(denoted by m - from English. magnitude) - a dimensionless quantity characterizing the brightness of a celestial body (the amount of light coming from it) from the point of view of an earthly observer. The brighter an object, the smaller its apparent magnitude.

The word "apparent" in the name only means that the magnitude is observed from the Earth, and is used to distinguish it from the absolute magnitude. This name refers not only to visible light. The quantity that is perceived by the human eye (or other receiver with the same spectral sensitivity) is called visual.

The magnitude is denoted by a small letter m as a superscript to a numerical value. For example, 2 m means the second magnitude.

Story

The concept of magnitude was introduced by the ancient Greek astronomer Hipparchus in the 2nd century BC. He distributed all the stars accessible to the naked eye into six magnitudes: he called the bright stars of the first magnitude, the naytmyanish - the sixth. For intermediate magnitudes, it was believed that, say, stars of the third magnitude, are as dimmer as the stars of the second magnitude, as they are brighter than the stars of the fourth. This method of measuring brilliance gained popularity thanks to the Almagest, the star catalog of Claudius Ptolemy.

Such a classification scale was used almost unchanged until the middle of the 19th century. The first who treated the stellar magnitude as a quantitative rather than a qualitative characteristic was Friedrich Argelander. It was he who began to confidently apply decimal fractions of stellar magnitudes.

1856 Norman Pogson formalized the magnitude scale, establishing that a first magnitude star is exactly 100 times brighter than a sixth magnitude star. Since, in accordance with the Weber-Fechner law, the change in illumination the same number of times perceived by the eye as a change by the same amount then a difference of one magnitude corresponds to a change in light intensity by a factor of ≈ 2.512. This is an irrational number that is called Pogson number.

So, the scale of stellar magnitudes is logarithmic: the difference in stellar magnitudes of two objects is determined by the equation:

, , are the stellar magnitudes of objects, , are the illuminations created by them.

This formula makes it possible to determine only the difference in stellar magnitudes, but not the magnitudes themselves. In order to build an absolute scale with its help, it is necessary to set a zero point — illumination, which corresponds to zero magnitude (0 m). At first, Pogson used the North Star as a standard, assuming that it has exactly the second magnitude. After it became clear that Polaris was a variable star, the scale began to be tied to Vega (which was assigned a zero value), and then (when Vega was also suspected of variability), the zero point of the scale was redefined with the help of several other stars. However, for visual observations, Vega can serve as a standard of zero magnitude even further, since its magnitude in visible light is 0.03 m, which does not differ from zero by eye.

The modern magnitude scale is not limited to six magnitudes or just visible light. The magnitude of very bright objects is negative. For example, Sirius, the brightest star in the night sky, has an apparent magnitude of -1.47m. Modern technology also makes it possible to measure the brightness of the Moon and the Sun: the full Moon has an apparent magnitude of -12.6 m, and the Sun -26.8 m. The Hubble Orbital Telescope can observe stars up to 31.5 m in the visible range.

Spectral dependence

The stellar magnitude depends on the spectral range in which the observation is carried out, since the luminous flux from any object in different ranges is different.

• Bolometric magnitude shows the total radiation power of the object, that is, the total flux in all spectral ranges. Bolometer is measured.

The most common photometric system, the UBV system, has 3 bands (spectral ranges in which measurements are made). Accordingly, there are:

• ultraviolet magnitude (U)- determined in the ultraviolet range;

• "Blue" magnitude (B) — is determined in the blue range;

• visual magnitude (V)- is determined in the visible range; the spectral response curve is chosen to better match human vision. The eye is most sensitive to yellow-green light with a wavelength of about 555 nm.

The difference (U-B or B-V) between the magnitudes of the same object in different bands shows its color and is called the color index. The higher the color index, the redder the object.

There are other photometric systems, each of which has different bands and, accordingly, different quantities can be measured. For example, in the old photographic system, the following quantities were used:

• photovisual magnitude (m pv)- a measure of blackening the image of an object on a photographic plate with an orange light filter;

• photographic magnitude (m pg)- measured on a conventional photographic plate, which is sensitive to the blue and ultraviolet ranges of the spectrum.

