Beyond the penumbra, the eclipse does not occur at all.

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Solar and lunar eclipses as natural phenomena. Abstract

Solar and lunar eclipses are extremely interesting natural phenomena, familiar to man since ancient times. They occur relatively often, but they can not be seen from anywhere on the planet, and therefore many seem rare

Solar eclipses take place in the new moon. During this period, the Moon, moving around the Earth, finds itself between the Sun and the Earth and completely or partially obscures the luminary. The moon is almost 400 times closer to the Earth than the Sun, and at the same time the Sun is almost 400 times larger than it. Therefore, the visible dimensions of the Sun and the Moon are almost the same (about 1⁄2˚), and the Moon can cover the Sun.

It would seem that lunar eclipses should occur every 29.5 days, ie every new moon, but in reality this is not the case. The fact is that the Moon moves around our planet in an orbit that (like the orbit of the planets) is slightly inclined to the plane of the Earth’s orbit. The visible path of the Moon in the sky intersects with the plane of the ecliptic (the ecliptic is the visible path of the Sun among the stars throughout the year). Such points of intersection are called lunar nodes, and between them buy compare and contrast essay now is 180 degrees.

When the new moon is far from the lunar nodes, the moon does not obscure the sun. But about every six months, the new moon is near one of the lunar nodes, and then there are solar eclipses. At that moment, the lunar shadow and penumbra fall to Earth in the form of oval spots, which at a speed of 1 km / sec. run across the earth’s surface from west to east.

In areas that are in the moon’s shadow, you can see a total solar eclipse, ie the sun is completely covered by the moon. In areas that are covered in partial shade, there is a partial solar eclipse – the moon covers only part of the solar disk. Beyond the penumbra, the eclipse does not occur at all. Thus, the eclipse is not visible on the entire surface of the Earth, but only where the shadow and penumbra run.

The path of the moon’s shadow on the earth’s surface is called the band of total solar eclipse. The width of this band and the time of a total solar eclipse depend on the mutual distances of the Sun, Earth and Moon at the time of the eclipse.

The maximum possible bandwidth of a total solar eclipse does not exceed 270 km., The longest time of the total eclipse phase does not exceed 7 minutes. 31 sec., But more often it lasts two or three minutes.

If the new moon comes at a time when the Moon passes through one of the nodes, then there is a central eclipse of the Sun. If the Moon is as close as possible to the Earth, and the Sun is in the farthest position from it, then the visible size of the satellite becomes larger than the visible size of the luminary, and then there is a total eclipse.

When the “small” Moon replaces the “big” Sun, a narrow solar rim is visible around the black lunar disk, when the center of the Moon’s disk coincides in the center of the Sun’s disk; such a ring eclipse. A partial solar eclipse occurs when in the new moon the satellite is not exactly at the node, but close enough to it that part of the solar disk is closed by the edge of the moon.

… An eclipse is approaching. The sun shines brightly in the sky. Nothing portends a future phenomenon. A solar eclipse begins at the right edge of the Sun. Here the solar disk takes the form of a sickle facing convexity to the left. Through the dark light filter it is well visible how the Moon obscures the Sun. Sunlight gradually weakens. It’s getting cooler. The sickle becomes very thin; and suddenly this narrow strip decomposes into two, and then the last bright spots disappear behind the black disk. The moon replaced the sun. Darkness falls all over the area, the brightest stars and planets appear in the darkened sky.

A black disk can be seen in the place of the extinguished luminary, and around the Sun there is a beautiful radiant silver-colored radiance – the solar corona, which is the outer layers of the solar atmosphere, not visible outside the eclipse due to their low brightness compared to daylight. (By the way, the type of crown changes from year to year depending on solar activity). A pink ring flashes over the entire horizon – it’s in the area,

covered with moonlight, sunlight penetrates from neighboring areas, where complete eclipse does not occur. There was a total solar eclipse.

Soon, in just two or three minutes, the Moon opens the right edge of the Sun, the full phase ends, the crown disappears, quickly shines around, the stars and planets go out. The sun again takes the form of a sickle facing convex to the right, which decreases over time. The chip on the left edge of the disk soon disappears. Now the eclipse is over.

Solar and lunar eclipses are such natural phenomena, the date of which is known in advance. Astronomers are always carefully preparing for the observation of eclipses, and to places where they can be seen, collect whole expeditions.

Among the interesting phenomena are also lunar eclipses. However, during an eclipse, the Moon does not disappear at all, like the Sun during a solar eclipse, but is only less visible. An eclipse can be observed when the full moon passes through the node. At this point, the Earth is exactly between the Sun and the Moon, so that the Earth’s shadow covers the Moon – the diameter of the Earth is four times larger than the Moon, and the shadow from the Earth, even at a distance from the Moon, is 2.5 times larger than the Moon. The moon can completely sink into the earth’s shadow.

