Solar dwarf planets. Pluto and other dwarf planets of the solar system: infographics. Dwarf planets of the solar system
Uralskaya B.C. (GAISH MSU) Sagitov readings-2007
Physical properties of dwarf planets Report
The 26th Assembly of the International Astronomical Union, which took place in Prague in 2006, decided to introduce a new class of celestial bodies, namely, dwarf planets. Today we will not discuss the issue of whether this issue is finally resolved or whether it will be revised and clarified, to what extent it has been worked out, especially since it has raised objections from many astronomers for various reasons, of a historical, ideological nature, for ethical reasons, etc. But the fact that this issue is ripe is beyond doubt.
Disturbances in the motion of Uranus and Neptune were explained by the existence of a planet beyond the orbit of Neptune and many astronomers were engaged in the search for it. Therefore, Pluto, discovered in 1930, was immediately ranked among the planets. However, after determining the mass and orbit of Pluto, it turned out that it could not be the planet X, which Lowell and others were looking for, due to its low mass and orbit. Astronomers saw that Pluto did not fit into the general picture of education Solar system, according to which solid and less massive planets formed closer to the Sun, and gas giants formed from planetesimals in the more distant vicinity of the Solar System. Pluto does not move in the plane of motion of all classical planets, its orbit has a significant inclination to the plane of the ecliptic
Pluto in its motion around the Sun is sometimes closer to the Sun than Neptune (for example, from 1979 to 1999), i.e. in projection onto the plane of the ecliptic, these orbits intersect, although in reality this does not happen due to the large inclination of Pluto's orbit to the ecliptic.
However, Pluto retained the status of a major planet. At the end of the 20th century, the situation changed significantly. The reasons that led to the change in Pluto's status are as follows:
1. Beyond the orbit of Neptune, a second belt of ice bodies is discovered - the Kuiper Belt, or the so-called trans-Neptune objects
2. Many objects have been discovered moving in orbits similar to the orbit of Pluto, i.e. in resonance 2: 3 with Neptune, but smaller.
3. An object larger than Pluto is discovered - Eris
MACorganized the Working Group of the International Astronomical Union (IAUWorkingGroup: " DefinitionofaPlanet"), headed by I. Williams(IwanWilliams). A controversy was organized on the Internet, which allowed for several years to express their proposals and wishes.
New definitions of classical planets, dwarf planets and small bodies of the solar system are shown on the slide.
■ "Classical planet" is a celestial body that (a) revolves around the Sun,
(b)has a sufficient mass so that self-gravity exceeds solid-body forces and the body can take a hydrostatically equilibrium (close to spherical) shape and
(c)cleans the surroundings of its orbit (i.e. there are no other bodies comparable to it near the planet)
Planets terrestrial group- Mercury, Venus, Earth, Mars Gas giants - Jupiter, Saturn, Uranus, Neptune
■ "Dwarf planet" - a celestial body that
(a)revolves around the sun,
(b)has a sufficient mass so that self-gravity exceeds solid-body forces and the body can take a hydrostatically equilibrium (close to spherical) shape,
(c)does not clear the vicinity of its orbit and
( d) is not a satellite (planet).
Dwarf planets Ceres, Pluto, Eris
■ All other objects orbiting the Sun are covered by the concept of "Small bodies of the solar system". These are asteroids, comets, almost all trans-Neptunian objects, excluding planetary satellites.
We will consider the other side of the question, how harmonious our solar system will appear, whether the physical properties of all three dwarf planets are common in order to combine them into one class and how this class differs from other objects in the solar system.
