Big Universe Star magnitude. Magnitude

The unequal brightness (or brilliance) of various objects in the sky is probably the first thing that a person notices when observing; therefore, in connection with this, a long time ago, there was a need to introduce a convenient value that would allow us to classify the luminaries by brightness.

Story

For the first time, such a value for his observations with the naked eye was used by the ancient Greek astronomer, the author of the first European star catalog - Hipparchus. He classified all the stars in his catalog by brightness, designating the brightest as stars of the 1st magnitude, and the dimmest as stars of the 6th magnitude. This system took root, and in the middle of the 19th century was improved to its modern look English astronomer Norman Pogson.

Thus, we obtained a dimensionless physical quantity, logarithmically related to the illumination that the luminaries create (actual magnitude):

m1-m2 \u003d -2.5 * lg (L1 / L2)

where m1 and m2 are the stellar magnitudes of the luminaries, and L1 and L2 are the illumination in lux (lx is the SI unit of illumination) created by these objects. If we substitute the value m1-m2 \u003d 5 into the left side of this equation, then after a simple calculation, it will be found that the illumination in this case correlates as 1/100, so that the difference in brightness by 5 magnitudes corresponds to the difference in illumination from objects in 100 once.

Continuing to solve this problem, we extract the 5th root of 100 and we get a change in illumination with a difference in brightness of one magnitude, the change in illumination will be 2.512 times.

This is all the basic mathematical apparatus necessary for orientation in a given brightness scale.

magnitude scale

With the introduction of this system, it was also necessary to set the origin of the magnitude scale. To do this, the brightness of the star Vega (alpha Lyrae) was initially taken as a zero magnitude (0m). At present, the most accurate reference point is the brightness of the star, which is 0.03m brighter than Vega. However, the eye will not notice such a difference, so for visual observations - the brightness corresponding to zero magnitude can still be taken according to Vega.

Another important thing to remember about this scale is that the smaller the magnitude, the brighter the object. For example, the same Vega with its magnitude of +0.03m will be almost 100 times brighter than a star with a magnitude of +5m. Jupiter, with its maximum brightness at -2.94m, will be brighter than Vega at:

2.94-0.03 = -2.5*lg(L1/L2)
L1/L2 = 15.42 times

You can solve this problem in another way - simply by raising 2.512 to a power equal to the difference in the magnitudes of the objects:

2,512^(-2,94-0,03) = 15,42

Magnitude classification

Now, having finally dealt with the materiel, we will consider the classification of stellar magnitudes used in astronomy.

The first classification is according to the spectral sensitivity of the radiation receiver. In this regard, the stellar magnitude is: visual (brightness is taken into account only in visible to the eye spectrum range); bolometric (brightness is taken into account in the entire range of the spectrum, not only visible light, but also ultraviolet, infrared and other spectra combined); photographic (brightness, taking into account the sensitivity to the spectrum of photocells).

This can also include stellar magnitudes in a specific part of the spectrum (for example, in the range of blue light, yellow, red or ultraviolet radiation).

Accordingly, the visual stellar magnitude is intended to assess the brightness of the stars in visual observations; bolometric - to estimate the total flux of all radiation from the star; and the photographic and narrow-band values ​​are used to evaluate the color indices of the luminaries in any photometric system.

Apparent and absolute stellar magnitudes

The second type of classification of stellar magnitudes is according to the number of dependent physical parameters. In this regard, the stellar magnitude can be - visible and absolute. Apparent stellar magnitude is that brilliance of an object that the eye (or other radiation receiver) perceives directly from its current position in space.

This brightness depends on two parameters at once - this is the radiation power of the star and the distance to it. The absolute stellar magnitude depends only on the radiation power and does not depend on the distance to the object, since the latter is accepted as common for a particular class of objects.

The absolute magnitude for stars is defined as their apparent magnitude if the distance to the star were 10 parsecs (32.616 light years). Absolute magnitude for objects solar system is defined as their apparent magnitude if they were 1 AU apart. from the Sun and would show their full phase to the observer, while the observer himself would also be at 1 AU. (149.6 million km) from the object (i.e. at the center of the Sun).