Apparent stellar magnitudes of some objects

An object	m
The sun	-26,73
Full moon	-12,92
Iridium flare (maximum)	-9,50
Venus (maximum)	-4,89
Venus (minimum)	-3,50
Jupiter (maximum)	-2,94
Mars (maximum)	-2,91
Mercury (maximum)	-2,45
Jupiter (minimum)	-1,61
Sirius (the brightest star in the sky)	-1,47
Canopus (2nd brightest star in the sky)	-0,72
Saturn (maximum)	-0,49
Alpha Centauri cumulative brightness A, B	-0,27
Arcturus (3rd brightest star in the sky)	0,05
Alpha Centauri A (4th brightest star in the sky)	-0,01
Vega (5th brightest star in the sky)	0,03
Saturn (minimum)	1,47
Mars (minimum)	1,84
SN 1987A - supernova 1987 in the Large Magellanic Cloud	3,03
Andromeda's nebula	3,44
Faint stars that are visible in metropolitan areas	3 … + 4
Ganymede is a moon of Jupiter, the largest moon in the solar system (maximum)	4,38
4 Vesta (bright asteroid), at maximum	5,14
Uranus (maximum)	5,32
Triangulum Galaxy (M33), visible to the naked eye in clear skies	5,72
Mercury (minimum)	5,75
Uranus (minimum)	5,95
Naymanishi stars visible to the naked eye in the countryside	6,50
Ceres (maximum)	6,73
NGC 3031 (M81), visible to the naked eye under perfect skies	6,90
Nightmanish stars visible to the naked eye in a perfect sky (Mauna Kea Observatory, Atacama Desert)	7,72
Neptune (maximum)	7,78
Neptune (minimum)	8,01
Titan is a moon of Saturn, the 2nd largest moon in the solar system (maximum)	8,10
Proxima Centauri	11,10
The brightest quasar	12,60
Pluto (maximum)	13,65
Makemake in opposition	16,80
Haumea in opposition	17,27
Eris in opposition	18,70
Faint stars seen in a 24" CCD image with a 30 minute exposure	22
The smallest object available on the 8-meter ground-based telescope	27
The smallest object available on the Hubble Space Telescope	31,5
The smallest object that will be available on the 42-meter ground-based telescope	36
The smallest object that will be available on the OWL orbiting telescope (launch is scheduled for 2020)	38

Each of these stars has a certain magnitude that allows you to see them.

A magnitude is a numerical dimensionless quantity that characterizes the brightness of a star or other cosmic body in relation to the apparent area. In other words, this value reflects the number of electromagnetic waves registered by the body by the observer. Therefore, this value depends on the characteristics of the observed object and the distance from the observer to it. The term covers only the visible, infrared and ultraviolet spectra of electromagnetic radiation.

In relation to point sources of light, the term "brilliance" is also used, and for extended ones - "brightness".

An ancient Greek scholar who lived in Turkey in the 2nd century BC. e., is considered one of the most influential astronomers of antiquity. He compiled a volumetric, the first in Europe, describing the location of more than a thousand heavenly bodies. Hipparchus also introduced such a characteristic as a magnitude. Observing the stars with the naked eye, the astronomer decided to divide them by brightness into six magnitudes, where the first magnitude is the brightest object, and the sixth is the dimmest.

In the 19th century, the British astronomer Norman Pogson improved the scale for measuring stellar magnitudes. He expanded the range of its values ​​and introduced a logarithmic dependence. That is, with an increase in magnitude by one, the brightness of the object decreases by a factor of 2.512. Then a star of the 1st magnitude (1 m) is a hundred times brighter than a star of the 6th magnitude (6 m).

Magnitude standard

The standard of a celestial body with zero magnitude was initially taken as the brilliance of the brightest point in. Somewhat later, a more accurate definition of an object of zero magnitude was presented - its illumination should be 2.54 10 −6 lux, and the luminous flux in the visible range is 10 6 quanta / (cm² s).

Apparent magnitude

The characteristic described above, which was identified by Hipparchus of Nicaea, later became known as "visible" or "visual". This means that it can be observed both with the help of human eyes in the visible range, and using various instruments such as a telescope, including ultraviolet and infrared range. The magnitude of the constellation is 2 m . However, we know that Vega with zero magnitude (0 m) is not the brightest star in the sky (the fifth in brightness, the third for observers from the territory of the CIS). Therefore, brighter stars can have a negative magnitude, for example, (-1.5 m). It is also known today that among the heavenly bodies there can be not only stars, but also bodies that reflect the light of stars - planets, comets or asteroids. The total magnitude is −12.7 m.

