Comets. Constellations. Star cards. Celestial coordinates Solution from the negative angular size of the comet's tail
Subject: Astronomy.
Class: 10 11
Teacher: Elakova Galina Vladimirovna.
Place of work: Municipal budgetary educational institution
"Average comprehensive school No. 7" Kanash, Chuvash Republic
Verification work on the topic “Comets, meteors and meteorites.”
Testing and assessing knowledge – required condition effectiveness of the educational process.
Test thematic control can be carried out in writing or in groups with different
level of training. Such a check is quite objective, time-saving,
provides an individual approach. Additionally, students can use tests
to prepare for tests and VPR. The use of the proposed work does not exclude
application of other forms and methods of testing students’ knowledge and skills, such as
oral questioning, preparation design work, abstracts, reports, essays, etc.
Option I:
1. What was the general historical view of comets?
2. Why does the comet move away from the Sun with its tail first?
A. Comet tails are formed as a result of the pressure of solar radiation, which
always points away from the Sun, so the comet's tail always points away from the Sun.
B. Comet tails are formed as a result of the pressure of solar radiation and solar
winds that are always directed away from the Sun, so that the comet's tail is also always directed
from the sun.
B. Comet tails are formed as a result of the solar wind, which is always directed
away from the Sun, so that the tail of a comet is always directed away from the Sun.
3. What is a "shooting star"?
A. Very small solid particles orbiting the Sun.
B. This is a strip of light that becomes visible at the moment of complete combustion of the meteoroid
bodies.
Q. This is a piece of stone or metal that flew from the depths of space.
4. How can you distinguish an asteroid from a star in the starry sky?
A. By movement relative to the stars.
B. Along elongated (with large eccentricity) elliptical orbits.
B. Asteroids do not change their position in the starry sky.
5. Is it possible to observe meteors on the Moon?
A. Yes, meteors can be seen everywhere.
B. No, due to the lack of atmosphere.
Q. Yes, meteors can be observed on the Moon, since the absence of an atmosphere does not play a role.
6. Where in the Solar System are the orbits of most asteroids located? How
Do the orbits of some asteroids differ from the orbits of major planets?
A. Between the orbits of Uranus and Jupiter. The orbits are characterized by low eccentricity.
B. Between the orbits of Mars and Jupiter. The orbits are characterized by low eccentricity.
B. Between the orbits of Mars and Jupiter. The orbits are characterized by high eccentricity.
7. How was it determined that some asteroids have an irregular shape?
A. By changing their apparent brightness.
B. By movement relative to the stars.
B. Along elongated (with large eccentricity) elliptical orbits.
8. What is special about the asteroids that make up the “Trojan” group? Answer
justify.
A. Asteroids, together with Jupiter and the Sun, form an equilateral triangle and
move around the Sun in the same way as Jupiter, but only in front of it.
B. Asteroids, together with Jupiter and the Sun, form an equilateral triangle and
move around the Sun in the same way as Jupiter, but either ahead of it or behind it.
B. Asteroids, together with Jupiter and the Sun, form an equilateral triangle and
move around the Sun in the same way as Jupiter, but only behind it.
9. Sometimes a comet develops two tails, one of which is directed towards
to the Sun, and the other from the Sun. How can this be explained?
A. The tail directed towards the Sun consists of larger particles for which the force
The solar attraction is greater than the repulsive force of its rays.
10. Flying past the Earth at a distance of 1 AU. a comet has a tail
corner
size 0°.5. Estimate the length of the comet's tail in kilometers.
≈
1.3 ∙ 106 km.
A.
≈
B.
13 ∙ 106 km.
≈
IN.
0.13 ∙ 106 km.
Option II:
1. What are the modern astronomical ideas about comets?
A. Comets were considered supernatural phenomena that brought misfortune to people.
B. Comets are members of the solar system, which in their movement obey
laws of physics and have no mystical significance.
2. Indicate the correct answers to changes in the appearance of the comet as it
movement in orbit around the Sun.
A. A comet is far from the Sun, it consists of a core (frozen gases and dust).
B. As it approaches the Sun, a coma forms.
B. A tail forms in close proximity to the Sun.
D. As it moves away from the Sun, cometary matter freezes.
D. On long distance the coma and tail disappear from the Sun.
E. All answers are correct.
3. Match each description with the correct title: (a) “Shooting Star.” 1.
Meteor; (b) A small particle orbiting the Sun. 2. Meteorite; (V)
A solid body that reaches the surface of the Earth. 3. Meteor body.
A. (a) 1; (b) 3; (at 2.
B. (a) 3; (b) 1; (at 2.
V. (a) 2; (b) 1; (at 3.
4. Achilles, Quaoar, Proserpina, Themis, Juno. Please indicate the odd one out on this list.
and justify your choice.
A. Achilles, a name taken from ancient mythology, is a main belt asteroid.
B. Quaoar - it belongs to the Kuiper belt, named after the creator deity
Tongva Indians.
V. Proserpina, a name taken from ancient mythology, is a main belt asteroid.
G. Themis is a name taken from ancient mythology, a main belt asteroid.
D. Juno, a name taken from ancient mythology, is a main belt asteroid.
5. What changes in the movement of comets cause disturbances from outside
Jupiter?
A. The shape of the comet's orbit changes.
B. The comet's orbital period changes.
B. The shape of the orbit and the period of revolution of the comet change.
6. In what state is the substance that makes up the comet’s nucleus and its
tail?
A. Comet nucleus - solid consisting of a mixture of frozen gases and solid particles
refractory substances, the tail is rarefied gas and dust.
B. The tail of a comet is a solid body consisting of a mixture of frozen gases and solid particles
refractory substances, the core is rarefied gas and dust.