The absolute magnitude of meteors is defined as their apparent magnitude if they were at a distance of 100 km from the observer and at the zenith point.

Application of stellar magnitudes

These classifications can be used together. For example, the absolute visual magnitude of the Sun is M(v) = +4.83. and the absolute bolometric M(bol) = +4.75, since the Sun shines not only in the visible range of the spectrum. Depending on the temperature of the photosphere (visible surface) of the star, as well as its belonging to the luminosity class (main sequence, giant, supergiant, etc.).

The visual and bolometric absolute stellar magnitudes of a star differ. For example, hot stars (spectral classes B and O) shine mainly in the ultraviolet range invisible to the eye. So their bolometric brilliance is much stronger than visual. The same applies to cold stars (spectral classes K and M), which shine mainly in the infrared range.

The absolute visual magnitude of the most powerful stars (hypergiants and Wolf-Rayet stars) is about -8, -9. The absolute bolometric can go up to -11, -12 (which corresponds to the apparent magnitude of the full moon).

The radiation power (luminosity) is millions of times greater than the radiation power of the Sun. The apparent visual magnitude of the Sun from the Earth's orbit is -26.74m; in the orbit of Neptune will be -19.36m. The apparent visual magnitude of the brightest star, Sirius, is -1.5m, and the absolute visual magnitude of this star is +1.44, i.e. Sirius is almost 23 times brighter than the Sun in the visible spectrum.

The planet Venus in the sky is always brighter than all the stars (its visible brightness ranges from -3.8m to -4.9m); Jupiter is somewhat less bright (from -1.6m to -2.94m); Mars during oppositions has an apparent stellar magnitude of the order of -2m and brighter. In general, most planets are in most cases the brightest objects in the sky after the Sun and Moon. Since there are no stars with high luminosity in the vicinity of the Sun.

Let's continue our algebraic excursion to the heavenly bodies. In the scale that is used to evaluate the brightness of stars, they can, in addition to fixed stars; find a place for yourself and other luminaries - the planets, the Sun, the Moon. We will talk separately about the brightness of the planets; here we indicate the stellar magnitude of the Sun and Moon. The star magnitude of the Sun is expressed by the number minus 26.8, and the full1) Moon - minus 12.6. Why both numbers are negative, the reader must think, is understandable after all that has been said before. But, perhaps, he will be perplexed by the insufficiently large difference between the magnitude of the Sun and the Moon: the first is “only twice as large as the second.”

Let's not forget, however, that the designation of magnitude is, in essence, a certain logarithm (based on 2.5). And just as it is impossible, when comparing numbers, to divide their logarithms one by another, so it makes no sense, when comparing stellar magnitudes, to divide one number by another. What is the result of a correct comparison, shows the following calculation.

If the magnitude of the Sun is "minus 26.8", then this means that the Sun is brighter than a star of the first magnitude

2.527.8 times. The moon is brighter than a star of the first magnitude

2.513.6 times.

This means that the brightness of the sun is greater than the brightness of the full moon at

2.5 27.8 2.5 14.2 times. 2.5 13.6

Calculating this value (using tables of logarithms), we get 447,000. Here, therefore, is the correct ratio of the brightness of the Sun and the Moon: a daytime star in clear weather illuminates the Earth 447,000 times stronger than the full Moon on a cloudless night.

Considering that the amount of heat thrown off by the Moon is proportional to the amount of light scattered by it - and this is probably close to the truth - we must admit that the Moon sends us heat 447,000 times less than the Sun. It is known that every square centimeter on the border earth's atmosphere receives from the Sun about 2 small calories of heat in 1 minute. This means that the Moon sends to 1 cm2 of the Earth every minute no more than 225,000th part of a small calorie (i.e., it can heat 1 g of water in 1 minute by 225,000th part of a degree). This shows how unsubstantiated all attempts to attribute any influence to the moonlight on the earth's weather2) .

1) In the first and last quarter, the magnitude of the Moon is minus 9.

2) The question of whether the Moon can influence the weather by its attraction will be considered at the end of the book (see "Moon and Weather").

