Comets asteroids interesting facts. What determines the shape of a comet's tail? Comets and the Earth - ideas of scientists
The small bodies of the Solar System include asteroids, meteoroids, comets, Kuiper belt bodies. Asteroids are less than a thousand kilometers in size. More small bodies, than asteroids, are called "meteoroids" or meteoroid bodies, they can be on the order of several meters or even smaller.
Asteroid- a small planet-like body in the solar system, ranging in size from several meters to thousands of kilometers, asteroids are often called minor planets(but not dwarf planets!) Most asteroid orbits are concentrated in the main asteroid belt between the orbits of Mars and Jupiter.
Astronomy: Solar system and the movement of its planets and data from the Sun
The smallest observables, measuring less than a few tens of meters, rarely cross the Earth's atmosphere; Friction with air evaporates them before they reach the surface. Asteroids larger than 100 m are real danger.
Astronomy: The Solar System and Its Planets
The dimensions of this system are given in terms of the average distance from the Earth to the Sun, called an astronomical unit.Counted in thousands, asteroids range in size from Ceres, up to 000 km in diameter, to microscopic grains. Some fall to Earth and appear in the night sky as rays of light; they are called meteors. The salvaged fragments are called meteorites. Research in meteorite laboratories has revealed much information about the primitive conditions of our solar system.
History of the discovery of asteroids.
On January 1, 1801, Italian astronomer Giuseppe Piazzi accidentally discovered a star whose declination changed noticeably over the course of 24 hours of observation; this object was located between Mars and Jupiter. This object was named Ceres after the ancient Roman goddess of fertility. Thus, astronomers discovered a new type of objects in the solar system, later called asteroids. Observing the movement of Ceres, the German physician Heinrich Wilhelm Olbers discovered a new asteroid in 1802, which was named Pallas in honor of the ancient Greek goddess Pallas Athena. Juno was discovered in 1804, Vesta in 1807. Friedrich Wilhelm Herschel proposed calling small planets asteroids. Asteroid means "star-shaped" in Greek.
The surfaces of Mercury, Mars, and various planetary moons show the effects of heavy asteroid impacts early in the solar system's history. On Earth, these marks have been erased, with the exception of some craters of recent impact. Some interplanetary dust may also come from comets, which consist mainly of dust and icy gases with a diameter of 5 to 10 km. Many comets orbit the Sun at such great distances that they can be distracted by stars into orbits that take them into the inner Solar System.
As comets approach the Sun, they release their dust and gases, creating spectacular hairs and glue. Under the influence of Jupiter's powerful gravitational field, comets sometimes occupy much smaller orbits. The most famous comet Halley, which returns to the inner Solar System every 75 years.
In 1804, Olbers expressed the famous hypothesis about the rupture of the hypothetical planet Phaeton between Mars and Jupiter and the formation of asteroids - its fragments. Since 2006, the first asteroid found, Ceres, has been classified as a dwarf planet. Asteroids near the Earth and their danger to the planet
Hazardous space objects, such as asteroids whose orbits intersect the Earth’s orbit, represent serious threat the existence of human civilization during a collision between the Earth and an asteroid. The number of asteroids crossing the Earth's orbit and having a diameter of more than 1 km is approximately 500.
His last appearance was in "With Impact", the massive kinetic energy of the debris turned into fire through giant explosions, creating fireballs larger than the Earth. The surfaces of the icy satellites of the outer planets are marked by impacts from cometary nuclei. In fact, the asteroid Chiron, which orbits between Saturn and Uranus, may be a huge inactive comet. Likewise, some of the asteroids that cross Earth's orbit may be the rocky remains of extinct comets.
The Sun is surrounded by three rings of interplanetary dust. One of them, between Jupiter and Mars, has long been known as the origin of the zodiacal light. If you could look at the solar system above the Earth's north pole, the planets would appear to move around the sun in the opposite direction, clockwise. All planets, except Venus and Uranus, turn their axis in the same direction. The entire system is quite flat - only the orbits of Mercury and Pluto are tilted. Pluto is so elliptical that there are moments that are closer to the Sun than Neptune.
Behind last years large asteroids flew by repeatedly, causing fear and anxiety. In 1936, the Adonis asteroid flew 2 million km from the Earth; in 1937, the Hermes asteroid flew at a distance of 800 thousand km from the Earth. In 1996, the Tautatis asteroid flew at a distance of 450 thousand km from Earth
A significant part of the main belt asteroids move along stable, stable orbits, which have changed little over the past 4.5 billion years, so collisions with such asteroids are practically unlikely.
Satellite systems follow the same behavior as their host planets, but there are many exceptions. Jupiter, Saturn, and Neptune have one or more moons that move in retrograde orbits, and many of the moons' orbits are highly elliptical. Comets show a more or less spherical distribution of orbits around the Sun.