B. The nucleus and tail of a comet are a solid body consisting of a mixture of frozen gases and solids
particles of refractory substances.
7. Which of the following phenomena can be observed on the Moon: meteors, comets,
eclipses, auroras.
A. Due to the lack of atmosphere on the Moon, meteors and polar stars cannot be observed there.
radiance. Comets and solar eclipses Can be seen.
B. On the Moon you can see meteors and auroras. Comets and solar
there is no eclipse.
B. All of the above phenomena can be observed.
8. How can you estimate the linear dimensions of an asteroid if its angular dimensions
cannot be measured even when observed through a telescope?
A. Knowing the distance from the Earth and from the Sun, and taking some average value
reflectivity of the asteroid's surface, its linear dimensions can be estimated.
B. Knowing the distance from the Earth and from the Sun, we can estimate its linear dimensions.
B. Knowing some average reflectivity of the asteroid surface
one can estimate its linear dimensions.
9. “If you want to see a comet worth seeing, you need to get outside
our solar system, to where they can turn around, you know? I am a friend
my, I saw such specimens there that could not even fit into the orbits
our most famous comets - their tails would definitely hang out."
Is the statement true?
A. Yes, because outside the solar system and far from other similar systems
comets have tails like this.
B. No, because outside the solar system and far from other similar systems
comets have no tails and are negligible in size.
10. Compare the reasons for the glow of a comet and a planet. Is it possible to notice
differences in the spectra of these bodies? Give a detailed answer.
Answers:
Option I: 1 – A; 2 – B; 3 – B; 4 – A; 5 B; 6 – B; 7 – A; 8 – B; 9 – A; 10 – A.
Option II: 1 – B; 2 – E; 3 –A; 4 B; 5 – B; 6 – A; 7 – A; 8A; 9 – B;
.α
Option I:
Solution to problems No. 10: Suppose that the comet's tail is directed perpendicular to the ray
vision. Then its length can be estimated as follows. Let us denote the angular size of the tail
/2α can be found from right triangle, one of the legs
Half this angle
which is half the length of the comet's tail p/2, and the other is the distance from Earth to
° .5 is small, so we can approximately assume that
comet L. Then tg
its tangent is equal to the angle itself (expressed in radians). Then we can write that α
≈
150 ∙ 106 km, we get p
Hence, remembering that the astronomical unit is
1.3 ∙ 106 km.
α
/2 = p/2 L . Angle 0
150 ∙ 106 ∙ (0.5/57)
p/L.
≈ α ≈
L∙
There is another assessment option. You can notice that the comet flies from Earth to
distance, equal to the distance from the Earth to the Sun, and its tail has an angular size,
equal to the apparent angular diameter of the Sun in the earth's sky. Therefore linear
the size of the tail is equal to the diameter of the Sun, the value of which is close to that obtained above
result. However, we have no information about how the comet's tail is oriented in
space. Therefore, it should be concluded that the estimate of the tail length obtained above is
this is the minimum possible value. So the final answer looks like this: length
The comet's tail is at least 1.3 million kilometers.
Option II:
Solution to problem No. 4: Extra Quaoar, because it belongs to the Kuiper belt. All
the remaining objects are main belt asteroids. All listed main asteroids
the belts have names taken from ancient mythology, and the name "Quaoar" clearly has
other semantic roots. Quaoar was named after the creator deity among the Indians
Tongva tribe.
Solution to problem No. 10: The comet nucleus and the dust located in the head and tail of the comet,
reflect sunlight. The gases that make up the head and tail themselves glow due to
energy received from the Sun. Planets reflect sunlight. So in both
absorption lines characteristic of the solar spectrum will be observed in the spectra. TO
these lines in the spectrum of the planet are added to the absorption lines of the gases that make up
atmosphere of the planet, and in the spectrum of the comet - the emission lines of the gases included in the composition
comets.
Literature:
1. G.I. Malakhova, E.K. Strout " Didactic material on astronomy": A manual for
teachers. M.: education, 1989.
2. Moshe D. Astronomy: Book. for students. Per. from English / Ed. A.A. Gurshtein. – M.:
Enlightenment, 1985.
3. V.G. Surdin. Astronomical Olympiads. Problems with solutions – Moscow, Publishing House
Educational and Scientific Center pre-university training Moscow State University, 1995.
4. V.G. Surdin. Astronomical problems with solutions - Moscow, URSS, 2002.
5. Objectives of the Moscow Astronomical Olympiad. 19972002. Ed. O.S.
Ugolnikova, V.V. Chichmarya - Moscow, MIOO, 2002.
6. Objectives of the Moscow Astronomical Olympiad. 20032005. Ed. O.S.
Ugolnikova, V.V. Chichmarya - Moscow, MIOO, 2005.
7. A.M. Romanov. Interesting questions on astronomy and more - Moscow, ICSME,
2005.
8. All-Russian Olympiad for schoolchildren in astronomy. Auto status A.V. Zasov, etc. –
Moscow, Federal Agency for Education, AIC and PPRO, 2005.
9. All-Russian Olympiad for schoolchildren in astronomy: content of the Olympiad and
preparation of competitors. Auto status O. S. Ugolnikov – Moscow, Federal Agency
on education, AIC and PPRO, 2006 (in press).
Internet resources:
1. Official website of everyone All-Russian Olympiads, created on the initiative
Ministry of Education and Science Russian Federation And Federal agency By
education http://www.rusolymp.ru
2. Official website of the All-Russian Astronomical Olympiad
http://lnfm1.sai.msu.ru/~olympiad
3. Website of the Astronomical Olympiads of St. Petersburg and Leningrad region -
problems and solutions http://school.astro.spbu.ru
Bright K. can have several. tails of different lengths and colors, parallel stripes may be observed in the tail, and concentric stripes around the “head” of K. rings-galos.