The common belief that clouds often melt under the action of the rays of the full moon is a gross misconception, explained by the fact that the disappearance of clouds at night (due to other reasons) becomes noticeable only under moonlight.

Let us now leave the Moon and calculate how many times the Sun is brighter than the most brilliant star in the entire sky - Sirius. Arguing in the same way as before, we obtain the ratio of their brightness:

2,5 27,8	2,5 25,2
2,52,6

i.e., the Sun is 10 billion times brighter than Sirius.

The following calculation is also very interesting: how many times is the illumination given by the full moon brighter than the total illumination of the entire starry sky, that is, all the stars visible to the naked eye in one celestial hemisphere? We have already calculated that stars from the first to the sixth magnitude inclusive shine together like a hundred stars of the first magnitude. The problem, therefore, comes down to calculating how many times the moon is brighter than a hundred stars of the first magnitude.

This ratio is equal

2,5 13,6

100 2700.

So, on a clear moonless night, we receive from the starry sky only 2700th of the light that the full Moon sends, and 2700 × 447,000, that is, 1200 million times less than the Sun gives on a cloudless day.

We also add that the magnitude of the normal international

"candles" at a distance of 1 m is equal to minus 14.2, which means that a candle at a specified distance illuminates brighter than the full moon by 2.514.2-12.6 i.e. four times.

It is perhaps also interesting to note that the searchlight of an aviation beacon with a power of 2 billion candles would be visible from the distance of the Moon as a star of 4½th magnitude, i.e., could be distinguished by the naked eye.

The true brilliance of the stars and the sun

All the brightness estimates we have made so far have only referred to their apparent brightness. The given numbers express the brightness of the luminaries at the distances at which each of them is actually located. But we know well that the stars are not equally distant from us; the apparent brilliance of the stars tells us, therefore, both of their true brilliance and of their distance from us—or, rather, of neither, until we have dissected both factors. Meanwhile, it is important to know what would be the comparative brightness or, as they say, the "luminosity" of various stars if they were at the same distance from us.

Putting the question in this way, astronomers introduce the concept of the "absolute" magnitude of stars. The absolute magnitude of a star is the one that the star would have if it were at a distance from us.

standing 10 "parsecs". Parsec is a special measure of length used for stellar distances; we will discuss its origin separately later, here we will only say that one parsec is about 30,800,000,000,000 km. It is not difficult to calculate the absolute magnitude itself, if you know the distance of the star and take into account that the brightness should decrease in proportion to the square of the distance1).

We will acquaint the reader with the result of only two such calculations: for Sirius and for our Sun. The absolute value of Sirius is +1.3, the Sun is +4.8. This means that from a distance of 30,800,000,000,000 km, Sirius would shine for us with a star of 1.3 magnitude, and for our Sun of 4.8 magnitude, i.e., weaker than Sirius in

2.5 3.8 2.53.5 25 times,

2,50,3

although the apparent brilliance of the Sun is 10,000,000,000 times that of Sirius.

We have seen that the Sun is far from being the brightest star in the sky. However, one should not consider our Sun as a completely pygmy among the stars surrounding it: its luminosity is still above average. According to stellar statistics, the average luminosity of the stars surrounding the Sun up to a distance of 10 parsecs are stars of the ninth absolute magnitude. Since the absolute magnitude of the Sun is 4.8, it is brighter than the average of the "neighboring" stars, in

	2,58	2,54,2	50 times.
	2,53,8

Being 25 times absolutely dimmer than Sirius, the Sun is still 50 times brighter than the average of the stars surrounding it.

The brightest star known

The largest luminosity is possessed by an asterisk of the eighth magnitude inaccessible to the naked eye in the constellation Dorado, designated

1) The calculation can be performed according to the following formula, the origin of which will become clear to the reader when a little later he gets to know the "parsec" and "parallax" more closely:

Here M is the absolute magnitude of the star, m is its apparent magnitude, π is the parallax of the star in

seconds. Successive transformations are as follows: 2.5M \u003d 2.5m 100π 2,

M lg 2.5 \u003d m lg 2.5 + 2 + 2 lgπ, 0.4M \u003d 0.4m +2 + 2 lgπ,

M = m + 5 + 5 lgπ .