These and other examples demonstrate the delicate balance of forces inherent in a gravitational system consisting of many bodies. Among the early attempts to explain the origin of this system is a vague hypothesis by the German philosopher Immanuel Kant and the French astronomer and mathematician. According to this theory, the gas cloud is fragmented into rings that condense into planets.
But the orbits of asteroids can change when approaching giant planets or when colliding with other asteroids and comets, so the orbits of asteroids can change.
The American astronomer R. Binzel developed a high-quality a scale for assessing the risk of collisions with the Earth by asteroids and comets, similar to the Richter scale, used to gradate earthquake hazards. In 1999, the scale was approved by the International Astronomical Union. (show table on presentation slide). According to various estimates, there is a high probability of an asteroid with a diameter of about 1 km falling to Earth once every 100 thousand years. But the greatest probability is that the Earth will encounter smaller celestial objects.
Doubts about the stability of these rings have prompted some scientists to consider some catastrophe scenarios, such as a violent collision between the Sun and another star. These collisions are very rare, and hot gases disorganized by the tides will disperse instead of condensing to form planets.
Modern theories link the formation of the solar system to the formation of the sun, which occurred 700 million years ago. Fragmentation and gravitational collapse of an interstellar cloud of gas and dust, possibly caused by nearby supernova explosions, could lead to the formation of a primordial solar nebula. Then the Sun would form in the central, denser region. The temperature near the Sun is so high that even relatively dense silicates have difficulty forming there.
Several double asteroids have been discovered.
In 1993, the American spacecraft Galileo, heading towards Jupiter, crossed the main asteroid belt. It turned out that the asteroid Ida has a small satellite called Dactyl.
Asteroid Eros revolves around the Sun with a period of 1.8 Earth years. Its dimensions are 40 x 14 x 14 km. In 2000, the robotic NEAR-Shoemaker spacecraft took many photographs of the asteroid. Studies of the asteroid have shown that Eros is a monolithic solid, that its chemical composition is approximately homogeneous, and that it was formed in the “young years” of the Solar System. In 2001, the device landed on the surface of an asteroid.
This phenomenon could explain the presence of a planet such as Mercury near the Sun, which has a small silicate shell and a denser, larger-than-usual iron core. At great distances from the center of the solar nebula, gases condense into solid particles similar to those found on the outer side of Jupiter today.
Evidence of a possible previous supernova explosion appears as traces of anomalous isotopes in small inclusions of some meteorites. This association of planet formation with star formation suggests that billions of other stars in our galaxy may also have planets. The abundance of multiple and binary stars, as well as large satellite systems around Jupiter and Saturn, indicate a tendency for gas clouds to break apart through fragmentation into multi-body systems.
Asteroid 216 Cleopatra consists mainly of metals such as nickel and iron, as shown by radar studies.
Asteroid 951 Gaspra has dimensions of 19x12x11 km and orbits in an almost circular orbit within the main asteroid belt. Gaspra consists of a mixture rocks and metal-containing minerals.
Asteroids beyond the orbit of Jupiter.
It is located at the center of the System. Composed primarily of hydrogen and helium, its enormous mass allowed it to once initiate nuclear reactions that give it the characteristics of a star. The process that occurs inside the solar core is very simple to explain, but extremely complex at the same time.
When the interstellar matter began to collapse, the hydrogen atoms bounced off each other, so that the temperature gradually increased, and at the same time, due to its enormous gravitational pull, everything was compressed more and more until it was dense and hot enough, so that the atoms, one day collided, no longer bounced off each other because the natural repulsive force was lower than the force of gravitational attraction, so they combined to form an atom belonging to the next element of the periodic table.
Other asteroids were discovered beyond the orbit of Jupiter at the end of the 20th century. The second asteroid belt is called the Kuiper belt.
The Kuiper Belt is a disk-shaped region beyond the orbit of Neptune, at a distance of 30 AU. up to 100 a.u. from the Sun, populated by asteroids and comet nuclei.
It is assumed that Kuiper belt objects are ice with small admixtures of organic substances, that is, they are close in composition to cometary matter. The mass of all Kuiper belt objects exceeds the mass of all asteroids in the main asteroid belt. But it is assumed that the mass of Orth cloud objects exceeds the mass of Kuiper belt objects.
In the case of hydrogen, which is the most abundant in the solar sphere, its fusion led to the transformation into helium, its next in the periodic table and therefore the important emission of heat and light. It should be noted that the Sun, because its mass is not significant enough, cannot transform elements located above iron. It took about one billion years for the Sun to begin its internal nuclear processes.
In the Middle Ages, the old geocentric model was used to predict the positions of stars and planets in the sky, including the Sun and Moon. However, it was clear that the predictions were not good for several days. Attempts to build models based on complex combinations of circular motions improved the situation somewhat, but were far from satisfactory. However, the geocentric model remained the rule mainly because it was accepted for philosophical reasons by the Catholic Church.