Title "K." comes from the Greek. the words kometes, literally - long-haired (bright K. look like a head with flowing hair, Fig. 1). 5-10 K are opened annually. Each of them is assigned a preliminary designation, including the name of the K. who discovered it, the year of discovery and a letter of the Latin alphabet in the order of discovery. Then he will be replaced and finished. a designation including the year of passage through perihelion and a Roman numeral in order of the dates of passage through perihelion.K. are observed when a small body - the K.'s core, resembling a lump of snow, contaminated with fine dust and larger solid particles, approaches the Sun closer than 4-6 AU. e., is heated by its rays and begins to release gases and dust particles. Gases and dust create a foggy shell around the core (C.'s atmosphere), called a coma, the brightness of the swarm quickly decreases towards the periphery. The atmosphere of the planet continuously dissipates into space and exists only when gases and dust are released from the core. In many comas, a star-shaped core is visible in the center of the coma, which is a dense part of the atmosphere that hides the true (solid) core, which is practically inaccessible to observation. The visible nucleus, together with the coma, makes up K.'s head (Fig. 2). From the side of the Sun, the K.'s head has the shape of a parabola or a chain line, which is explained by the constant action of light pressure and solar wind on the K.'s atmosphere. The K.'s tails consist of ionized gases and dust carried away in the direction from the Sun (dust is mainly under the influence of light pressure , and ionized gases - as a result of interaction with ). Large solid particles, under the influence of light pressure, acquire small accelerations and, having low velocities relative to the nucleus (due to their weak entrainment by gases), gradually spread along the orbit of the meteor, forming a meteor swarm. Neutral atoms and molecules experience only a small amount. light pressure and therefore scatter almost evenly in all directions from the K nucleus.
As the moon approaches the Sun and the heating of the core increases, the intensity of the release of gases and dust sharply increases, which is manifested in a rapid increase in the brightness of the moon and an increase in the brightness of the tails. As stars move away from the Sun, their brightness quickly decreases. If we approximate the change in the brightness of K.’s head by law 1/ rn, r- distance from the Sun), then on average 4 (individual K. have significant deviations from this law). On the smooth change in the shine of K.’s head associated with changes r, brightness fluctuations are superimposed and bright flashes, caused by the “explosive” ejection of matter from cometary nuclei with a sharp increase in the flow of particles of solar origin.
The diameters of K.'s nuclei are presumably 0.5-20 km, and, therefore, with a density of ~ 1 g/cm 3, their masses are within the range of 10 14 -10 19 g.
However, cells with significantly larger nuclei occasionally appear. Numerous nuclei smaller than 0.5 km generate weak nuclei that are practically inaccessible to observation. The visible diameters of the stars' heads are 10 4 -10 6 km, varying with distance from the Sun. Some K. have max. the size of the head exceeded the size of the Sun. Even larger sizes (over 10 7 km) have shells made of atomic hydrogen around the head, the existence of which was established by observations in the spectrum, lines during extra-atmospheric studies of K. As a rule, the tails are less bright than the head, and therefore they can not be observed in all K. The length of their visible part is 10 6 -10 7 km, i.e. They are usually immersed in a hydrogen shell (Fig. 2). In some K., the tail could be traced to distances of more than 10 8 km from the nucleus. In the heads and tails of K. the substance is extremely rarefied; Despite the gigantic volume of these formations, almost the entire mass of the crystal is concentrated in its solid core.
Kernels consist mainly of water ice (snow) and ice (snow) of CO or CO 2 with an admixture of ice and other gases, which also means. amounts of non-volatile (stony) substances. Apparently, an important component of the nuclei of the phenomenon. clathrates, i.e. ices, crystalline the lattice of which includes atoms and molecules of other substances. Judging by the abundance of chemicals. elements in the substance of K., the nucleus of K. should consist (by mass) of approx. of 2/3 ice and 1/3 rocky substances. The presence of a certain amount of radioactive elements in the rocky component of K.'s nuclei should have led, in the distant past, to the heating of their interior by several degrees. dec. Kelvin. At the same time, the presence of highly volatile ice in K.'s cores shows that their internal. the temperature never exceeded ~ 100 K. Thus, the nuclei of the solar system are, apparently, the least altered samples of the primary matter of the Solar system. In this regard, projects for direct research of the substance and structure of carbon using an automatic spacecraft are being discussed and prepared.
Activity of K nuclei at distances less than 2-2.5 a. e. from the Sun, is associated with the sublimation of water ice, and at large distances - with the sublimation of ice from CO 2 and other more volatile ices. At a distance of 1 a. i.e. from the Sun, the rate of sublimation of the water component is ~ 10 18 molecules/(cm 2 s). K. has perihelia of about earth's orbit During one approach to the Sun, the outer layer of the core, several times thick, is lost. m (K., flying through the solar corona, can lose a layer of hundreds of m).
The long existence of a series of periodic K., which repeatedly flew near the Sun, is, apparently, insignificantly explained. loss of substance during each flight (due to the formation of a porous heat-insulating layer on the surface of the cores or the presence of refractory substances in the cores).
It is assumed that K.'s cores include blocks of different composition (macro-breccia structure) with different volatility, which can lead, in particular, to the appearance of jet outflows noticed near certain cores.
During the sublimation of ice, not only rocky particles are separated from the surface of the ice core, but also ice particles, which then evaporate into the interior. parts of the head. Non-volatile dust grains are apparently also formed in the immediate vicinity of the nucleus as a result of the condensation of atoms and molecules of non-volatile substances. Dust particles simply reflect and scatter sunlight, which gives a continuous component of the spectra of the K. With a small emission of dust, a continuous spectrum is observed only in the central part of the head of the K., and with its abundant release - in almost the entire head and in the tails of certain types (see . below).