Jan 1, 1801 Piazzi (Piazzi) discovered Ceres, which was immediately recognized as a planet, since it satisfied the Titius-Bode rule r = 0.4 + 0.3x2n (au), where n = 0 - Venus, n = 1 - Earth, n = 2 - Mars, n = 3 - Ceres, n = 4 Jupiter, ... A few years later it turned out that there are many such objects and they all form a torus, which was called the Main asteroid belt, and Ceres - an asteroid. In 2006, the status of Ceres was changed for the third time and she was ranked as a dwarf planet. As already mentioned, its orbit is between Mars and Jupiter at an average distancea =AU 2.77 Orbital eccentricitye =0.08 causes the distance to vary from 2.5 to 3 AU. The orbital inclination isi= 10 ° .6, orbital period 4.6 years. An interesting feature of the orbit is that the perihelion and aphelion of Ceres and Mars are on opposite sides of the Sun. This orbital feature is also present in some large asteroids in the Main Belt.
O physical properties ah the planet is still little known. The size of Ceres is almost 1000 km, namely, 975x909 km, i.e. it has an almost spherical shape with a density of 2.08 g / cm. Albedo 0.13. Weight 9.5 x 10 kg
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makes up almost 1/3 of the mass of the Main Belt (3.0 ± 0.2) xY. Ceres's surface is relatively warm and can have a thin atmosphere and ice. The surface temperature is from 167 to 235 Kelvin, the maximum temperature recorded on the surface is -38 ° C. The internal structure assumes a differentiated structure - a rocky core and an ice mantle 60-120 km thick, which contains 200 million cubic kilometers of water, t .e. the amount of fresh water is greater than that of the earth. Space telescope HubbleHSTrevealed two dark spots, one with a mysteriously bright area, the nature of which is unknown. Presumably, these features on the surface are craters.
The Keck telescope has obtained a map of the reflecting surface (albedo) in the near infrared range. Distinct geographic features ranging in size from 40 to 160 km across. Reflectivity varies within 12%. According to scientists, these differences are due to both the presence of a complex relief and the inhomogeneous chemical composition of the rocks on the surface of Ceres.
The direction of the axis of rotation (for the 2000 epoch) is 287 ° R. and 69 ° declination (accuracy ± 5 °).
To study the physical properties of CeresNASAplanned the launch of the space mission Dawn (MissionDawn) in June 2007. With the help of the gravity assist maneuver near Mars in 2009, the approach with Vesta should occur in 2011, and with Ceres in 2015. NowNASAannounced the cancellation of this mission due to financial difficulties and technical problems.
Observations of Ceres on large telescope The European Southern Observatory in Chile is slated for November 2007.
The second dwarf planet, Pluto, can only be considered a double planet.MACfound a fundamental difference between the conceptdouble planetfrom the systemsatellite planet,namely indouble planetthe center of mass of the system is at open space(Pluto - Charon), in the systemsatellite planetit is inside the planet (Earth - Moon). The binary planet moves at an average distance of 39.5294 (AU), in an elongated orbit with an eccentricity of almost 0.25. Orbital inclination 17.148 (deg) (to the ecliptic). The orbital period is 248.54 (years). The rotation period is 6.38725 (days). Pluto and Charon move around the barycenter of the system in circular orbits at a distance of 19,640 km from each other. The inclination of the orbit to the plane of the Earth's equator is 98.1. The period of revolution of Charon in orbit coincides with the period of rotation of Pluto around the axis and the period of rotation of Charon, i.e. Pluto and Charon always face each other with one of their sides. The diameter of Pluto is 2306 km, Charon is 1250 km.
Physical properties of Pluto. Surface temperature from -220 to -240 ° С. The surface is covered with frozen nitrogen ice with a small amount of methane. In some areas, water ice and even some carbon monoxide ice (carbon monoxide) come to the surface. Particles of complex organic compounds, which are formed from atoms of carbon, nitrogen, hydrogen and oxygen under the influence of sunlight, give a yellowish-pinkish hue.
