Celestial bodies of the solar system comets asteroids. Astronomy. Comets. Gas giants and Pluto

Comets are cosmic snowballs made of frozen gases, rocks and dust and are roughly the size of a small city. When a comet's orbit brings it close to the Sun, it heats up and spews out dust and gas, causing it to become brighter than most planets. Dust and gas form a tail that stretches from the Sun for millions of kilometers.

10 facts you need to know about comets

1. If the Sun were as big as a front door, the Earth would be the size of a dime, the dwarf planet Pluto would be the size of a pinhead, and the largest comet of the Kuiper Belt (which is about 100 km across, which is about one twentieth of Pluto ) will be the size of a speck of dust.
2. Short-period comets (comets that orbit the Sun in less than 200 years) live in an icy region known as the Kuiper Belt, located beyond the orbit of Neptune. Long comets (comets with long, unpredictable orbits) originate in the far reaches of the Oort Cloud, which is located at a distance of up to 100 thousand AU.
3. Days on the comet change. For example, a day on Halley's Comet ranges from 2.2 to 7.4 Earth days (the time required for the comet to complete a revolution on its axis). Halley's Comet makes a complete revolution around the Sun (a year on the comet) in 76 Earth years.
4. Comets are cosmic snowballs consisting of frozen gases, rocks and dust.
5. The comet heats up as it approaches the Sun and creates an atmosphere or com. The lump can be hundreds of thousands of kilometers in diameter.
6. Comets do not have satellites.
7. Comets do not have rings.
8. More than 20 missions were aimed at studying comets.
9. Comets cannot support life, but may have brought water and organic compounds - the building blocks of life - through collisions with Earth and other objects in our solar system.
10. Halley's Comet was first mentioned in Bayeux from 1066, which recounts the overthrow of King Harold by William the Conqueror at the Battle of Hastings.

Comets: The Dirty Snowballs of the Solar System

Comets On our journeys through the solar system, we may be lucky enough to encounter giant balls of ice. These are comets of the solar system. Some astronomers call comets "dirty snowballs" or "icy mud balls" because they are made mostly of ice, dust and rock debris. Ice can consist of either ice water or frozen gases. Astronomers believe that comets may be composed of primordial material that formed the basis for the formation of the solar system.

Although most of the small objects in our solar system are very recent discoveries, comets have been well known since ancient times. The Chinese have records of comets that date back to 260 BC. This is because comets are the only small bodies in the solar system that can be seen with the naked eye. Comets that orbit the Sun are quite a spectacular sight.

Comet tail

Comets are actually invisible until they begin to approach the Sun. At this moment they begin to heat up and an amazing transformation begins. Dust and gases frozen in the comet begin to expand and escape with explosive speed.

The solid part of a comet is called the comet's nucleus, while the cloud of dust and gas around it is known as the comet's coma. Solar winds pick up material in the coma, leaving a tail behind the comet that extends several million miles. As the sun illuminates, this material begins to glow. Eventually the comet's famous tail forms. Comets and their tails can often be seen from Earth with the naked eye.

The Hubble Space Telescope captured Comet Shoemaker-Levy 9 as it struck the surface of Jupiter.

Some comets can have up to three separate tails. One of them will consist mainly of hydrogen, and is invisible to the eye. The other tail of dust will glow bright white, and the third tail of plasma will usually have a blue glow. When the Earth passes through these dust trails left by comets, the dust enters the atmosphere and creates meteor showers.

Active jets on Comet Hartley 2

Some comets fly in an orbit around the Sun. They are known as periodic comets. A periodic comet loses a significant portion of its material each time it passes near the Sun. Eventually, after all this material is lost, they will cease to be active and wander around the solar system like a dark rocky ball of dust. Halley's Comet is probably the most famous example of a periodic comet. The comet changes its appearance every 76 years.

History of comets
The sudden appearance of these mysterious objects in ancient times was often seen as a bad omen and a warning of natural disasters in the future. We currently know that most comets reside in a dense cloud located at the edge of our solar system. Astronomers call it the Oort Cloud. They believe that gravity from the stray passage of stars or other objects could knock some of the Oort Cloud comets off and send them on a journey into the inner solar system.

Manuscript depicting comets among the ancient Chinese

Comets can also collide with the Earth. In June 1908, something exploded high in the atmosphere above the village of Tunguska in Siberia. The explosion had the force of 1,000 bombs dropped on Hiroshima and leveled trees for hundreds of miles. The absence of any meteorite fragments led scientists to believe that it may have been a small comet that exploded upon impact with the atmosphere.

Comets may also have been responsible for the extinction of the dinosaurs, and many astronomers believe that ancient comet impacts brought much of the water to our planet. While there is a possibility that the Earth could be hit by a large comet again in the future, the chances of this event happening in our lifetime are better than one in a million.

For now, comets simply continue to be objects of wonder in the night sky.

The most famous comets

Comet ISON

Comet ISON was the subject of the most coordinated observations in the history of comet studies. Over the course of a year, more than a dozen spacecraft and numerous ground-based observers collected what is believed to be the largest collection of data on a comet.

Known in the catalog as C/2012 S1, Comet ISON began its journey to the inner Solar System about three million years ago. It was first spotted in September 2012, at a distance of 585,000,000 miles. This was its very first trip around the Sun, that is, it was made of primordial matter that arose in the early days of the formation of the Solar System. Unlike comets that have already made multiple passes through the inner Solar System, the upper layers of Comet ISON have never been heated by the Sun. The comet represented a kind of time capsule, which captured the moment of the formation of our solar system.

Scientists from around the world launched an unprecedented observing campaign, using many ground-based observatories and 16 spacecraft (all but four successfully studied the comet).

On November 28, 2013, scientists observed Comet ISON being torn apart by the Sun's gravitational forces.

Russian astronomers Vitaly Nevsky and Artem Novichonok discovered the comet using a 4-meter telescope in Kislovodsk, Russia.

ISON is named after the night sky survey program that discovered it. ISON is a group of observatories in ten countries that work together to detect, monitor and track objects in space. The network is managed by the Institute of Applied Mathematics of the Russian Academy of Sciences.

Comet Encke

Comet 2P/EnckeComet 2P/Encke is a small comet. Its core measures approximately 4.8 km (2.98 mi) in diameter, about one-third the size of the object thought to have killed off the dinosaurs.

The comet's orbital period around the Sun is 3.30 years. Comet Encke has the shortest orbital period of any known comet within our Solar System. Encke last passed perihelion (closest point to the Sun) in November 2013.

Photo of a comet taken by the Spitzer telescope

Comet Encke is the parent comet of the Taurids meteor shower. The Taurids, which peak in October/November each year, are fast meteors (104,607.36 km/h or 65,000 mph) known for their fireballs. Fireballs are meteors that are as bright or even brighter than the planet Venus (when viewed in the morning or evening sky with an apparent brightness value of -4). They can create large explosions of light and color and last longer than the average meteor shower. This is because fireballs come from larger particles of material from the comet. Often, this special stream of fireballs occurs on or around the day of Halloween, making them known as Halloween Fireballs.

Comet Encke approached the Sun in 2013 at the same time that Comet Ison was much talked about and presented, and because of this was photographed by both the MESSENGER and STEREO spacecraft.

Comet 2P/Encke was first discovered by Pierre F.A. Mechain on January 17, 1786. Other astronomers found this comet on subsequent passages, but these observations were not identified as the same comet until Johann Franz Encke calculated its orbit.

Comets are typically named after their discoverer(s) or the name of the observatory/telescope used in the discovery. However, this comet is not named after its discoverer. Instead, it was named after Johann Franz Encke, who calculated the comet's orbit. The letter P indicates that 2P/Encke is a periodic comet. Periodic comets have orbital periods of less than 200 years.

Comet D/1993 F2 (Shoemaker - Levy)

Comet Shoemaker-Levy 9 was captured by Jupiter's gravity, dispersed, and then crashed into the giant planet in July 1994.

When the comet was discovered in 1993, it was already fragmented into more than 20 fragments traveling around the planet in a two-year orbit. Further observations revealed that the comet (believed to have been a single comet at the time) made a close approach to Jupiter in July 1992 and was fragmented by tidal forces as a result of the planet's powerful gravity. The comet is believed to have orbited Jupiter for about ten years before its death.

A comet breaking into many pieces was rare, and seeing a comet captured in orbit near Jupiter was even more unusual, but the biggest and rarest discovery was that fragments crashed into Jupiter.

