# Earth Science Research Paper

Only available on StudyMode
• Published : October 8, 2012

Text Preview
-------------------------------------------------
Research Paper III

Earth’s place in the universe

Part I. Definition

1. Aphelion - Aphelion: (opposite of perihelion) the point in its orbit where a planet is farthest from the Sun; when referring to objects orbiting the Earth the term apogee is used; the term apoapsis is used for orbits around other bodies.

2. Astronomical unit – (1 AU = 149,597,870.691 kilometers) An Astronomical Unit is approximately the mean distance between the Earth and the Sun. It is a derived constant and used to indicate distances within the solar system. Its formal definition is the radius of an unperturbed circular orbit a massless body would revolve about the sun in 2*(pi)/k days (i.e., 365.2568983.... days), where k is defined as the Gaussian constant exactly equal to 0.01720209895. Since an AU is based on radius of a circular orbit, one AU is actually slightly less than the average distance between the Earth and the Sun (approximately 150 million km or 93 million miles). 3. Celestial sphere - The celestial sphere is an imaginary sphere of gigantic radius with the earth located at its center. The poles of the celestial sphere are aligned with the poles of the Earth. The celestial equator lies along the celestial sphere in the same plane that includes the Earth's equator. * North Celestial Pole (NCP) and the South Celestial Pole (SCP) - these are just the north and south poles extended into space. * Celestial Equator - The earth's equator, but at a much greater radius. If the earth's equator was a rubber band, then the celestial equator is the same rubber band just stretched away from the earth. * Horizon - The horizon changes depending on your position on earth. * Zenith- The point on the celestial sphere directly overhead. * Meridian- The line that extends from the north point on the horizon upwards through the zenith and then downward to the south point on the horizon.  4. Constellation -

In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms (which themselves are generally referred to in non-technical language as "constellations"), which are patterns formed by prominent stars within apparent proximity to one another on Earth's night sky. There are 88 standard constellations recognized by the International Astronomical Union (IAU) since 1922. The majority of these go back to the 48 constellations defined by Ptolemy in his Almagest (2nd century). The remaining ones were defined in the 17th and 18th century; the most recent ones are found on the southern sky, defined in Coelum australe stelliferum by Nicolas Louis de Lacaille (1763). There are also numerous historical constellations not recognized by the IAU, or constellations recognized in regional traditions of astronomy or astrology, such as Chinese, Hindu and Australian Aboriginal.

5. Declination - On the celestial sphere, the position of a celestial object north or south of the celestial equator. Declination is measured in degrees along a great circle drawn through the object being measured and the north and south celestial poles, with positive values north of the celestial equator and negative values south of it, so that the equator itself is 0° and the north and south celestial poles are +90° and -90° declination respectively. one of the two direction coordinates of a point on the celestial sphere in the equatorial coordinate system, the other being either right ascension or hour angle. Declination's angular distance is measured north or south of the celestial equator, along the hour circle passing through the point in question.

6. Ecliptic - the great circle on the celestial sphere that lies in the plane of the earth's orbit (called the plane of the ecliptic). Because of the earth's yearly revolution around the sun, the sun appears to move in an annual journey through the heavens with the ecliptic as...