Strong variations in brightness are seen along the surface. The visual geometric albedo ranges from 0.49 to 0.66. O internal structure can be judged by the low average density of 1.7 g / cm3, i.e. Pluto is 1/3 rocky and 2/3 water ice. The core of stone, 1,500 km in diameter, is surrounded by a 400 km thick layer of water ice. The atmosphere was discovered in 1988. It is composed of nitrogen mixed with methane and carbon monoxide. The pressure is negligible 0.3 pascal. A weak gravitational field is not able to hold the atmosphere, and it constantly escapes into space, new molecules come in its place, evaporating from the ice surface, i.e. Pluto is characterized by the "comet" nature of the atmosphere. The biggest changes in the atmosphere are associated with the seasons. In winter - freezing of the atmosphere. An increase in the temperature of nitrogen ice on the planet's surface by only 2 ° leads to a 2-fold increase in the mass of the atmosphere. The "summer" period will continue in 2015, when the New Horizons spacecraft will approach Pluto.
In 2006, two new satellites of Pluto were discovered. Objects previously namedS / 2005P1 andS / 2005P2, named Nikta and Hydra, were observed with the Hubble Space Telescope. Provided that the orbits are circular and located in the plane of Charon's orbit, their sizes and periods of rotation of satellites around Pluto were calculated. For the first satellite, the semi-major axis of the circular orbit is approximately 64,700 km, the period P = 38.2 days. For the second satelliteS / 2005P2 semi-major axis of the circular orbit is 49400 km, and the orbital period is 25.5 days. If we assume that the satellites have a reflectivity of 4%, like the darkest comet nuclei, then the diameter of the largest of Hydra's satellites is 160 km. With an albedo characteristic of the Centaurs, namely 15%, the satellite size is 80 km; if the albedo is 38% like that of Charon, then the satellite's diameter is 52 km. Satellite Nikta is 25% weaker than the first, and provided that they have the same reflectivity, the size of the second satellite is 10% or 15% smaller than the first. Searches for unknown satellites in the orbital stability zone of (± 100 ") around Pluto did not reveal any potential satellites brighter than an apparent magnitude of V = 27.1.
Charon is covered with water ice, not methane-nitrogen ice, like Pluto The moons Nikta and Hydra are neutral gray like Charon, do not have photometric variations, apparently spherical in shape (DRP = 170 km,DPIII= 110 km).
The common origin of the system is assumed by a giant collision with proto-Pluto, as a result of which Charon received an eccentric orbit. Subsequently, the tidal interaction led to resonant, coplanar and almost circular orbits of Charon, Nikta and Hydra, as well as synchronization of the rotation of Charon with the orbital motion and with the rotation of Pluto.
In July 2005 M. Brown, C. Trujillo and B. Rabinovich announced the discovery of three more large trans-Neptunian objects 2003UB313, 2005 FY9 and 2003EL61 (Table 2). The largest of them 2003UB313 has an absolute valueH= -1.48, i.e. it is brighter than Pluto, for whichH= -1.0
It turned out that this is an object of a crumbling belt (Scattered- Beltobject) with an orbit with a semi-major axis of 67.66 AU, an eccentricity of 0.44 and a large inclination of 44 ° .2 to the plane of the ecliptic. The object was discovered almost at aphelion - at the farthest distance from the Sun, 97 AU. - and had an apparent value of V = 18.5. The object's period of revolution around the Sun is 560 years, so it will reach the closest distance from the Sun at a perihelion of 37.8 AU. only in 2257
Visible photometry at 1.3 mSMARTStelescope and infrared photometry (GeminiNorthObservatory) showed very high reflectivity. The Hubble Space Telescope has refined the geometric albedo and size of Eris. The reflectivity due to frozen methane is 0.85 ± 0.07. The size of Eris exceeds the diameter of Pluto by only 5% and is approximately (2400 ± 100) km (the diameter of Pluto is 2306 km).
The near-infrared spectrum of Eris is dominated by the absorption lines of methane, i.e. the object is largely similar to Pluto. Its surface is covered with solid frozen methane and is a mixture of rock and ice. Nitrogen lines are present in the near infraredN 2 and carbon monoxide CO, characteristic of Pluto, as well as the carbon dioxide lineCO2,present on Triton.