NASA had a spacecraft that observed - for the first time in history - a collision between two bodies in the solar system.

NASA's Galileo orbiter (then on its way to Jupiter) was able to establish a direct view of the parts of the comet, labeled A through W, that collided with Jupiter's clouds. The clashes began on July 16, 1994 and ended on July 22, 1994. Many ground-based observatories and orbiting spacecraft, including the Hubble Space Telescope, Ulysses and Voyager 2, have also studied the collisions and their consequences.

The trail of a comet on the surface of Jupiter

A “freight train” of fragments crashed on Jupiter with the force of 300 million atomic bombs. They created huge plumes of smoke that were 2,000 to 3,000 kilometers (1,200 to 1,900 miles) high, and heated the atmosphere to very hot temperatures of 30,000 to 40,000 degrees Celsius (53,000 to 71,000 degrees Fahrenheit). Comet Shoemaker-Levy 9 left dark, ring-shaped scars that were eventually worn away by Jupiter's winds.

When the clash happened in real time, it was more than just a show. This gave scientists a new look at Jupiter, Comet Shoemaker-Levy 9, and cosmic collisions in general. Researchers were able to deduce the composition and structure of the comet. The collision also left behind dust that is found at the top of Jupiter's clouds. By observing dust spreading across the planet, scientists were able to track the direction of high-altitude winds on Jupiter for the first time. And by comparing changes in the magnetosphere with changes in the atmosphere after the impact, scientists were able to study the relationship between the two.

Scientists estimate that the comet was originally about 1.5 - 2 kilometers (0.9 - 1.2 miles) wide. If an object of this size struck the Earth, it would have devastating consequences. The impact could send dust and debris into the sky, creating a fog that would cool the atmosphere and absorb sunlight, shrouding the entire planet in darkness. If the fog lasts long enough, plant life will die - along with the people and animals that depend on them to survive.

These types of collisions were more common in the early Solar System. It is likely that comet collisions occurred mainly because Jupiter lacked hydrogen and helium.

Currently, collisions of this magnitude probably occur only once every few centuries - and pose a real threat.

Comet Shoemaker-Levy 9 was discovered by Caroline and Eugene Shoemaker and David Levy in an image taken on March 18, 1993, by the 0.4-meter Schmidt Telescope on Mount Palomar.

The comet was named after its discoverers. Comet Shoemaker-Levy 9 was the ninth short-period comet discovered by Eugene and Caroline Shoemaker and David Levy.

Comet Tempel

Comet 9P/TempelComet 9P/Tempel orbits the Sun in the asteroid belt located between the orbits of Mars and Jupiter. The comet last passed its perihelion (closest point to the Sun) in 2011 and will return again in 2016.

Comet 9P/Tempel belongs to the Jupiter family of comets. Jupiter-family comets are comets that have an orbital period of less than 20 years and orbit near a gas giant. Comet 9P/Tempel takes 5.56 years to complete one full period around the Sun. However, the comet's orbit gradually changes over time. When Comet Tempel was first discovered, its orbital period was 5.68 years.

Comet Tempel is a small comet. Its core is about 6 km (3.73 miles) in diameter, believed to be half the size of the object that killed off the dinosaurs.

Two missions have been sent to study this comet: Deep Impact in 2005 and Stardust in 2011.

Possible impact track on the surface of Comet Tempel

Deep Impact fired an impact projectile onto the surface of a comet, becoming the first spacecraft capable of extracting material from a comet's surface. The collision produced relatively little water and a lot of dust. This suggests that the comet is far from being a “block of ice.” The impact of the impact projectile was later captured by the Stardust spacecraft.

Comet 9P/Tempel was discovered by Ernst Wilhelm Leberecht Tempel (better known as Wilhelm Tempel) on April 3, 1867.

Comets are usually named after their discoverer or the observatory/telescope used in the discovery. Because Wilhelm Tempel discovered this comet, it is named after him. The letter "P" means that Comet 9P/Tempel is a short-period comet. Short-period comets have an orbital period of less than 200 years.

Comet Borelli

Comet 19P/Borelli Resembling a chicken leg, the small nucleus of Comet 19P/Borelli is about 4.8 km (2.98 miles) in diameter, about a third the size of the object that killed off the dinosaurs.

Comet Borelli orbits the Sun in the asteroid belt and is a member of the Jupiter family of comets. Jupiter-family comets are comets that have an orbital period of less than 20 years and orbit near a gas giant. It takes about 6.85 years to complete one full revolution around the Sun. The comet passed its last perihelion (closest point to the Sun) in 2008 and will return again in 2015.

The Deep Space 1 spacecraft flew close to Comet Borelli on September 22, 2001. Traveling at 16.5 km (10.25 miles) per second, Deep Space 1 passed 2,200 km (1,367 miles) above the nucleus of Comet Borelli. This spacecraft took the best photo of a comet's nucleus ever.

Comet 19P/Borrelli was discovered by Alphonse Louis Nicolas Borrelli on December 28, 1904 in Marseille, France.

Comets are usually named after their discoverer or the observatory/telescope used in the discovery. Alphonse Borrelli discovered this comet and that is why it is named after him. The "P" means that 19P/Borelli is a short-period comet. Short-period comets have an orbital period of less than 200 years.

Comet Hale-Bopp

Comet C/1995 O1 (Hale-Bopp) Also known as the Great Comet of 1997, Comet C/1995 O1 (Hale-Bopp) is a fairly large comet, with a nucleus measuring up to 60 km (37 miles) in diameter. This is about five times larger than the supposed object that killed the dinosaurs. Due to its large size, this comet was visible to the naked eye for 18 months in 1996 and 1997.

Comet Hale-Bopp takes about 2,534 years to complete one revolution around the Sun. The comet passed its last perihelion (closest point to the Sun) on April 1, 1997.

Comet C/1995 O1 (Hale-Bopp) was discovered in 1995 (July 23), independently by Alan Hale and Thomas Bopp. Comet Hale-Bopp was discovered at an astonishing distance of 7.15 AU. One AU is equal to approximately 150 million km (93 million miles).

Comets are usually named after their discoverer or the observatory/telescope used in the discovery. Because Alan Hale and Thomas Bopp discovered this comet, it is named after them. The letter "S" stands for. That Comet C/1995 O1 (Hale-Bopp) is a long-period comet.

Comet Wild

Comet 81P/Wilda81P/Wilda (Wild 2) is a small comet with a flattened ball shape and a size of about 1.65 x 2 x 2.75 km (1.03 x 1.24 x 1.71 mi). Its period of revolution around the Sun is 6.41 years. Comet Wild last passed perihelion (closest point to the Sun) in 2010 and will return again in 2016.

Comet Wild is known as a new periodic comet. The comet orbits the Sun between Mars and Jupiter, but it has not always traveled this orbital path. Initially, the orbit of this comet passed between Uranus and Jupiter. On September 10, 1974, gravitational interactions between this comet and the planet Jupiter changed the comet's orbit into a new shape. Paul Wild discovered this comet during its first revolution around the Sun in a new orbit.

Animated image of a comet

Since Wilda is a new comet (it didn't have as many close orbits around the Sun), it is an ideal sample for discovering something new about the early Solar System.

NASA used this special comet when, in 2004, they assigned the Stardust mission to fly to it and collect coma particles—the first collection of this kind of extraterrestrial material beyond the orbit of the Moon. These samples were collected in an airgel collector as the craft flew 236 km (147 miles) from the comet. The samples were then returned to Earth in an Apollo-like capsule in 2006. In those samples, scientists discovered glycine: a fundamental building block of life.

Comets are typically named after their discoverer(s) or the name of the observatory/telescope used in the discovery. Because Paul Wild discovered this comet, it was named after him. The letter "P" means that 81P/Wilda (Wild 2) is a "periodic" comet. Periodic comets have orbital periods of less than 200 years.

Comet Churyumov-Gerasimenko

Comet 67P / Churyumova-Gerasimenko may go down in history as the first comet on which robots from Earth will land and who will accompany it throughout its orbit. The Rosetta spacecraft, which carries the Philae lander, plans to rendezvous with the comet in August 2014 to accompany it on its journey to and from the inner solar system. Rosetta is a mission of the European Space Agency (ESA), which is provided with essential instruments and support by NASA.

