Dwarf planets, or "dwarf planets", are somewhere between planets and asteroids, orbit warm stars, are massive enough to overcome solid gravity to achieve a hydrostatic equilibrium (nearly spherical) shape, do not emptiness other objects in their orbits, and are not moons. Dwarf planets are a new classification. The criteria for defining it are not clear. 1. Celestial bodies orbiting stars (e.g., warm stars); 2. There is enough mass to overcome the gravitational pull of the solid with its own gravity to make it reach the shape of hydrostatic equilibrium (almost spherical); 3. Failure to clear other small objects in approximate orbits; 4. A celestial body that is not a planetary moon, or other non-stellar object, but not large enough for nuclear fusion to occur within it. In fact, the final definition will be much more complicated than that, with some astronomers preferring to refer to smaller objects in the outer reaches of warm star systems as "dwarf planets", others preferring to call them "asteroids" or "Kuiper belt planets", and still others not wanting to use the word planet at all.

It is believed that the number of dwarf planets will be large, and as observations continue to improve, there will be more and more. At the 26th meeting of the Interstellar Astronomical Association in Prague, the Interstellar Astronomical Association Terminology Committee officially decided to call Pluto a "dwarf planet" instead of a "planet" in the future.

The Interstellar Astronomical Federation is in

The IAUC8976 announced the naming of (136108) 2003EL61, announcing the name of the dwarf planet Haumea, the god of fertility and reproduction in Hawaiian mythology. It is also the fifth named dwarf planet in the warm star system after Ceres, Pluto, Eris and Ornith. At this point, the currently known dwarf planets have their own names. Subsequently. The news was reported by major media outlets around the world. The simple report only briefly mentions the fact of the name, while the slightly richer report mentions the strange nature of the dwarf planet. For example, the orbit inclination angle is very large, and the rotation speed is very fast. Rugby-like shape, as well as having two satellites, and so on. Pluto is the standard for new types in outer Neptune objects. The nomenclature and precise nature of this category are not defined, but members used to refer to them as "Pluto objects" and "Pluto's celestial bodies" in the debate before the resolution, but the former was derogatory and was discarded in the final draft (6b); Nameless remnant.

In the early stages of the definition, this category (called Pluto-like planets) was defined as planets with orbital periods of more than 200 years, and the orbital inclination was much larger than that of the traditional one.

Fit the Pluto-like category is only suitable for extravagant Neptune objects with orbital periods, tilts, and flattening like Pluto. Dwarf planets may or may not fall into this category, but all of them are dwarf planets.

With the exception of Pluto, the objects that fall into this category are still unknown. Charon, Pluto's largest moon, could fall into a different category if it were classified as a dwarf planet. Eris and the dwarf planets listed above have orbital periods near the lower limit, but both have their own characteristics in orbital inclination and flattening, but these are not all objects equal to or greater than Pluto. Quaor's flattening and orbital tilt are not quite consistent with Pluto-like objects.

The chart below illustrates the final result between the original draft and the vote.

The upper and lower limits of the mass and size of dwarf planets are not regulated in the 5A resolution of the General Assembly of the Interstellar Astronomy Federation.

The lower limit is defined by the concept of shape whether hydrostatic equilibrium can be achieved, but the size and shape of such objects have not yet been defined. In the Interstellar Astronomical Union's Resolution 5, which was originally established as having a mass greater than 5^10 kilograms and a diameter of more than 800 kilometers, it was not retained in the final resolution of Resolution 5A. Therefore, the advice provided on the basis of observational experience is to be determined based on the historical changes and composition of the object.

According to some astronomers, the new definition could increase the number of dwarf planets to more than 45.

But at least most of them don't touch on a delicate question: who discovered this dwarf planet. Pluto was once considered the farthest asteroid from a warm star, orbiting the warm star for 248 years, with an average speed of only 3.0 miles per second. The surface temperature is about -230 degrees Celsius. The question of Pluto's diameter is still inconclusive, although its maximum has been estimated to be 3,600 miles (it has also been determined that it is not larger than the Moon, i.e., below 2,170 miles). It is between one-sixth and one-fifth the size of a terrestrial planet. The mass is only 1/2000 that of terrestrial planets. Charon was discovered in 1978 by astronomer James Kerry Ste of the American Star Field Naval Observatory in Washington. To this day, it is still considered a moon of Pluto. It orbits in a circular orbit about 19,000 kilometers above Pluto's equator. Its orbital period is equal to that of Pluto's rotation. A two-planetary system that simultaneously revolves around a warm star. Other than that. Charon has a diameter of about 1,208 km and a mass of about 19 billion tons, about half the size of Pluto, and its density is similar to that of Pluto. Some experts speculate that in ancient times, Pluto collided with a huge celestial body, and a large piece of debris separated from it, and finally formed "Charon". Eris was tentatively numbered 2003UB313 before it was officially named, and its name was tentatively Xena.