For Sirius, for example, m = –1.6π = 0 "38. Therefore, its absolute value

M = –l.6 + 5 + 5 log 0.38 = 1.3.

Latin letter S. The constellation Dorado is located in the southern hemisphere of the sky and is not visible in the temperate zone of our hemisphere. The mentioned asterisk is part of the neighboring star system - the Small Magellanic Cloud, the distance of which from us is estimated to be about 12,000 times greater than the distance to Sirius. At such a huge distance, a star must have a completely exceptional luminosity in order to appear even eighth magnitude. Sirius, thrown just as deep in space, would shine as a star of the 17th magnitude, i.e., would be barely visible in the most powerful telescope.

What is the luminosity of this wonderful star? The calculation gives the following result: minus the eighth value. This means that our star is absolutely: 400,000 times (roughly) brighter than the Sun! With such an exceptional brightness, this star, if placed at a distance from Sirius, would appear nine magnitudes brighter than it, that is, it would have approximately the brightness of the Moon in the quarter phase! A star that, from the distance of Sirius, could flood the Earth with such a bright light, has an indisputable right to be considered the brightest star known to us.

The star magnitude of the planets on the earth and alien sky

Let us now return to the mental journey to other planets (done by us in the section “Alien Skies”) and evaluate more accurately the brilliance of the luminaries shining there. First of all, let us indicate the stellar magnitudes of the planets at their maximum brightness in the earth's sky. Here is the plate.

In the sky of the Earth:

Venus.............................		Saturn..............................
Mars..................................		Uranus..................................
Jupiter...........................		Neptune.............................
Mercury......................

Looking through it, we see that Venus is brighter than Jupiter by almost two magnitudes, i.e. 2.52 = 6.25 times, and Sirius 2.5-2.7 = 13 times

(the brightness of Sirius is 1.6th magnitude). From the same plate it can be seen that the dim planet Saturn is still brighter than all the fixed stars, except for Sirius and Canopus. Here we find an explanation for the fact that the planets (Venus, Jupiter) are sometimes visible to the naked eye during the day, while the stars in daylight are completely inaccessible to the naked eye.

Imagine that somewhere in the sea in the darkness of the night, a light flickers quietly. If an experienced sailor does not explain to you what it is, you often will not know whether it is a flashlight on the bow of a passing boat in front of you, or a powerful searchlight from a distant lighthouse.

We are in the same position on a dark night, looking at the twinkling stars. Their apparent brilliance also depends on their true power of light, called luminosity, and from their distance to us. Only knowing the distance to a star allows us to calculate its luminosity compared to the Sun. Thus, for example, the luminosity of a star ten times less luminous in reality than the Sun is expressed by the number 0.1.

The true strength of the light of a star can be expressed in another way, by calculating what magnitude it would seem to us if it were at a standard distance of 32.6 light years from us, that is, at such that light, rushing at a speed of 300,000 km /sec, would pass it during this time.

Accepting such a standard distance proved to be convenient for various calculations. The brightness of a star, like any light source, varies inversely with the square of the distance from it. This law allows you to calculate the absolute magnitudes or luminosities of stars, knowing the distance to them.

When the distances to the stars became known, we were able to calculate their luminosities, that is, we could, as it were, line them up in one line and compare them with each other in same conditions. It must be confessed that the results were astonishing, since it had previously been assumed that all stars were "similar to our Sun." The luminosities of the stars turned out to be amazingly diverse, and they cannot be compared in our line with any line of pioneers.

Let us give only extreme examples of luminosity in the world of stars.

The weakest known for a long time was a star, which is 50 thousand times weaker than the Sun, and its absolute luminosity value: +16.6. However, even fainter stars were subsequently discovered, the luminosity of which, compared to the sun, is millions of times less!