Comet Churyumov-Gerasimenko makes a loop around the Sun in an orbit intersecting the orbits of Jupiter and Mars, approaching but not entering Earth's orbit. Like most Jupiter-family comets, it is believed to have fallen from the Kuiper Belt, the region beyond Neptune's orbit, as a result of one or more collisions or gravitational tugs.

Close-up of the surface of comet 67P/Churyumov-Gerasimenko

Analysis of the comet's orbital evolution indicates that until the mid-19th century, the closest distance to the Sun was 4.0 AU. (about 373 million miles or 600 million kilometers), which is about two-thirds of the way from the orbit of Mars to Jupiter. Because the comet is too far from the heat of the Sun, it has not grown a ball (shell) or tail, so the comet is not visible from Earth.

But scientists estimate that in 1840, a fairly close encounter with Jupiter must have sent the comet flying deeper into the solar system, down to about 3.0 AU. (about 280 million miles or 450 million kilometers) from the Sun. The Churyumov-Gerasimenko perihelion (closest approach to the Sun) was slightly closer to the Sun for the next century, and then Jupiter gave the comet another gravitational shock in 1959. The comet's perihelion has since stopped at 1.3 AU, about 27 million miles (43 million kilometers) beyond Earth's orbit.

Dimensions of comet 67P/Churyumov-Gerasimenko

The comet's nucleus is considered to be quite porous, giving it a density much lower than that of water. When heated by the Sun, the comet is believed to emit about twice as much dust as gas. A small detail known about the comet's surface is that a landing site for Philae will not be selected until Rosetta surveys it at close range.

During recent visits to our part of the solar system, the comet was not bright enough to be seen from Earth without a telescope. This coming year we will be able to see the fireworks close up, thanks to the eyes of our robots.

Discovered on October 22, 1969 at the Alma-Ata Observatory, USSR. Klim Ivanovich Churyumov found an image of this comet while examining a photographic plate of another comet (32P/Comas Sola), taken by Svetlana Ivanova Gerasimenko on September 11, 1969.

67P indicates that it was the 67th periodic comet discovered. Churyumov and Gerasimenko are the names of the discoverers.

Comet Siding Spring

Comet McNaught Comet C/2013 A1 (Siding Spring) heads toward Mars on a low-level flight on October 19, 2014. The comet's nucleus is expected to zip past the planet within a cosmic hair, which is 84,000 miles (135,000 km), about one-third the distance from Earth to the Moon and one-tenth the distance that any known comet has passed Earth. This represents both an excellent opportunity for study and a potential hazard for spacecraft in this area.

Because the comet will approach Mars almost head-on, and because Mars is in its own orbit around the Sun, they will pass each other at a tremendous speed of about 35 miles (56 kilometers) per second. But the comet can be so large that Mars can fly through high-speed particles of dust and gas for several hours. The Martian atmosphere will likely protect rovers on the surface, but spacecraft in orbit will be bombarded by particles moving two or three times faster than the meteorites that spacecraft typically withstand.

NASA spacecraft transmits first photographs of Comet Siding Spring to Earth

“Our plans for using spacecraft on Mars to observe Comet McNaught will be coordinated with plans for how orbiters can stay out of the flow and be protected if necessary,” said Rich Zurek, chief scientist for the Mars program at NASA Jet Propulsion Laboratory.

One way to protect orbiters is to position them behind Mars during the riskiest surprise encounters. Another way is for the spacecraft to “dodge” the comet, trying to shield the most vulnerable equipment. But such maneuvers could cause changes in the orientation of solar panels or antennas in ways that interfere with the vehicles' ability to generate power and communicate with Earth. "These changes will require an enormous amount of testing," said Soren Madsen, chief engineer for the Mars exploration program at JPL. “There are a lot of preparations that need to be made now to prepare ourselves for the eventuality that we learn in May that the demonstration flight will be risky.”

Comet Siding Spring fell from the Oort Cloud, a huge spherical region of long-period comets that circles the Solar System. To get an idea of ​​how far away that is, consider this situation: Voyager 1, which has been traveling in space since 1977, is much further away than any of the planets, and has even emerged from the heliosphere, a huge bubble of magnetism and ionized gas. radiating from the Sun. But it will take the ship another 300 years to reach the inner "edge" of the Oort Cloud, and at its current speed of a million miles a day it will take about 30,000 more years to finish passing through the cloud.

Every once in a while, some gravitational pull - perhaps from passing a star - will push the comet to break free from its impossibly vast and distant vault, and it will fall into the Sun. This is what should have happened to Comet McNaught several million years ago. All this time the fall was directed towards the inner part of the solar system, and it gives us only one chance to study it. According to available estimates, her next visit will be in about 740 thousand years.

"C" indicates that the comet is not periodic. 2013 A1 shows that it was the first comet discovered in the first half of January 2013. Siding Spring is the name of the observatory where it was discovered.

Comet Giacobini-Zinner

Comet 21P/Giacobini-Zinner is a small comet with a diameter of 2 km (1.24 mi). The period of revolution around the Sun is 6.6 years. The last time Comet Giacobini-Zinner passed perihelion (closest point to the Sun) was on February 11, 2012. The next perihelion passage will be in 2018.

Every time Comet Giacobini-Zinner returns to the inner Solar System, its core sprays ice and rocks into space. This shower of debris leads to the annual meteor shower: the Draconids, which occurs every year in early October. The Draconids radiate from the northern constellation Draco. For many years the shower is weak and very few meteorites are visible during this period. However, there are occasional references in the records to Draconid (sometimes called Jacobinid) meteor storms. A meteor storm occurs when a thousand or more meteors are visible within an hour at the observer's location. At its peak in 1933, 500 Draconid meteors were seen within a minute in Europe. 1946 was also a good year for the Draconids, with about 50-100 meteors being seen in one minute in the US.

Coma and nucleus of comet 21P/Giacobini-Zinner

In 1985 (September 11), a re-designated mission called ICE (International Comet Explorer, formally International Sun-Earth Explorer-3) was assigned to collect data from this comet. ICE was the first spacecraft to follow a comet. ICE later joined the famous "armada" of spacecraft sent to Halley's Comet in 1986. Another mission, called Sakigaki, from Japan, was scheduled to follow the comet in 1998. Unfortunately, the spacecraft did not have enough fuel to reach the comet.

Comet Giacobini-Zinner was discovered on December 20, 1900 by Michel Giacobini at the Nice Observatory in France. Information about this comet was later restored by Ernst Zinner in 1913 (October 23).

Comets are typically named after their discoverer(s) or the name of the observatory/telescope used in the discovery. Since Michel Giacobini and Ernst Zinner discovered and recovered this comet, it is named after them. The letter "P" means that Comet Giacobini-Zinner is a "periodic" comet. Periodic comets have orbital periods of less than 200 years.

Comet Thatcher

Comet C/1861 G1 (Thatcher)Comet C/1861 G1 (Thatcher) takes 415.5 years to complete one revolution around the Sun. Comet Thatcher passed its final perihelion (closest point to the Sun) in 1861. Comet Thatcher is a long-period comet. Long-period comets have orbital periods of more than 200 years.

When comets pass around the Sun, the dust they emit spreads into a dust trail. Every year, when Earth passes through this comet trail, space debris collides with our atmosphere, where it breaks up and creates fiery, colorful streaks in the sky.

Chunks of space debris coming from Comet Thatcher and interacting with our atmosphere create the Lyrid meteor shower. This annual meteor shower occurs every April. The Lyrids are among the oldest known meteor showers. The first documented Lyrid meteor shower dates back to 687 BC.

Comets are usually named after their discoverer or the observatory/telescope used in the discovery. Since A.E. Thatcher discovered this comet, it is named after him. The "C" means that Comet Thatcher is a long-period comet, meaning its orbital period is more than 200 years. 1861 is the year of its opening. "G" denotes the first half of April, and "1" means Thatcher was the first comet discovered during that period.

Comet Swift-Tuttle

Comet Swift-Tuttle Comet 109P/Swift-Tuttle takes 133 years to complete one revolution around the Sun. The comet passed its last perihelion (closest point to the Sun) in 1992 and will return again in 2125.

Comet Swift-Tuttle is considered a large comet - its nucleus is 26 km (16 miles) across. (That is, more than twice the size of the supposed object that killed the dinosaurs.) Chunks of space debris ejected from Comet Swift-Tuttle and interacting with our atmosphere create the popular Perseid meteor shower. This annual meteor shower occurs every August and peaks in the middle of the month. Giovanni Schiaparelli was the first to realize that the source of the Perseids was this comet.

