Airglow
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Airglow Layers.jpg
"Stretching from roughly 50 to 400 miles above the surface, this region, called the ionosphere, is an electrified layer of the upper atmosphere, generated by extreme ultraviolet radiation from the Sun. Understanding the ionosphere’s extreme variability is tricky because it requires detangling interactions between the different factors at play — interactions of which we don’t have a clear picture. That’s where airglow comes in. Airglow occurs when atoms and molecules in the upper atmosphere, excited by sunlight, emit light in order to shed their excess energy. The phenomenon is similar to auroras, but where auroras are driven by high-energy particles originating from the solar wind, airglow is sparked by day-to-day solar radiation.
"Stretching from roughly 50 to 400 miles above the surface, this region, called the ionosphere, is an electrified layer of the upper atmosphere, generated by extreme ultraviolet radiation from the Sun. Understanding the ionosphere’s extreme variability is tricky because it requires detangling interactions between the different factors at play — interactions of which we don’t have a clear picture. That’s where airglow comes in. Airglow occurs when atoms and molecules in the upper atmosphere, excited by sunlight, emit light in order to shed their excess energy. The phenomenon is similar to auroras, but where auroras are driven by high-energy particles originating from the solar wind, airglow is sparked by day-to-day solar radiation.
Airglow carries information on the upper atmosphere’s temperature, density, and composition, but it also helps us trace how particles move through the region itself. Vast, high-altitude winds sweep through the ionosphere, pushing its contents around the globe — and airglow’s subtle dance follows their lead, highlighting global patterns.
Credit: NASA's Goddard Space Flight Center/Mary Pat Hrybyk-Keith"
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Airglow timelapse from the ISS
Airglow timelapse from the ISS
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City lights and two separate atmospheric optical phenomena were captured in this 35mm camera's time exposure photograph from the Space Shuttle Endeavour. The thin greenish band stretching along the Earth's horizon is airglow; light emitted by the atmosphere from a layer about 30 kilometers thick and about 100 kilometers in altitude. The predominant emission in airglow is the green 5577 Angstrom wavelength light from atomic oxygen atoms. Airglow is always and everywhere present in the atmosphere; it results from the recombination of molecules that have been broken apart by solar radiation during the day. But airglow is so faint that it can only be seen at night by looking "edge on" at the emission layer, such as the view astronauts and cosmonauts have in orbit. The second phenomenon in the photo is the green color of the aurora borealis, or "northern lights". Bright patches of aurora are superimposed on the fainter airglow, and a band of aurora is also clearly visible in the far right side of the scene. Aurora occur from about 100 km to 300 km altitude only in the auroral zones at polar latitudes. The green color is also caused by the emission of 5577 Angstrom wavelength light from oxygen atoms that have been raised to a higher energy level (excited) by collisions with energetic electrons pouring down from the Earth's magnetosphere. The light is emitted when the atoms return to their original unexcited state. Astronauts often comment that their photography does not do justice to just how spectacular the view of the aurora is from space. The unidentified city lights are smeared because of the time exposure.
City lights and two separate atmospheric optical phenomena were captured in this 35mm camera's time exposure photograph from the Space Shuttle Endeavour. The thin greenish band stretching along the Earth's horizon is airglow; light emitted by the atmosphere from a layer about 30 kilometers thick and about 100 kilometers in altitude. The predominant emission in airglow is the green 5577 Angstrom wavelength light from atomic oxygen atoms. Airglow is always and everywhere present in the atmosphere; it results from the recombination of molecules that have been broken apart by solar radiation during the day. But airglow is so faint that it can only be seen at night by looking "edge on" at the emission layer, such as the view astronauts and cosmonauts have in orbit. The second phenomenon in the photo is the green color of the aurora borealis, or "northern lights". Bright patches of aurora are superimposed on the fainter airglow, and a band of aurora is also clearly visible in the far right side of the scene. Aurora occur from about 100 km to 300 km altitude only in the auroral zones at polar latitudes. The green color is also caused by the emission of 5577 Angstrom wavelength light from oxygen atoms that have been raised to a higher energy level (excited) by collisions with energetic electrons pouring down from the Earth's magnetosphere. The light is emitted when the atoms return to their original unexcited state. Astronauts often comment that their photography does not do justice to just how spectacular the view of the aurora is from space. The unidentified city lights are smeared because of the time exposure.
Airglow over La Silla’s Great Dane.jpg
Författare/Upphovsman: P. Horálek/ESO, Licens: CC BY 4.0
This week’s featured image highlights a handful of the telescopes residing at ESO’s La Silla Observatory in northern Chile. The star of the show, framed perfectly by the beautiful arch of the Milky Way, sits directly in the middle of the photograph — the Danish 1.54-metre telescope.
Författare/Upphovsman: P. Horálek/ESO, Licens: CC BY 4.0
This week’s featured image highlights a handful of the telescopes residing at ESO’s La Silla Observatory in northern Chile. The star of the show, framed perfectly by the beautiful arch of the Milky Way, sits directly in the middle of the photograph — the Danish 1.54-metre telescope.
Operational since 1979, this trusty telescope has helped astronomers to make all kinds of cosmic discoveries, from understanding more about violently merging neutron stars to detecting planets around other stars. It now performs follow-up observations of gamma-ray bursts, some of the most energetic events in the Universe.
This image, taken by ESO Photo Ambassador Petr Horálek, shows the heart of the Milky Way, both the Large and Small Magellanic Clouds, the constellations of Orion (The Hunter) and the Southern Cross, and the glare of distant settlements, all of which create vibrant bursts and flashes of colour across the frame. Towards the distant horizon, hues of red and green light up the sky — these colours are produced by a phenomenon called airglow.