Make a Wish

Vocabulary/new concepts:

The Sun is the central and largest body in the Solar system. It is a star around which eight planets orbit.

Moons are natural satellites that orbit most of the major planets (except Mercury and Venus).

Comets are interesting bodies in the solar system. They orbit the Sun on very elongated ellipses.

A meteorite is a relatively small piece of debris, part of a meteoroid. Upon entering the Earth’s atmosphere, a light phenomenon and subsequent ionization of the air particles is observed. This phenomenon is called a meteor or shooting star. If any part of the meteoroid persists on the surface of the Earth, it is called a meteorite.

The universe and its evolution

The Universe is a vast and complex place. It contains everything that exists – all the stars, galaxies, planets, comets, asteroids, dust and gas. The universe began to form about 13.8 billion years ago and has been expanding and changing its structure ever since. Science allows us to understand the Universe better, but we are still learning new things and many mysteries remain unexplained.

There are many theories about how the Universe began and what will happen to it in the future. According to the Big Bang theory, the Universe began to form as a result of the Big Bang, when all the material objects in the Universe came together in one big chunk and then scattered into space. There is also the infinite universe theory, which states that the universe is infinite and that it contains an infinite number of galaxies and other objects.

The universe is incredibly large and it is impossible to determine its exact size as it is constantly expanding and changing. It is known that there are a vast number of galaxies in the universe that are billions and billions of light years apart. According to some estimates, there may be as many as 100 billion galaxies in our known Universe. There are likely even more galaxies that we cannot see because of the limitations of our observational equipment.

The Universe is mostly made up of dark matter and dark energy, for which there is still not enough scientific research and they remain unknown to us. About 5% of the Universe is visible matter, consisting of a vast number of material objects such as stars, galaxies, planets, comets, asteroids, dust and gas. It also consists of immaterial substances such as light, radio waves, gamma rays and cosmic rays. There are many things we don’t know about it and many questions we are interested in unravelling its mysteries. Studying the universe helps us to understand our place in it and to realise the grandeur of nature.

The Solar system

The Solar system refers to the region of space under the influence of the Sun’s gravitational field. It consists of the eight major planets (including Earth), the moons that orbit them, and countless other objects (e.g., dwarf planets, asteroids, and comets). All these objects are held in their orbit by the Sun’s gravitational field.

The central and largest body in the solar system is the Sun. Its diameter is about 109 times that of the Earth, and its mass is up to 333,000 times greater. The mass of the Sun makes up more than 99% of the mass of the solar system, so only a small fraction is left for other bodies. The Sun is a star of medium size, its surface temperature is about 6000°C and inside almost 20 106°C. It gets its energy from fusion reactions. Most of the energy is radiated into space, but only a small fraction reaches the Earth’s surface (visible light – 48%, thermal infrared – 45%, ultraviolet – 7%). The rotation period of the Sun is about 25-27 days.

The planets in the solar system are divided into two main groups: the inner planets Mercury, Venus, Earth and Mars, which are closer to the Sun, and the outer planets Jupiter, Saturn, Uranus, Neptune, (Pluto), which are larger and farther from the Sun. Planets are large spherical bodies that orbit stars and have sufficient mass to keep other objects out of their orbits. The first five planets (excluding Earth) can be observed without any equipment. In terms of physical properties, we distinguish between Earth-like planets (Mercury, Venus, Mars) and giant planets (Jupiter, Saturn, Uranus, Neptune). The relative sizes of the planets and their orbits are shown in tables and geographical atlases. The four innermost planets of the solar system are rocky – solid spheres of stone and metal. The outer planets of the solar system are much larger and farther apart. They all have a thick layer of gaseous atmosphere that contains both hydrogen and helium, and they each have rings and moons orbiting them.

In addition to the planets, numerous smaller bodies called asteroids orbit the Sun. Their trajectories are between those of Mars and Jupiter. Asteroids range in diameter from a few metres to several hundred kilometres. The largest of these is the asteroid Ceres which has a diameter of about 1,000 km.
Most of the large planets have moons orbiting them. Jupiter (14), Saturn (23) and Uranus have the most, while Mercury and Venus have no moons. Several hundred moons are currently recorded in the solar system. The most studied is “our” Moon. Since the Moon’s rotation time is equal to its orbital period around the Earth, the same hemisphere of the Moon is always facing us. The inverted hemisphere has only recently been mapped using images from space probes. An important milestone in lunar exploration was the landing of the first manned spacecraft on the Moon in 1969 as part of the US Apollo programme.

Comets are interesting objects in the Solar system. They are small but bright bodies in the solar system, composed mostly of ice, dust and rock. They will be the focus of the first activity in the lesson.

The vast space between bodies in the solar system is not empty. It contains many small particles of dust and gases (mainly hydrogen) – interplanetary material. There are also many artificial bodies currently being launched and moving in the gravitational fields of the Earth, Moon and Sun. These are artificial satellites of the Earth, orbital stations, space probes, space shuttles, spacecraft… They perform both research tasks (exploration of planets, moons, interplanetary space) and practical tasks (weather forecasting, positioning, television signal transmission).

Halley’s Comet

Comets are interesting objects in the solar system. They orbit the Sun on very elongated ellipses. They have a nucleus several kilometres across and are made up of a group of small bodies. Near the Sun, dust particles and gases are emitted from the nucleus and form the comet’s luminous atmosphere, the coma. With more gas and dust particles, the comet’s luminous tail is formed, which can be up to several million kilometres long. The comet and tail are surrounded by a faint gas layer called a halo. The most famous comet is Halley’s Comet with an orbital period of 76 years. It was last observed in 1986.
Comets have limited lifetimes. They gradually break up and form meteor showers. Individual flying meteors, ranging in size from grains to large boulders, slow down due to friction. Once they enter the Earth’s atmosphere, they gradually become hotter and brighter. The phenomenon is observed as a “shooting star” (meteor) occurs. Most meteorites evaporate into the atmosphere, but if they do hit the Earth’s surface, we call them meteorites.

Source: https://www.esa.int/ESA_Multimedia/Images/2016/03/Giotto_approaching_Comet_Halley

This image shows the nucleus of Halley’s Comet, taken by the Giotto spacecraft on March 13-14, 1986. The nucleus of the comet looks like a “potato” about 15 km in size.

Halley’s Comet is one of the most famous and can be seen from Earth. It has been found to return periodically every 75-76 years. It has been observed in 29 returns. The first time was in 239 B.C. In 1705, the English astronomer Edmund Haley proved that the comets observed in 1531, later in 1607 and for the third time in 1682 were not three different comets, but a single comet. He therefore predicted its return in 1758.

By return, we mean approaching the Sun at such a distance that the Sun’s rays begin to heat and melt the ice into gas and dust. Subsequently, the comet began to reflect the sunlight and we often observe its beautiful tail from Earth.

The shortest distance the comet is from the Sun is 88 million kilometres, its distance to the Sun then being comparable to that of Mercury. When the comet is farthest from the Sun, it is at a distance of 5.2 billion kilometres.