Comet Swift-Tuttle was discovered in 1862 independently by Lewis Swift and Horace Tuttle.

Comets are usually named after their discoverer or the observatory/telescope used in the discovery. Since Lewis Swift and Horace Tuttle discovered this comet, it is named after them. The letter "P" means that Comet Swift-Tuttle is a short-period comet. Short-period comets have orbital periods of less than 200 years.

Comet Tempel-Tuttle

Comet 55P/Tempel-Tuttle is a small comet whose nucleus is 3.6 km (2.24 mi) across. It takes 33 years to complete one revolution around the Sun. Comet Tempel-Tuttle passed its perihelion (closest point to the Sun) in 1998 and will return again in 2031.

Chunks of space debris coming from the comet interact with our atmosphere and create the Leonid meteor shower. This is typically a weak meteor shower that peaks in mid-November. Every year, the Earth passes through this debris, which, when interacting with our atmosphere, disintegrates and creates fiery, colorful streaks in the sky.

Comet 55P/Tempel-Tuttle in February 1998

Every 33 years or so, the Leonid meteor shower turns into a full-blown meteor storm, during which at least 1,000 meteors per hour burn up in Earth's atmosphere. Astronomers in 1966 observed a spectacular sight: the remains of a comet crashed into the Earth's atmosphere at a rate of thousands of meteors per minute during a 15-minute period. The last Leonid meteor storm occurred in 2002.

Comet Tempel-Tuttle was discovered twice independently - in 1865 and 1866 by Ernst Tempel and Horace Tuttle, respectively.

Comets are usually named after their discoverer or the observatory/telescope used in the discovery. Since Ernst Tempel and Horace Tuttle discovered it, the comet is named after them. The letter "P" means that Comet Tempel-Tuttle is a short-period comet. Short-period comets have orbital periods of less than 200 years.

Halley's Comet

Comet 1P/Halley is perhaps the most famous comet, having been observed for thousands of years. The comet was first mentioned by Halley in the Bayeux Tapestry, which recounts the Battle of Hastings in 1066.

Halley's Comet takes about 76 years to complete one revolution around the Sun. The comet was last seen from Earth in 1986. That same year, an international armada of spacecraft converged on the comet to collect as much data as possible about it.

Halley's Comet in 1986

The comet will not arrive into the solar system until 2061. Every time Halley's Comet returns to the inner Solar System, its core sprays ice and rock into space. This debris flow results in two weak meteor showers: the Eta Aquarids in May and the Orionids in October.

Dimensions of Comet Halley: 16 x 8 x 8 km (10 x 5 x 5 miles). This is one of the darkest objects in the solar system. The comet has an albedo of 0.03, meaning it reflects only 3% of the light that hits it.

The first sightings of Halley's Comet are lost in time, more than 2,200 years ago. However, in 1705, Edmond Halley studied the orbits of previously observed comets and noted some that appeared to appear again and again every 75-76 years. Based on the similarity of orbits, he proposed that it was in fact the same comet, and correctly predicted the next return in 1758.

Comets are usually named after their discoverer or the observatory/telescope used in the discovery. Edmond Halley correctly predicted the return of this comet - the first prediction of its kind and that is why the comet is named after him. The letter "P" means that Halley's Comet is a short-period comet. Short-period comets have orbital periods of less than 200 years.

Comet C/2013 US10 (Catalina)

Comet C/2013 US10 (Catalina) is an Oort Cloud comet discovered on October 31, 2013 by the Catalina Sky Survey Observatory with an apparent magnitude of 19, using the 0.68-meter (27 in) Schmidt-Cassegrain Telescope. As of September 2015, the comet has an apparent magnitude of 6.

When Catalina was discovered on October 31, 2013, the preliminary determination of its orbit used observations of another object made on September 12, 2013, which gave an incorrect result suggesting an orbital period of only 6 years for the comet. But on November 6, 2013, with a longer observation of the arc from August 14 to November 4, it became obvious that the first result on September 12 was obtained at a different object.

By early May 2015, the comet had an apparent magnitude of 12 and was 60 degrees away from the Sun as it moved further into the southern hemisphere. The comet came to solar conjunction on November 6, 2015, when it was around magnitude 6. The comet approached perihelion (closest approach to the Sun) on November 15, 2015 at a distance of 0.82 AU. from the Sun and had a speed of 46.4 km/s (104,000 mph) relative to the Sun, slightly faster than the Sun's receding velocity at that distance. Comet Catalina crossed the celestial equator on December 17, 2015 and became a northern hemisphere object. On January 17, 2016, the comet will pass 0.72 astronomical units (108,000,000 km; 67,000,000 mi) from Earth and should be magnitude 6, located in the constellation Ursa Major.

Object C/2013 US10 is dynamically new. It came from the Oort Cloud from a loosely coupled, chaotic orbit that could easily be disturbed by galactic tides and traveling stars. Before entering the planetary region (around 1950), Comet C/2013 US10 (Catalina) had an orbital period of several million years. After leaving the planetary region (around 2050), it will be on an ejection trajectory.

Comet Catalina is named after the Catalina Sky Survey, which discovered it on October 31, 2013.

Comet C/2011 L4 (PANSTARRS)

C/2011 L4 (PANSTARRS) is a non-periodic comet discovered in June 2011. It was only noticed with the naked eye in March 2013, when it was near perihelion.

It was discovered using the Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) telescope located near the top of Halikan on the island of Maui in Hawaii. Comet C/2011 L4 probably took millions of years to travel from the Oort cloud. After leaving the planetary region of the Solar System, the post-perihelion orbital period (epoch 2050) is estimated to be approximately 106,000 years. Made from dust and gas, this comet's nucleus is about 1 km (0.62 miles) in diameter.

Comet C/2011 L4 was at a distance of 7.9 AU. from the Sun and had a brilliance of 19 stars. Vel., when she was discovered in June 2011. But already at the beginning of May 2012 it revived to 13.5 stars. Vel., and this was visible visually when using a large amateur telescope from the dark side. As of October 2012, the coma (expanding thin dust atmosphere) was about 120,000 kilometers (75,000 mi) in diameter. Without optical assistance, C/2011 L4 was seen on February 7, 2013 and had a magnitude of 6. led Comet PANSTARRS was observed from both hemispheres in the first weeks of March, and it passed closest to Earth on March 5, 2013 at a distance of 1.09 AU. It approached perihelion (closest approach to the Sun) on March 10, 2013.

Preliminary estimates predicted that C/2011 L4 would be brighter, at about 0 magnitude. led (approximate brightness of Alpha Centauri A or Vega). Estimates from October 2012 predicted that it could be brighter, at -4 magnitude. led (roughly corresponds to Venus). In January 2013, there was a noticeable drop in brightness, which suggested that it could be brighter, having only +1 magnitude. led In February the light curve showed a further slowdown, suggesting a perihelion at +2 mag. led

However, a study using a secular light curve indicates that Comet C/2011 L4 experienced a "braking event" when it was at a distance of 3.6 AU. from the Sun and had 5.6 AU. The rate of increase in brightness decreased, and the magnitude at perihelion was predicted to be +3.5. For comparison, at the same perihelion distance, Halley's Comet would have a magnitude of -1.0. led The same study concluded that C/2011 L4 is a very young comet and belongs to the class of “children” (that is, those whose photometric age is less than 4 years of the comet).

Image of Comet Panstarrs taken in Spain

Comet C/2011 L4 reached perihelion in March 2013, and was estimated to have an actual peak of +1 magnitude by various observers around the planet. led However, its low location above the horizon makes it difficult to obtain certain data. This was facilitated by the lack of suitable reference stars and the impossibility of differential atmospheric extinction corrections. As of mid-March 2013, due to the brightness of twilight and its low position in the sky, C/2011 L4 was best visible through binoculars 40 minutes after sunset. On March 17-18, the comet was close to the star Algenib with 2.8 stars. led April 22 near Beta Cassiopeia, and May 12-14 near Gamma Cepheus. Comet C/2011 L4 continued to move north until May 28th.

Comet PANSTARRS bears the name of the Pan-STARRS telescope, with which it was discovered in June 2011.