Atoms and molecules located in the heads and gas tails of celestial molecules absorb quanta of sunlight and then re-emit them (resonant fluorescence). Neutral (apparently complex) molecules sublimating from the nucleus do not reveal themselves in the optical. areas of the spectrum. When do they disintegrate under the influence sunlight(photodissociation), then the radiation of some of their fragments falls on optical. part of the spectrum. Study of optical K.'s spectra showed that the heads contain the following neutral atoms and molecules (more precisely, chemically unstable radicals): C, C 2, C 3, CH, CN, CO, CS, HCN, CH 3 CN; H, 0, OH, HN, H 2 O, NH 2; There are also ions C0 +, CH +, CN +, OH +, CO, H 2 O +, etc. The nature of the K spectrum changes as they approach the Sun. In K. located at a distance from the Sun r> 3-4 a. That is, the spectrum is continuous (solar radiation at such distances cannot excite a significant number of molecules). When K. crosses the asteroid belt (3 AU), the emission band of the CN molecule appears in its spectrum. At 2 a. e. molecules C 3 and NH 2 are excited and begin to emit at 1.8 a. That is, carbon bands appear in the spectrum. At the distance of the orbits of Mars (1.5 AU), lines of OH, NH, CH, etc. are observed in the spectrum of the heads of the planet, and lines of CO +, CO, CH +, OH +, H 2 O + ions are observed in the tails. etc. When crossing the orbit of Venus (at distances of the Earth from the Sun less than 0.7 AU), Na lines appear, from which an independent tail is sometimes formed. In rare K. that flew extremely close to the Sun (for example, K. 1882 II and 1965 VIII), sublimation of rocky dust particles occurred and a spectrum was observed. lines of metals Fe, Ni, Cu, Co, Cr, Mn, V. During observations of comet Kohoutek 1973 XII and comet Bradfield 1974 III, it was possible to detect radio emission lines of acetylnitrile (CH 3 CN, = 2.7 mm), hydrocyanic acid (HCN, = 3.4 mm) and water (H 2 O, = 13.5 mm) - molecules that are directly released from the nucleus and represent some of the parent molecules (with respect to atoms and radicals observed in the optical region of the spectrum). Radio lines of CH (= 9 cm) and OH (= 18 cm) radicals were observed in the centimeter range.
The radio emission of some of these molecules is due to their thermal excitation (collisions of molecules in the perinuclear region), while for others (for example, hydroxyl OH) it apparently has a maser nature (see). In the tails of the sun, directed almost directly from the Sun, ionized molecules CO +, CH +, C0, OH + are observed, i.e., these tails are phenomena. plasma. When observing the spectrum of the tail of comet Kohoutek 1973 XII, it was possible to identify the H 2 O + lines. Emission from ionized molecules occurs at a distance of ~ 10 3 km from the nucleus.
According to the classification of K. tails, proposed in the 2nd half of the 19th century. F. Bredikhin, they are divided into three types: type I tails are directed almost directly from the Sun; Type II tails are curved and deviate from the extended radius vector backwards with respect to the orbital motion of the star; Type III tails are short, almost straight, and from the very beginning, deflected in the direction opposite to the orbital motion. At certain mutual positions of the Earth, Earth, and the Sun, tails of types II and III can be projected onto the sky in the direction of the Sun, forming a tail called anomalous. If, in addition, the Earth is near the plane of the comet's orbit at this time, then a layer of large particles leaving the core with small particles is visible in the form of a thin peak. relative speeds and therefore propagating near the orbital plane K. Explanation of physics. The reasons leading to the appearance of tails of different types have changed significantly since the time of Bredikhin. According to modern According to data, type I tails are plasma: they are formed by ionized atoms and molecules, which are carried away from the nucleus at speeds of tens and hundreds of km/s under the influence of the solar wind. Due to the non-isotropic release of plasma from the perinuclear region of the solar system, as well as due to plasma instabilities and inhomogeneities of the solar wind, type I tails have a stream structure. They are almost cylindrical. shape [diameter km] with an ion concentration of ~ 10 8 cm -3. The angle at which the type I tail deviates from the Sun-K line depends on the speed v sv of the solar wind and on the speed of orbital motion K. Observations of type I cometary tails made it possible to determine the speed of the solar wind up to distances of several. A. e. and far from the ecliptic plane. Theoretical An examination of the solar wind flow around the celestial body allowed us to conclude that in the celestial head, on the side facing the Sun, at a distance of ~ 10 5 km from the core, there should be a transition layer separating the solar wind plasma from the plasma of the solar wind, and at a distance of ~ 10 6 km - a shock wave separating the region of supersonic solar wind flow from the region of subsonic turbulent flow adjacent to the head of the solar wind.
Types II and III tailings are dusty; Dust grains continuously released from the nucleus form type II tails; type III tails appear in cases where a whole cloud of dust particles is simultaneously released from the nucleus. Motes of dust different sizes receive different accelerations under the influence of light pressure, and therefore such a cloud stretches into a strip - the tail of the sky. Di- and triatomic radicals, observed in the head of the sky and responsible for resonance bands in the visible region of the spectrum of the sky (in the region of maximum solar radiation), receive under the influence of light pressure, acceleration close to the acceleration of small dust particles. Therefore, these radicals begin to move in the direction of the type II tail, but do not have time to move far along it due to the fact that their lifetime (before photodissociation or photoionization) is ~ 10 6 s.
