Asteroids are celestial bodies, which were formed due to the mutual attraction of dense gas and dust orbiting our Sun at an early stage of its formation. Some of these objects, like an asteroid, have reached enough mass to form a molten core. At the moment Jupiter reached its mass, most of the planetosimals (future protoplanets) were split and ejected from the original asteroid belt between Mars and. During this epoch, part of the asteroids formed due to the collision of massive bodies within the impact gravitational field Jupiter.
Orbit classification
Asteroids are classified according to features such as visible reflections of sunlight and characteristics of their orbits.
According to the characteristics of the orbits, asteroids are combined into groups, among which families can be distinguished. A group of asteroids is considered to be a certain number of such bodies whose orbital characteristics are similar, that is, semiaxis, eccentricity and orbital inclination. A family of asteroids should be considered a group of asteroids that do not just move in close orbits, but are probably fragments of one large body, and were formed as a result of its split.
The largest of the known families may contain several hundred asteroids, while the most compact families may contain up to ten. Approximately 34% of asteroid bodies are members of asteroid families.
As a result of the formation of most groups of asteroids solar system, their parent body was destroyed, however, there are also groups whose parent body survived (for example).
Classification by spectrum
The spectral classification is based on the spectrum of electromagnetic radiation, which is the result of the asteroid reflecting sunlight. Registration and processing of this spectrum makes it possible to study the composition of a celestial body and assign an asteroid to one of the following classes:
- Group of carbon asteroids or C-group. Representatives of this group consist mostly of carbon, as well as elements that were part of the protoplanetary disk of our solar system in the early stages of its formation. Hydrogen and helium, as well as other volatile elements, are practically absent in carbonaceous asteroids, however, the presence of various minerals is possible. Another distinguishing feature of such bodies is their low albedo - reflectivity, which requires the use of more powerful observation tools than in the study of asteroids of other groups. More than 75% of the asteroids in the solar system are representatives of the C-group. The most famous bodies of this group are Hygiea, Pallas, and once - Ceres.
- A group of silicon asteroids or S-group. Asteroids of this type are composed mainly of iron, magnesium and some other rocky minerals. For this reason, silicon asteroids are also called stony asteroids. Such bodies have a fairly high albedo, which allows you to observe some of them (for example, Irida) simply with binoculars. The number of silicon asteroids in the solar system is 17% of the total, and they are most common at a distance of up to 3 astronomical units from the Sun. The largest representatives of the S-group: Juno, Amphitrite and Herculina.
Judging by disaster films, asteroids can be considered the main enemies of humanity along with viruses, zombies and irresponsible politicians. Dozens of films tell about the disasters that begin on Earth after the collision of even a relatively small celestial body. A non-exhaustive list includes tsunamis, earthquakes, climate change and other phenomena that are not very useful to humans.
The probability of a collision of the Earth with an asteroid exists, but, fortunately, it is extremely small. Still, the Universe in general and the Solar System in particular, it is more correct to imagine as an empty space in which large bodies like planets, their satellites and asteroids come across very rarely. This fact is indicative: despite the fact that thousands of large and small celestial bodies have been discovered in the space between Mars and Jupiter, spacecraft cross this zone not only without damage, but also without threatening encounters with asteroids.
The history of the discovery of asteroids in popular science literature is usually presented sparing scientists. Like, Johann Titius in the 18th century calculated the regularity of the removal of planets from the Sun, and a little later, his namesake Bode calculated that there should be a planet between Mars and Jupiter. Astronomers began to look for it and in 1801 they did find it. Since then it all started...
In this version, everything looks natural and beautiful, but there are a number of nuances. The Titius formula turned out to be a well-chosen empirical combination. Astronomers were indeed looking for the first asteroid. Baron Xaver even created the sky police for this search. Two dozen astronomers were assigned equal parts of the sky in which machinations took place.
But the future Ceres was discovered not by any of the "heavenly policemen", but by the Italian Giuseppe Piazza. The astronomer was not looking for anything new - he was compiling a catalog of stars, and on New Year's Eve in 1801, he accidentally stumbled upon a rapidly moving point. Moreover, Piazza immediately lost his discovery, barely having time to name the new, as he thought, planet, Ceres. Carl Gauss helped. Using mathematical calculations, he found a place where to look for replenishment in the solar system, and Ceres was rediscovered. That is, the discovery of Piazza is to some extent similar to the discovery of America by Columbus - both were looking for the wrong thing, but chance does not diminish the significance of these discoveries.