The main difference in the visible spectrum is that Pluto's surface is red on average, while the new object is nearly gray. The difference can be explained by the fact that the new object at a distance of 3 times more than Pluto is colder, and methane ice covers the surface more evenly. Therefore, the albedo is more uniform over the surface and is equal to or higher than that of Pluto. The discovery of an object at such a large distance from the Sun (97 AU) represents a lower-temperature laboratory for studying the phenomena inherent in Pluto - freezing of the atmosphere, ice chemistry, nitrogen phase transitions. Temperature variations from aphelion to perihelion are even more extreme than Pluto's.
In September 2005, at the Keck Observatory, using adaptive optics, a faint satellite was discovered near the object 2003UB313. It was at a distance of 0 ".53 from the main body and had an apparent magnitude of 4 Ш.43 less, ie 60 times weaker than the main body. The approximate diameter of the satellite is 350 km.
The Keck telescope has captured images of the largest trans-Neptunian objects. Three out of four have satellites. Two objects are classified as dwarf planets. Consider if the other two objects can also be classified as dwarf planets.
The next brightest object 2005FY9 turned out to be a classical Kuiper belt object with a semi-major axis of 45.7 AU, an eccentricity of 0.15 and an inclination of 29 °. The period of revolution around the Sun is 309 days. The size is 1500 km at the albedo of Pluto. The spectrum is similar to Pluto. Solid methane lines dominate, with methane ice lines stronger than Pluto's. Red indicates the presence of organic molecules. Presence of nitrogen and carbon monoxide. An atmosphere comparable to that of Pluto is possible. Potential dwarf planet candidate.
Object 2003EL61 - the fourth brightest body after 2003UB313, Pluto and 2005FY9. This is a typical classical Kuiper belt object with a semi-major axis of 43.3 AU, an eccentricity of 0.19 and an orbital inclination to the ecliptic plane of 28 ° .2. The orbital period is 286 years.
However, the period of rotation of the body 2003EL61 on the order of four hours turned out to be very unusual for a large body over 100 km in size. Even a medium-sized solid deforms significantly when rotating at such a high speed. The body is a highly elongated ellipsoid with a longest axis of 1960 km and an albedo of 0.6 - 0.7. Object 2003EL61 is the third body after Pluto and Eris, which is covered with frozen methane and water ice and is relatively neutral in color, in which there are inclusions of darker and more red material.
Observations with the Keck telescope showed the presence of two satellites of the object 2003EL61 in an almost circular orbit with periods
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circulation 49 and 25 days. The mass of the system was determined to be 4.21x10 kg, which is 32% of the mass of Pluto. The satellites are very small, weighing only 1% of the body weight. Infrared spectra from the 8-m Gemini telescope and the 10-m Keck telescope showed clear lines of water ice on the satellite. However, the study of the satellite orbit of the asteroid 2003EL61 showed that the system is only 4 degrees from the position when it was edge to the observer (Fig. 7). Overlapping and eclipses in the system occurred in 1999 and will not occur for another 133 years until 2138.
An even weaker companion of Santa, which has a temporary designationS/2005 (2003 EL61) 2, found in images obtained at the Keck Observatory in June 2005 (IAUC8636). Brightness of the second satellite of the trans-Neptunian object 2003EL61 is only 1.5% of the brightness of the main body. The period of revolution of this satellite around the main body was calculated on the assumption of a circular orbit. It was 34.7 days. It is interesting that the two satellites orbit around the main body are not in the same plane, as one might assume. The orbital planes of the two satellites are inclined to each other at an angle of (39 ± 6) degrees. For a more accurate determination of the parameters of the orbit of the second satellite, additional observations are required.
The New Horizons spacecraft was launched in 2006, with the help of the gravity assist maneuver near Jupiter in 2007, it will reach Pluto in 2015. Its tasks include studying the composition of Pluto's atmosphere and the processes occurring in it. Geological structures of Pluto and Charon and the chemical composition of the material of the surface of the planet and its satellite. Interaction of a stream of charged particles ejected by the Sun (solar wind) with Pluto's atmosphere and at what speed atmospheric gases escape into space.
The flight through the Kuiper belt may take another three to six years, when the study of other bodies continues - the remnants of the oldest material preserved from the time of the formation of the planets of the solar system.