K. yavl. members of the Solar System and, as a rule, move around the Sun in elongated ellipticals. orbits of various sizes, arbitrarily oriented in space. The dimensions of the orbits of most planets are thousands of times larger than the diameter of the planetary system. The stars are located near the aphelion of their orbits most of the time, so that on the distant outskirts of the solar system there is a cloud of stars - the so-called. Oort cloud. Its origin is apparently connected with gravity. the ejection of icy bodies from the zone of the giant planets during their formation (see). The Oort cloud contains ~10 11 cometary nuclei. In K., moving away to the peripheral. parts of the Oort cloud (their distances from the Sun can reach 10 5 AU, and the periods of revolution around the Sun - 10 6 -10 7 years), orbits change under the influence of the attraction of nearby stars. At the same time, some K. become parabolic. speed relative to the Sun (for such long distances~ 0.1 km/s) and forever lose contact with solar system. Others (very few) acquire speeds of ~ 1 m/s, which leads to their movement in an orbit with perihelion near the Sun, and then they become available for observation. For all planets, as they move in the region occupied by planets, their orbits change under the influence of the planets' attraction. Moreover, among the K. who came from the periphery of the Oort cloud, i.e. moving along quasi-parabolic lines. orbits, about half becomes hyperbolic. orbit and is lost in interstellar space. For others, on the contrary, the size of their orbits decreases, and they begin to return to the Sun more often. Changes in orbits are especially great during close encounters with giant planets. ~100 short-periods are known. K., which approach the Sun after several. years or tens of years and therefore relatively quickly waste the substance of their core. Most of these K. belong to the Jupiter family, i.e. they acquired their modern small orbits as a result of approaching it.
The orbits of spacecraft intersect with the orbits of the planets, so collisions of spacecraft with planets should occasionally occur. Some of the craters on the Moon, Mercury, Mars and other bodies were formed as a result of impacts from K nuclei. The Tunguska phenomenon (the explosion of a body flying into the atmosphere from space on Podkamennaya Tunguska in 1908) may also have been caused by a collision of the Earth with a small comet core.
Lit.:
Orlov S.V., On the nature of comets, M., 1960; Dobrovolsky O.V. Comets, meteors and zodiacal light, in the book. Astrophysics course and stellar astronomy t. 3, M., 1964; him. Comets, M., 1966; Whipple F.L., Comets, in the book: Cosmochemistry of the Moon and Planets, M., 1975; Churyumov K.I., Comets and their observation, M., 1980; Tomita Koichiro, Discourses on Comets, trans. from Japanese, M., 1982.
(B.Yu. Levin)
1. Constellations
Get to know starry sky It is necessary on a cloudless night, when the light of the Moon does not interfere with observing faint stars. A beautiful picture of the night sky with twinkling stars scattered across it. Their number seems endless. But it only seems so until you take a closer look and learn to find familiar groups of stars in the sky, unchanged in their relative positions. These groups, called constellations, were identified by people thousands of years ago. A constellation is an area of the sky within certain established boundaries. The entire sky is divided into 88 constellations, which can be found by their characteristic arrangement of stars.
Many constellations have retained their names since ancient times. Some names are associated with Greek mythology, For example Andromeda, Perseus, Pegasus, some - with objects that resemble the figures formed bright stars constellations: Arrow, Triangle,Scales etc. There are constellations named after animals, for example a lion,Cancer, Scorpion.
Constellations in the sky are found by mentally connecting their brightest stars with straight lines into a certain figure, as shown on star maps (see star map in Appendix VII, as well as Fig. 6, 7, 10). In each constellation, bright stars have long been designated by Greek letters *, most often the brightest star of the constellation - by the letter α, then by the letters β, γ, etc. in alphabetical order as brightness decreases; For example, polar Star there are constellations Ursa Minor.
* (The Greek alphabet is given in Appendix II.)
Figures 6 and 7 show the location of the main stars Ursa Major and the figure of this constellation, as it was depicted on ancient star maps (the method of finding the North Star is familiar to you from your geography course).
On a moonless night, about 3,000 stars can be seen above the horizon with the naked eye. Currently, astronomers have determined the exact location of several million stars, measured the energy flows coming from them and compiled catalog lists of these stars.
2. Apparent brightness and color of stars
During the day, the sky appears blue because the heterogeneity of the air environment scatters the blue rays of sunlight most strongly.
Outside the Earth's atmosphere, the sky is always black, and the stars and the Sun can be observed on it at the same time.
Stars have different brightness and color: white, yellow, reddish. How redder star, the colder it is. Our Sun is a yellow star.
The ancient Arabs gave bright stars proper names. White stars: Vega in the constellation Lyra, Altair in the constellation Aquila (visible in summer and autumn), Sirius- the brightest star in the sky (visible in winter); red stars: Betelgeuse in the constellation Orion And Aldebaran in the constellation Taurus (visible in winter), Antares in the constellation Scorpio (visible in summer); yellow Chapel in the constellation Auriga (visible in winter) *.
* (Titles bright stars are given in Appendix IV.)
Even in ancient times, the brightest stars were called stars of the 1st magnitude, and the faintest, visible at the limit of vision, were called stars of the 6th magnitude. This ancient terminology has been preserved to this day. The term “stellar magnitude” (denoted by the letter m) has nothing to do with the true size of stars; it characterizes the light flux coming to Earth from a star. It is accepted that with a difference of one magnitude, the apparent brightness of stars differs by about 2.5 times. Then a difference of 5 magnitudes corresponds to a difference in brightness of exactly 100 times. So, 1st magnitude stars are 100 times brighter than stars bth magnitude. Modern methods observations make it possible to detect stars up to about the 25th magnitude.
Accurate measurements show that stars have both fractional and negative magnitudes, for example: for Aldebaran the magnitude is m = 1.06, for Bega m = 0.14, for Sirius m = - 1.58, for the Sun m = - 26.80.