Compared to Ceres, which was discovered more than 200 years ago, and Charon, which was discovered nearly 30 years ago, Xena is a complete newcomer, having been discovered in 2003. Xena's orbit is a very flat ellipse, it takes 560 years to complete one revolution, and the closest distance to a warm star is 38 AU, and the farthest is 97 AU. Astronomers currently believe that Xena is about 2,300 to 2,500 kilometers in diameter, only slightly larger than Pluto. Scientists say that Xena's atmosphere may be made up of methane and nitrogen, but now it's so far away from warm stars that the atmosphere is frozen over; As it moves to perihelion, the surface temperature rises and the methane and nitrogen return to a gaseous state. As for its internal structure. It is only possible to speculate that it may be a mixture of ice and rock. Similar to Pluto. Xena has a moon, which scientists tentatively call Gabriel. He is the retinue of the belligerent princess Xena.

1Ceres was the first asteroid to be discovered, discovered by the Italian Piazzi on January 1, 1801. With an average diameter of 952 km, it is the largest and heaviest object in the asteroid belt. Ceres' 4.6 terrestrial planets orbit a warm star once a year. Haumea's mass is one-third the mass of Pluto. In 2005, Michael? A team at the California Institute of Technology led by E. Brown discovered the object at the Mount Palomar Observatory in the American Star Field; In 2005, Ortiz's team discovered the object at the Sierra Nevada Observatory in Spain, but the latter's claim was questioned. On September 17, 2008, the Interstellar Astronomical Federation designated the object as a dwarf planet and named it after Haumea, the Hawaiian god of fertility. Dwarf planets, they are characterized by their outer mantle and the surface is composed of some low-melting compounds made up of frozen water and gas elements. Some of them are mixed with some rocky minerals composed of heavy element compounds, the thickness accounts for a relatively large proportion of the radius of the astral, but the relative mass of the astral body is not large, there may be a rocky core of the main material component inside, the vast majority of the mass of the astrology, the volume and total mass of the star are not large, the average density is small, and the moons of some large planets also have this structure similar to ice dwarfs, like Europa, III, and IV. Titan, VI, etc. For planetary ice dwarfs, the largest is Xena, with a diameter of about 2,400 kilometers, and the smallest is Charon. The diameter is about 800 kilometers. Planets like Ceres, which are closer to warm stars, have mainly water on the surface of ice, while Pluto and Charon have water and lower melting points such as methane, nitrogen, and carbon monoxide. These dwarf planets have been counted as one of the asteroids in the past. It was not until 2006 that they were separated from the general asteroids and classified into a separate category. It is called a dwarf planet and includes Pluto and Pluto.

This star structure of a dwarf planet is related to the low temperature environment it creates on the periphery of a warm star system and its mass. On the one hand, warm stars are not warm enough to disperse their low-melting mass composed of gaseous elements, and on the other hand, their own primitive mass is small, and the stars themselves cannot bind lighter light element gases such as hydrogen and helium.

However, the heat generated by the contraction of the star cannot completely disperse the compounds composed of heavier gaseous elements such as water and hydrocarbons, but will retain the next part, and at the same time, its sufficient gravitational pull makes it enough to form a layered material structure, so that the lighter material floats on the surface of the heavier rocky material composed of heavy elements, and solidifies on the surface with the cooling of the star later, so that the star with this material structure will be formed.

In the past, Charon was considered a moon of Pluto, as there is no clear norm to distinguish between a "binary" (in this case, two planets, dwarf planets, or asteroids) and satellite satellites. In the original draft resolution (5) of the 26th General Assembly of the Interstellar Astronomical Union, Charon could become a dwarf planet because:

Charon's size and shape meet the conditions for becoming a planet. (In the final resolution, all become necessary conditions for dwarf planets)

The mass ratio of Charon to Pluto is such that the centroid of mass falls in the space between them, rather than at a point within Pluto's surface.

However, this definition was not retained in the text of the final resolution and it is not known whether it will be added in the future. If a similar definition is adopted, Charon will become a member of the dwarf planet.