Processing scientific data at two operational science centers - Tombaugh in Boulder, Colorado and Christie in Laurel, Maryland, named after the discoverers of Pluto and its moon Charon.
So, the general properties of dwarf planets follow from the definition itself - bodies have sufficient mass for the body to take a hydrostatic equilibrium form. The lower limit of the mass and size of the body is not determined, but for the three indicated bodies it is of the order of 10 21-1022 kg.
According to their orbital characteristics, they belong to different classes of orbits, namely, the Main Asteroid Belt, the Kuiper Belt and the Scattered Belt, i.e. bodies that have undergone layer differentiation and processing based on processes taking place inside are present in all regions of the solar system. This is how they differ from asteroids and other trans-Neptune objects, which are remnants of primary matter that have not undergone processing and have remained unchanged since the formation of the solar system. The study of processes that could lead to hydrostatic equilibrium under different conditions of formation, illumination, solar radiation and temperatures - distinguishes these objects into one class, the number of objects of which may increase in the coming years to 45 or more members.
>- celestial bodies of the solar system: characteristics, features, history of Pluto, definition, requirements for planets, list and candidates.
Term dwarf planet officially appeared in 2006, when planets the size of Pluto and larger were found outside the orbit of Neptune. Since then, many bodies in the solar system have been called dwarf planets.
In addition, the concept has generated a lot of controversy, especially regarding the status and nature of Pluto. Now the IAU recognizes the existence of 5 dwarf planets, and about two hundred are awaiting confirmation. Let's see what the characteristics of dwarf planets look like.
Definition of dwarf planets
Dwarf planet is a celestial object that:
- revolves around the sun;
- Has enough mass to become nearly round;
- but cannot clear its orbital path.
In short, this is the name for any object with planetary massiveness, but not a protruding planet or moon. But the body must revolve around the sun and have a spherical shape. Below is a list of dwarf planets, where their features, descriptions and photos are indicated.
Potential dwarf planets:
The size and mass of dwarf planets
For a body to acquire a rounded shape, it must have enough mass that resists its own gravity. The internal pressure then forms the surface layer, ensuring plasticity filling the elevations and depressions. This does not happen with asteroids.
For celestial bodies with a diameter of a couple of kilometers, the most significant force is gravity, so they stretch out in the form of a potato. The larger the object, the higher the level of internal pressure until it reaches the point of internal balance. Admire the table of the main characteristics of dwarf planets, which includes a description of the orbit.
| Name | Ceres | Pluto | Haumea | Makemake | Eris |
|---|---|---|---|---|---|
| CMP number | 1 | 134340 | 136108 | 136472 | 136199 |
| Solar system region | Asteroid belt | Kuiper Belt | Kuiper Belt | Kuiper Belt | Scattered disc |
| Dimensions (km) | 975 × 909 | 2306 ± 20 | 1960 × 1518 × 996 | 1500 × 1420 | 2326 ± 12 |
| Weight in kg. Relative to earth |
9.5 10 20 0,00016 |
1.305 10 22 0,0022 |
4.2 10 21 0,0007 |
? | ~ 1.67 10 22 0,0028 |
| Average equatorial radius the same in km |
0,0738 471 |
0,180 1148,07 |
~750 | ? | 0,19 ~1300 |
| Volume* | 0,0032 | 0,053 | 0,013 | 0,013 | 0,068 |
| Density (g / m³) | 2,08 | 2,0 | 2.6–3.3 | > 1.4 | 2,5 |
| Acceleration of gravity at the equator (m / s²) | 0,27 | 0,60 | 0.44 | ? | ≈ 0.8 |
| First space velocity (km / s) | 0,51 | 1,2 | 0.84 | ? | 1.3 |
| Rotation period (days) | 0,3781 | −6.38718 (retrograde) | 0.16 | 0.32 | ≈ 1 (0.75–1.4) |
| Orbital radius (a.u.) | 2,5-2,9 | 29,66-49,30 | 43.13 | 45.79 | 67.67 |
| Circulation period (years) | 4,599 | 248,09 | 283.28 | 309.9 | 557 |
| Average orbital speed (km / s) | 17,882 | 4,666 | ? | 4.419 | 3,437 |
| Eccentricity | 0,080 | 0,24880766 | 0.195 | 0.159 | 0,44177 |
| Orbit tilt | 10.587 ° | 17.14175 ° | 28.22 ° | 28.96 ° | 44.187 ° |
| Inclination of the equatorial plane to the orbital plane | 4 ° | 119.61 ° | ? | ? | ? |
| Average surface temperature | 167 C | 44 C | 32 ± 3K | ≈ 30 K | ≈ 42 K |
| Number of known satellites | 0 | 5 | 2 | 0 | 1 |
| opening date | 01.01.1801 | 18.02.1930 | 28.12.2004 | 31.03.2005 | 5.01.2005 |
But the appearance of small bodies in the solar system can also be influenced by the rotation of the axis. If it is not there, then we get a sphere. The higher the speed, the more noticeable the level of flattening. As a result, the object goes to extremes, like Haumea, which is twice as long along the main axis. Tidal forces close objects, forcing them to show only one side. This is seen in the Pluto-Charon connection.
