double stars Often the stars in pairs differ greatly in brightness; the dim star is overshadowed by the bright one. Sometimes in such cases, astronomers learn about the duality of a star by deviations in the movement of a bright star under the influence of an invisible satellite from the trajectory in space calculated for a single star. Such pairs are called astrometric binaries. In particular, Sirius was classified as this type of binary for a long time, until the power of telescopes made it possible to discern a hitherto invisible satellite - Sirius B. This pair became visually double. It happens that the plane of revolution of stars around their common center of mass passes or almost passes through the eye of the observer. The orbits of the stars of such a system are located, as it were, edge-on to us. Here the stars will periodically eclipse each other, the brightness of the entire pair will change with the same period. This type of binary is called an eclipsing binary. If we talk about the variability of a star, then such a star is called an eclipsing variable, which also indicates its duality. The very first discovered and most famous binary of this type is the star Algol (Eye of the Devil) in the constellation Perseus.
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Spectrally binary stars The last type of binary is the spectrally binary. Their duality is determined by studying the spectrum of the star, in which periodic shifts of absorption lines are noticed or it is clear that the lines are double, on which the conclusion about the duality of the star is based.
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Why are double stars interesting? Firstly, they make it possible to find out the masses of stars, since it is easiest and most reliable to calculate from the visible interaction of two bodies. Direct observations make it possible to find out the total “weight” of the system, and if we add to them the known relationships between the masses of stars and their luminosities, which were discussed above in the story about the fate of stars, then we can find out the masses of the components and test the theory. Single stars do not provide us with such an opportunity. In addition, as was also mentioned earlier, the fate of stars in such systems can be strikingly different from the fate of the same single stars. Celestial pairs, the distances between which are large compared to the size of the stars themselves, at all stages of their lives live according to the same laws as single stars, without interfering with each other. In this sense, their duality does not manifest itself in any way.
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Close pairs: the first exchange of masses Binary stars are born together from the same gas and dust nebula; they have the same age, but often have different masses. We already know that more massive stars live “faster”, therefore, a more massive star will overtake its peer in the process of evolution. It will expand, turning into a giant. In this case, the size of the star can become such that matter from one star (inflated) begins to flow to another. As a consequence, the mass of the initially lighter star can become greater than the initially heavy one! In addition, we will get two stars of the same age, and the more massive star is still on the main sequence, that is, in its center the synthesis of helium from hydrogen is still ongoing, and the lighter star has already used up its hydrogen, and a helium core has formed in it. Let us remember that in the world of single stars this cannot happen. Due to the discrepancy between the age of the star and its mass, this phenomenon is called the Algol paradox, in honor of the same eclipsing binary. The star Beta Lyrae is another pair that is exchanging mass right now.
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The matter from the inflated star, flowing onto the less massive component, does not immediately fall on it (the mutual rotation of the stars prevents this), but first forms a rotating disk of matter around the smaller star. The frictional forces in this disk will reduce the speed of the particles of matter, and it will settle on the surface of the star. This process is called accretion, and the resulting disk is called accretion. As a result, the initially more massive star has an unusual chemical composition: all the hydrogen in its outer layers flows to another star, leaving only a helium core with admixtures of heavier elements. Such a star, called a helium star, quickly evolves to form a white dwarf or a relativistic star, depending on its mass. At the same time, an important change occurred in the binary system as a whole: the initially more massive star gave up this superiority.
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Second mass exchange In binary systems, there are also X-ray pulsars emitting in a higher energy wavelength range. This radiation is associated with the accretion of matter near the magnetic poles of a relativistic star. The source of accretion is stellar wind particles emitted by the second star (the solar wind has the same nature). If the star is large, the stellar wind reaches a significant density, and the energy of the X-ray pulsar radiation can reach hundreds and thousands of solar luminosities. An X-ray pulsar is the only way to indirectly detect a black hole, which, as we remember, cannot be seen. And a neutron star is a rare object for visual observation. This is far from all. The second star will also sooner or later inflate, and matter will begin to flow to its neighbor. And this is already the second exchange of matter in a binary system. Having reached large sizes, the second star begins to “return” what was taken during the first exchange.