Introduction

Asteroids

Meteorites

Small fragments

5. Search for planets in the solar system

Literature

Introduction

In addition to the large planets and their satellites, many so-called small bodies move in the Solar System: asteroids, comets and meteorites. Small bodies of the Solar System range in size from hundreds of microns to hundreds of kilometers

Asteroids. From the point of view of physics, asteroids or, as they are also called, small planets, are dense and durable bodies. Based on their composition and properties, they can be divided into three groups: stone, iron-stone and iron. An asteroid is a cold body. But it, like the Moon, reflects sunlight, and therefore we can observe it in the form of a star-shaped object. This is where the name “asteroid” comes from, which in Greek means star-shaped. Since asteroids move around the Sun, their position in relation to the stars is constantly and quite quickly changing. Observers use this initial feature to discover asteroids.

Comets, or "tailed stars", have been known since time immemorial. A comet is a complex physical phenomenon that can be briefly described using several concepts. The comet's nucleus is a mixture or, as they say, a conglomerate of dust particles, water ice and frozen gases. The ratio of dust to gas content in cometary nuclei is approximately 1:3. The sizes of cometary nuclei, according to scientists, range from 1 to 100 km. The possibility of the existence of both smaller and larger nuclei is now being discussed. Known short-period comets have nuclei ranging in size from 2 to 10 km. The size of the nucleus of the brightest comet Haley-Bopp, which was observed with the naked eye in 1996, is estimated at 40 km

A meteoroid is a small body orbiting the Sun. A meteor is a meteoroid that flew into the atmosphere of a planet and became heated to the point of brilliance. And if its remnant fell on the surface of the planet, it is called a meteorite. A meteorite is considered to have “fallen” if there are eyewitnesses who observed its flight in the atmosphere; otherwise it is called "found"

Let us consider the above small bodies of the Solar System in more detail.

Asteroids

These cosmic bodies differ from planets primarily in their size. Thus, the largest of the small planets, Ceres, has a diameter of 995 km; the next one (in size): Palada - 560 km, Hygea - 380 km, Psyche - 240 km, etc. For comparison, we can point out that the smallest of the major planets, Mercury, has a diameter of 4878 km, i.e. 5 times larger than the diameter of Ceres, and their masses differ many hundreds of times.

The total number of small planets accessible to observation by modern telescopes is determined to be 40 thousand, but their total mass is 1 thousand times less than the mass of the Earth

The movement of small planets around the Sun occurs in elliptical orbits, but more elongated (the average eccentricity of their orbits is 0.51) than that of the large planets, and the inclination of their orbital planes to the ecliptic is greater than that of the large planets (the average angle is 9.54) . The bulk of the planets revolve around the Sun between the orbits of Mars and Jupiter, forming the so-called asteroid belt. But there are also small planets whose orbits are closer to the Sun than the orbit of Mercury. The most distant ones are located behind Jupiter and even behind Saturn

Space researchers have expressed various ideas about the reason for the large concentration of asteroids in the relatively narrow space of the interplanetary medium between the orbits of Mars and Jupiter. One of the most common hypotheses for the origin of the bodies of the asteroid belt is the idea of ​​​​the destruction of the mythical planet Phaethon. The very idea of ​​the existence of a planet is supported by many scientists and even seems to be supported by mathematical calculations. However, the reason for the destruction of the planet remains inexplicable. Various assumptions have been made. Some researchers believe that the destruction of Phaeton occurred as a result of its collision with some large body. According to others, the reasons for the collapse of the planet were explosive processes in its bowels. Currently, the problem of the origin of bodies in the asteroid belt is an integral element of an extensive space research program at the international and national levels

Among the small planets, there is a peculiar group of bodies whose orbits intersect with the Earth’s orbit, and therefore, there is a potential possibility of their collision with it. The planets of this group began to be called Apollo objects, or simply Apollo (Wetherill, 1979). The existence of Apollo first became known in the 30s of this century. In 1932, an asteroid was discovered. He was named

Apollo 1932 HA. But it did not arouse much interest, although its name became a household name for all asteroids crossing the earth’s orbit

In 1937, a cosmic body with a diameter of approximately 1 km passed 800 thousand km from the Earth and twice the distance from the Moon. Subsequently he was named Hermes. To date, 31 such bodies have been identified, and each of them has received its own name. The sizes of their diameters range from 1 to 8 km, and the inclination of the orbital planes to the ecliptic ranges from 1 to 68. Five of them rotate in orbits between Earth and Mars, and the remaining 26 - between Mars and Jupiter (W etherill, 1979). It is believed that out of 40 thousand small planets in the asteroid belt with a diameter of more than 1 km, there may be several hundred Apollo. Therefore, the collision of such celestial bodies with the Earth is quite likely, but at very long intervals of time

It can be assumed that once a century one of these cosmic bodies may pass near the Earth at a distance less than from us to the Moon, and once in 250 thousand years it may collide with our planet. The impact of such a body releases energy equal to 10 thousand. Hydrogen bombs each with a power of 10 Mt. This should form a crater with a diameter of about 20 km. But such cases are rare and unknown in human history. Hermes belongs to class III asteroids, but there are many such bodies of larger size - classes II and I. The impact of their collision with the Earth will naturally be even more significant

When Uranus was discovered in 1781, its average heliocentric distance turned out to correspond to the Titius-Bode rule, then in 1789 the search began for a planet which, according to this rule, should have been located between the orbits of Mars and Jupiter, at an average distance a = 2, 8 a.u. from the sun. But scattered surveys of the sky did not bring success, and therefore on September 21, 1800, several German astronomers, led by K. Zach, decided to organize a collective search. They divided the entire search for zodiac constellations into 24 sections and distributed them among themselves for thorough research. But before they had time to begin a systematic search, on January 1, 1871. Italian astronomer G. Piazii (1746-1826) discovered through a telescope a star-shaped object of the seventh magnitude, slowly moving across the constellation Taurus. The orbit of the object calculated by K. Gaus (1777-1855) turned out to be a planet corresponding to the Titius-Bode rule: semimajor axis a = 2.77 AU. and eccentricity e=0.080. Piatsi named the newly discovered planet Ceres.

On March 28, 1802, the German doctor and astronomer W. Olbers (1758-1840) discovered another planet (8 m) near Ceres, called Pallas (a = 2.77 AU, e = 0.235). On September 2, 1804, the third planet, Juno (a=2.67 AU), was discovered, and on March 29, 1807, the 4th, Vesta (a=2.36 AU). All newly discovered planets had a star-shaped appearance, without disks, indicating their small geometric dimensions. Therefore, these celestial bodies were called small planets or, at the suggestion of V. Herschel, asteroids (from the Greek “aster” - star and “eidos” - type)

By 1891, about 320 asteroids had been discovered by visual methods. At the end of 1891, the German astronomer M. Wolf (1863-1932) proposed a photographic search method: with a 2-3 hour exposure, the images of stars on the photographic plate were dotted, and the trace of a moving asteroid was in the form of a small dash. Photographic techniques have led to a dramatic increase in asteroid discoveries. Particularly intensive studies of small planets are now being carried out at the Institute of Theoretical Astronomy (in St. Petersburg) and at the Crimean Astrophysical Observatory of the Russian Academy of Sciences

Asteroids whose orbits are reliably determined are given a name and a serial number. There are now over 3,500 such asteroids known, but there are much more in the Solar System

Of the indicated number of known asteroids, astronomers of the Crimean Astrophysical Observatory discovered about 550, immortalizing the names of famous people in their names

The vast majority (up to 98%) of known asteroids move between the orbits of Mars and Jupiter, at average distances from the Sun from 2.06 to 4.30 AU. (circulation periods from 2.96 to 8.92 years). However, there are asteroids with unique orbits, and they are given masculine names, usually from Greek mythology

The first three of these minor planets move outside the asteroid belt, and at perihelion Icarus approaches the Sun twice as close as Mercury, and Hermes and Adonis as close as Venus. They can approach the Earth at a distance of 6 million to 23 million km, and Hermes in 1937 passed close to the Earth even at a distance of 580 thousand km, i.e. only one and a half times further than the Moon. At aphelion, Hidalgo goes beyond the orbit of Saturn. But Hidalgo is no exception. In recent years, about 10 asteroids have been discovered, the perihelia of which are located near the orbits of the terrestrial planets, and the aphelion - near the orbits of Jupiter. Such orbits are characteristic of Jupiter-family comets and indicate a possible common origin of asteroids and comets

In 1977, a unique asteroid was discovered that revolves around the Sun in an orbit with a semi-major axis a = 13.70 AU. and eccentricity e = 0.38, so that at perihelion (q = 8.49 AU) it enters the orbit of Saturn, and at aphelion (Q = 18.91 AU) it approaches the orbit of Uranus. He is named Chiron. Apparently, there are other similar distant asteroids, the search for which continues

The brightness of most known asteroids during opposition is from 7 m to 16 m, but there are also fainter objects. The brightest (up to 6 m) is Vesta

The diameters of asteroids are calculated by their brightness and reflectivity in visual and infrared rays. It turned out that there are not so many large asteroids. The largest are Ceres (1000 km across), Pallas (610 km), Vesta (540 km) and Hygia (450 km). Only 14 asteroids have diameters of more than 250 km, while the rest have smaller diameters, up to 0.7 km. Bodies of such small sizes cannot have a spheroidal shape, and all asteroids (except, perhaps, the largest) are shapeless blocks

The masses of asteroids are extremely different: the largest is close to 1.5 . 10 21 kg (i.e. 4 thousand times less than the mass of the earth), Ceres has. The total mass of all asteroids does not exceed 0.001 Earth masses. Of course, all these celestial bodies are devoid of atmosphere. Axial rotation has been detected in many asteroids based on regular changes in their brightness.

