Solar and moon eclipses

In the Earth-Moon system, the alternating "eclipses" of one cosmic body are solar and moon eclipses. When you turn around the planet, its satellite, illuminated by the Sun, sometimes casts a shadow on the planet, and at other times it falls into its shadow. Similar phenomena are often observed, for example, in the satellite system Jupiter, where the four giant moons that pass before the disk of the planet (and then the dark speck of their shadow runs along the surface of Jupiter), then, on the contrary, they themselves are shaded by the greatest of the planets. All this is perfectly visible even in small telescopes.

In the Earth-Moon system, the alternating eclipses of one cosmic body are solar and moon eclipses

Solar eclipses come when the Moon blocks the Sun, and moon eclipses - when the Moon falls into the shadow cast by the Earth into the world space. If the plane of the moon orbit coincided with the plane of the Earth's orbit, solar and moon eclipses would occur regularly twice a month: solar - at the time of the new moon, and the moon - at the time of the full moon. In fact, the plane of the moon orbit is inclined to the plane of the Earth's orbit at an angle of about 5 degrees, and therefore solar and moon eclipses belong to a number of relatively rare astronomical phenomena. Recall that the points of intersection of the moon orbit with the plane of the earth's orbit are called nodes, and the segment connecting them, - the line of nodes. It is not difficult to imagine that solar and moon eclipses can only occur when the Moon is near the nodes of its orbit and the line of nodes is directed toward the Sun.

Since this line is slowly turning in space, and the motion of the Earth and the Moon is rather difficult, precomputation of the moments of the onset of solar and moon eclipses is not an easy matter. At present, the theory has been developed in great detail. It turns out that annually there must be at least two and not more than five solar, and also no more than three moon eclipses, and in other years the moon may not be at all. Most often in a year there are two solar eclipses and two moon eclipses. During a solar eclipse, the Moon sometimes blocks the Sun completely (total eclipse) or partially (partial eclipse). Solar eclipses can occur, obviously, only in the new moon.

Solar eclipses are observed in a limited area of the earth's surface: complete there, where the spot of the moon's shadow, whose diameter does not exceed 300 km, is private, on the sides of this spot in a radius of up to 4000 km (this is the area of the so-called penumbra). Since the Moon moves around the Earth, and the Earth rotates around its axis, the shadow and penumbra move very quickly along the earth's surface, tracing the bands of total and particular eclipses. The moon revolves around the Earth in an ellipse and therefore its distance from the Earth changes all the time. Together with it, the visible dimensions of the moon disk change. If, at the time of the solar eclipse, the Moon is near the apogee, its apparent dimensions decrease so much that it can not completely cover the Sun and instead of a total solar eclipse, a so-called annular solar eclipse is observed.

During the solar eclipse, the Moon, moving from right to left (from west to east), slowly blocks the Sun. The solar eclipse lasts a total of usually about two hours, while the total phase of the solar eclipse lasts no more than 7,5 minutes. With the onset of the full phase, the brightest stars and planets appear in the sky, and around the sun there is a pearl-silver glow - the solar corona, the uppermost part of the solar atmosphere. In the telescope around the Sun closed by the Moon, pinkish protrusions that resemble flames - gas clouds of the solar atmosphere, called protuberances.

Total solar eclipses, repeated on average once every 1,5 years, may not be observed at any one place of the Earth for hundreds of years. Observations of solar eclipses are of great scientific value. On them, you can clarify the movement of the moon, which is very difficult. In moments of total solar eclipses, it is especially convenient to observe the solar atmosphere and its external weakly luminous parts.

Total solar eclipses, repeated on average once every 1,5 years, may not be observed at any one place of the Earth for hundreds of years

During the moon eclipses, the moon enters the cone of the earth shadows. Lunar eclipses occur only in the full moon. If the Moon is completely immersed in the earth's shadow, a total moon eclipse occurs, if only partially - a partial eclipse. The lunar eclipse occurs for the whole Earth at the same physical time and can be observed in all those places of the Earth where the Moon will be at this time above the horizon. The shadow of the Earth on the Moon due to the sphericity of the Earth has the form of a circle. At the distance of the moon, the diameter of the earth's shadow is 2,5 times the area of the Moon's disk. Therefore, the Moon can completely enter the earth's shadow for a long time. The full phase of the moon eclipse can last up to 1 h 40 min, and all this usually lasts more than three hours.

Currently, solar and lunar eclipses are used for scientific observations. In particular, by coloring the moon during a total moon eclipse, one can learn some properties of Earth's atmosphere.