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If a white dwarf appears in the place of the first star, then as a result of the second exchange, flares can occur on its surface, which we observe as new stars. At one point, when there is too much material falling onto the surface of a very hot white dwarf, the temperature of the gas near the surface rises sharply. This provokes an explosive burst of nuclear reactions. The star's luminosity increases significantly. Such outbreaks can be repeated, and they are called repeated new ones. Repeated flares are weaker than the first, as a result of which the star can increase its brightness tens of times, which we observe from Earth as the appearance of a “new” star.
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Another outcome in a white dwarf system is a supernova explosion. The consequence of the flow of matter from the second star may be that the white dwarf reaches a maximum mass of 1.4 solar. If it is already an iron white dwarf, then it will not be able to maintain gravitational compression and will explode. Supernova explosions in binary systems are very similar in brightness and development to each other, since stars always explode with the same mass - 1.4 solar. Let us recall that in single stars the central iron core reaches this critical mass, and the outer layers can have different masses. In binary systems, as is clear from our narrative, these layers are almost absent. That is why such flares have the same luminosity. By noticing them in distant galaxies, we can calculate distances much greater than can be determined using stellar parallax or Cepheids. The loss of a significant portion of the mass of the entire system as a result of a supernova explosion can lead to the disintegration of a binary. The force of gravitational attraction between the components is greatly reduced, and they can fly apart due to the inertia of their movement.
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Double stars The sun is a single star. But sometimes two or more stars are located close to each other and revolve around each other. They are called double or multiple stars. There are a lot of them in the Galaxy. So, the star Mizar in the constellation Ursa Major has a satellite - Alcor. Depending on the distance between them, double stars orbit each other quickly or slowly, and the orbital period can range from a few days to many thousands of years. Some double stars are turned towards the Earth with the edge of the plane of their orbit, then one star regularly eclipses the other. At the same time, the overall brightness of the stars weakens. We perceive this as a change in the brightness of the star. For example, the “devil star” Algol in the constellation Perseus has been known since ancient times as a variable star. Every 69 hours, the orbital period of the stars in this binary system, a brighter star is eclipsed by its cooler, less luminous neighbor. From the Earth, this is perceived as a decrease in its brightness. Ten hours later, the stars disperse, and the brightness of the system again reaches its maximum.
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Mizar and Alcor are not only projected side by side on the celestial sphere, but also move around a common center of mass. The orbital period is about 2 billion years. There are many double and multiple stars in the Galaxy. Mira – Omicron Ceti – double star. Photo a shows the components of a binary star located at a distance of 0.6". Photos b and c show that their shape is not spherical, a tail is visible from Mira towards the smaller star. This may be due to the gravitational interaction of Mira Ceti with its companion ac b
Multiple systems often appear to the naked eye as single stars. With good binoculars and telescopes you can notice their duality or multiplicity. The star ε Lyrae is a physical system consisting of two close stellar pairs ε 1 and ε 2. Multiple stars
The star θ Orionis is a complex multiple system. θ 1 and θ 2 when observed through a small telescope appear as a quadruple system and a triple system. With a strong telescope, you can see even more stars. The entire system is called the Trapezium of Orion. Trapezium of Orion (center)
An example of a multiple system is α Centauri (Rigil Centaurus), located 4.3 light years from the Sun. Component C has coordinates α = 14 h 26 m, δ = –62°28 "and is the closest star to the Sun. Its proper name is Proxima Centauri. Rigil Centaurus is the closest star system to the Sun
The law of universal gravitation and Kepler's laws generalized by Newton are applicable to systems of double stars. This allows us to estimate the mass of stars in binary systems. According to Kepler's third law, we can write the proportion where m 1 and m 2 are the masses of two stars with an orbital period P, A is the semimajor axis of the orbit of a star orbiting another star. Masses M and m are the masses of the Sun and the Earth, T = 1 year, and is the distance from the Earth to the Sun. This formula gives the sum of the masses of the components of a binary star, i.e. members of this system. α – angular distance between the components π – annual parallax of the star If the distances of the stars to their common center of gravity are determined from observations, then the mass of each star can be determined.
