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Asteroids are classified by their characteristic emission spectra, with the majority falling into three main groups: C-type, M-type, and S-type. These describe carbonaceous (carbon-rich), metallic, and silicaceous (stony) compositions, respectively. The physical composition of asteroids is varied and in most cases poorly understood.
Asteroids are given minor planet numbers, but not all minor planets are asteroids. Minor planet numbers are also given to objects of the Kuiper belt , which is similar to the asteroid belt but farther out (around 30–60 AU), whereas asteroids are mostly between 2–3 AU from the Sun or at the orbit of Jupiter 5 AU from the Sun.
Over 200 asteroids are known to be larger than 100 km, [63] and a survey in the infrared wavelengths has shown that the asteroid belt has between 700,000 and 1.7 million asteroids with a diameter of 1 km or more. [64] The number of asteroids in the main belt steadily increases with decreasing size.
The fossils were between 35.5 to 35.9 million years old and were found in a nearly 10-foot-long rock core: a tube-like sample taken from underneath the Gulf of Mexico by the scientific Deep Sea ...
The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, discovered by German astronomer Karl Reinmuth in the 1930s. They are Earth-crossing asteroids that have an orbital semi-major axis greater than that of the Earth (a > 1 AU ) but perihelion distances less than the Earth's aphelion distance (q < 1.017 AU).
The asteroid and comet belts orbit the Sun from the inner rocky planets into outer parts of the Solar System, interstellar space. [16] [17] [18] An astronomical unit, or AU, is the distance from Earth to the Sun, which is approximately 150 billion meters (93 million miles). [19]
They found that the dust could have blocked out the sun for up to two years and potentially stayed within the atmosphere for 15 years, restricting photosynthesis for plants and, therefore ...
Approximately 8% of known main belt asteroids are similar in composition to 16 Psyche. [10] [11] One company, Planetary Resources, is already aiming to develop technologies with the goal of using them to mine asteroids. Planetary Resources estimates some 30-meter long asteroids to contain as much as $25 to $50 billion worth of platinum. [12]