The IAU did not provide upper and lower bounds for the mass of dwarf planets. But the lower one is displayed as the point that allows you to achieve hydrostatic balance. Size and weight are based on composition and heat history.
For example, silicate asteroids reach balance with a diameter of 600 km and a mass of 3.4 x 10 20 kg. If the object has less hard water ice, then the limit will be 320 km and 10 19 kg. It turns out that there is no standard for size or weight. Therefore, the basis is still form.
Orbital dominance of dwarf planets
Many scientists insisted that the ability to clear the space around itself should be added to the hydrostatic balance. In general, this is the ability of the planets to eliminate smaller bodies next to them, attracting or repelling them. The dwarfs simply do not have enough mass.
To define this, Alan Stern and Harold Levison introduced a parameter, a lambda. Scientists like Stephen Soter use it to separate dwarf planets from ordinary ones. He also put forward a parameter - the planetary discriminant (μ), determined by dividing the mass of a body by the mass of other objects with which it shares an orbit.
Dwarf planets and pretenders
The list of dwarf planets in the solar system includes Pluto, Makemake, Eris, Haumea and Ceres. Only the first and the last are not controversial. The IAU determined that among trans-Neptunian objects (TNOs) they become dwarf only with a diameter of 838 km and brighter 1. The lower diagram shows a comparison of the sizes of dwarf planets.
Among the contenders: Orc, 2002 MS4, Acteya, Kvavar, 2007 OR10 and Sedna. They all reside in the Kuiper belt or the Scattered Disc. Sedna stands out, which stands in a separate class. It is believed that there may be 40 more known objects that should be categorized as dwarf planets. But there are more than two hundred more in the Kuiper belt, and the total number is capable of exceeding 1000.
Dwarf planet controversy
When the IAS adopted the new criteria, many scientists disagreed and a controversy ensued. Mike Brown (who discovered Eris) agreed to the new rules and to reduce the official number of planets to 8. But Alan Stern came out with serious criticism.
He said that Mars, Jupiter, Neptune and Earth also did not completely clear the space around them. With our planet, another 10,000 near-Earth asteroids revolve around the Sun, and Jupiter has 100,000 Trojans. Therefore, Stern stubbornly regarded Pluto as a planet, and Ceres and Eris as complementary.
There are also problems for the classification of exoplanets. We can distinguish characteristics only indirectly, so we do not know if the orbit has cleared. Because of this, criteria appeared for the minimum mass and size.
Dwarf planets
The term "dwarf planet" was adopted in 2006. This definition met with both approval and criticism, and is still disputed by some scientists. For example, as the simplest alternative, they propose a conditional division between planets and dwarf planets in size or even
Moons: if more then - planet, if less - planetoid. This term can only be applied to celestial objects located in.