"Neutron star" - 7. 8. Measured masses of neutron stars. Stars with higher central density and higher mass turn out to be unstable. Internal structure of neutron stars. 2. Direct introduction of many-particle forces in isovector channels: Relativistic mean field (RMF) model. Introduction of many-particle forces.
“Binary stars” - Visually double, astrometrically double, eclipsingly double, spectrally double. First, let's find out which stars are called this. Why are double stars interesting? Single stars do not provide us with such an opportunity. The last type of binary is the spectroscopic binary. Spectrally double. Eclipsing doubles.
“Mass of stars” - Mass almost equal to the Sun, and 2.5 times larger than the Earth. Source of energy from the Sun and stars. Main sequence. The densities of main sequence stars are comparable to the solar density. The masses of stars range from approximately 1/20 to 100 times the mass of the Sun. Betelgeuse is a red supergiant.
"Constellations" - There are also stars of the seventh, eighth and even eighteenth magnitude. A first magnitude star is exactly 2.512 times brighter than a second magnitude star. On a cloudless and moonless night, far from populated areas, about 3,000 stars can be distinguished. The winter triangle is made up of the brightest stars Orion, Canis Major and Canis Minor.
"Constellation Astronomy" - Based primarily on observations. But not only Akid fell in love with Galatea. Spiral galaxy M74. The names of the constellations were associated with myths, names of gods, names of devices and mechanisms. Let's start getting acquainted with the constellations in the summer sky. Ursa Minor. Zodiacs. In the north hangs the inverted dipper of the Big Dipper.
Stars.
Double stars.
Variable stars
Distance to stars
Annual parallax of a star p is the angle at which the semi-major axis of the earth's orbit (equal to 1 AU) could be seen from the star, perpendicular to the direction to the star.
where is the semimajor axis of the earth's orbit
At small angles sin p = p = 1 au, then
Physical nature of stars
Stars are different
structure
luminosity
sizes
age
temperature (color)
Star luminosity
Stars located at the same distance may differ in apparent brightness (i.e., brightness). Stars have different luminosity .
Luminosity is the total energy emitted by a star per unit time.
Expressed in watts or in units of solar luminosity .
In astronomy, it is customary to compare stars by luminosity, calculating their brightness (stellar magnitude) for the same standard distance - 10 pc.
The apparent magnitude that the star would have if it were at a distance D from us 0 = 10 pc, called absolute magnitude M.
The luminosity of a star is determined through the absolute magnitude in the luminosity of the Sun, using the following relation
Color and temperature of stars
Stars come in a variety of colors.
Arcturus has a yellow-orange hue,
White-blue crossbar,
Antares is bright red.
Color and temperature of stars
The dominant color in a star's spectrum depends on temperature its surface.
For different stars, the maximum radiation occurs at different wavelengths.
Wine's Law
Maximum solar radiation λ = 4.7x 10 m
Harvard Spectral Classification of Stars
Sun
Radii of stars
Stars
Neutron stars (pulsars)
giants
dwarfs
black holes
supergiants
Aldebaran is a red giant in the constellation Taurus
Alpha Orionis – Betelgeuse (Supergiant)
A small dot next to Sirius is its satellite, the white dwarf Sirius B.
Naked eye near Mizar
(middle star of the handle of the Ursa Major Dipper)
faint star Alcor visible (5 m)
In ancient times, it was believed that a person who sees the small neighbor of this star has acute vision.