Absolute magnitude and luminosity

In order to be able to compare the true brightness of cosmic bodies, such a characteristic as absolute magnitude was developed. According to it, the value of the apparent stellar magnitude of the object is calculated if this object were located 10 (32.62) from the Earth. In this case, there is no dependence on the distance to the observer when comparing different stars.

Absolute magnitude for space objects uses a different distance from the body to the observer. Namely, 1 astronomical unit, while, in theory, the observer should be in the center of the Sun.

A more modern and useful quantity in astronomy has become "luminosity". This characteristic determines the total that the cosmic body radiates over a certain period of time. For its calculation, the absolute stellar magnitude is just used.

Spectral dependence

As mentioned earlier, the magnitude can be measured for different types of electromagnetic radiation, and therefore has different values ​​for each range of the spectrum. To obtain a picture of any space object, astronomers can use, which are more sensitive to the high-frequency part of visible light, and the stars turn out to be blue in the image. Such a stellar magnitude is called "photographic", m Pv . To get a value close to visual (“photovisual”, m P), the photographic plate is covered with a special orthochromatic emulsion and a yellow light filter is used.

Scientists have compiled a so-called photometric system of ranges, thanks to which it is possible to determine the main characteristics of cosmic bodies, such as: surface temperature, degree of light reflection (albedo, not for stars), degree of light absorption, and others. To do this, the luminary is photographed in different spectra of electromagnetic radiation and the subsequent comparison of the results. The following filters are most popular for photography: ultraviolet, blue (photographic magnitude) and yellow (close to the photovisual range).

A photograph with captured energies of all ranges of electromagnetic waves determines the so-called bolometric magnitude (m b). With its help, knowing the distance and the degree of interstellar extinction, astronomers calculate the luminosity of a cosmic body.

Star magnitudes of some objects

• Sun = -26.7 m
• Full Moon = -12.7 m
• Flash Iridium = -9.5 m. Iridium is a system of 66 satellites that orbit the Earth and serve to transmit voice and other data. Periodically, the surface of each of the three main vehicles reflects sunlight towards the Earth, creating the brightest smooth flash in the sky for up to 10 seconds.

Stars are the most common type of celestial bodies in the universe. There are about 6000 stars up to the 6th magnitude, about a million up to the 11th magnitude, and about 2 billion of them in the entire sky up to the 21st magnitude.

All of them, like the Sun, are hot self-luminous gas balls, in the depths of which huge energy is released. However, the stars, even in the most powerful telescopes, are visible as luminous points, since they are very far from us.

1. Annual parallax and distances to stars

The radius of the Earth turns out to be too small to serve as a basis for measuring the parallactic displacement of stars and for determining the distances to them. Even in the time of Copernicus, it was clear that if the Earth really revolves around the Sun, then the apparent positions of the stars in the sky must change. In six months, the Earth moves by the diameter of its orbit. Directions to the star from opposite points of this orbit must be different. In other words, the stars should have a noticeable annual parallax (Fig. 72).

The annual parallax of a star ρ is the angle at which one could see the semi-major axis of the earth's orbit (equal to 1 AU) from a star if it is perpendicular to the line of sight.

The greater the distance D to the star, the smaller its parallax. The parallactic shift of the star's position in the sky during the year occurs along a small ellipse or circle if the star is at the ecliptic pole (see Fig. 72).

Copernicus tried but failed to detect the parallax of the stars. He correctly asserted that the stars were too far from the Earth for the then existing instruments to detect their parallactic displacement.

The first reliable measurement of the annual parallax of the star Vega was made in 1837 by the Russian academician V. Ya. Struve. Almost simultaneously with him in other countries, the parallaxes of two more stars were determined, one of which was α Centauri. This star, which is not visible in the USSR, turned out to be the closest to us, its annual parallax is ρ = 0.75". At this angle, a wire 1 mm thick is visible to the naked eye from a distance of 280 m. small angular displacements.

Distance to the star where a is the semi-major axis of the earth's orbit. At small angles if p is expressed in arcseconds. Then, taking a = 1 a. e., we get:

Distance to the nearest star α Centauri D \u003d 206 265 ": 0.75" \u003d 270,000 a. e. Light travels this distance in 4 years, while it takes only 8 minutes from the Sun to the Earth, and about 1 s from the Moon.