3. Apparent daily motion of stars. Celestial sphere
Because of axial rotation On Earth, the stars seem to us to be moving across the sky. If you stand facing the southern side of the horizon and observe the daily movement of stars in the middle latitudes of the northern hemisphere of the Earth, you will notice that the stars rise on the eastern side of the horizon, rise highest above the southern side of the horizon and set on the western side, i.e. they move from left to right, clockwise (Fig. 8). Upon careful observation, you will notice that the North Star almost does not change its position relative to the horizon. However, other stars describe complete circles during the day with a center near Polaris. This can be easily verified by performing the following experiment on a moonless night. Let's point the camera, set to "infinity", at the North Star and securely fix it in this position. Open the shutter with the lens fully open for half an hour or an hour. Having developed the image obtained in this way, we will see concentric arcs on it - traces of the paths of the stars (Fig. 9). The common center of these arcs - a point that remains motionless during the daily movement of stars, is conventionally called north pole peace. The polar star is very close to it (Fig. 10). The point diametrically opposite to it is called south pole peace. For an observer in the northern hemisphere of the Earth, it is below the horizon.
It is convenient to study the phenomena of the daily motion of stars using mathematical construction - celestial sphere, i.e., an imaginary sphere of arbitrary radius, the center of which is located at the observation point. The visible positions of all the luminaries are projected onto the surface of this sphere, and for the convenience of measurements, a series of points and lines are constructed (Fig. 11). Thus, the plumb line ZCZ" passing through the observer intersects the sky overhead at the zenith point Z. Diametrically opposite point Z" is called the nadir. The plane (NESW) perpendicular to the plumb line ZZ" is the horizon plane - this plane touches the surface of the globe at the point where the observer is located (point C in Fig. 12). She divides the surface celestial sphere into two hemispheres: the visible, all points of which are above the horizon, and the invisible, the points of which lie below the horizon.
The axis of apparent rotation of the celestial sphere connecting both poles of the world(R and R") and passing through the observer(WITH), calledaxis mundi(Fig. 11). The axis of the world for any observer will always be parallel to the axis of rotation of the Earth (Fig. 12). On the horizon below the north celestial pole lies north point N (see Fig. 11 and 12), the diametrically opposite point S is the south point. The NCS line is called noon line(Fig. 11), since along it on horizontal plane At noon, a shadow falls from a vertically placed rod. (You studied how to draw a noon line on the ground and how to use it and the North Star to navigate the sides of the horizon in the V class in the course physical geography.) Eastern points E and west W lie on the horizon line. They are spaced 90° from the points north N and south S. Through point N, stripes of the world, zenith Z and point S passes celestial meridian plane(see Fig. 11), coinciding for observer C with the plane of his geographical meridian (see Fig. 12). Finally, the plane (QWQ"E) passing through the center of the sphere (point C) perpendicular to the axis of the world forms a plane celestial equator, parallel to the plane the earth's equator (see Fig. 12). The celestial equator divides the surface of the celestial sphere into two hemispheres: northern with its peak at the north celestial pole and southern with its peak at the south celestial pole.
4. Star charts and celestial coordinates
To make a star map depicting constellations on a plane, you need to know the coordinates of the stars. The coordinates of stars relative to the horizon, for example altitude, although visual, are unsuitable for making maps, since they change all the time. It is necessary to use a coordinate system that rotates with the starry sky. This coordinate system is equatorial system, it is so named because the equator serves as the plane from which and in which coordinates are measured. In this system, one coordinate is the angular distance of the star from the celestial equator, called declination δ (Fig. 13). It varies within ±90° and is considered positive north of the equator and negative south. Declination is similar to geographic latitude.
The second coordinate is similar geographic longitude and is called right ascensionα.
The right ascension of the luminary M is measured by the angle between the planes of the great circles, one passes through the poles of the world and the given luminary M, and the other - through the poles of the world and the point spring equinox, lying on the equator (see Fig. 13). This point was named so because the Sun appears there (on the celestial sphere) in the spring of March 20-21, when day is equal to night.
Right ascension is measured along the arc of the celestial equator from the vernal equinox counterclockwise, as viewed from the north pole. It varies from 0 to 360° and is called right ascension because the stars located on the celestial equator rise (and set) in order of increasing right ascension. Since this phenomenon is associated with the rotation of the Earth, right ascension is usually expressed not in degrees, but in units of time. In 24 hours, the Earth (and it seems to us that the stars) makes one revolution - 360°. Therefore, 360° corresponds to 24 hours, then 15°-1 hour, 1°-4 minutes, 15"-1 minute, 15"-1 s. For example, 90° is 6 hours, and 7 hours 18 minutes is 109°30".
In time units, right ascension is indicated on the coordinate grid of star maps, atlases and globes, including on the map attached to the textbook and the School Astronomical Calendar.
Exercise 1
1. What does stellar magnitude characterize?
2. Is there a difference between the north celestial pole and the north point?
3. Express 9 hours 15 minutes 11 seconds in degrees.
Exercise 1
1. According to Appendix VII, familiarize yourself with the handling and installation of a moving star map.
2. Using the table of coordinates of bright stars given in Appendix IV, find some of the indicated stars on the star map.
3. Using the map, count the coordinates of several bright stars and check yourself using Appendix IV.
HOW TO OBSERVE COMETS
Vitaly Nevsky
Observing comets is a very exciting activity. If you haven't tried your hand at this, I highly recommend giving it a try. The fact is that comets are very unstable objects by nature. Their appearance can change from night to night and quite significantly, especially for bright comets visible to the naked eye. Such comets, as a rule, develop decent tails, which prompted ancestors to various prejudices. Such comets do not need advertising, this is always an event in the astronomical world, but quite rare, but weak telescopic comets are almost always available for observation. I will also note that the results of observations of comets have scientific value, and amateur observations are constantly published in the American journal Internatoinal Comet Quarterly, on the C. Morris website and not only.