According to Mizar and Alcor, the ancient Greeks tested the vigilance of the eye
Mizar and Alcor are not only projected side by side on the celestial sphere,
but also move around a common center of mass. The orbital period is about 2 billion years.
There are many double and multiple stars in the Galaxy.
Mira – Omicron Ceti – double star.
In the Foto A The components of a binary star are depicted at a distance of 0.6".
On photos b And With it is clear that their shape is not spherical; a tail is visible from Mira towards the smaller star.
This may be due to the gravitational interaction of Mira Ceti
with your companion
Types of double stars
- visually double
- astrometric binaries
- eclipsing binaries
- spectrally double
Astrometrically doubles
Often stars in pairs differ greatly in brightness; the dim star is overshadowed by the bright one. Sometimes in such cases, astronomers learn about the duality of a star by deviations in the movement of a bright star under the influence of an invisible satellite from the trajectory in space calculated for a single star. Such pairs are called astrometric binaries. In particular, Sirius was classified as this type of binary for a long time, until the power of telescopes made it possible to discern a hitherto invisible satellite - Sirius B. This pair became visually double.
Eclipsing binaries
It happens that the plane of revolution of stars around their common center of mass passes or almost passes through the eye of the observer. The orbits of the stars of such a system are located, as it were, edge-on to us. Here the stars will periodically eclipse each other, the brightness of the entire pair will change with the same period. This type of binary is called an eclipsing binary. If we talk about the variability of a star, then such a star is called an eclipsing variable, which also indicates its duality. The very first discovered and most famous binary of this type is the star Algol (Eye of the Devil) in the constellation Perseus.
Spectral doubles
Duality is determined by studying the spectrum of a star, in which periodic shifts of absorption lines are noticed or it is clear that the lines are double, on which the conclusion about the duality of the star is based.
The universal law applies to systems of double stars.
Gravity and Kepler's laws generalized by Newton. This allows us to estimate the mass of stars in binary systems.
According to Kepler's third law, we can write the proportion
Where m 1 and m 2 – masses of two stars with an orbital period R ,
A is the semimajor axis of the orbit of a star orbiting another star.
Masses M and m– masses of the Sun and Earth, T= 1 year, a is the distance from the Earth to the Sun.
This formula gives the sum of the masses of the components of a binary star, i.e. members of this system.
Variable stars
Variable stars are stars whose brightness changes, sometimes at regular intervals. There are quite a lot of variable stars in the sky. Currently, there are more than 30,000 known.
Many of them are quite observable in small and medium sizes
optical instruments - binoculars, spotting scope or school telescope.
Amplitude and period of a variable star
Physical variables are stars that change their luminosity as a result of physical processes occurring in the star itself.
Such stars may not have a constant light curve.
The first pulsating variable was discovered in 1596 by Fibrizius.
in the constellation Cetus. He named her Mira, which means “wonderful, amazing.”
At maximum, Mira is clearly visible to the naked eye, its visible stellar
magnitude 2 m, during the period of minimum it decreases to 10 m and is visible only through a telescope.
The average period of variability of Mira Ceti is 332 days.
Cepheids are pulsating stars of high luminosity, named after one of the first discovered variable stars - δ Cephei.
These are yellow supergiants of spectral classes F and G, whose mass exceeds the mass of the Sun several times.
During their evolution, Cepheids acquire a special structure.
At a certain depth, a layer appears that accumulates energy coming from the star’s core and then releases it.
Cepheids periodically contract, the temperature of Cepheids increases,
the radius decreases. Then the surface area
grows, its temperature decreases, which causes a general change in brightness.
Cepheids play a special role in astronomy.
In 1908, Henrietta Leavitt, while studying Cepheids in the Small Magellanic Cloud, noticed that the smaller the apparent magnitude of the Cepheid,
the longer the period of change in its brightness.
Large Magellanic Cloud
Small Magellanic Cloud
Henrietta Leavitt
A star that increases its brilliance thousands or millions of times in a few hours, and then dims, returning to its original brilliance, is called new.