A dwarf planet is a celestial body that has a number of distinctive features:
1. orbits around; 2. has sufficient mass in order to maintain hydrostatic equilibrium under the influence of gravitational forces and have a nearly round shape; 3. is not a satellite of the planet; 4. does not dominate in its orbit (cannot clear space from other objects).
Five dwarf planets are officially recognized by the International Astronomical Union (IAU).
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However, it is possible that at least 40 more of the known objects in the world belong to this category. Scientists estimate that up to 200 dwarf planets can be found in the Kuiper belt and up to 2,000 dwarf planets beyond.
The sizes and masses that dwarf planets should have are not specified in the IAS decision. There are no strict upper limits. Even an object larger or more massive than Mercury with unrefined orbital surroundings can be classified as a dwarf planet. The lower limit is determined by the concept of a hydrostatically equilibrium shape, however, the size and mass of an object that has reached this shape is unknown. Empirical observations suggest that they can vary greatly depending on the composition and history of the object. The primary source of the preliminary solution of the MAS, which determines the hydrostatic equilibrium shape, is applied "to objects with a mass of more than 5 · 1020 kg and a diameter of more than 800 km." The latter was not included in the final decision, although it was approved. According to some astronomers, the new definition means the addition of up to 45 new dwarf planets.Dwarf planets are celestial bodies revolving around the Sun like the full-fledged eight planets, but also having some resemblance to asteroids.
According to the definition of the International Astronomical Union, dwarf planets are an intermediate link between planets and asteroids and must meet 4 requirements:
- orbit around the sun;
- have a sufficiently high mass in order to maintain hydrostatic equilibrium under the influence of their own gravity and have a spherical or close to such shape;
- not be a satellite of the planet;
- not the ability to clear the surroundings of its own orbit from other celestial bodies.
Dwarf planets of the solar system
At the moment, science knows only the small planets of the solar system. There are six of them. This is Ceres from the main asteroid belt between the orbits of Mars and Jupiter, and 5 planetoids or trans-Neptunian objects: Pluto, Haumea, Makemake, Eris and Sedna. All these bodies differ from each other as much as the 8 "big" planets.
Only 2 of them were fully investigated. is still in orbit of the nearest dwarf planet, Ceres, and has long managed to transmit the first photos of the dwarf planet. And the device on July 14, 2015 made a historical approach with the largest trans-Neptunian object Pluto, the photos arrived at Earth a few days later. The remaining 4 planetoids are still a mystery to us.
However, the question How many dwarf planets are in the solar system remains open. Already today, astronomers have 40 candidates located beyond the orbit of Neptune, further study of which may allow them to be attributed to this category. Other scientists are convinced that the total number of minor planets in the Kuiper belt, scattered disk and Oort cloud reaches at least 2,000.
Extrasolar small planets
As for extrasolar small planets, they are unlikely to be discovered with the current generation of telescopes. And the point here is not even the relatively modest size of such bodies, the catch lies in the 4th point of the definition, which in practice will be very difficult to verify in a distant planetary system. However, there is still some information about the existence of dwarf exoplanets, so according to one of the popular hypotheses, Sedna has an extrasolar origin and was captured by the gravity of our system 4 billion years ago.
Our solar system is rich in many interesting phenomena. Dwarf planets deserve special attention. They are objects orbiting the sun, with some resemblance to asteroids.
Dwarf planets of our solar system
Our solar system is rich in many interesting phenomena. The most attention among them deserves. All of them are objects orbiting the Sun, with some similarities to asteroids. In this article we will take a look at what it is in general terms. Then we will dwell in more detail on the dwarf planet Sedna.
Main characteristics of objects
In relation to dwarf planets, there are requirements from the International Astronomical Union. Objects must strictly comply with them. Otherwise, they cannot be called dwarf planets, but must have a different name. So, the considered objects meet the following requirements:
- Are weighted to maintain hydrostatic equilibrium and are spherical in appearance;
- are unable to clear the surroundings of their own orbit from other space objects;
- revolve around the sun;
- should not be satellites of other planets.