In particular, the rotation period of Ceres is 9.1 hours, and Pallas - 7.9 hours

Icarus rotates the fastest, in 2 hours 16 m

The study of the reflectivity of many asteroids made it possible to combine them into three main groups: dark, light and metallic. The surface of dark asteroids reflects only up to 5% of the sunlight falling on it and consists of substances similar to black basalt and carbonaceous rocks. These asteroids are often called carbonaceous. Light asteroids reflect from 10% to 25% of sunlight, which makes their surface similar to silicon compounds - these are rocky asteroids. Metallic asteroids (their absolute minority) are also light, but in their reflective properties their surface is similar to iron-nickel alloys. This division of asteroids is also confirmed by the chemical composition of meteorites falling on Earth. A small number of studied asteroids do not belong to any of the three main groups

It is significant that the absorption band of water (l = 3 µm) was detected in the spectra of carbonaceous asteroids. In particular, the surface of the asteroid Ceres consists of minerals similar to earthly clays and containing about 10% water

With small sizes and masses of asteroids, the pressure in their interiors is low: even for the largest asteroids it does not exceed 7 10 5

8 10 5 GPa (700 - 800 atm) and cannot cause heating of their cold solid interior. Only the surface of asteroids is very slightly heated by the distant Sun, but even this insignificant energy is radiated into interplanetary space. The surface temperature of the vast majority of asteroids, calculated according to the laws of physics, turned out to be close to 150 - 170 K (-120...-100 ° C)

And only a few asteroids that pass close to the Sun have a very hot surface during such periods. Thus, the surface temperature of Icarus rises to almost 1000 K (+730 ° C), and with distance from the Sun it sharply decreases again

The orbits of the remaining asteroids are subject to significant disturbances from the gravitational influence of large planets, mainly Jupiter. Small asteroids experience especially strong disturbances, which leads to collisions of these bodies and their fragmentation into fragments of a wide variety of sizes - from hundreds of meters in diameter to dust particles

Currently, the physical nature of asteroids is being studied, because it can be used to trace the evolution (development) of the matter from which the Solar system was formed

Meteorites

A variety of meteoroids (cosmic fragments of large asteroids and comets) move in near-Earth space. Their speeds range from 11 to 72 km/s. It often happens that their paths of movement intersect with the Earth’s orbit and they fly into its atmosphere

Meteorites are stone or iron bodies falling to Earth from interplanetary space. The fall of meteorites to Earth is accompanied by sound, light and mechanical phenomena. A bright fireball called a fireball rushes across the sky, accompanied by a tail and flying sparks. After the car disappears, a few seconds later there are explosion-like impacts called shock waves, which sometimes cause significant shaking of the ground and buildings

The phenomena of intrusion of cosmic bodies into the atmosphere have three main stages:

1. Flight in a rarefied atmosphere (up to altitudes of about 80 km), where the interaction of air molecules is carpuscular in nature. Air particles collide with the body, stick to it or are reflected and transfer part of their energy to it. The body heats up from the continuous bombardment of air molecules, but does not experience noticeable resistance, and its speed remains almost unchanged. At this stage, however, the outer part of the cosmic body is heated to a thousand degrees or more. Here, the characteristic parameter of the problem is the ratio of the mean free path to the size of the body L, which is called the Knudsen number K n. In aerodynamics, it is customary to take into account the molecular approach to air resistance at K n >0.1

2. Flight in the atmosphere in the mode of continuous flow of air around the body, that is, when the air is considered a continuous medium and the atomic-molecular nature of its composition is clearly not taken into account. At this stage, a head shock wave appears in front of the body, followed by a sharp increase in pressure and temperature. The body itself is heated due to convective heat transfer, as well as due to radiation heating. Temperatures can reach several tens of thousands of degrees, and pressures up to hundreds of atmospheres. When braking sharply, significant overloads appear. Deformations of bodies, melting and evaporation of their surfaces, and mass entrainment by the incoming air flow (ablation) occur.

3. When approaching the surface of the Earth, the air density increases, the resistance of the body increases, and it either practically stops at some height, or continues its path until it directly collides with the Earth. In this case, large bodies are often divided into several parts, each of which falls separately to the Earth. With strong deceleration of the cosmic mass above the Earth, the accompanying shock waves continue their movement to the Earth's surface, are reflected from it and produce disturbances in the lower layers of the atmosphere, as well as the Earth's surface

The fall process of each meteoroid is individual. It is not possible to describe all possible features of this process in a short story.

There are significantly more “found” meteorites than “fallen” ones. They are often found by tourists or peasants working in the fields. Since meteorites are dark in color and easily visible in the snow, Antarctic ice fields are an excellent place to look for them, where thousands of meteorites have already been found. The meteorite was first discovered in Antarctica in 1969 by a group of Japanese geologists studying glaciers. They found 9 fragments lying nearby, but belonging to four different types of meteorites. It turned out that meteorites that fell on the ice in different places gather where ice fields moving at a speed of several meters per year stop, resting against mountain ranges. The wind destroys and dries the upper layers of ice (dry sublimation occurs - ablation), and meteorites concentrate on the surface of the glacier. Such ice has a bluish color and is easily distinguishable from the air, which is what scientists use when studying places that are promising for collecting meteorites.

An important meteorite fall occurred in 1969 in Chihuahua (Mexico). The first of many large fragments was found near a house in the village of Pueblito de Allende, and, following tradition, all the found fragments of this meteorite were united under the name Allende. The fall of the Allende meteorite coincided with the start of the Apollo lunar program and gave scientists the opportunity to develop methods for analyzing extraterrestrial samples. In recent years, it has been established that some meteorites containing white fragments embedded in darker parent rock are lunar fragments

The Allende meteorite is a chondrite, an important subgroup of stony meteorites. They are called so because they contain chondrules (from the Greek chondros, grain) - the oldest spherical particles that condensed in a protoplanetary nebula and then became part of later rocks. Such meteorites make it possible to estimate the age of the Solar System and its original composition. The calcium- and aluminum-rich inclusions of the Allende meteorite, the first to condense due to their high boiling point, have a radioactive decay age of 4.559 ? 0.004 billion years. This is the most accurate estimate of the age of the solar system. In addition, all meteorites carry “historical records” caused by the long-term influence of galactic cosmic rays, solar radiation and solar wind. By studying the damage caused by cosmic rays, we can tell how long the meteorite was in orbit before it came under the protection of the Earth's atmosphere.

The direct connection between meteorites and the Sun follows from the fact that the elemental composition of the oldest meteorites - chondrites - exactly repeats the composition of the solar photosphere. The only elements whose contents differ are volatile ones, such as hydrogen and helium, which evaporated abundantly from meteorites during their cooling, as well as lithium, which was partially “burned” in the Sun in nuclear reactions. The terms “solar composition” and “chondrite composition” are used interchangeably when describing the above-mentioned “recipe for solar matter”. Stony meteorites whose composition differs from that of the sun are called achondrites.

Small fragments.