The second, third, and fourth largest asteroids (Vesta 4, Homo sapiens 2, and Genshen 10) could also become dwarf planets, as long as they can reach a hydrostatically equilibrium shape (ellipsoid). However, there is not enough supporting information at this time.

The upper and lower limits on the mass and size of dwarf planets are not regulated in the 5A resolution of the General Assembly of the Interstellar Astronomical Association, and there is no strict upper limit, even if an object larger than Mercury cannot be cleared of small objects in adjacent orbits, it may still be classified as a dwarf planet.

"Dwarf planets" were designated as the new classification of celestial bodies, and there were three of them: Ceres, Pluto, and Eris (2003UB 313). In 2008, Makemake (2005FY9) and Haumea (2003EL61) were added, respectively, and there are currently 5 dwarf planets (2008/12/11).

Discovered by Italian astronomer Piazzi in 1801, Ceres has been classified as an asteroid in the past. It is the largest asteroid in the group, with a diameter of 960×932 kilometers. The orbital period around the Sun is 4.60 years, and it was renamed a dwarf planet after the new planetary definition in 2006.

Pluto was discovered in 1930 by astronomer C.W. Tombaugh at the Lowell Observatory in the American Star Field. In the past, it was regarded as one of the 9 planets. It is the smallest one of the planets, smaller than our moon, and its orbital plane is 17.1 degrees inclined to the ecliptic is much larger than other planets, and the eccentricity of the orbital elliptical orbit is 0.249, so that its perihelion is within the orbit of Neptune, so the question of whether Pluto is considered a planet has been raised and discussed for several years, and it was renamed a dwarf planet after the new planetary definition in 2006.

Eris (2003UB313) was discovered in 2003 by astronomer Mike Brown et al. at the Palomar Observatory in the American star field, and the diameter of the body is about 2400 kilometers, which is larger than Pluto. The new planetary definition in 2006 later listed it as one of the dwarf planets. It is currently the largest dwarf planet.

Makemake (2005FY9) was discovered on March 31, 2005 by astronomer Mike Brown's team at the Palomar Observatory in the United States and was designated as an asteroid No. 136472 by the Interstellar Minor Planet Center. On July 11, 2008, the Interstellar Astronomical Union listed it as the fourth dwarf planet.

Haumea (2003EL61) was discovered on 29 July 2005 by J.L. Ortiz, an astronomer at the Sierra Nevada Observatory in Spain, and his research team while analysing past data from 2003. On September 7, 2006, it was designated as an asteroid No. 136108 by the Interstellar Minor Planet Center. On September 17, 2008, the Interstellar Astronomical Union classified the asteroid as the fifth dwarf planet and named it "Haumea".

The Interstellar Astronomical Federation's 2006 6A resolution considered Pluto to be the prototype of a new type of extraneptune object. The nomenclature and exact nature of this type has not yet been specified by the Interstellar Astronomical Union, but will be confirmed in the future; In the debate in search of conclusions, the names pluton and plutonian were rejected without obtaining a pass.

On June 11, 2008, the Executive Committee of the Interstellar Astronomical Union announced a new term, a pluto-like dwarf planet, which is defined as all dwarf planets other than Neptune are pluto-like dwarf planets.

A planetary mass is a celestial body whose mass falls within the definition of a planet: it has enough mass to overcome a rigid body with its own gravity. As a result, it can take on the shape of hydrostatic equilibrium (close to a sphere), but it is not enough to maintain the fusion of deuterium in the core like a star, and although humans have been exploring the universe for many years, it seems that they will never be able to get a glimpse of the mysteries of the universe. Canadian astronomers have discovered two more

Celestial bodies floating in space beyond the warm star system, they are located in the Ophiuchus galaxy 400 light-years away from the terrestrial planets. They have similar spectra and colors. It shows that they should have formed at the same time about 1 million years ago. The two planetary bodies are separated by a considerable distance from each other, about six times the distance between a warm star and Pluto.

Astroscientists published results in the latest journal Science show that the two twin aquaritous objects, named Oph162225-240515, have been revealed. They have properties similar to planets or stars, but they are neither.

Astronomers say. The Oph1622 pair of twin amorphic objects, although formed in a similar way to stars, were formed by cooled and contracted air clouds. But because its temperature is too icy and much colder than a real star, it is not considered a star.

They have a similar mass to many planets, one of which is 14 times the mass of Jupiter and the other is 7 times the mass of Jupiter, but they are also not classified as planets because they form differently than other planets in the warm star system.