A nova occurs in close binary systems, in which one of the components of the binary system is a white dwarf or neutron star.
When a critical mass accumulates on the surface of a white dwarf (neutron star)
mass of matter, a thermonuclear explosion occurs, tearing off the shell from the star
and increasing its luminosity thousands of times.
Nebula after explosion
Nova in the constellation Cygnus
in 1992 visible as
small red spot
slightly above the middle
photos.
Novae are exploding variable stars.
Remnant of the nova GK Persei
Supernovas are called stars that suddenly explode and reach
at maximum absolute magnitude from –11 m to –21 m.
The luminosity of a supernova increases tens of millions of times, which can exceed the luminosity of the entire galaxy.
Supernova explosions are one of the most powerful catastrophic natural processes.
A huge release of energy (the amount of energy the Sun produces over billions of years) accompanies a supernova explosion.
A supernova can emit more radiation than all the stars in the galaxy combined.
Supernova 1987A in the Large Magellanic Cloud is located there,
where in old photographs there was only a 12th magnitude asterisk.
Its maximum value reached 2.9m,
which made it easy to observe the supernova with the naked eye.
The dense core collapses, dragging it with it into free fall towards the center
outer layers of the star. When the core becomes strongly compacted, its compression stops,
and a counter shock wave hits the upper layers, and also splashes out
the energy of a huge number of neutrinos. As a result, the shell scatters
speed of 10,000 km/s, exposing a neutron star or black hole.
A supernova explosion releases 10 46 J of energy.
The center of the Gum Nebula, left behind after a supernova explosion,
located in the constellation Velas
Supernova 1987A 4 years after the outburst.
The ring of glowing gas reached
1.37 light years across.
Remnant of Supernova 1987
twelve years after the outbreak
The most famous supernova remnant in our Galaxy is
Crab Nebula.
This is the remnant of a supernova explosion in 1054.
Major milestones in the history of astronomy are associated with her research.
The Crab Nebula was the first source of cosmic radio emission
in 1949 identified with a galactic object.
At the site of a supernova explosion in the Crab Nebula
a neutron star formed
A neutron star would easily fit inside the Moscow
Beltway or New York
The outer shell of a neutron star is a crust consisting of iron nuclei
at a temperature of 10 5 –10 6 K. The entire remaining volume, with the exception of a small
The area in the center is occupied by “neutron liquid”. In the center it is expected
the presence of a small hyperonic core. Neutrons obey the Pauli principle.
At such densities, the “neutron liquid” becomes degenerate
and stops further compression of the neutron star.
Matchbox with neutron star matter
would weigh about ten billion tons on Earth
In the 60s of the 20th century, completely by accident, when observing with a radio telescope,
which was intended to study the scintillations of cosmic radio sources,
Jocelyn Bell, Anthony Hewish and other Cambridge University staff
Great Britain discovered a series of periodic pulses.
The pulse duration was 0.3 seconds at a frequency of 81.5 MHz, which
repeated at a remarkably constant time, 1.3373011 seconds.
Millisecond pulsar PSR J1959+2048 in the visible range.
The pulses are interrupted for 50 minutes every 9 hours,
indicating that the pulsar is being eclipsed by its companion star
It was completely different from the usual chaotic picture of random
irregular flickering.
There was even an assumption about an extraterrestrial civilization,
sending its signals to Earth.
Therefore, the designation LGM was introduced for these signals
(short for little green men).
Serious attempts have been made
recognize any code in
received impulses.
This turned out to be impossible, though,
as they say, they were to the point
attracted the most
qualified specialists
on encryption technology.
Pulsars in MMOs
Six months later, three more similar pulsating radio sources were discovered.
It became obvious that the sources of radiation are natural celestial
bodies. They were called pulsars.
For the discovery and interpretation of radio emissions from pulsars to Anthony Hewish
was awarded the Nobel Prize in Physics.
Pulsar model
