A comet is a space object that moves at high speed around the Sun. Translated from Greek, the name means “long-tailed”. Sometimes these space objects come close to the Earth, then they can be seen in the starry sky with the naked eye. The brightest comet is Halley, which passes the Earth every 75 years. We present interesting facts about comets.
Astronomy
Astronomers have counted four thousand comets that originate from the Kuiper belt (the planet Pluto is located in this belt). In the Oort Belt, which is further from the Sun than the Kuiper Belt, there may be millions of comets (sometimes even a trillion of these cosmic objects are quoted). Scientists discover an average of five comets each year.
The diameter of the nucleus of the smallest comet is 16 kilometers, the record diameter of the nucleus is 40 kilometers.
Photo by Kohoutek
Jupiter has such a large mass that it influences the direction of movement of comets. In July 1994, astronomers witnessed Comet Shoemaker Levy 9 disintegrate as it crashed into Jupiter.
For the first time, Halley's Comet (it was not called that at that time) was mentioned in Chinese chronicles in 240 BC.
In 2014, the Rosetta probe landed on comet Churyumov-Gerasimenko. The spacecraft approached this space object for about ten years.
Properties
This space object is actually a dirty snowball consisting of water, frozen ammonia, dust and rocks. The core is dark in color, its composition is unknown, perhaps the composition of the core is the same as that of meteorites that fall to Earth - they are iron, stone and iron-stone.
In fact, it is an asteroid that becomes noticeable due to its long tail. This tail appears when this block of ice approaches the Sun as close as possible, then the ice melts and a dust cloud forms behind the comet. When the ice block is even closer to the Sun, the process of sublimation occurs (this phenomenon of physics is also called sublimation - a transition from a solid to a gaseous state without remaining in a liquid state). When ice is close to the surface, it heats up and creates a stream of gas, a phenomenon similar in appearance to a geyser eruption.
The tail can be very long; Comet Hyakutake's tail is 580 million kilometers long, three times the distance from the Earth to the Sun.
A comet has two tails. The first tail consists of dust, which we see with naked gas. The second is invisible because it consists of gases that are blown by the solar wind.
As it moves away from the Sun, the comet becomes like an asteroid, its tail disappears, leaving only a rocky core surrounded by ice.
Hyakutake Photography
Craters
Perhaps dinosaurs became extinct due to a collision between the Earth and a comet. On our earth there are many meteorite craters that could have been left by comets. According to some data, the Gulf of Mexico is the largest meteorite crater on Earth with a diameter of more than 1 thousand kilometers.
120 kilometers from Johannesburg, South Africa, there is a large meteorite crater called Vredefort (diameter about 300 kilometers). An even larger crater is located in Antarctica - the Wilkes Land crater has a diameter of 500 kilometers, but it has not been studied well enough, since it is located under a layer of ice.
Large craters were discovered in the Canadian province of Ontario (Sudbury, diameter 200 kilometers) and on the Yucatan Peninsula, North America (Chicxulub, diameter 170 kilometers). Such large craters could be formed by the impact of asteroids or comets.
Each fall of a cosmic body, which formed such large craters on the surface of the earth, led to disasters on Earth. For example, the Chicxulub crater was formed from the fall of a block with a diameter of about 10 kilometers; the energy from the fall is estimated at 100 teratons in TNT equivalent; for comparison, the most powerful thermonuclear bomb had a power two million times less. The fall of a meteorite or comet that formed the Chicxulub crater should have caused a tsunami up to 100 meters high, rocks should have been lifted into the air 100 kilometers (that is, into space), when falling back they would become hot and could cause forest fires thousands of kilometers away from the crash site of the car. It is believed that the ash that entered the atmosphere led to a cooling of the air by 28 degrees, the water became colder by 11 degrees, which led to the extinction of many species of animals and plants.
Comets are small solar system objects that orbit the Sun and can be observed as a bright point with a long tail. They are interesting for several reasons.
Since ancient times, people have observed comets in the sky. Only once every 10 years can we see a comet from Earth with the naked eye. Its impressive tail flashes across the sky for days or weeks.
In ancient times, comets were considered a curse or a sign that preceded disaster. So in 1910, when the tail of Halley’s Comet hit the Earth, some entrepreneurs took advantage of the situation and sold people gas masks, comet pills, and umbrellas for protection against comets.
The comet got its name from the Greek word for “long-haired,” as people in Ancient Greece thought that comets looked like stars with flowing hair.
