Astronomical objects are gravitationally bound structures that are associated with a position in space, but may consist of multiple independent astronomical bodies or objects. These objects range from single planets to star clusters, nebulae or entire galaxies. A comet may be described as a body, in reference to the frozen nucleus of ice and dust, or as an object, when describing the nucleus with its diffuse coma and tail.
High-impact journals are those considered to be highly influential in their respective fields. The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field. It is first devised by Eugene Garfield, the founder of the Institute for Scientific Information. The impact factor of a journal is evaluated by dividing the number of current year citations to the source items published in that journal during the previous two years.
Last date updated on June, 2014