Glossary term: Infrared Astronomy

Description: Infrared astronomy is a branch of astronomy that looks at infrared light. It is more sensitive to cool objects than observations in visible light and can observe very distant galaxies whose light has been redshifted a lot. Infrared observations are less affected by extinction and can thus see deeper into interstellar clouds of gas and dust.

Molecules in Earth's atmosphere absorb much of the infrared light coming from space and thus infrared astronomy on the ground is done mostly in wavelength ranges where this absorption is lower. Both Earth and its atmosphere radiate in the infrared so special techniques are required to remove this background radiation. For infrared radiation with longer wavelengths, this background plus atmospheric absorption makes observing on the ground almost impossible. As a result many infrared observations are carried out using space telescopes. However, for the longest infrared wavelengths ground-based observations are possible from very dry sites. This is typically called submillimeter astronomy.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

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The silver-coloured Hubble Space Telescope with the blue ocean and white clouds of the Earth visible underneath.

Hubble Space Telescope over Earth

Caption: The NASA/ESA Hubble Space Telescope orbiting Earth. This picture was taken by astronauts on board the space shuttle Columbia, right after the Servicing Mission 3B to the space telescope itself. The telescope has an opening that allows light in (seen here on the left). The light travels through the telescope optics to the cameras and spectrographs located in the bulge at the other end of the observatory (seen here on the right). Data from these instruments is then sent back to Earth using an antenna. The black rectangles on either side of the observatory are the solar panels that provide it with power.
Credit: NASA/ESA credit link

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons

Keck Telescopes

Caption: The two Keck telescopes on Mauna Kea on the island of Hawai`i. These two telescopes are reflecting telescopes with primary mirrors 10m across.
Credit: NASA/JPL credit link

License: PD Public Domain icons

The left image has finger-shaped clouds with bright edges. In the right image we see stars shining through those clouds

The Pillars of Creation in comparison

Caption: The 'Pillars of Creation' are a renowned astronomical feature situated within the Eagle Nebula in the Serpens constellation. The illustration provides a direct comparison between images captured by the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST), showcasing the pillars, which span several light years in diameter, in both visible light (also known as optical light) and infrared light. On the left are the pillars as seen by Hubble in visual light, taken in 2014. It displays dark pillars against an opaque background, with only a handful of visible stars. Conversely, the counterpart on the right is Webb’s near-infrared view published in 2022, penetrating the dust and revealing numerous stars of varying sizes. Their distance from Earth is approximately 6,500 to 7,000 light years. Within these pillars, new stars are constantly forming, making them a subject of extensive study by astronomers. Composed mostly of cool molecular hydrogen and small amounts of interstellar dust, they are subject to erosion by the intense ultraviolet radiation emitted by nearby massive and newborn stars, a process known as photoevaporation.
Credit: NASA, ESA, CSA, STScI credit link

License: CC-BY-2.0 Creative Commons Attribution 2.0 Generic icons

A red patch mass of gas with a few dark bubbles with lighter edges and several lighter colored clusters and filaments

Herschel’s view of new stars and molecular clouds

Caption: This image shows the Westerhout 3, 4 and 5 star formation regions. This area has huge amounts of gas and dust. This gas and dust hides the physical processes going on in this region from studies using visible light. This image was taken in infrared light by the Herschel Space Observatory. This infrared light allowed Herschel to see deep into these star forming regions. In Westerhout 3, 4 and 5, huge, cold clouds of molecular hydrogen have collapsed into dense knots and filaments. Within these new structures the gas is dense and cold enough for it to collapse and form stars. These new stars give off powerful winds of charged particles, like stronger versions of the solar wind our sun gives off. These winds have combined to blow massive bubbles in the surrounding gas and dust. These are visible as the large darker voids in the image.
Credit: ESA/Herschel/NASA/JPL-Caltech; acknowledgement: R. Hurt (JPL-Caltech) credit link

License: CC-BY-3.0-IGO Creative Commons Attribution 3.0 IGO icons

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