More asteroids
Since 1802, two parallel processes have been going on in the astronomical community. Astronomers have discovered many new asteroids, while debating about their status and origin. They were proposed to be considered minor planets, even the exact, but not sounding, term “Zenareids” (“located between Jupiter and Mars”) was invented. But the current name won. It was neutral - any body can be called an "asteroid", regardless of its relative size, origin, composition and orbit. And practical searches have led to the fact that about 300 thousand asteroids have already been discovered in the solar system.
The largest asteroids
It is clear that in the gigantic number of discovered asteroids, the vast majority are small objects. All honors, including proper names, go to large asteroids. If we take into account the size, the list of the largest asteroids will be something like this:
10. Euphrosyne
Asteroid Euphrosyne, despite its proximity to Earth and large size, even from the very short distance it is difficult to see from the Earth - due to the large amount of carbon in the composition, it is very dark. An asteroid with a diameter of 256 kilometers moves in an orbit close to vertical to the plane of the ecliptic, and completes a revolution around the Sun in 5.6 years.
Hector was discovered in 1907, but due to its great distance from the Earth (it is closer to Jupiter) and low reflectivity, it was only in the 21st century that they could really see it. It turned out that an asteroid with a maximum length of 370 kilometers is similar in shape to a bean or a dumbbell, and only gravity can connect its two massive parts.
It takes Hector almost 12 years to fly around the Sun. At the same time, the speed of its own rotation is close to the speed of other asteroids and is less than 7 hours.
8. Sylvia
Strictly speaking, Sylvia is not a single asteroid, but a system with two satellites - Romulus and Remus. And the main asteroid is most likely not a monolith, but small stones gathered together by gravity - Sylvia has too low an average density.
The Sylvia system makes a revolution around the Sun in 6.5 years, and around its axis a little longer than 5 hours. While orbiting, Sylvia's size can change by 10%.
7. David
This asteroid had to be slightly renamed to suit tradition. The American Raymond Dugan, who discovered it, gave his discovery the name David in honor of Professor David Todd. But there was a tradition to give asteroids female names, and the title has been adjusted.
With the help of the largest telescopes at that time located in Hawaii, they not only determined the size of Davida (at least 231 kilometers), but also saw a huge crater on the surface. It is characteristic that in the course of calculations of the mass of Davida, the results gave a twofold spread. A year on this asteroid lasts 5.6 years, and a day is a little more than 5 hours.
6. Europe
Asteroid Europa is lighter than its counterparts in the group of large asteroids. This allowed astronomers to assume that it consists of porous substances. And because of the low luster, it is believed that these are compounds containing carbon.
An asteroid with a diameter of 302.5 kilometers rotates in an elongated orbit. The difference in distance to the Sun ranges from 413 to 512 million kilometers. A day in Europe lasts 5.6 hours, and a year is 5.5 Earth hours.
This asteroid is still a big mystery. It is known that its diameter is 326 kilometers, Interamnia makes a revolution around the Sun in 5.4 years, and a day lasts almost 8 hours. However, due to the remoteness and very dark surface, astronomers do not have any information about the composition of the asteroid. Even common physical information were obtained not by direct observations, but during the occultation of a bright star by Interamnia.
The asteroid, named after the goddess of health, was discovered rather late - in 1849. Hygiea is quite far from the Earth compared to other large asteroids, and its surface reflects little light.
A year on Hygiea, which has a diameter of 407 kilometers, lasts 5.5 Earth years, but a day is three hours longer than Earth years.
Pallas occupies the third place among asteroids in size, and the second in time of discovery - Heinrich Olbers discovered it in 1802. For a long time, she owned the second place in both categories, but after clarifications, Pallada became the third.
The diameter of Pallas is 512 km. It rotates in an inclined and strongly elongated orbit in an oval, so the year on it lasts more than 4.5 Earth years.
Ranking second among asteroids, Vesta bypassed Pallas in size quite slightly - its average diameter is 525 kilometers, and its maximum value is 573 kilometers (Vesta has a rather irregular shape).
There are many deep craters on the surface of the asteroid, including the Reyasilvia crater, the diameter of which is comparable to the diameter of Vesta itself. In the center of the crater, a mountain rises 22 kilometers up. Scientists still do not know how the asteroid survived the impact of such a monstrous force.