Comets- the most numerous, most extensive and most amazing celestial bodies of the Solar System. The word “comet” translated from Greek means “hairy”, “long-haired”. As the comet approaches the Sun, it takes on a spectacular appearance, heating up under the influence of the sun's heat so that gas and dust fly away from the surface, forming a bright tail.
Nicholas Copernicus proposed a model of the Universe that was, for a time, flat and flat heresy: The Earth and planets revolve around the Sun in circular orbits. This model was able to predict apparent changes in the celestial sphere with greater accuracy and in a much simpler mathematical way, which was very attractive for navigation. Copernicus could not provide observational evidence for the validity of his theory, so for the Church it was a simple calculation tool. Either for this reason, or for the obvious economic advantages of having simpler and more accurate tables, the truth is that Copernicus did not end up at the stake because he was the first to propose the heliocentric model: Giordano Bruno.
According to scientists, on the distant outskirts of the solar system, in the so-called Oort cloud - a giant spherical accumulation of cometary matter - there are about 10 12 -10 13 comets orbiting the Sun. As the comet approaches the Sun, the ice of the comet's nucleus begins to evaporate, and streams of gas and dust begin to be released into space.
Galileo Galilei, an Italian whose passion for physics was rivaled only by his love of good taste, knew about the recent invention of the telescope, quickly made one and pointed it towards the sky. Among the many things he saw, he discovered that the planet Jupiter was courted by four small stars, which he named the Medici stars after the duke who financed him economically. Conventional observation convinced him that the four stars were moons revolving around Jupiter, as the Moon revolves around the Earth.
His discovery was severely criticized by the Church, but the death blow to the heliocentric theory was given: not everything in the Universe revolved around the Earth. It was a matter of time before heliocentrism changed from a convenient theory to a theory accepted as correct.
- Comet structure
Each comet has several different parts:
- Core: Relatively solid and stable, consisting mainly of ice and gas with minor additions of dust and other solids.
- Head (coma): a luminous gas shell arising under the influence of electromagnetic and corpuscular radiation from the Sun. A dense cloud of water vapor, carbon dioxide and other neutral gases sublimating from the core.
- Dust tail: consists of very small dust particles carried away from the core by a gas flow. This part of the comet is best visible to the naked eye.
- Plasma (ion) tail: consists of plasma (ionized gases), interacts intensely with the solar wind.
The structure of comets and the features of comet tails are best illustrated using the “Comets” and “Comets: structure” models.
Despite all these, although simpler, predictions remained erroneous. Clearly there is something wrong with the model. And it cannot be said that the observations were made erroneously. Tycho Brahe was, like Galileo, a lover of astronomy, good food and the best wine. Fortunately, he had a habit of observing in an ideal state of sobriety and was very good in itself, even without a telescope, which would not appear until several years later.
After the death of Tycho, one of his students, he came up with little effort to study the family observations. Kepler then had the best set of observations of Mars at the time, which he used to derive his famous three descriptive laws from the orbital motion of the red planet.
Meteor bodies
There is no clear distinction between meteoroids (meteor bodies) and asteroids. Usually meteoroids are bodies measuring less than a hundred meters, and larger ones by asteroids. The collection of meteoroids forming around the Sun forms meteoric material in interplanetary space. A certain proportion of meteoroids are the remnants of the substance from which they were once formed. solar system, some are remnants of the constant destruction of comets, fragments of asteroids.
The figure above shows the characteristics of an ellipse. The minimum distance point is called perihelion and the maximum distance is called aphelion. The center-to-center distance of the ellipse indicates the degree of separation of the spherical shape, and its value in terms of the semi-major axis is called the "eccentricity" of the ellipse. The figure shows that the distance to perihelion.
The Earth, for example, is two and a half million miles closer to the Sun at perihelion than at aphelion. Do you dare to calculate it? Second Law: Not only are distances variable, but so is the speed of planets in their orbits. Since angular momentum must be conserved, the planet must move faster when it is near the Sun than when it is at aphelion.
meteor body or meteoroid- a solid interplanetary body that, when entering the atmosphere of a planet, causes a phenomenon meteor and sometimes ends with a fall to the surface of the planet meteorite.
What usually happens when a meteoroid reaches the Earth's surface? Usually nothing, since due to their small size meteor bodies burn up in the Earth's atmosphere. Large clusters meteor bodies are called meteor swarm. During the approach of a meteor swarm to the Earth, meteor showers .
Third Law: Also known as the Harmonic Law, was the result of Kepler's efforts to find some kind of pattern in the mechanics of the Universe. In this case, he discovered that a planet's orbital period is related to its average distance from the Sun, so.