There is a lunar eclipse so. The full light circle of the Moon begins to darken on its left side, a brown shadow appears on the lunar disk, it moves on and in an hour covers the entire Moon. The Earth’s satellite becomes reddish-brown, with a bloody tinge, color.

This happens because part of the sun’s rays passes through the Earth’s atmosphere, refracts in it, enters the Earth’s shadow and falls on the Moon. Since the red rays of the spectrum are the least scattered and attenuated in the atmosphere, the Moon takes on a copper-red or brown hue during an eclipse. A total lunar eclipse is much longer than a solar eclipse, it can last 1 hour 40 minutes.

Solar and lunar eclipses are periodically repeated (this was known to the ancient Chaldeans), and they can be predicted with high accuracy. During the period of 18 years and 11 days there are an average of 71 eclipses: from 39 to 48 solar and from 25 to 30 lunar. This period is called saros (Greek repetition).

Although solar eclipses occur more often than lunar eclipses, they are much harder to see because a total solar eclipse is visible within a fairly narrow strip of the Earth on which the lunar shadow falls. At the same time, a lunar eclipse can be observed immediately in the entire hemisphere.

If the plane of the Moon’s orbit coincided with the plane of the Earth’s orbit, solar eclipses would occur every new moon, and lunar eclipses every full moon. Then modern astronomers would be delighted, unlike our ancestors: they did not know the causes of eclipses and therefore were very afraid of these mysterious and incomprehensible phenomena.

08/16/2011

Stars, their mass and size. Abstract

The abstract provides information about some types of stars, calculations of their mass and size

Double stars. Masses of vision. As we have seen in the example of the Sun, the mass of the star is one of the most important characteristics on which the physical conditions in its bowels depend. Direct determination of mass is possible only for double stars.

Double stars are said to be visually double if their duality can be seen during direct observations through a telescope.

An example of a visual double star, visible even to the naked eye, is the Ursa Major, the second star from the end of the “handle” of its “bucket”. At normal dawn, a second faint star can be seen very close to it, it was noticed by the ancient Arabs and named Alcor (Rider). They named the bright star Mitsar. Mitsar and Alcor are separated from each other by 1 G. In the binoculars of such stellar pairs can be found a lot.

Systems with the number of stars n ³3 are called multiples. Thus, binoculars show that Mr. Leary consists of two identical stars of magnitude 4, the distance between which is 3 ‘. When observed in the telescope E Leary – visually quadruple star.

However, some stars are only optically binary, ie, the proximity of such two stars is the result of their random projection into the sky. In fact, in space they are far from each other. And if during observation it turns out that they form a single system and rotate under the action of mutual attraction around a common center of mass, they are called physical doubles.

Many double stars were discovered and studied by the famous Russian scientist V. Ya. Struve. The shortest known period of rotation of visual double stars is several years. Pairs in which the period of rotation is tens of years are studied, and pairs with periods in hundreds of years will be studied in the future. The nearest star to us, Centaurus, is double.

The period of rotation of its components is 70 years. Both stars in this pair are similar in mass and temperature to the Sun.

The main star is usually not in the focus of the visible ellipse that describes the satellite, because we see its orbit distorted in projection. But knowledge of geometry makes it possible to establish the true shape of the orbit and measure its major half-axis in seconds of arc. If the known distance O to the double star in parsecs and the major half-axis of the orbit of the satellite star in seconds of the arc is equal to a “then in astronomical units it will be equal to:

Aa. e. = a ” x Dpc, or Aa. e. = a “/ p”,

since Dpk = 1 / p “.

Comparing the motion of the star’s satellite with the Earth’s motion around the Sun (for which the period of rotation Tl = 1 year, and the major half-axis of the orbit – a.o.), according to Kepler’s third law we can write:

where m1 and m2 are the masses of the components in the pair of stars, M © and MÅ are the masses of the Sun and the Earth, and T is the period of rotation of the pair in years. Neglecting the mass of the Earth compared to the mass of the Sun, we obtain the sum of the masses of stars that make up the pair, in the masses of the Sun:

m1 + m2 = A3: T2

To determine the mass of each star, it is necessary to study the motion of the components relative to the surrounding stars and calculate their distances A1 and A2 from the common center of mass. Then we have the second equation:

m1 + m2 = A2: A1

and from the system of two equations we find both masses separately.

In the telescope, double stars are often a beautiful sight: the main star is yellow or orange, and the satellite is white or blue.

If the components of a double star in close rotation are close to each other, then even in the strongest telescope they can not be seen separately.