Vesta's weight shows that her core is composed of metals. Perhaps in the future, the asteroid, which now revolves around the Sun at a speed of one revolution in 42 Earth months, will become a source of raw materials for the earth's metallurgy.
The largest asteroid officially had this status until 2006. Discovered by Giuseppe Piazza Ceres, having existed as an asteroid for 200 years, became a minor planet. So decided the International Astronomical Union. However, with all due respect to the vote of astronomers, Ceres does not reach the planet in any way - its diameter of 950 kilometers, impressive in the company of asteroids, is almost five times smaller than Mercury, which became the smallest planet after the disqualification of Proton.
Unlike small asteroids, Ceres has an almost regular ball shape. About a third of the asteroid is ice, the rest is ores containing iron and carbonates. A year on an asteroid orbiting the Sun between the orbits of Jupiter and Mars lasts more than 4.5 Earth years, and a day is shorter than Earth years - Ceres makes a revolution around its axis in 9 hours.
The science
Our quest for knowledge of the universe is still in its infancy, and we are constantly surprised by any new discoveries.
There are still many mysteries that we have to solve, even in our small corner of the universe called the solar system.
Here are a few interesting facts about the highest mountain, the largest asteroid, the largest object and other cr secrets of our solar system.
1. The highest mountain
Mount Olympus- the famous Martian mountain, in comparison with which Everest seems like a small hill. At height 21,900 meters, this volcanic mountain has long been considered the highest in the entire solar system.
Mount Olympus on Mars
However, a recently discovered peak located on Vesta, one of the largest asteroids in the solar system, overthrew Olympus from the first place. The height of the peak, named Rheasilvia, is 22 km. m, which is 100 meters higher than Olympus.
Since these measurements are not absolutely accurate, and the difference between these peaks is not so big, it cannot be said with certainty that one is higher than the other.
Rheasilvia on the asteroid Vesta
When in 2011 spacecraft Dawn studied Vesta and found that Rheasilvia is the central mountain in a giant crater 505 km in diameter, almost as long as the entire asteroid.
2. The largest asteroid
Pallas considered the largest asteroid in the solar system, but under certain circumstances.
Comparison of large asteroids
To begin with, it is worth noting Ceres - the first asteroid discovered, and by far the largest. It contains almost a third of the total mass of the asteroid belt. That is, technically, Ceres can be considered the largest asteroid, but its upgraded to dwarf planet status.
Besides asteroid Vesta actually heavier than Pallas, but the latter is larger in volume.
It is possible that Pallas will not hold the title of the largest asteroid for long, since according to latest pictures Hubble she is dynamic protoplanet.
In other words, this is not just a giant ball of stone and ice, but it undergoes internal changes with the change of dark and light areas. Perhaps in the near future it will become a candidate for dwarf planets.
3. The largest impact crater
There are currently three candidates claiming the title of the largest impact crater, and they are all on Mars.
Hellas Plain on Mars
The first and smallest of the three candidates is Hellas plain, whose diameter is 2300 km. However, it is the only one we know to have formed as a result of the impact.
The second largest crater is much larger than the previous one and is called Utopia plain. However, most likely, both of them look tiny compared to the largest crater in our solar system.
Great Northern Plain on Mars (center)
Diameter Great Northern Plain is 8500 km, and it is almost three times the size of the plain of Utopia.
However, it remains to be confirmed that it is an impact crater. If so, it must have been the result of a very large impact, and its formation will help us learn more about the formation of Mars as a planet.
4. The most volcanically active body
Volcanic activity is not as common in the solar system as one might think. Although many cosmic bodies, such as Mars and the Moon, show signs of volcanic activity, so far there are four more bodies in which it is also observed.
Volcanic activity on Jupiter's moon Io.
In addition to the Earth, there are three volcanic satellites in the solar system: Triton(satellite of Neptune) And about(moon of Jupiter), and Enceladus(Saturn's moon).
Of all of them Io is the most active. On satellite images, they counted about 150 volcanoes, and astronomers believe that their total number is about 400. It is surprising that there are volcanic activity, given its icy surface and distance from the Sun.
According to one theory explaining how a hot interior is preserved in such a cold place, Io's volcanic activity is caused by internal friction .
Volcano on Io
The moon is constantly deforming internally due to the outward thrust of Jupiter and the two large moons of Ganymede and Europa. The backlash creates internal tides that cause friction and generate heat to keep volcanoes active.