Dimensions in space are deceptive: Deneb from Earth shines brighter than Antares, but the Pistol is not visible at all. However, to an observer from our planet, both Deneb and Antares seem to be just insignificant points compared to the Sun. How wrong this is can be judged by a simple fact: A gun releases as much light in a second as the Sun does in a year!

On the other side of the line of stars stands "S" Dorado, visible only in the countries of the Southern Hemisphere of the Earth as an asterisk (that is, not even visible without a telescope!). In fact, it is 400 thousand times brighter than the Sun, and its absolute luminosity value is -8.9.

Absolute the magnitude of the luminosity of our Sun is +5. Not so much! From a distance of 32.6 light years, we would not have seen it well without binoculars.

If the brightness of an ordinary candle is taken to be the brightness of the Sun, then in comparison with it, the “S” of Doradus will be a powerful searchlight, and the faintest star is fainter than the most miserable firefly.

So, the stars are distant suns, but their light intensity can be completely different from that of our luminary. Figuratively speaking, it would be necessary to change our Sun for another one with caution. From the light of one we would be blind, by the light of the other we would wander as in twilight.

Magnitudes

Since the eyes are the first instrument of measurement, we must know simple rules, to which our estimates of the brightness of light sources obey. Our estimate of the brightness difference is relative rather than absolute. Comparing two faint stars, we see that they differ noticeably from each other, but for two bright stars the same difference in brightness remains unnoticed by us, since it is negligible compared to the total amount of light emitted. In other words, our eyes evaluate relative, but not absolute gloss difference.

Hipparchus first divided the stars visible to the naked eye into six classes, according to their brightness. Later, this rule was somewhat improved without changing the system itself. The magnitude classes were distributed so that a 1st magnitude star (the middle of 20) gave a hundred times more light than a 6th magnitude star, which is at the limit of visibility for most people.

A difference of one magnitude equals the square of 2.512. A difference of two magnitudes corresponds to 6.31 (2.512 squared), three magnitudes to 15.85 (2.512 to the third power), four magnitudes to 39.82 (2.512 to the fourth power), and five magnitudes to 100 (2.512 to the power of fifth degree).

A 6th magnitude star gives us a hundred times less light than a 1st magnitude star, and an 11th magnitude star ten thousand times less. If we take a star of the 21st magnitude, then its brightness will be less than 100,000,000 times.

As it is already clear - the absolute and relative driving value,
things are completely incomparable. To a "relative" observer from our planet, Deneb in the constellation Cygnus looks something like this. And in fact, the entire orbit of the Earth would barely be enough to completely contain the circumference of this star.

In order to correctly classify stars (and they all differ from each other), one must carefully ensure that a brightness ratio of 2.512 is maintained along the entire interval between neighboring stellar magnitudes. It is impossible to do such work with a simple eye; special tools are needed, according to the type photometers Pickering, who use the Polar Star or even an "average" artificial star as a standard.

Also, for the convenience of measurements, it is necessary to weaken the light of very bright stars; this can be achieved either with a polarizing device, or with the help of photometric wedge.

Purely visual methods, even with the help of large telescopes, cannot extend our scale of stellar magnitudes to faint stars. In addition, visual methods of measurement should (and can) be made only directly at the telescope. Therefore, a purely visual classification has already been abandoned in our time, and the photoanalysis method is used.

How can you compare the amount of light received by a photographic plate from two stars of different brightness? To make them appear the same, it is necessary to attenuate the light from the brighter star by a known amount. The easiest way to do this is to put the aperture in front of the telescope lens. The amount of light entering a telescope varies with the area of ​​the lens, so that any star's light attenuation can be accurately measured.

Let's choose some star as a standard one and photograph it with a full aperture of the telescope. Then we determine which aperture should be used at a given exposure so that when shooting a brighter star, we get the same image as in the first case. The ratio of the areas of the reduced and full holes gives the ratio of the brightness of the two objects.

This method of measurement gives an error of only 0.1 magnitude for any of the stars in the range from 1st to 18th magnitude. The magnitudes obtained in this way are called photovisual.

Solving problems on the topic: "Sparkle of stars and stellar magnitudes."

#1 How many times brighter is Sirius than Aldebaran? Is the sun brighter than Sirius?