The near-solar space is filled with small particles, the sources of which are the collapsing nuclei of comets and collisions of bodies, mainly in the asteroid belt. The smallest particles gradually approach the Sun as a result of the Poynting-Robertson effect (it consists in the fact that the pressure of sunlight on a moving particle is not directed exactly along the Sun-particle line, but as a result of light aberration is deflected back and therefore slows down the movement of the particle). The fall of small particles on the Sun is compensated by their constant reproduction, so that in the ecliptic plane there is always an accumulation of dust that scatters the sun's rays. On the darkest nights, it is noticeable in the form of the zodiacal light, stretching in a wide strip along the ecliptic in the west after sunset and in the east before sunrise. Near the Sun, the zodiacal light turns into a false corona ( F-corona, from false - false), which is visible only during a total eclipse. With increasing angular distance from the Sun, the brightness of the zodiacal light quickly decreases, but at the antisolar point of the ecliptic it intensifies again, forming counterradiance; this is caused by the fact that small dust particles intensely reflect light back

From time to time, meteoroids enter the Earth's atmosphere. The speed of their movement is so high (on average 40 km/s) that almost all of them, except the smallest and largest, burn up at an altitude of about 110 km, leaving long luminous tails - meteors, or shooting stars. Many meteoroids are associated with the orbits of individual comets, so meteors are observed more often when the Earth passes near such orbits at certain times of the year. For example, many meteors are observed around August 12 each year as Earth crosses the Perseid shower, associated with particles lost by comet 1862 III. Another shower - the Orionids - around October 20 is associated with dust from Comet Halley

Particles smaller than 30 microns can slow down in the atmosphere and fall to the ground without burning up; such micrometeorites are collected for laboratory analysis. If particles of several centimeters or more in size consist of a fairly dense substance, then they also do not burn entirely and fall to the surface of the Earth in the form of meteorites. More than 90% of them are stone; Only a specialist can distinguish them from earthly rocks. The remaining 10% of meteorites are iron (they are actually an alloy of iron and nickel)

Meteorites are considered to be asteroid fragments. Iron meteorites were once part of the cores of these bodies, destroyed by collisions. It is possible that some loose, volatile-rich meteorites originated from comets, but this is unlikely; Most likely, large particles of comets burn up in the atmosphere, and only small ones are preserved. Considering how difficult it is for comets and asteroids to reach Earth, it is clear how useful it is to study meteorites that independently “arrived” to our planet from the depths of the solar system

Comets

Comets are the most effective celestial bodies in the solar system. Comets are a kind of cosmic icebergs consisting of frozen gases, complex chemical composition, water ice and refractory mineral matter in the form of dust and larger fragments

Although comets, like asteroids, move around the Sun in conical curves, their appearance is strikingly different from asteroids. If asteroids shine with reflected sunlight and in the field of view of a telescope resemble slowly moving faint stars, then comets intensively scatter sunlight in some of the most characteristic parts of the spectrum for comets, and therefore many comets are visible to the naked eye, although the diameters of their nuclei rarely exceed 1 - 5 km

Comets are of interest to many scientists: astronomers, physicists, chemists, biologists, gas dynamics, historians, etc. And this is natural. After all, comets told scientists that the solar wind was blowing in interplanetary space; perhaps comets are the “culprits” for the emergence of life on Earth, since they could have introduced complex organic compounds into the Earth’s atmosphere. In addition, comets apparently carry valuable information about the initial stages of the protoplanetary cloud from which the Sun and planets were also formed

When first meeting a bright comet, it may seem that the tail is the most important part of the comet. But if in the etymology of the word “comet” the tail was the main reason for such a name, then from a physical point of view the tail is a secondary formation that developed from a rather tiny nucleus, the most important part of the comet as a physical object. Comet nuclei are the root cause of the rest of the complex of cometary phenomena, which are still not accessible to telescopic observations, since they are veiled by the luminous matter surrounding them, continuously flowing from the nuclei. Using high magnifications, you can look into the deeper layers of the gas-dust shell glowing around the core, but what remains will still be significantly larger in size than the true size of the core. The central condensation visible in the diffuse atmosphere of the comet visually and in photographs is called the photometric nucleus. It is believed that in its center there is the actual nucleus of the comet, i.e. the comet's center of mass is located

The hazy atmosphere surrounding the photometric core and gradually fading away, merging with the background of the sky, is called coma. The coma and nucleus make up the head of the comet. Far from the Sun, the head looks symmetrical, but as it approaches the Sun, it gradually becomes oval, then the head lengthens even more, and a tail develops from it on the side opposite to the Sun.

So, the nucleus is the most important part of the comet. However, there is still no consensus on what it actually is. Even in the times of Bessel and Laplace, there was an idea of ​​the comet's nucleus as a solid body consisting of easily evaporating substances such as ice or snow, which quickly transform into the gas phase under the influence of solar heat. This icy classical model of the cometary nucleus has been significantly expanded and developed recently. The model of the nucleus developed by Whipple, a conglomerate of refractory rocky particles and frozen volatile components (CH4, CO2, H2O, etc.), is the most widely recognized among comet researchers. In such a core, ice layers of frozen gases alternate with dust layers. As the sun's heat warms it, gases such as evaporating "dry ice" burst out, carrying clouds of dust with it. This allows, for example, to explain the formation of gas and dust tails in comets, as well as the ability of small comet nuclei to actively release gases

The heads of comets take on a variety of shapes as comets move in orbit. Far from the SUN, the heads of comets are round, which is explained by the weak influence of solar radiation on the particles of the head, and its outlines are determined by the isotropic expansion of the cometary gas into interplanetary space. These are tailless comets that resemble globular star clusters in appearance. As it approaches the Sun, the comet's head takes the shape of a parabola or chain line. The parabolic shape of the head is explained by the “fountain” mechanism. The formation of heads in the form of a chain line is associated with the plasma nature of the cometary atmosphere and the influence of the solar wind on it and the magnetic field transferred by it

Sometimes the comet's head is so small that the comet's tail appears to emerge directly from the nucleus. In addition to changing outlines, various structural formations appear and disappear in the heads of comets: tacks, shells, rays, outpourings from the nucleus, etc.

Large comets with tails stretching far across the sky have been observed since ancient times. It was once assumed that comets were atmospheric phenomena. This misconception was refuted by Brahe, who discovered that the comet of 1577 occupied the same position among the stars when observed from different points, and, therefore, is further from us than the Moon

The movement of comets across the sky was first explained by Halley (1705), who found that their orbits were close to parabolas. He determined the orbits of 24 bright comets, and it turned out that the comets of 1531 and 1682. have very similar orbits. From this, Halley concluded that this is the same comet, which moves around the Sun in a very elongated ellipse with a period of about 76 years. Halley predicted that it should appear again in 1758, and in December 1758 it was actually discovered. Halley himself did not live to see this time and could not see how brilliantly his prediction was confirmed. This comet (one of the brightest) was named Halley's Comet

Comets are designated by the names of the people who discovered them. In addition, the newly discovered comet is assigned a provisional designation based on the year of discovery with the addition of a letter indicating the sequence of the comet's passage through perihelion in that year

Only a small part of comets observed annually are periodic, i.e. known from their previous appearances. Most comets move in very elongated ellipses, almost parabolas. Their periods of revolution are not precisely known, but there is reason to believe that they reach many millions of years. Such comets move away from the Sun at distances comparable to interstellar ones. The planes of their almost parabolic orbits are not concentrated towards the ecliptic plane and are randomly distributed in space. The forward direction of movement occurs as often as the reverse

Periodic comets move in less elongated elliptical orbits and have completely different characteristics. Of the 40 comets observed more than once, 35 have orbits inclined less than 45° to the ecliptic plane. Only Halley's comet has an orbit with an inclination greater than 90^ and, therefore, moves in the opposite direction. Among the short-period (i.e., having periods of 3–10 years) comets, the “Jupiter family” stands out, a large group of comets whose aphelions are removed from the Sun at the same distance as the orbit of Jupiter. It is assumed that the “Jupiter family” was formed as a result of the planet’s capture of comets that had previously moved in more elongated orbits. Depending on the relative position of Jupiter and the comet, the eccentricity of the comet's orbit can either increase or decrease. In the first case, there is an increase in the period or even a transition to a hyperbolic orbit and the loss of the comet by the Solar System; in the second, a decrease in the period

The orbits of periodic comets are subject to very noticeable changes. Sometimes a comet passes near the Earth several times, and then, by the attraction of the giant planets, it is thrown into a more distant orbit and becomes unobservable. In other cases, on the contrary, a comet that has never been observed before becomes visible because it passed near Jupiter or Saturn and abruptly changed its orbit. Apart from such abrupt changes, known only for a limited number of objects, the orbits of all comets experience gradual changes

