Astro Glossary

Impacts and Impact Craters

Inca Astronomy and Folklore

Inflation

The ultra-fast expansion of the universe in the instant before the Big Bang.

Infrared Astronomy

The study of infrared energy produced by astronomical objects. Infrared is a form of energy with a longer wavelength and lower frequency than visible light. It is produced by relatively cool objects, such as planetary systems and clouds of interstellar dust. Earth’s atmosphere absorbs most infrared energy, so it is best studied with telescopes in space or aboard high-altitude balloons or aircraft.

Interferometry

The technique of diagnosing the properties of two or more waves by studying the pattern of interference, which is the superposition of two or more waves that results in a new wave pattern. Astronomers use this technique to combine the signals from two or more telescopes to produce images that are much sharper than those obtained by a single telescope. The technique is most often applied to radio astronomy, in which up to 30 or more radio dishes are combined into a single array. Optical interferometers, which are more difficult to align and operate, are also becoming more common.

International Space Station

An orbiting outpost for scientific, medical, and engineering experiments. Construction began in 1998. The last American component of the station was delivered in 2011. Crews of three spend several months aboard the station, with two crews inhabiting the station simultaneously. International partners in the project include the United States, Russia, Europe, Canada, and Japan.

Interstellar Gas and Dust

The gas between stars is mostly hydrogen and helium scattered at varying densities between the stars in our galaxy and other galaxies. The proportions of the gases are similar to those in the Sun. Interstellar gas supplies the raw material for star formation. Carbon monoxide and hydroxyl molecules (CO and OH) have also been detected within interstellar gas, along with highly ionized oxygen, nitrogen, carbon and silicon, which are likely remnants of past supernovae. The dust is made up of tiny grains of carbon, iron, and iron-magnesium silicates scattered at varying densities between the stars in our galaxy and other galaxies.

Irregular Galaxies

Galaxies that have no easily discernible shape. Such galaxies are generally small, but are giving birth to new stars at a rapid pace. In the early universe, such galaxies served as the building blocks for larger galaxies, merging to form larger and larger agglomerations of stars.