The distance light travels in a year is called a light year.. This unit is used to measure distance along with the parsec (pc).

A parsec is the distance from which the semi-major axis of the earth's orbit, perpendicular to the line of sight, is visible at an angle of 1".

The distance in parsecs is equal to the reciprocal of the annual parallax, expressed in arcseconds. For example, the distance to the star α Centauri is 0.75" (3/4"), or 4/3 pc.

1 parsec = 3.26 light years = 206,265 AU e. = 3 * 10 13 km.

At present, the measurement of the annual parallax is the main method for determining the distances to stars. Parallaxes have already been measured for very many stars.

By measuring the annual parallax, one can reliably determine the distance to stars located no further than 100 pc, or 300 light years.

Why is it not possible to accurately measure the annual parallax of more than o distant stars?

The distance to more distant stars is currently determined by other methods (see §25.1).

2. Apparent and absolute magnitude

The luminosity of the stars. After astronomers were able to determine the distances to the stars, it was found that the stars differ in apparent brightness, not only because of the difference in their distance, but also because of the difference in their luminosity.

The luminosity of a star L is the power of emission of light energy in comparison with the power of emission of light by the Sun.

If two stars have the same luminosity, then the star that is farthest from us has a lower apparent brightness. Comparing stars by luminosity is possible only if their apparent brightness (magnitude) is calculated for the same standard distance. Such a distance in astronomy is considered to be 10 pc.

The apparent stellar magnitude that a star would have if it were at a standard distance D 0 \u003d 10 pc from us was called the absolute magnitude M.

Let us consider the quantitative ratio of the apparent and absolute stellar magnitudes of a star at a known distance D to it (or its parallax p). Recall first that a difference of 5 magnitudes corresponds to a brightness difference of exactly 100 times. Consequently, the difference in apparent stellar magnitudes of two sources is equal to one, when one of them is brighter than the other exactly one time (this value is approximately equal to 2.512). The brighter the source, the smaller its apparent magnitude is considered. In the general case, the ratio of the apparent brightness of any two stars I 1:I 2 is related to the difference in their apparent magnitudes m 1 and m 2 by a simple relationship:

Let m be the apparent magnitude of a star located at a distance D. If it were observed from a distance D 0 = 10 pc, its apparent magnitude m 0 would, by definition, be equal to the absolute magnitude M. Then its apparent brightness would change by

At the same time, it is known that the apparent brightness of a star varies inversely with the square of its distance. So

(2)

Hence,

(3)

Taking the logarithm of this expression, we find:

(4)

where p is expressed in arcseconds.

These formulas give the absolute magnitude M from the known apparent magnitude m at a real distance to the star D. From a distance of 10 pc, our Sun would look approximately like a star of the 5th apparent magnitude, i.e. for the Sun M ≈5.

Knowing the absolute magnitude M of a star, it is easy to calculate its luminosity L. Taking the luminosity of the Sun L = 1, by definition of luminosity, we can write that

The values ​​of M and L in different units express the radiation power of the star.

The study of stars shows that they can differ in luminosity by tens of billions of times. In stellar magnitudes, this difference reaches 26 units.

Absolute values stars of very high luminosity are negative and reach M = -9. Such stars are called giants and supergiants. The radiation of the star S Doradus is 500,000 times more powerful than the radiation of our Sun, its luminosity is L=500,000, dwarfs with M=+17 (L=0.000013) have the lowest radiation power.

To understand the reasons for the significant differences in the luminosity of stars, it is necessary to consider their other characteristics, which can be determined on the basis of radiation analysis.

3. Color, spectra and temperature of stars

During your observations, you noticed that the stars have a different color, which is clearly visible in the brightest of them. The color of a heated body, including stars, depends on its temperature. This makes it possible to determine the temperature of stars from the distribution of energy in their continuous spectrum.

The color and spectrum of stars are related to their temperature. In relatively cold stars, radiation in the red region of the spectrum predominates, which is why they have a reddish color. The temperature of red stars is low. It rises sequentially as it goes from red to orange, then to yellow, yellowish, white, and bluish. The spectra of stars are extremely diverse. They are divided into classes, denoted by Latin letters and numbers (see back flyleaf). In the spectra of cool red stars of class M with a temperature of about 3000 K, absorption bands of the simplest diatomic molecules, most often titanium oxide, are visible. The spectra of other red stars are dominated by oxides of carbon or zirconium. Red stars of the first magnitude class M - Antares, Betelgeuse.