Which is obviously not very convenient to remember. So for any planet, 3rd. The law simply becomes. Example: The average distance from Neptune to the Sun is 515 million kilometers. It is estimated that there are about a thousand stars similar to the Sun in our galaxy.
Stars produce energy, almost always, through nuclear fusion. For example, in the nearby star, the Sun, hydrogen nuclei combine to form helium and release energy, consuming about 700 million tons of hydrogen per second. This fusion occurs inside the star and the energy slowly moves towards its surface until it is released as light.
- Meteors and fireballs
The phenomenon of combustion of a meteoroid in the atmosphere of a planet is called meteor. A meteor is a short-term flash, the combustion trail disappears after a few seconds.
About 100,000,000 meteoroids burn up in the Earth's atmosphere per day.
If the meteor trails are continued back, they will intersect at one point called meteor shower radiant.
Many meteor showers are periodic, repeating year after year, and are named after the constellations in which their radiants lie. Thus, the meteor shower, observed annually from approximately July 20 to August 20, is called the Perseids because its radiant lies in the constellation Perseus. The Lyrids (mid-April) and Leonids (mid-November) meteor showers respectively get their name from the constellations Lyra and Leo.
It is extremely rare that meteoroid bodies are relatively large in size, in which case they say that they are observing car. Very bright fireballs are visible during the day.
- Meteorites
If the meteor body is large enough and could not completely burn up in the atmosphere during its fall, then it falls onto the surface of the planet. Such fallen to the Earth or other heavenly body meteor bodies are called meteorites.
The most massive meteoroids with high speed fall onto the Earth's surface to form crater.
Depending on the chemical composition meteorites are divided into stone (85 %), iron (10%) and iron-stone meteorites (5%).
Stone meteorites consist of silicates with inclusions of nickel iron. Therefore, heavenly stones are usually heavier than earthly ones. The main mineralogical components of the meteorite substance are iron-magnesium silicates and nickel iron. More than 90% of stony meteorites contain round grains - chondrules . Such meteorites are called chondrites.
Iron meteorites almost entirely composed of nickel iron. They have an amazing structure, consisting of four systems of parallel kamacite plates with a low nickel content and interlayers consisting of taenite.
Stone-iron meteorites consist half of silicates, half of metal. They have a unique structure, not found anywhere except meteorites. These meteorites are either metallic or silicate sponges.
One of the largest iron meteorites, the Sikhote-Alin meteorite, which fell on the territory of the USSR in 1947, was found in the form of a scattering of many fragments.
Cold objects, consisting of solid rocks (including metals) and ice, are part of the Solar System. These objects are asteroids, comets, meteoroids.
Comet
Comets are composed of a mixture of ice, frozen gas and dust. They travel around the Sun in very elongated orbits. As a comet approaches the Sun, ice and other volatile substances on its surface quickly evaporate, creating a stream of gas and dust. The solar wind and light pressure “blow away” the resulting gases with other substances away from the Sun. This is how the luminous tail of a comet is formed. The comet's tail can reach 10 million km.
Long-period comets with an orbital period around the Sun of more than 200 years, they arrive from regions located further than the outer planets of the system, in the Oort cloud, which probably exists at a distance of almost a light year from the Sun, about a quarter of the way to our nearest star Proxima Centauri (distance to it is 4.3 light years, or 40 trillion km). It is believed that there are about a trillion comets in the Oort cloud. Short-period comets (periods of less than 200 years) come from the region of the outer planets - these are objects from the Kuiper belt located beyond the orbit of Neptune. Halley's Comet orbits the Sun every 76 years and is the most famous comet in history.
Asteroid
Most of the solar system's asteroids are concentrated in the belt between the orbits of Mars and Jupiter. Asteroids are, in all likelihood, part of protoplanetary matter - planetesimals, formed at the boundary of the hot and cold zones of the protoplanetary disk and preserved to this day. Carbon, metallic, silicate, etc. asteroids are known.
An asteroid may fall out of orbit under the influence of a gravitational field major planets or another asteroid. Such a stray asteroid could collide with a planet or satellite and fall to the surface as a meteorite. Sometimes this leads to destruction. Some scientists believe that about 65 million years ago a meteorite crashed into the Earth, which led to the extinction of the dinosaurs.
Cosmic dust, meteoroids - bodies larger than dust, but smaller than an asteroid, and asteroids themselves, which do not burn up, but crash into the Earth in the form of meteorites, fall to the Earth from space. Some of the meteorites are so large that they leave craters. The most famous place The Berringer impact crater in Arizona, USA is considered to be the site of a meteorite impact on Earth. This is the result of the fall of an iron meteorite weighing about 300 thousand tons, which collided with the Earth at a speed of 45-60 thousand km/h about 50,000 years ago.