Today, only six dwarf planets are known. These include Sedna, Eris, Makemake, Haumea, Pluto, and Ceres. Each of the listed objects differs from the other as much as the "big" planets are among themselves.
Only two of the six "dwarfs" were investigated. One of NASA's interplanetary stations is still orbiting one dwarf planet - Ceres. High quality images of the surface of a celestial body were obtained. Photos taken by AMC Dawn. It is cutting edge spacecraft... Its engines are powered by ion propulsion. Therefore, with the help of AMC Dawn, it became possible to study several space objects at once.
It was this apparatus for the first time in history that entered the orbit of an asteroid, collected all the necessary information about it. After which he retired to explore the next celestial body - the dwarf planet Ceres. The use of this automatic station made it possible to make a breakthrough in the study of the main asteroid belt. AMC Dawn has created an accurate and detailed map of the surface of asteroids and dwarf planets.
Two years ago, the New Horizons spacecraft made its first approach to the largest of the six objects, Pluto. As a result, images of its surface were also obtained. The appearance of the rest of the dwarf planets is not known to mankind today.
The list of objects under consideration may be enlarged. Astronomers have about forty candidates for the dwarf planet title. They are all located outside of Neptune. But there is no unambiguous data on these objects. Therefore, while they are not officially ranked among the dwarf planets. There is also an opinion that at least two thousand objects of the type under consideration are located in the Kuiper belt, the Oort cloud and the scattered disk.
It is safe to say that there are also extrasolar dwarf planets. But in our time they are unlikely to be open. Modern telescopes do not provide this opportunity. But science does not stand still. Perhaps in the near future we will learn a lot of interesting things.
Sedna: what do astronomers know?
There is a popular theory according to which the Sun has stolen by its gravity several hundred dwarf planets and asteroids from another star passing nearby. For the most part, this was considered a bold assumption. But nowadays there is already some confirmation of this hypothesis.
Astronomers were attracted by the dwarf planet Sedna. She and several neighboring celestial objects move in rather strange orbits. In particular, Sedna is the most distant object in our solar system. In this case, the near point of its orbit is located at 76 AU from the star, and the far one is at 1007 AU. e. This object has a huge orbital period. It is eleven thousand four hundred and eighty-seven years old. It is considered the longest among the large celestial bodies.
Scientists have tried to figure out the nature of this strange behavior of the sednoids. They first tried to do this in 2003. It was then that they were discovered. At first, scientists could not find a rational explanation. Then the theory was put forward that the orbits of the sednoids were elongated by a passing star about four billion years ago.
Subsequently, a computer simulation of the previously described hypothesis was carried out. It happened at the Leiden Observatory. It turned out that a nearby star did not affect the orbits of the sednoids. Rather, it was the Sun that drew them to itself.
During the study, more than ten thousand variations of scenarios were taken into account, where various combinations of distances, travel speeds and masses of stellar systems were taken into account. The modeling was carried out under the guidance of the famous astronomer Lucy Zhilkova.
The calculations made it possible to calculate the most probable scenario. The passing star was eighty percent larger than the Sun. The convergence indicator has reached a maximum of about thirty-four billion kilometers. In this case, the exchange of objects took place from two sides. Some of the objects were added to the orbit of the Sun, some, on the contrary, went into another system. This event appears to have taken place about four billion years ago.
The work carried out by Zhilkova received good feedback and the recognition of scientists around the world. At the same time, do not forget that this is just a theory, albeit a highly probable one. It still requires additional confirmation. This can be achieved by performing chemical analysis. If its results differ from the data from trans-Neptunian objects, this will mean that sednoids have a foreign origin. It is not possible to see the results of this analysis in the near future.
There is also a theory asserting the presence of not yet open planet whose orbit is located in hundreds of a. e. from the Sun. It is she who makes adjustments to the trajectory of Sedna's flight. Again, this is just a bold assumption that requires serious scientific research.
Outcomes
There are many gaps in the study of dwarf planets. But with the development of new technologies for space exploration, all of them will be quickly replenished. Modern scientific stations pay great attention to the study of this issue.