5. The largest object in the solar system
The sun, which represents 99 percent of the mass of the solar system, is its largest object. However, in 2007, for a short period, the comet became larger than the Sun.
Or rather we are talking about the comet's coma - the cloudy region that surrounds the comet and consists of ice and dust. Comet 17P/Holmes was discovered in 1892 and was named after the astronomer who discovered it - Edwin Holmes.
Comparison of Comet 17P/Holmes and the Sun
Since then, scientists have tried to trace her, despite losing her for nearly 60 years between 1906 and 1964.
Although it is not typical for a comet to experience bursts of brightness, on October 23, 2007, Comet Holmes suddenly increased its brightness to nearly half a million.
It was the strongest comet flare which was visible to the naked eye.
Over the next month, the comet continued to expand until it reached diameter 1.4 million kilometers, officially becoming larger than the Sun.
We still do not know why this outbreak occurred, and in the future it may surprise astronomers more than once.
6. The longest channel
In 1989, the Magelan spacecraft was launched to Venus, which carried out the largest mapping of its surface. Also in 1991, he discovered the longest known riverbed in our solar system.
It was named Baltis Valley, whose length was 6800 km. Subsequently, many similar channels were discovered on the surface of Venus, but none could compare with the Baltis Valley.
But what surprises astronomers the most is how these channels could have come about, given that Venus is known for its harsh environment.
superficial the pressure there is 90 times greater than the earth, and the temperature can reach 462 degrees Celsius.
According to some assumptions, these channels appeared due to molten lava after volcanic eruptions. These lava beds are unlike anything we have on Earth, although there may have been similar characteristics on our planet billions of years ago.
7. The largest lava lake
As mentioned earlier, Jupiter's moon Io is one of the few bodies in the solar system that is still volcanically active, and quite strong. All molten lava must go somewhere, and often this leads to the formation of lava lakes.
Patera Loki on Jupiter's moon Io
One of them Patera Loki is the largest lava lake in the entire solar system.
Although something similar is observed on Earth, none of these lakes is active. The biggest - Nyiragongo volcano in the Democratic Republic of the Congo reaches about 700 meters in diameter.
Volcano Nyiragongo on Earth
However, there is evidence indicating that masaya volcano in Nicaragua in the past formed an even larger lava lake, reaching 1 km in diameter.
Masaya Volcano on Earth
All this allows you to look at Patera Loki from the outside, whose diameter was 200 km. Considering that its total surface area is not directly proportional, since the lake has an unusual U-shape, it is very large.
The lake is almost twice as big Pateri Gish Bar- the second largest lava lake on Io with a diameter of 106 km.
8 Ancient Asteroids
Despite all the research that has been done, we still cannot say with 100 percent certainty how asteroids are formed.
There are currently two main theories: they formed like the planets(pieces of material collide with other pieces and get bigger and bigger), or they could be ancient planets between Mars and Jupiter, whose destruction led to the creation of the asteroid belt.
Our understanding of asteroid formation advanced in 2008 when researchers at the Mauna Kea Observatory in Hawaii discovered the oldest known asteroids in our solar system.
Asteroids whose age was 4.55 billion years, were older than any meteorites that fell to Earth, and close to the age of the solar system itself.
Their age was determined by analyzing the composition, and found that all three asteroids contain a large number of aluminum and calcium, more than any other space rock ever found.
9 Longest Comet Tail
Comet Hyakutake or Big Comet 1996 known for the longest tail in history.
Hyakutake or Big Comet 1996
When Hyakutake flew by in 1996, it was closer than any comet as it approached Earth. The comet became very bright and was visible to the naked eye.
