Astronomy Words

The science of space beyond Earth’s atmosphere, astronomy deals with celestial objects like stars, planets, comets and galaxies. It includes the study of their physical and chemical properties as well as the large-scale properties of the Universe. In addition to examining the history and evolution of these objects, astronomers also try to understand what makes them tick. There are many different astronomy words that are used to describe these various elements of the discipline.

The equator of the sky is the imaginary line that divides the celestial sphere into two equal parts, the North and South poles being opposite to each other. This is a key concept to know because it defines the position of the planets and their satellites in relation to the Sun. The point of opposition for a planet is when it is at its closest approach to the Sun.

A type of nuclear reaction that occurs when several small nuclei fuse into a larger one, such as hydrogen fusion in the Sun, where it produces helium. The theory is that this is how stars generate energy and light.

An observation arc is the period of time between the earliest and latest observations of an astronomical object made by a telescope. The length of this arc is important because it helps astronomers determine an object’s orbit, which in turn allows them to calculate its movements and track it over time. Astronomers use observation arcs to identify new objects and monitor their movement, particularly for asteroids and comets that are difficult to continuously track because of their size and distance from Earth.

The light reflected from the surface of a moon, planetary atmosphere or star is called luminosity. The luminosity of a body is determined by its temperature and its surface composition. A hotter star emits more luminosity than a cooler one, and the light from a redder planet is brighter than that of a blue one. This is because the emission of a star or planet is due to its radiation, which is absorbed and scattered by the surrounding matter.

A nebula is an interstellar cloud of dust and gas that is illuminated by a star. It is composed mainly of neutral hydrogen and may include traces of other elements that have been expelled from the stars in which it formed. The bright spots on the Sun’s photosphere are known as faculae.

An asteroid or comet is any solid, naturally occurring celestial object that is smaller than a planet. It is believed that such bodies were once part of larger celestial objects, and they are classified based on their orbital planes, masses and diameters. They are classified as meteoroids if they reach the Earth, and if they travel through the atmosphere before reaching the ground, as meteors.

A supernova is a massive star that explodes after exhausting its fuel and collapses into a black hole. This event releases enormous amounts of radiation, primarily electromagnetic, which can be detected by observatories on the Earth and in outer space. The theory is that such events are a precursor to the formation of a galaxy.