In the spectra of yellow G stars, which include the Sun (with a temperature of 6000 K on the surface), thin lines of metals predominate: iron, calcium, sodium, etc. A star like the Sun in terms of spectrum, color and temperature is the bright Chapel in the constellation Auriga.

In the spectra of white class A stars, like Sirius, Vega and Deneb, the hydrogen lines are the strongest. There are many weak lines of ionized metals. The temperature of such stars is about 10,000 K.

In the spectra of the hottest, bluish stars with a temperature of about 30,000 K, lines of neutral and ionized helium are visible.

The temperatures of most stars are between 3,000 and 30,000 K. A few stars have temperatures around 100,000 K.

Thus, the spectra of stars are very different from each other, and they can be used to determine the chemical composition and temperature of the atmospheres of stars. The study of the spectra showed that hydrogen and helium are predominant in the atmospheres of all stars.

The differences in stellar spectra are explained not so much by the diversity of their chemical composition as by the difference in temperature and other physical conditions in stellar atmospheres. At high temperatures, molecules break down into atoms. At an even higher temperature, less durable atoms are destroyed, they turn into ions, losing electrons. Ionized atoms of many chemical elements, like neutral atoms, emit and absorb energy of certain wavelengths. By comparing the intensity of the absorption lines of atoms and ions of the same chemical element, their relative number is theoretically determined. It is a function of temperature. So, from the dark lines of the spectra of stars, you can determine the temperature of their atmospheres.

Stars of the same temperature and color, but different luminosities, have the same spectra in general, but one can notice differences in the relative intensities of some lines. This is due to the fact that at the same temperature the pressure in their atmospheres is different. For example, in the atmospheres of giant stars, the pressure is less, they are rarer. If this dependence is expressed graphically, then the absolute magnitude of the star can be found from the intensity of the lines, and then, using formula (4), the distance to it can be determined.

Problem solution example

Task. What is the luminosity of the star ζ Scorpio, if its apparent magnitude is 3, and the distance to it is 7500 sv. years?

Exercise 20

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

2. One star is 16 times brighter than the other. What is the difference between their magnitudes?

3. The parallax of Vega is 0.11". How long does it take the light from it to reach the Earth?

4. How many years would it take to fly towards the constellation Lyra at a speed of 30 km / s for Vega to become twice as close?

5. How many times is a star of magnitude 3.4 fainter than Sirius, which has an apparent magnitude of -1.6? What are the absolute magnitudes of these stars if the distance to both is 3 pc?

6. Name the color of each of the stars in Appendix IV according to their spectral type.

(from Wikipedia)

Magnitude - a numerical characteristic of an object in the sky, most often a star, showing how much light comes from it to the point where the observer is located.

Visible (visual)

The modern concept of apparent stellar magnitude is made in such a way that it corresponds to the magnitudes attributed to the stars by the ancient Greek astronomer Hipparchus in the 2nd century BC. e. Hipparchus divided all the stars into six magnitudes. He called the brightest stars of the first magnitude, the dimmest - the stars of the sixth magnitude. Intermediate values ​​he distributed evenly among the remaining stars.

The apparent stellar magnitude depends not only on how much light an object emits, but also on how far it is from the observer. Apparent stellar magnitude is considered a unit of measurement shine stars, and the greater the brilliance, the smaller the magnitude, and vice versa.

In 1856, N. Pogson proposed a formalization of the magnitude scale. The apparent stellar magnitude is determined by the formula:

Where I- luminous flux from the object, C- constant.

Since this scale is relative, its zero point (0 m ) is defined as the brightness of such a star, in which the luminous flux is 10³ quanta / (cm² s Å) in green light (UBV scale) or 10 6 quanta / (cm² ) s·Å) in the entire visible range of light. A star 0 m outside the earth's atmosphere creates an illumination of 2.54 10 −6 lux.

The scale of stellar magnitudes is logarithmic, since a change in brightness by the same number of times is perceived as the same (Weber-Fechner law). In addition, since Hipparchus decided that the magnitude of the topics smaller than a star brighter, then there is a minus sign in the formula.