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I1 / I2 - ? !!! mi –star magnitude.

I3 / I1 - ? II- the brightness of a star, the brilliance of a star.

No. 2 How many times a star of 3.4 magnitude is fainter than Sirius, which has a magnitude of -1.6?

https://pandia.ru/text/78/246/images/image004_26.gif">M1=3, 4 I1/I2= 1/ 2.512 5 =1/100.

M2= - 1, 6 Answer: Sirius is 100 brighter than this star

Solve the next problem yourself.

No. 3 How many times Sirius (m1 \u003d -1.6) Polaris

(m2 = + 2, 1)?

Complete test tasks.

We wish you success!!!

Test tasks in astronomy. Topic: “The subject and significance of astronomy. Starry sky. »

1. Astronomy studies:

a) heavenly laws;

b) stars and other celestial bodies;

c) laws of structure, movement and evolution celestial bodies.

2.Physicists gave astronomy:

a) tools for space exploration;

b) forms for calculating and solving problems;

c) methods of studying the Universe.

3. Astronomy you need to know:

a) in order to navigate by the stars;

b) to form a scientific worldview;

c) because it is interesting to know how the world works.

4. The telescope lens is needed in order to:

a) collect light from a celestial object and obtain its image;

b) collect light from a celestial object and increase the angle of view under which the object is visible;

c) get an enlarged image of a celestial body.

5. The telescope eyepiece is needed in order to:

a) get an enlarged image of a celestial body;

b) see the image of a celestial body obtained with the help of a lens;

c) to see at a large angle the image of a celestial body obtained with the help of a lens.

6. An astrograph is different from a telescope designed for visual observations:

a) a smaller increase;

b) a large increase;

c) the absence of an eyepiece.

7. Is it possible to characterize an astrograph intended for photographing in the focus of a lens with its magnification?

a) yes, since the astrograph has a lens;

b) no, because the astrograph does not have an eyepiece;

c) yes, since an important characteristic of any telescope is its magnification.

8. When observing, magnification over 500 times is rarely used, since:

a) images are distorted due to the atmosphere;

b) images are distorted due to lenses;

c) a combination of factors a) and b).

9. The difference between the refractor system and the reflector system is that:

a) the first has an eyepiece against the lens, and the second has it on the side;

b) the reflector has a lens-lens, and the refractor has a mirror;

c) in the refractor, the lens is a lens, and in the reflector, a mirror.

10. To view remote objects in more detail, you need to:

a) increase the diameter of the telescope lens;

b) increase the magnification of the telescope;

c) make wider use of observations in the radio range;

d) in the aggregate a) - c);

e) raise research instruments into space.

11. Astronomy arose:

a) out of curiosity;

b) to navigate along the sides of the horizon;

c) to predict the fate of people and nations;

d) for measuring time and navigation

12. Continue the messages about the starry sky 1)-4), using fragments A-D.

1) We look at the world around us from the Earth, and it always seems to us that a spherical dome strewn with stars extends above us.

2) In the starry sky, the stars maintain their relative position for a long time. For this seeming peculiarity, in ancient times the stars were called fixed.

3) The total number of stars, visible to man with the naked eye in the entire sky, is about 6000, and on one half of it we see about 3000 stars. Stars differ in brilliance, and the brightest and in color.

4) The names of many constellations have been preserved since ancient times. Among the names of the constellations are the names of objects that resemble figures formed by the bright stars of the constellation.

1. The brilliance of a star is understood as the illumination that the light of a star creates on Earth. The brilliance of stars is measured in stellar magnitudes.

2. Separate stars of the constellation from the 17th century. began to be denoted by the letters of the Greek alphabet: "alpha", "beta", "gamma", etc., as a rule, in descending order of brilliance.

3. That is why the idea of ​​a crystal vault arose in ancient times.

4. In reality, all stars move, have their own movements, but since they are very far from us, their annual shift in the sky is only a fraction of an arc second.

