Physical Characteristics Essay Example | Topics and Well Written Essays - 1250 words

Physical Characteristics - Essay Example All scientists do not unanimously accept the latest IAU launched definition of a planet that changed the status of Pluto. They continue to view Pluto as the ninth planet. (Spinrad, 2004), (Stern, 2007) Kuiper Belt is an unexplored region of the solar system that extends from just outside the orbit of Neptune to quite a distance from the orbit of Pluto. It is similar to the asteroid belt in that it consists chiefly of small bodies and one known dwarf planet, Pluto. But while the asteroid belt is made up of metal and hard rock, the Kuiper Belt is composed mainly of frozen objects made up of dust and ice, called KBO's. They vary in size from small clumps of ice and dust to large bodies like the Pluto. It is the revolution of these objects that determines the disc-shaped structure of the Kuiper Belt. If their orbits are interrupted in order to bring them into the inner solar system, they can be seen as comets which turn into gas and dust when they get too near to the sun. (Stern, 2007) During the year 1905, an American astronomer named Percival Lowell, observed that some kind of gravitational force seemed to be disturbing the revolutions of Uranus and Neptune. In 1915, he postulated the existence of another planet beyond Neptune and started his research from his Arizona observatory. Unfortunately, he found his death in 1916 before he could discover Pluto. But his works were carried on by the Lowell Observatory staff, and in 1929, Clyde W. Tombaugh, an assistant at the observatory, took pictures of the part of the sky that was in question with a very powerful wide-angled telescope. The next year he discovered Pluto on three of the photographs. (Spinrad, 2004) However, the newly discovered planet seemed to be quite small to cause interruptions in the orbits of Uranus and Neptune. So, the calculations of Percival Lowell were rechecked by the later astronomers, and were found to be inaccurate confirming no disturbances in the orbits of Uranus and Neptune. Hence, discovery of Pluto was just luck through hard work. Later, in 1978, the U.S naval observatory at Flagstaff observed discovered a moon orbiting Pluto very closely, and named it Charon. (Stern, 2007) In 1951, Gerard Kuiper, a renowned Dutch American astronomer, predicted the presence of the Kuiper Belt. He and his colleagues expected that a belt composed of frozen volatile material might exist beyond the orbit of Neptune, just like the rocky asteroid belt lying between mars and Jupiter. Although the first few searches were unsuccessful, introduction of the charge-coupled device (CCD) in the late 1980's opened up a new gateway to space research. These devices were a lot more efficient in absorbing light than the obsolete photographic technology, allowing them to capture extremely dim objects. Thence in 1992, two astronomers, Jane Luu and David Jewitt, discovered the first Kuiper Belt Object, 1992QB1. (Stern, 2007) Physical Characteristics: Size and Orbit Pluto is approximately 39 times as far from the sun as the earth that is a distance of about 5.9 billion kilometers. It has an approximate diameter of 1,400 miles, which is about two-thirds the size of earth's moon and less than a fifth of the earth itself. (Spinrad, 2004) It takes about 248 earth years to complete a full revolution around the sun, while it takes 6 earth days for a full rotation around its axis. As its orbit is elliptical in shape as

Surface and Interface States of Ga Compound Research Paper

Surface and Interface States of Ga Compound - Research Paper Example The paper discusses various issues related to the gallium compound semiconductors including both the interface and the surface properties. It discusses the formation of the surface state and the charges at the interface state when interfaced with various metals. Background Surface state: Intrinsic and extrinsic A considerable number of clean semiconductor surfaces show signs of both intrinsic and extrinsic surface states. Surface states of materials can be defined as the electronic states that are found at the material’s surface. Surface states are formed as a result of the sharp transition from solid materials that terminates with the surface. Surface states are usually found close to the surface in the atomic layer. The changes of the electronic band structure to vacuum from the bulk materials are caused by the surface material termination. After the termination of the surface material, a weakened potential is created at the surface which leads to the formation of new electr onic states know as the surface state [3]. The bands of the solid on the surface of semiconductor crystals get related to vacuum energy since it takes a considerable amount of energy to remove the electrons from the crystal to the vacuum. This due to the fact that the formation of crystal from far separate atoms lower the energy hence the high amount of energy involved in the electron removal. The chemical bonds at the surface of the crystal have their periodic pattern interrupted at the surface which in turn results into unsaturated bonds [1]. After the interruption, the unsaturated bonds then rearrange themselves through surface reconstruction which may be saturated by a layer of atoms. The re-arrangement of the saturated bonds results in changes in both the allowed energies and the surface crystal structure. The formation of surface states can be best described by Bloch’s Theorem which allows the wave vector function to be a complex number. In principle, an imaginary wave vector corresponds to a damped wave function which is exponential in nature. In perfect finite non physical crystal that does not experience periodicity violation and experiences a translational symmetrical break allowing wave vector with nonzero imaginary components [6]. With the conditions fulfilled, it can therefore be shown that the resulting states are localized at the surface. The energies of the formed states are located at the surface which forms a separate band of surface states. The number of atoms per area at the surface of a crystal greatly determines the number of surface states per area of the crystal. The number of states can however be compromised of states in the crystal without boundary would have contributed to the conduction bands or the valence bands [5]. In the case of intrinsic semiconductors, the number of filled surface states is equivalent to the number of electrons removed from the bulk valence band due to the change in neutrality. The filled surface state s are considered donor like states given that they have electrons that can be donated to the empty available states. Empty surfaces states on the other hand can be considered as acceptor like given that they have empty available surface states which can be occupied by electrons [3]. Intrinsic surface states Intrinsic surface