Orbital changes are not the only possible reason for the disappearance of comets. It has been reliably established that comets are quickly destroyed. The brightness of short-period comets fades over time, and in some cases the destruction process has been observed almost directly. A classic example is Comet Biely. It was discovered in 1772 and observed in 1813, 1826 and 1832. In 1845, the size of the comet turned out to be increased, and in January 1846. Observers were surprised to find two very close comets instead of one. The relative movements of both comets were calculated, and it turned out that Comet Biely split into two about a year ago, but at first the components were projected on top of each other, and the separation was not immediately noticed. Comet Biely was observed one more time, with one component much fainter than the other, and it could not be found again. But a meteor shower was repeatedly observed, the orbit of which coincided with the orbit of Comet Biely

When deciding the question of the origin of comets, one cannot do without knowledge of the chemical composition of the substance from which the cometary nucleus is composed. It would seem, what could be simpler? We need to photograph more spectra of comets, decipher them - and the chemical composition of cometary nuclei will immediately become known to us. However, the matter is not as simple as it seems at first glance. The spectrum of the photometric core can be simply the reflected solar spectrum or the emission molecular spectrum. The reflected solar spectrum is continuous and does not reveal anything about the chemical composition of the region from which it was reflected - the core or the dust atmosphere surrounding the core. The emission gas spectrum carries information about the chemical composition of the gas atmosphere surrounding the core, and also does not tell us anything about the chemical composition of the surface layer of the core, since molecules emitting in the visible region, such as C2, CH, CH, MH, OH and others, are secondary, daughter molecules - “fragments” of more complex molecules or molecular complexes that make up the cometary nucleus. These complex parent molecules, evaporating into the perinuclear space, are quickly exposed to the destructive action of solar wind and photons, or decay or dissociate into simpler molecules, the emission spectra of which can be observed from comets. The parent molecules themselves produce a continuous spectrum

The Italian Donati was the first to observe and describe the spectrum of the comet's head. Against the background of the faint continuous spectrum of comet 1864, he saw three wide luminous bands: blue, green and yellow. As it turned out, this confluence belonged to C2 carbon molecules, which found themselves in abundance in the cometary atmosphere. These emission bands of C2 molecules are called Swan bands, named after the scientist who studied the spectrum of carbon. The first slit spectrogram of the head of the Great Comet 1881 was obtained by the Englishman Heggins, who discovered in the spectrum the radiation of the chemically active cyanide radical C N

Far from the Sun, at a distance of 11 AU, the approaching comet appears as a small nebulous speck, sometimes with signs of the beginning formation of a tail. The spectrum obtained from a comet located at such a distance, and up to a distance of 3-4 AU, is continuous, because at such large distances the emission spectrum is not excited due to weak photon and corpuscular solar radiation

This spectrum is formed as a result of reflection of sunlight from dust particles or as a result of its scattering on polyatomic molecules or molecular complexes. At a distance of about 3 AU. from the Sun, i.e. When the cometary nucleus crosses the asteroid belt, the first emission band of the cyanogen molecule appears in the spectrum, which is observed in almost the entire head of the comet. At a distance of 2 AU The radiation of triatomic molecules C3 and N H3 is already excited, which are observed in a more limited region of the comet's head near the nucleus than the ever-increasing radiation of C N. At a distance of 1.8 AU carbon emissions appear - Swan stripes, which immediately become noticeable throughout the entire head of the comet: both near the nucleus and at the boundaries of the visible head

The mechanism of the glow of cometary molecules was deciphered back in 1911. K. Schwarzschild and E. Kron, who, studying the emission spectra of Halley's comet (1910), came to the conclusion that the molecules of cometary atmospheres resonantly re-emit sunlight. This glow is similar to the resonant glow of sodium vapor in the famous experiments of Auda, who was the first to notice that when illuminated with light having the frequency of the yellow sodium doublet, the sodium vapor themselves begin to glow at the same frequency with a characteristic yellow light. This is a mechanism of resonant fluorescence, which is a frequent case of the more general mechanism of luminescence. Everyone knows the glow of fluorescent lamps above shop windows, in fluorescent lamps, etc. A similar mechanism causes gases in comets to glow.

To explain the glow of the green and red oxygen lines (similar lines are also observed in the spectra of auroras), various mechanisms were used: electron impact, dissociative recombination and photodissipation. Electron impact, however, cannot explain the higher intensity of the green line in some comets compared to the red line. Therefore, more preference is given to the photodissociation mechanism, which is supported by the brightness distribution in the comet's head. However, this issue has not yet been completely resolved and the search for the true mechanism of luminescence of atoms in comets continues. The question of the parent, primary molecules that make up the cometary nucleus still remains unresolved, and this question is very important, since it is the chemistry of the nuclei that predetermines the unusually high activity of comets, capable of developing gigantic atmospheres and tails from very small nuclei in size. the size of all known bodies in the solar system

5. Search for planets in the solar system.

Suggestions have been made more than once about the possibility of the existence of a planet closer to the Sun than Mercury. Le Verrier (1811–1877), who predicted the discovery of Neptune, examined anomalies in the perihelion motion of Mercury's orbit and, on the basis of this, predicted the existence of a new unknown planet within its orbit. Soon a message about her observation appeared and the planet was even given a name - Vulcan. But the discovery was not confirmed

In 1977, American astronomer Cowell discovered a very faint object, which was dubbed the “tenth planet.” But the object turned out to be too small for a planet (about 200 km). It was named Chiron and was classified among the asteroids, among which it was then the most distant: the aphelion of its orbit was removed at 18.9 AU. and almost touches the orbit of Uranus, and the perihelion lies just beyond the orbit of Saturn at a distance of 8.5 AU. from the sun. With an orbital inclination of only 7 ? it can actually come close to Saturn and Uranus. Calculations show that such an orbit is unstable: Chiron will either collide with the planet or be thrown out of the solar system

From time to time, theoretical predictions about the existence of large planets beyond the orbit of Pluto are published, but so far they have not been confirmed. Analysis of cometary orbits shows that up to a distance of 75 AU. There are no planets larger than Earth beyond Pluto. However, it is quite possible that there are a large number of small planets in this area, which are not easy to detect. The existence of this cluster of trans-Neptunian bodies has been suspected for a long time and even received a name - the Kuiper belt, after the famous American planetary explorer. However, it was only recently that the first objects were discovered in it. In 1992–1994, 17 minor planets were discovered beyond the orbit of Neptune. Of these, 8 move at distances of 40–45 AU. from the Sun, i.e. even beyond the orbit of Pluto

Due to their great distance, the brightness of these objects is extremely weak; Only the largest telescopes in the world are suitable for searching for them. Therefore, only about 3 square degrees of the celestial sphere have been systematically examined so far, i.e. 0.01% of its area. Therefore, it is expected that beyond the orbit of Neptune there may be tens of thousands of objects similar to those discovered, and millions of smaller ones, with a diameter of 5–10 km. Judging by estimates, this cluster of small bodies is hundreds of times more massive than the asteroid belt located between Jupiter and Mars, but is inferior in mass to the giant Oort comet cloud

Objects beyond Neptune are still difficult to classify as any class of small bodies in the Solar System - asteroids or comet nuclei. The newly discovered bodies are 100–200 km in size and have a rather red surface, indicating its ancient composition and the possible presence of organic compounds. Kuiper belt bodies have recently been discovered quite often (by the end of 1999, about 200 of them had been discovered). Some planetary scientists believe that it would be more correct to call Pluto not “the smallest planet,” but “the largest body in the Kuiper belt.”

Literature

V.A. Brashtein “Planets and their observation” Moscow “Science” 1979

S. Dole “Planets for People” Moscow “Science” 1974

K.I. Churyumov “Comets and their observation” Moscow “Science” 1980

E.L. Krinov “Iron Rain” Moscow “Science” 1981

K.A. Kulikov, N.S. Sidorenkov “Planet Earth” Moscow “Science”

B.A. Vorontsov - Velyaminov “Essays on the Universe” Moscow “Science”

N.P. Erpyleev “Encyclopedic Dictionary of a Young Astronomer” Moscow “Pedagogy” 1986

E.P. Levitan “Astronomy” Moscow “Enlightenment” 1994