1. The stars we observe are located at a wide variety of distances from us, significantly exceeding half a kilometer

2. If it was necessary to designate any more stars in the constellation, but there were not enough letters of the Greek alphabet, then for the following stars they used the letters of the Latin alphabet, and then serial numbers.

3.Now the constellation is understood as a certain area of ​​the sky with visible stars, the boundaries of the constellations are strictly defined.

4. The brightness of stars of the 1st magnitude is 2.512 times greater than the brightness of stars of the second magnitude, 2.512 times the brightness of stars of the 3rd magnitude, etc.

1. Since the stars retain their relative position, already in ancient times people used them as landmarks, in connection with which they identified characteristic combinations of stars in the sky and called them constellations.

2. In ancient times, all stars were divided into six groups according to their brightness: the brightest were assigned to the stars of the first magnitude, the weakest - to the stars of the sixth magnitude.

3. Therefore, the star "alpha" for most constellations is the brightest star in this constellation.

4. In reality, there is no vault, and the impression of the sky in the form of a sphere is explained by the peculiarities of our eye not to catch differences in distances, these distances exceed 0.5 km.

1. The brightest or anything remarkable stars, except for the letter designation, are given proper names(usually Arabic, Greek and Roman). So, the star "alpha" from the constellation Big Dog called Sirius, "alpha" from the constellation Lyra - Vega, "theta" Ursa Major - Alkor, etc.

2. With the help of magnitude, one can express the brilliance of any star, and celestial bodies are brighter than stars of the first magnitude, have zero or negative magnitude. The brilliance of celestial objects not visible to the naked eye is expressed by magnitudes greater than six.

3. In the entire sky, 88 constellations are marked, which completely occupy the starry sky.

4. Therefore, it seems to us that all the stars and other celestial objects are located at the same distances, that is, as if on the surface of a certain sphere in the center of which the observer is always located.

13. Continue statements 1.-4 using fragments:

1). Astronomy is the science of celestial bodies. Modern astronomy studies the movement, structure, interconnection, formation and development of celestial bodies and their systems ...

2). Astronomy is the oldest science on Earth. Astronomy arose from the practical needs of man ...

3). And in our time, astronomy solves a number of practical problems.

4) The development of astronomy contributes to progress in physics, mathematics, chemistry and technology ...

5). Astronomy is of exceptional importance for the formation of a scientific worldview. Observations of the starry sky, the movement of the Sun, Moon and other celestial bodies without scientific knowledge can lead (and actually led) to incorrect views on the structure of the surrounding world and to all sorts of superstitions ...

A . These tasks include exact time, calculation and compilation of a calendar, determination of geographic coordinates on Earth.

B. . As an example, it suffices to point to achievements in the asti rocket technology, the creation of artificial satellites and spaceships. These achievements, in turn, caused the rapid development of radio electronics. This is the practical meaning of astronomy.

V. Astronomy, studying the physical nature of celestial bodies, revealing the actual laws of the structure and movement of them and their systems, asserts the unity of the world, proving that the world is material, that all processes in the Universe proceed as a result natural development without the intervention of any supernatural forces. On the basis of the vast factual material about the world around us, astronomy affirms the scientific worldview.

G. As a result, we get an idea of ​​the structure and development of the part of the Universe accessible to our observations.

D. Where there is no pronounced change of seasons (for example, in Egypt), only by observing starry sky it was possible to set when to start sowing; pastoralists and sailors had a need for orientation both in the desert and at sea - this also forced them to observe the movement of celestial bodies; the development of society gave rise to the calendar.

Write down your homework:

1) Task: Which star is brighter - a 2 m star or a 5 m star?

(2 m is a star of the second magnitude, ...)

2) ??? : a ) What do you think, is it possible to fly to any constellation?

b) How long does it take the light from Sirius to reach us (distance 8.1 * 1016 m)?

literature:

1. "Astronomy-11", Moscow, "Enlightenment", 1994, paragraphs 1, 2.

2., "Astronomy-11", Moscow, "Enlightenment", 1993, paragraphs 1, 2 (2.1), 13.

Check the correctness of the tasks:

No. 3. Answer: Sirius is 30 times brighter than the North Star.