Comets only develop tails when they are close to the Sun. When they are far from the Sun, comets are exceptionally dark, cold, icy objects. The ice body is called the core. It makes up 90% of the comet's mass. The core is made up of various types of ice, dirt and dust. In turn, ice includes frozen water, as well as impurities of various gases, such as ammonia, carbon, methane, etc. And in the center there is a small core of stone.
As it approaches the Sun, the ice begins to heat up and evaporate, releasing gases and dust particles that form a cloud or atmosphere around the comet called a coma. As the comet continues to move closer to the Sun, dust particles and other debris in the coma begin to be blown away due to the pressure of sunlight from the Sun. This process forms a dust tail.
If the tail is bright enough, we can see it from Earth when sunlight reflects off dust particles. As a rule, comets also have a second tail. It's called an ion or gas, and it forms when core ices heat up and change directly into gases without going through a liquid stage, a process called sublimation. The residual gas is visible due to the glow caused by solar radiation.
After comets begin to move in the opposite direction from the Sun, their activity decreases, and their tails and coma disappear. They turn into a simple ice core again. And when the orbits of comets return them to the Sun again, the head and tails of the comet begin to form again.
Comets have a wide range of sizes. The smallest comets can have a nucleus size of up to 16 kilometers. The largest core was observed to be about 40 kilometers in diameter. The tails of dust and ions can be huge. Comet Hyakutake's ion tail extended over a distance of about 580 million kilometers.
There are many versions of the formation of comets, but the most common is that comets arose from the remains of matter during the formation of the Solar System.
Some scientists believe that it was comets that brought water and organic substances to Earth, which became the source of the origin of life.
Meteor showers can be observed when the Earth's orbit intersects the trail of debris left behind by a comet.
It is unknown how many comets exist, since most have never been seen. But there is a cluster of comets called the Kuyper Belt, located 480 million kilometers from Pluto. There is another such cluster surrounding the solar system called the Oort Cloud - it can simultaneously contain more than a trillion comets that are moving in different directions. As of 2010, astronomers have discovered about 4,000 comets in our solar system.
To a greater extent, seeing a comet is a miracle that many dream of seeing at least once in their life. But in extremely rare cases, comets can cause problems on Earth. Most scientists believe that a very large asteroid or comet may have struck the Earth approximately 65 million years ago. As a result, the resulting changes on Earth led to the extinction of the dinosaurs. Very large asteroids, as well as very large comets, could cause severe damage if they reached Earth. However, scientists believe that major impacts like those that killed the dinosaurs occur once every few hundred million years.
Comets can change direction for several reasons. If they pass close enough to a planet, the pull of that planet's gravity can slightly change the comet's path. Jupiter, the largest planet, is the most suitable planet to change the path of a comet. Telescopes and spacecraft have captured images of at least one comet, Shoemaker-Levy 9, crashing into Jupiter's atmosphere. In addition, sometimes comets moving towards the Sun fall directly into it.
Over millions of years, most comets gravitationally fly out of the solar system or lose their ices and disintegrate as they move.
© Inga Korneshova article written specifically for the site 100facts.ru
Since ancient times, people began to distinguish comets from other celestial bodies, attributing to them completely extraordinary properties. Although Halley's comet was the first of those that natural scientists began to study seriously, great fears were associated with it for a very long time. They persisted even into the twentieth century.
History of Halley's Comet
Although today we already know everything about Halley’s comet (or almost everything), it is very useful to understand why it provoked such fear in the past (like other “shaggy stars”). Extremely poor knowledge about cosmic processes in the past led to their mystification.
From time to time, suddenly appearing comets, which soon just as suddenly disappeared from sight, were perfectly suited to the role of a scarecrow. Wars, upheavals, famines and natural disasters were expected in each such case. It must be said that at that time such incidents were not uncommon, and often coincided with the arrival of comets.
But what can we say about ancient and medieval people! When Halley's comet approached the Earth in 1910 and our planet passed through its tail, such a famous astronomer as Flammarion, wittingly or unwittingly, caused panic. Poisonous gases, he said, are capable of destroying all living things. Some merchants took advantage of the general shock and sold a lot of gas masks, pills and even... umbrellas!
When was Halley's Comet last seen?
Halley's comet is classified as short-period - it makes a revolution around the Sun in strictly 74-79 years, on average 76 years. The last such appearance occurred in the spring of 1986. The distance between it and our planet was about sixty-three million kilometers even at the moment of closest approach.
Of course, the researchers could not help but take advantage of this opportunity. Spacecraft were launched in advance to photograph the nucleus of Halley's Comet. By the way, it turned out to be very dark - blacker than any coal. The density of the core is very low, and it appears to be porous.