First, I’ll tell you what you should pay attention to when observing a comet. One of the most important characteristics- the magnitude of the comet, it must be estimated using one of the methods described below. Then - the diameter of the comet's coma, the degree of condensation, and, if there is a tail, its length and positional angle. This is the data that is valuable to science.
Moreover, comments on observations should note whether a photometric core was observed (not to be confused with the true core, which cannot be seen with a telescope) and what it looked like: star-shaped or disk-shaped, bright or faint. For bright comets, phenomena such as halos, shells, separation of tails and plasma formations, and the presence of several tails at once are possible. In addition, nuclear disintegration has already been observed in more than fifty comets! Let me explain these phenomena a little.
- Halos are concentric arcs around the photometric core. They were clearly visible near the famous comet Hale-Bopp. These are dust clouds that are regularly ejected from the nucleus, gradually moving away from it and disappearing against the background of the comet's atmosphere. They must be sketched indicating the angular dimensions and time of sketching.
- Nuclear decay. The phenomenon is quite rare, but has already been observed in more than 50 comets. The onset of decay can only be seen at maximum magnifications and should be reported immediately. But you need to be careful not to confuse the decay of the nucleus with the separation of the plasma cloud, which happens more often. The decay of the nucleus is usually accompanied by a sharp increase in the brightness of the comet.
- Shells - appear on the periphery of the cometary atmosphere (see figure), then begin to shrink, as if collapsing on the nucleus. When observing this phenomenon, it is necessary to measure the vertex height (V) in arcminutes - the distance from the core to the top of the shell and the diameter P = P1 + P2 (P1 and P2 may not be equal). These assessments need to be done several times throughout the night.
Assessing the brightness of a comet
The accuracy of the estimate should be no lower than +/-0.2 magnitude. In order to achieve such accuracy, the observer must make several brightness estimates during work for 5 minutes, preferably using different comparison stars, finding the average magnitude of the comet. It is in this way that the resulting value can be considered quite accurate, but not the one obtained as a result of just one estimate! In such a case, when the accuracy does not exceed +/-0.3, a colon (:) is placed after the comet's magnitude. If the observer was unable to find the comet, then he estimates the maximum stellar magnitude for his instrument on a given night at which he would still be able to observe the comet. In this case, a left square bracket ([) is placed before the evaluation.
The literature provides several methods for estimating the magnitude of a comet. But the method of Bobrovnikov, Morris and Sidgwick remains the most applicable.
Bobrovnikov's method.
This method is used only for comets whose degree of condensation is in the range of 7-9! Its principle is to move the telescope eyepiece out of focus until the out-of-focal images of the comet and comparison stars are approximately the same diameter. Complete equality cannot be achieved, since the diameter of the comet image is always larger than the diameter of the star image. It should be taken into account that the out-of-focal image of the star has approximately the same brightness, but the comet appears as a spot of uneven brightness. The observer must learn to average the comet's brightness over its entire out-of-focal image and compare this average brightness with comparison stars. Comparison of the brightness of off-focal images of the comet and comparison stars can be made using the Neyland-Blazhko method.
Sidgwick's method.
This method is only used for comets whose degree of condensation is in the range of 0-3! Its principle is to compare the focal image of a comet with off-focal images of comparison stars, which, when defocused, have the same diameters as the focal comet. The observer first carefully studies the image of the comet, “recording” its brightness in memory. Then it defocuses the comparison stars and evaluates the brightness of the comet recorded in memory. A certain skill is required here in order to learn to evaluate the brilliance of a comet recorded in memory.
Morris method.
The method combines the features of the Bobrovnikov and Sidgwick methods. it can be used for comets with any degree of condensation! The principle boils down to the following sequence of techniques: an out-of-focal image of the comet is obtained that has approximately uniform surface brightness; remember the size and surface brightness of the out-of-focal image of the comet; they defocus the images of the comparison stars so that their sizes are equal to the sizes of the remembered image of the comet; estimate the brightness of a comet by comparing the surface brightnesses of off-focal images of the comet and comparison stars.
When estimating the brightness of comets, in the case where the comet and comparison stars are at different heights above the horizon, a correction for atmospheric absorption must be introduced! This is especially significant when the comet is below 45 degrees above the horizon. Amendments should be taken from the table and the results must indicate whether an amendment was introduced or not. When using an adjustment, you need to be careful not to make a mistake about whether it should be added or subtracted. Let's say the comet is located below the comparison stars, in this case the correction is subtracted from the comet's brightness; if the comet is higher than the comparison stars, then the correction is added.
Special stellar standards are used to estimate the brightness of comets. Not all atlases and catalogs can be used for this purpose. Of the most accessible and widespread at present, the Ticho2 and Drepper catalogs should be highlighted. For example, directories such as AAVSO or SAO are not recommended. You can see more details about this.
If you do not have recommended catalogs, you can download them from the Internet. An excellent tool for this is the Cartes du Ciel program.
Comet coma diameter
The coma diameter of a comet should be estimated using as low a magnification as possible! It is noticed that the lower the magnification is applied, the larger the diameter of the coma, since the contrast of the comet's atmosphere in relation to the sky background increases. Poor transparency of the atmosphere and a light background of the sky (especially under the Moon and urban illumination) greatly influence the estimate of the diameter of the comet, so in such conditions it is necessary to be very careful when measuring.