Ceres This is a rather large celestial body (diameter 975 * 909 km) who has not been since the discovery: both a full-fledged planet of the solar system, and an asteroid, and since 2006 it has acquired a new status - dwarf planet. last name the most correct, since Ceres is not the main one in its orbit, but only the largest in the asteroid belt. It was discovered quite by accident by the Italian astronomer Piazzi in 1801. Ceres is spherical (unusual for asteroids) with a rocky core and a crust of water ice and minerals. The distance between the nearest point in the orbit of this satellite of the Sun and the Earth is 263 million kilometers. Its path lies between Mars and Jupiter, but there is some tendency to chaotic movement (which increases the chances of colliding with other asteroids and changing the orbit). It is not visible to the naked eye from the surface of our planet - this is a star of only 7 magnitudes. Pallas Size 582 * 556 kilometers, and it is also part of the asteroid belt. The angle of the axis of rotation of Pallas is very high - 34 degrees (for other celestial bodies it does not exceed 10). Pallas moves in an orbit with a large degree of deviation, which is why its distance from the Sun changes all the time. It is a silicon-rich carbon asteroid and is of further interest from a mining standpoint. Vesta This is the heaviest asteroid at the moment, although it is inferior in size to the previous ones. Due to the composition of the rock, Vesta reflects 4 times more light than the same Ceres, although its diameter is half that. It turns out that this is the only asteroid whose movement can be observed with the naked eye from the surface of the Earth, when it approaches once every 3-4 years at a minimum distance of 177 million kilometers. Its movement is carried out along the inside of the asteroid belt and never crosses our orbit. It is interesting that with a length of 576 kilometers on its surface there is a crater with a diameter of 460 kilometers. In general, the entire asteroid belt around Jupiter is a giant quarry where celestial bodies collide with each other, scatter into pieces and change their orbits - but how did Vesta survive the collision with such large object and retained its integrity remains a mystery. Its core consists of heavy metal, and the bark is from light rocks. Hygiea This asteroid does not intersect with our orbit and revolves around the Sun. A very dim celestial body, although it has a diameter of 407 kilometers, was discovered later than the others. This is the most common type of asteroid, with a carbonaceous content. Normally, a telescope is required to observe Hygia, but at its closest approach on Earth, it can be viewed with binoculars.
In the very early XIX in. Italian astronomer Piazzi (1746-1826) accidentally discovered the first minor planet (asteroid). She was named Ceres. Subsequently, many other minor planets were discovered, forming an asteroid belt between the orbits of Mars and Jupiter.
asteroid movement
In photographs of the starry sky, taken with long exposures, they are obtained in the form of light dashes. More than 5500 minor planets have been registered. Total number there should be ten times more asteroids. Asteroids whose orbits are established receive designations (sequential numbers) and names. Some new asteroids are named after great people (1379 Lomonosov), states (1541 Estonia, 1554 Yugoslavia), observatories (1373 Cincinnati - an American observatory, which is the International Asteroid Observation Center), etc.
Asteroids move around the Sun in the same direction as the big planets. Their revolutions have larger eccentricities (0.15 on average) than the orbits of the major planets. Therefore, some small planets go far beyond the asteroid belt. Some of them at aphelion move beyond the orbit of Saturn, others at perihelion approach Mars and Earth. For example, Hermes in October 1937 passed from the Earth at a distance of 580,000 km (only one and a half times further than the Moon), and the asteroid Icarus, discovered in 1949, when moving, even gets inside the orbit of Mercury and every 19 years approaches the Earth . AT last time this happened in June 1987. Then Icarus approached the Earth at a distance of several million kilometers, he was observed at many observatories. Of course, this is not the only case. It is possible, for example, that the collision of an asteroid with the Earth led to the death of dinosaurs 65 million years ago. And in March 1989, an asteroid about 300 m in size passed from the Earth at a distance of less than 650 thousand km. Therefore, it is no coincidence that scientists began to develop effective methods timely detection and, if necessary, destruction of dangerous asteroids.
Physical characteristics of asteroids
Asteroids are not visible to the naked eye. The largest asteroid is Ceres (diameter 1000 km). In general, asteroids have diameters from several kilometers to several tens of kilometers, and most asteroids are shapeless blocks. The masses of asteroids, although different, are too small for these celestial bodies to hold an atmosphere. The total mass of all the asteroids put together is about 20 times less than the mass of the moon. Of all the asteroids, one planet with a diameter of less than 1500 km would have turned out.
AT last years managed to discover satellites (!) of some asteroids. For the first time, an asteroid was photographed from a distance of only 16 thousand km on October 29, 1991 from an American spaceship Galileo, launched October 18, 1982 to explore Jupiter. Crossing the asteroid belt, Galileo photographed the minor planet 951, the asteroid Gaspra. This is a typical asteroid. The semi-major axis of its orbit is 2.21 AU. He turned out irregular shape and may have formed as a result of the collision of larger bodies in the asteroid belt. The photographs show craters (their diameter is 1-2 km, the consecrated part of the asteroid is 16x12 km). In the images, it is possible to distinguish the details of the surface of the Gaspra asteroid 60-100 m in size.