The following two properties help to use apparent stellar magnitudes in practice:

1. An increase in the luminous flux by a factor of 100 corresponds to a decrease in the apparent stellar magnitude by exactly 5 units.
2. A decrease in magnitude by one unit means an increase in the luminous flux by 10 1/2.5 = 2.512 times.

Today, the apparent stellar magnitude is used not only for stars, but also for other objects, for example, for the Moon and the Sun and planets. Because they can be brighter than the brightest star, they can have a negative apparent magnitude.

The apparent stellar magnitude depends on the spectral sensitivity of the radiation receiver (eye, photoelectric detector, photographic plate, etc.)

• visual magnitude ( V or m v ) is determined by the sensitivity spectrum of the human eye (visible light), which has a maximum sensitivity at a wavelength of 555 nm. or photographically with an orange filter.

• photographic or "blue" magnitude ( B or m p ) is determined by photometering the image of a star on a photographic plate sensitive to blue and ultraviolet rays, or using an antimony-cesium photomultiplier with a blue filter.

• ultraviolet magnitude ( U) has a maximum in the ultraviolet at a wavelength of about 350 nm.

Differences in magnitudes of one object in different ranges U−B and B−V are integral indicators of the color of the object, the larger they are, the more red the object is.

• Bolometric the magnitude corresponds to the total radiation power of the star, i.e., the power summed over the entire radiation spectrum. To measure it, a special device is used - a bolometer.

absolute

Absolute magnitude (M ) is defined as the apparent magnitude of an object if it were located at a distance of 10 parsecs from the observer. The absolute bolometric magnitude of the Sun is +4.7. If the apparent stellar magnitude and the distance to the object are known, the absolute stellar magnitude can be calculated using the formula:

where d 0 = 10 pc ≈ 32.616 light years.

Accordingly, if the apparent and absolute stellar magnitudes are known, the distance can be calculated using the formula

Absolute magnitude is related to luminosity by the following relationship: where and are the luminosity and absolute magnitude of the Sun.

Star magnitudes of some objects

An object	m
The sun	−26,7
moon at full moon	−12,7
Iridium Burst (maximum)	−9,5
Supernova 1054 (maximum)	−6,0
Venus (maximum)	−4,4
Earth (as seen from the Sun)	−3,84
Mars (maximum)	−3,0
Jupiter (maximum)	−2,8
International Space Station (maximum)	−2
Mercury (maximum)	−1,9
Andromeda Galaxy	+3,4
Proxima Centauri	+11,1
The brightest quasar	+12,6
The faintest stars visible to the naked eye	+6 to +7
The faintest object captured by an 8-meter ground-based telescope	+27
The faintest object captured by the Hubble Space Telescope	+30

An object	Constellation	m
Sirius	big dog	−1,47
Canopus	Keel	−0,72
α Centauri	Centaurus	−0,27
Arcturus	Bootes	−0,04
Vega	Lyra	0,03
Chapel	Auriga	+0,08
Rigel	Orion	+0,12
Procyon	small dog	+0,38
Achernar	eridanus	+0,46
Betelgeuse	Orion	+0,50
Altair	Eagle	+0,75
Aldebaran	Taurus	+0,85
Antares	Scorpion	+1,09
Pollux	Twins	+1,15
Fomalhaut	southern fish	+1,16
Deneb	Swan	+1,25
Regulus	a lion	+1,35

Sun from different distances

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?

https://pandia.ru/text/78/246/images/image002_37.gif" width="158" height="2 src=">

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) the laws of the structure, movement and evolution of 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 the naked eye in the whole sky is about 6000, and in 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 most remarkable stars, in addition to the letter designation, are given their own names (usually Arabic, Greek and Roman). So, the star "alpha" from the constellation Canis Major is 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 kinds of superstitions ...

BUT . These tasks include accurate 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 spacecraft. These achievements, in turn, caused the rapid development of radio electronics. This is the practical meaning of astronomy.

AT. Astronomy, studying the physical nature of celestial bodies, revealing the actual laws of the structure and movement of them and their systems, affirms the unity of the world, proving that the world is material, that all processes in the Universe proceed as a result of 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.

E. Where there is no pronounced change of seasons (for example, in Egypt), it was only by observing the starry sky that it was possible to establish 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.