There are several methods for determining the coma diameter of a comet:
- Using a micrometer, which is easy to make yourself. Under a microscope, stretch thin threads in the eyepiece diaphragm at certain intervals, or it is better to use an industrial one. This is the most accurate method.
- "Drift" method. It is based on the fact that with a stationary telescope, the comet, due to the daily rotation of the celestial sphere, will slowly cross the field of view of the eyepiece, passing a 15" arc near the equator in 1 second. Using an eyepiece with a cross of threads stretched in it, you should rotate it so that the comet moves along one thread and, therefore, perpendicular to the other thread of the cross. Having determined with a stopwatch the period of time in seconds during which the comet's coma will cross the perpendicular thread, it is easy to find the diameter of the coma in minutes of arc using the formula.
d=0.25 * t * cos(b)
where (b) is the declination of the comet, t is the time period. This method cannot be used for comets located in the near-polar region at (b) > +70 degrees!
- Comparison method. Its principle is based on measuring the coma of a comet using the known angular distance between stars located near the comet. The method is applicable if a large-scale atlas is available, for example, Cartes du Ciel.
Its values range from 0 to 9.
0 - completely diffuse object, uniform brightness; 9 is practically a star-shaped object. This can be most clearly represented from the figure
Determination of comet tail parameters
When determining the length of the tail, the accuracy of the estimate is greatly influenced by the same factors as when estimating the coma of a comet. Urban illumination has a particularly strong effect, underestimating the value several times, so in the city you will certainly not get an accurate result.
To estimate the length of a comet's tail, it is best to use the comparison method based on the known angular distance between stars, since with a tail length of several degrees, small-scale atlases available to everyone can be used. For small tails, a large-scale atlas or micrometer is needed, since the "drift" method is only suitable if the tail axis coincides with the declination line, otherwise additional calculations will have to be performed. If the tail length is more than 10 degrees, it must be assessed using a formula, since due to cartographic distortions the error can reach 1-2 degrees.
D = arccos * ,
where (a) and (b) are the right ascension and declination of the comet; (a") and (b") - right ascension and declination of the end of the comet's tail (a - expressed in degrees).
Comets have several types of tails. There are 4 main types:
Type I - straight gas tail, almost coinciding with the radius vector of the comet;
Type II - a gas-dust tail slightly deviating from the radius vector of the comet;
Type III - a dust tail spreading along the comet's orbit;
Type IV - anomalous tail directed towards the Sun. Consists of large dust particles that sunny wind unable to push comets out of coma. Very a rare event, I had a chance to observe it only on one comet C/1999H1 (Lee) in August 1999.
It should be noted that a comet can have one tail (most often type I) or several.
However, for tails whose length is more than 10 degrees, due to cartographic distortions, the position angle should be calculated using the formula:
Where (a) and (b) are the coordinates of the comet’s nucleus; (a") and (b") are the coordinates of the end of the comet's tail. If the result is a positive value, then it corresponds to the desired value; if it is negative, then 360 must be added to it to obtain the desired value.
In addition to the fact that you eventually obtained the photometric parameters of the comet, in order for them to be published, you need to indicate the date and moment of observation in universal time; characteristics of the tool and its magnification; a method of estimating and source of comparison stars that was used to determine the brightness of a comet. After which you can contact me to send this data.
I will again use the brochure “Didactic Material on Astronomy” written by G.I. Malakhova and E.K. Strout and published by the Prosveshcheniye publishing house in 1984. This time the first tasks of the final test work on page 75.
To visualize formulas, I will use the LaTeX2gif service, since the jsMath library is not able to render formulas in RSS.
Task 1 (Option 1)
Condition: The planetary nebula in the constellation Lyra has an angular diameter of 83″ and is located at a distance of 660 pc. What are the linear dimensions of the nebula in astronomical units?
Solution: The parameters specified in the condition are related to each other by a simple relationship:
1 pc = 206265 AU, respectively:
Task 2 (Option 2)
Condition: The parallax of the star Procyon is 0.28″. The distance to the star Betelgeuse is 652 light years. of the year. Which of these stars and how many times is farther from us?
Solution: Parallax and distance are related by a simple relationship:
Next, we find the ratio of D 2 to D 1 and find that Betelgeuse is approximately 56 times further than Procyon.
Task 3 (Option 3)
Condition: How many times did the angular diameter of Venus, as seen from Earth, change as a result of the planet moving from its minimum distance to its maximum? The orbit of Venus is considered to be a circle with a radius of 0.7 AU.
Solution: We find the angular diameter of Venus for the minimum and maximum distances in astronomical units and then their simple ratio:
We get the answer: it decreased by 5.6 times.
Task 4 (Option 4)
Condition: What angular size will our Galaxy (whose diameter is 3 × 10 4 pc) be seen by an observer located in the M 31 galaxy (Andromeda nebula) at a distance of 6 × 10 5 pc?
Solution: An expression connecting the linear dimensions of an object, its parallax and angular dimensions is already in the solution to the first problem. Let's use it and, slightly modifying it, substitute required values from the condition:
Problem 5 (Option 5)
Condition: Resolution of the naked eye is 2′. What size objects can an astronaut discern on the surface of the Moon when flying above it at an altitude of 75 km?
Solution: The problem is solved similarly to the first and fourth:
Accordingly, the astronaut will be able to distinguish surface details measuring 45 meters.
Problem 6 (Option 6)
Condition: How many times is the Sun larger than the Moon if their angular diameters are the same and their horizontal parallaxes are respectively 8.8″ and 57′?
Solution: This is a classic problem of determining the size of luminaries by their parallax. The formula for the connection between the parallax of a luminary and its linear and angular dimensions has been repeatedly found above. As a result of reducing the repeating part, we get: 
The answer is that the Sun is almost 400 times larger than the Moon.