"Research Carbon Weng Says Carbon" (VI): From the Diamond Planet "Lucy"-Talking about Carbon in the Universe

Although the dazzling and crystal clear diamond is also a form of carbon, it is the most anticipated gift for young women on Valentine's Day. The heaviest diamond ever found on Earth is the 3106 karat "Culinan" rough diamond produced in South Africa in 1905. According to the calculation of 0.2 grams per carat, its weight is equivalent to 621.2 grams, which is less than one kilogram. However, did you know that in Sagittarius, 50 light-years away from our earth, there is a planet named "BPM37093" which is the largest diamond in the known universe so far. It has a diameter of 4000 kilometers and a weight of 1034 karat tons, or 2 × 1027 tons. Astronomers named it "Lucy" according to the Beatles song "That's Lucy with Diamonds in the Sky". In fact, it is the carbon core formed after the nuclear reaction in the star is completely completed and transformed into a white dwarf. With the decrease of temperature, the carbon element in it will gradually form extremely high-density crystals, thus becoming the largest diamond in the Milky Way. After 5 billion years, the sun will also morph into a white dwarf star, and then after 2 billion years, it will also become a big sparkling diamond.

Figure 1 Diamond Planet

Figure 2 Buckyballs in the universe

In addition to the large diamonds that are converted directly from the star, there are also carbon planets that form around the star. More than 100 planets outside our solar system have been observed. In these planets, there are some are rich in carbon gas and dust, which is the main component of some planets is silicon carbide (carborundum) and so on. There are also some planets whose top case may be graphite, and the interior is natural diamond converted into natural diamond due to high pressure. There may also be hydrocarbons on the surface, and lakes or sea areas of liquid hydrocarbons such as methane may also be formed. Some scientists even think that these carbon planets outside the solar system may contain life, even intelligent life. For example, around a star called "Beta Pictoris", which is only more than 2000 million years old and about 60 light-years away from the earth, a cloud of gas and dust with a diameter of 300 billion kilometers has been found, including a large amount of gaseous carbon. They are forming planets rich in methane and graphite. In 2008, NASA released the "Cassini" spacecraft detection results, saying that the amount of natural gas and other liquid hydrocarbons in the surface lakes and seas of Titan, Saturn's largest satellite, is amazing, which is the total proven oil and gas reserves on Earth. Hundreds of times. Liquid hydrocarbons exist on Titan's surface not as water, but as methane and ethane.

Cosmic dust particles are mainly in the nanometer to micrometer range in size, and there may be larger particles in primitive planets. Two types of pre-solar carbon particles have been found in primitive chondrites: nanodiamonds and graphite particles. The typical size of nanodiamond is 2 nm, which is equivalent to 100 carbon atoms; while the size of graphite particles is about 1~20 nm. Many different structures of carbon and amorphous carbon particles are found in the effluents of some carbon-rich stars. Many organic substances have also been found in the original carbon-containing spheroidal meteorites. For example, sugars and their derived polyhydroxy compounds have been found in carbon-containing meteorites. Therefore, comets and meteorites may have brought the seeds of organic life to the earth when they bombarded the earth millions of years ago. Studies of meteorites that have fallen to Earth show that 3% of the carbon is in the form of nano-scale diamonds. It is estimated that one gram of dust and gas in the cosmic dust cloud may contain one trillion nanoscale diamonds. NASA's "spitzer" (Spitzer) infrared space telescope is conducting this search. In the universe, there are many other forms of carbon besides diamond and graphite. For example, the Hubble Telescope has also found carbon dioxide gas on a series of planets 65 light-years away from Earth, the size of Jupiter, and designated as "HD189733.

Since the discovery of the first interstellar molecule in 1937, more than 130 kinds of interstellar molecules have been identified, and 75% of them are carbon-containing molecules. Carbon is the main source of free electrons in diffusing interstellar clouds, which can heat the interstellar gas, so carbon plays an important role in the physical evolution of the interstellar medium. Because carbon has a stronger bonding ability, it can form a variety of molecules. Carbonaceous molecules that have been identified in space include simple diatoms (e. g., CO, CN, C2, etc.), simple polyatoms (CH2, CH4, C2H2, etc.), and more complex unsaturated and polycyclic aromatic molecules. Ethylene glycol has been detected about 26000 light-years from Earth. Ethylene glycol is a 10-atom molecule composed of carbon, hydrogen and oxygen, and is one of the five largest molecules found in the universe. This finding suggests that there may be more complex sugar molecules like ribose in interstellar clouds. Ribose is the main component that makes up ribonucleic acid, and ribonucleic acid is the main component that makes up deoxyribonucleic acid. The discovery further suggests that the discovery of interstellar chemicals is important for understanding the creation of biological molecules in early Earth.

Six carbon atoms can be joined together to form hexagonal benzene ring molecules, and multiple benzene rings can be joined together to form various polycyclic aromatic hydrocarbon molecules of naphthalene, phenanthrene, anthracene and other planes. The parallel connection of benzene rings can continue indefinitely, and planar graphene molecules of different sizes can be formed in extreme cases. Polycyclic aromatic hydrocarbon molecules are considered to be the most abundant space on behalf of complex molecules, such molecules have a high photodecomposition stability, which can exist in the harsh interstellar environment. Polycyclic aromatic hydrocarbon molecules are produced in the carbon-rich giant effluent in a process similar to the formation of soot during combustion. It is the basic raw material of carbon black particles and is the gas phase of molecular carbon and dust particles (or carbonaceous solids) Intermediate products. Polycyclic aromatic hydrocarbon molecules and carbon-carbon chains with an average size of 20-30 carbon atoms are common components of the "hot" molecular cloud core (100-200K) and the periphery of carbon stars in interstellar clouds.

In 2010, the Spitzer infrared space telescope was used to capture infrared spectral disturbances caused by buckyballs (I. e. fullerenes: C60, C70, etc.) in the cosmic dust around a star in the Tiantan constellation 6500 light-years away from the earth. Because buckyballs are one of the most stable substances, they can be preserved in the powerful interstellar radiation field of space, a finding that proves that fullerenes can also form in space. Because of their unique characteristics, C60 and C70 play a very important role in various physical and chemical reactions in space. This discovery may even help scientists explain the unexplained chemical signals that have been detected in cosmic dust.

95% of the mass of the universe is invisible dark matter, dark energy and neutrinos. Stars, comets, cosmic gases and dust account for only 5% of the mass of the entire universe, all of which are composed of nearly 100 elements and more than 300 isotopes. Of all the elements in the universe, carbon accounts for only 0.3 percent, but its abundance ranks sixth. Among the elements and isotopes of the solar system, carbon and oxygen rank almost fourth in order of atomic ratio, only below hydrogen and helium. Carbon is also the main constituent element of the earth's cosmic particles. With the continuous evolution and development, carbon is used as the skeleton, and finally a world of various animals and plants has been formed on the earth. Please see in detail the cycle of carbon (VII) carbon on the earth.

This article is from Wang Maozhang Science Net blog.

Link address: http://blog.sciencenet.cn/blog-526286-414690.html