Answer codes for test tasks:

1-B 6-B 11-D 13:

2-B 7-B 12:1-G

3-B 8-B 1) A3-B4-B1-G4. 2-D

4-B 9-B 2) A4-B1-B3-G3. 3-A

5-B 10-D 3) A1-B2-B4-G2. 4-B

4) A2-B3-B2-G1. 5-B.

Tired? Relax! Look!

How beautiful is this world!

GOODBYE!!!

Homework answers:

1) a 2m star is 2.5123 times brighter than a 5m star.

2) A constellation is a conditionally defined section of the sky, within which there are luminaries located at different distances from us. Therefore, the expression "fly to the constellation" is meaningless.

magnitude

Dimensionless physical quantity characterizing , created by a celestial object near the observer. Subjectively, its meaning is perceived as (y) or (y). In this case, the brightness of one source is indicated by comparing it with the brightness of another, taken as a standard. Such standards are usually specially selected non-variable stars. The magnitude was first introduced as an indicator of the apparent brightness of optical stars, but later extended to other radiation ranges:,. The magnitude scale is logarithmic, as is the decibel scale. In the magnitude scale, a difference of 5 units corresponds to a 100-fold difference in the fluxes of light from the measured and reference sources. Thus, a difference of 1 magnitude corresponds to a ratio of light fluxes of 100 1/5 = 2.512 times. Designate the magnitude of the Latin letter "m"(from Latin magnitudo, value) as a superscript in italics to the right of the number. The direction of the magnitude scale is reversed, i.e. the larger the value, the weaker the brilliance of the object. For example, a star of 2nd magnitude (2 m) is 2.512 times brighter than a 3rd magnitude star (3 m) and 2.512 x 2.512 = 6.310 times brighter than a 4th magnitude star (4 m).

Apparent magnitude (m; often referred to simply as "magnitude") indicates the radiation flux near the observer, i.e. the observed brightness of a celestial source, which depends not only on the actual radiation power of the object, but also on the distance to it. The scale of apparent magnitudes originates from the stellar catalog of Hipparchus (before 161 ca. 126 BC), in which all the stars visible to the eye were first divided into 6 classes according to brightness. The stars of the Bucket of the Great Bear have a shine of about 2 m, Vega has about 0 m. For particularly bright luminaries, the magnitude value is negative: for Sirius, about -1.5 m(i.e. the flux of light from it is 4 times greater than from Vega), and the brightness of Venus at some moments almost reaches -5 m(i.e. the light flux is almost 100 times greater than from Vega). We emphasize that the apparent stellar magnitude can be measured both with the naked eye and with the help of a telescope; both in the visual range of the spectrum, and in others (photographic, UV, IR). In this case, "apparent" (English apparent) means "observed", "apparent" and is not specifically related to the human eye (see:).

Absolute magnitude(M) indicates what apparent stellar magnitude the luminary would have if the distance to it were 10 and there would be no . Thus, the absolute stellar magnitude, in contrast to the visible one, allows one to compare the true luminosities of celestial objects (in a given range of the spectrum).

As for the spectral ranges, there are many systems of magnitudes that differ in the choice of a specific measurement range. When observed with the eye (with the naked eye or through a telescope), it is measured visual magnitude(m v). From the image of a star on a conventional photographic plate, obtained without additional light filters, the photographic magnitude(mP). Since photographic emulsion is sensitive to blue light and insensitive to red light, blue stars appear brighter (than it appears to the eye) on the photographic plate. However, with the help of a photographic plate, using orthochromatic and yellow, one obtains the so-called photovisual magnitude scale(m P v), which almost coincides with the visual one. By comparing the brightness of a source measured in different ranges of the spectrum, one can find out its color, estimate the surface temperature (if it is a star) or (if it is a planet), determine the degree of interstellar absorption of light, and other important characteristics. Therefore, standard ones have been developed, mainly determined by the selection of light filters. The most popular tricolor: ultraviolet (Ultraviolet), blue (Blue) and yellow (Visual). At the same time, the yellow range is very close to the photovisual one (B m P v), and blue to photographic (B m P).