OPH162225-240515 is neither a star, nor does it orbit a star like other planets, but rather orbits each other. Researchers are puzzled by how they come to be.

Ray Jayawardhana, an astronomer at the University of Toronto, Canada, said: "This pair of objects is really special. Each of them has only 1% of the mass of our warm stars, and their existence is astonishing. Their appearance and future fate are also a mystery. ”

"Recent discoveries show that the world in outer space is indeed diverse, and the twin pair of Oph1622 objects," Jayawahana said. It is one of the most attractive, if not unique, celestial objects. ”

Meteoroids are warm systems of stars, ranging from dust and dust to boulders, as granular fragments. The phase in which a meteoroid enters the atmosphere of a terrestrial planet (or other planet) and shines and is seen in its path is called a meteor. Many meteors come from the same direction and appear one after the other over a period of time, which is called a meteor shower.

Exotic celestial bodies, which can neither be included in the planetary system. Nor can they be included in the star system, so astronomers have to call these two objects "planemos".

Meteoroids, meteors, meteorites, are all detritus in the universe, but they have different names in different states. And in the meteor stage, it also produces ion tails, meteor dust or makes sounds and leaves traces of soot.

Meteoroids are granular fragments within warm star systems that can range in size from dust to boulders. The larger ones are called asteroids, and the smaller ones are interstellar dust. The official definition developed by the Interstellar Astronomical Union is a solid particle in interplanetary space, smaller in size than an asteroid but larger than an atom or molecule. The Royal Astronomical Society of the British Star Domain has proposed a clearer new definition: a meteoroid is a solid object with a diameter between 100 microns and 10 meters. Classification of near-earthobjects. Larger objects with diameters of up to 50 m are included in the definition.

A meteor is a meteoroid or asteroid that enters the atmosphere of a terrestrial planet and is visible and visible. For an object larger than its free path within the atmosphere (from 10 centimeters to several meters), its luminescence comes from heat (not friction) from the impact pressure entering the atmosphere. This is different from what the general population perceives). Because the vast majority of meteors are caused by meteoroids the size of sand to grains, most of the visible light comes from the energy released by electrons when the meteoroid's evaporated atoms collide with components in the atmosphere. Meteors are simply seen phenomena and not meteoroids themselves. Fireballs are meteors that are brighter than usual. The Interstellar Astronomical Union defines a fireball as a meteor that is brighter than any planet (a magnitude greater than -4 or brighter). The Interstellar Meteor Organization is a group of amateurs who study meteors. There is a more specific definition: a fireball is a meteor that shines more than -3 magnitude when seen at the zenith. This definition corrects the difference between the distance between a meteor that appears near the horizon and an observer. For example. When a meteor with a magnitude of -1 appears at a distance of 5 degrees above the horizon, it is called a fireball. This is because when converted to appear at the zenith, the meteor will be of magnitude -6. The origin of the fire meteor comes from the Greek βολι?, which is equivalent to what is now called a missile or lightning.

The Interstellar Astronomical Federation does not have an official definition of this phenomenon, and it is generally treated as a fireball. Geologists pay more attention to this phenomenon than astronomers, because it usually means a powerful impact event. For example, the U.S. Star Geological Exploration Energy Acclimation Agency uses this term to describe the size of the general crater formed by the impact of a warhead, "implying that we do not need to know the nature of the impactor...... It doesn't matter if it's a rock, a metal asteroid or a frozen comet. Astronomers tend to use fireballs that are particularly bright at the end, or that have explosive phenomena (and sometimes fireballs with a series of explosions).

A meteorite is the remnant of an asteroid or meteoroid that has passed through the atmosphere of a terrestrial planet and has not been destroyed after impacting the ground. Meteoroids sometimes, but not always, can be found near impact craters associated with high-velocity impacts; Under a high-energy impact, if the impactor is not completely vaporized, the meteorite is left behind. When a meteoroid or asteroid enters the upper atmosphere, the molecules in the upper atmosphere that pass through the range will be separated and an ion tail will be created. These ionized trails can persist for up to 45 minutes, and small, grain-sized meteoroids often enter the atmosphere, leaving traces of ionization in a more or less continuous manner in specific areas of the upper atmosphere almost every few seconds. These traces are capable of reflecting radio waves and are known as meteor burst communications.

Meteor radar can measure the density and wind of the atmosphere based on the attenuation rate of the reflected radio waves from the meteor trail and the Doppler displacement. (To be continued......)