Comet meaning
Halley's Comet is interesting to scientists primarily because it was the first to be studied in detail. However, it is hardly possible to extend the conclusions drawn to comets in general. After all, Halley's comet is atypical in size, in the definiteness of its orbit, and in other parameters.
The next appearance of Halley's Comet will occur in the second half of this century, or more precisely, in 2061. Well, forty-six years just seems like a long time. Surely many of those who are now reading this article will still be able to enjoy the spectacle of the “shaggy star”.
The largest collection of amazing information about celestial bodies. Interesting facts about comets and asteroids will open you up to a whole new world that you never knew existed.
Translated from Greek, “comet” means “long-haired,” since ancient people associated a star with a long tail with hair blowing in the wind.
Comets are dirty ice
A comet's tail only forms when it is in close proximity to the Sun. Far from this celestial body, comets appear as icy, dark objects.
90% of a comet is ice, dirt and dust. In the center is a stone core. As it approaches the Sun, the ice melts, forming a dust cloud behind it. This is the tail we see.
Incredible amount
The smallest comets reach a core diameter of 16 km. The largest recorded is 40 km. The length of the tails can be very long. For example, comet Hyakutake's tail length was 580 million km.
A cluster of comets can number in the trillions. This is exactly what is found in the Oort Cloud, a cluster surrounding the Solar System. Within the solar system, astrologers count at least 4,000 comets.
Jupiter, as the largest planet in the solar system, is capable of changing the direction of comets by the force of its gravity. So, one day comet Shoemaker-Levy 9 crashed into the atmosphere of Jupiter.
Shapeless asteroids
Cosmic bodies form a spherical shape under the influence of their gravity. Asteroids are too small to form a sphere, so they look like ellipsoids or dumbbells.
Integrity of form is rare for an asteroid. More often it is a pile of compounds, which is held by its own gravity. The accumulations contain coal, stone, iron, and volcanic materials.
The diameter of the largest asteroid, Caecesere, is 950 km.
If an asteroid enters a planet's atmosphere, it is a meteor. If it falls to the ground, then it is a meteorite.
Is there a threat to us?
Asteroids pose a potential threat to the planet, but modern technology can easily prevent this.
To imagine how an asteroid falls onto the surface of the planet, you can look. Interesting fact - the Earth can be destroyed with just one meteor with a diameter of 1 km.
Halley's Comet is a "periodic" comet that returns to Earth every 75 years, allowing humans to see it twice in their lifetime. She was last around in 1986, and is predicted to return again in 2061.
The comet is named after English astronomer Edmund Halley, who investigated reports of a comet approaching Earth in 1531, 1607 and 1682. He came to the conclusion that these three comets were in fact the same comet, returning again and again, and predicted that the comet would appear again in 1758. However, the scientist did not live to see this event.
According to historical data provided by the European Space Agency, the first known sighting of Halley's Comet occurred in 239 BC. Chinese astronomers.
In those days, each appearance of Halley's comet was considered an isolated event, which was a sign of a great catastrophe or serious changes.
Photo: This part of the Bayeux Tapestry shows Halley's Comet as it appeared in 1066
The comet's passage in 1910 was particularly impressive, as the comet passed Earth at a distance of about 22.4 million kilometers and was captured on camera for the first time.
Interestingly, the writer Mark Twain, according to his biographer Albert Bigelow Paine, said in 1909 that he was born with Halley's Comet in 1835 and when it came again, he would go with it. Twain died on April 21, 1910, the day after the comet appeared above the Earth.
In 1986, the first spacecraft was sent to take a closer look at Halley's Comet and take important pictures. Then several spaceships successfully made this journey and even received the humorous name Halley Armada.
Photo: Halley's Comet captured by the Russian space probe Vega 2 during its 1986 flyby through the solar system. Vega 1's closest approach to the comet was 8,890 km, and Vega 2's closest approach was 8,030 km.
It will be many decades before Halley's Comet approaches Earth again, but in the meantime, observers around the world can see the remains of its tail every year. The Orionid meteor shower, which is produced by Halley's fragments, occurs annually in October.
When Halley's Comet approaches Earth in 2061, it will be on the same side of the Sun as Earth and much brighter than it was in 1986.
At least one study has found that it is difficult to predict Halley's orbit beyond 100 years, and that the comet could collide with another object (or be ejected from the solar system) in as little as 10,000 years, although not all scientists agree with this hypothesis .
