APOD: Aurora Slathers Up the Sky (2021 Jan 14)

[APOD Robot]

Aurora Slathers Up the Sky

Explanation: Like salsa verde on your favorite burrito, a green aurora slathers up the sky in this 2017 June 25 snapshot from the International Space Station. About 400 kilometers (250 miles) above Earth, the orbiting station is itself within the upper realm of the auroral displays. Aurorae have the signature colors of excited molecules and atoms at the low densities found at extreme altitudes. Emission from atomic oxygen dominates this view. The tantalizing glow is green at lower altitudes, but rarer reddish bands extend above the space station's horizon. The orbital scene was captured while passing over a point south and east of Australia, with stars above the horizon at the right belonging to the constellation Canis Major, Orion's big dog. Sirius, alpha star of Canis Major, is the brightest star near the Earth's limb.

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[Sa Ji Tario]

To the left of Sirius is Mirzum on the horizon and above Sirius is Adhara. The reddish star above Sirius appears to be Messier 41

[E Fish]

I prefer fajitas myself.

That is an amazing picture, though. I've only ever seen the aurora once. To see them from above like that would be awesome.

[johnnydeep]

Aurora Slathers Up the Sky

Explanation: Like salsa verde on your favorite burrito, a green aurora slathers up the sky in this 2017 June 25 snapshot from the International Space Station. About 400 kilometers (250 miles) above Earth, the orbiting station is itself within the upper realm of the auroral displays. Aurorae have the signature colors of excited molecules and atoms at the low densities found at extreme altitudes. Emission from atomic oxygen dominates this view. The tantalizing glow is green at lower altitudes, but rarer reddish bands extend above the space station's horizon. The orbital scene was captured while passing over a point south and east of Australia, with stars above the horizon at the right belonging to the constellation Canis Major, Orion's big dog. Sirius, alpha star of Canis Major, is the brightest star near the Earth's limb.

As a "getting my bearings" exercise for myself and in the hope that it will help others, here's how this star view relates to a chart of Canis Major:

Aurora and Canis Major

[orin stepanek]

I can see the green aurora; and the red! I was wondering about the pink band that seems to outline it all! Is that a natural phenomena or is it privy to this particular aurora!
Anyway this aurora seems familiar! Wondering if is a repeat?

[neufer]

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<<Peaches and nectarines are the same species, the skin of nectarines lacks the fuzz (fruit-skin trichomes) that peach skin has; a mutation in a single gene (MYB25) is thought to be responsible for the difference between the two.

A common type of trichome is a hair. Plant hairs may be unicellular or multicellular, branched or unbranched. Multicellular hairs may have one or several layers of cells. Branched hairs can be dendritic (tree-like) as in kangaroo paw (Anigozanthos), tufted, or stellate (star-shaped), as in Arabidopsis thaliana.

The size, form, density and location of hairs on plants are extremely variable in their presence across species and even within a species on different plant organs. Several basic functions or advantages of having surface hairs can be listed. It is likely that in many cases, hairs interfere with the feeding of at least some small herbivores and, depending upon stiffness and irritability to the palate, large herbivores as well. Hairs on plants growing in areas subject to frost keep the frost away from the living surface cells. In windy locations, hairs break up the flow of air across the plant surface, reducing transpiration. Dense coatings of hairs reflect sunlight, protecting the more delicate tissues underneath in hot, dry, open habitats. In addition, in locations where much of the available moisture comes from fog drip, hairs appear to enhance this process by increasing the surface area on which water droplets can accumulate.>>

[XgeoX]

Interesting, I never knew that aurora bands could be two tone, oxygen on the bottom and nitrogen on top! Very Christmasy.
Being at 40 degrees I have only seen the display once but it was incredible. Instead of bands the whole northern sky just turned a deep blood red, I will never forget it!

Eric

[XgeoX]

aurora_iss052e007857.jpg


I can see the green aurora; and the red! I was wondering about the pink band that seems to outline it all! Is that a natural phenomena or is it privy to this particular aurora!
Anyway this aurora seems familiar! Wondering if is a repeat?

I am going to guess that since it’s following the horizon it’s the glow from the horizon shining through that is lightening the red to make it look pink. Also the airglow is densest at the horizon and it is green which could contribute...

Eric

[Lasse H]

There is a strange dark red band in the upper left part of the dark sky, and some other artifacts left and right of it.
What are they?

[DL MARTIN]

How accurate is it to describe a vehicle moving through Earth's atmosphere by essentially falling around the planet as a space station? That's equivalent to someone who jumps up being regarded as an astronaut.

[neufer]

How accurate is it to describe a vehicle moving through Earth's atmosphere by essentially falling around the planet as a space station? That's equivalent to someone who jumps up being regarded as an astronaut.

The interface between the Earth's surface and outer space. The Kármán line at an altitude of 100 km is shown. The layers of the atmosphere are drawn to scale, whereas objects within them, such as the International Space Station, are not.

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<<The thermosphere is the layer in the Earth's atmosphere directly above the mesosphere and below the exosphere. The thermosphere is completely uninhabited with the exception of the International Space Station. The International Space Station orbits the Earth within the middle of the thermosphere, between 408 and 410 kilometres. Within this layer of the atmosphere, ultraviolet radiation causes photoionization/photodissociation of molecules, creating ions; the thermosphere thus constitutes the larger part of the ionosphere. Taking its name from the Greek θερμός (pronounced thermos) meaning heat, the thermosphere begins at about 80 km above sea level. At these high altitudes, the residual atmospheric gases sort into strata according to molecular mass. Thermospheric temperatures increase with altitude due to absorption of highly energetic solar radiation. Temperatures are highly dependent on solar activity, and can rise to 1,700 °C or more. Radiation causes the atmosphere particles in this layer to become electrically charged particles, enabling radio waves to be refracted and thus be received beyond the horizon. In the exosphere, beginning at about 600 km above sea level, the atmosphere turns into space, although, by the judging criteria set for the definition of the Kármán line, the thermosphere itself is part of space.

The highly attenuated gas in this layer can reach 2,500 °C during the day. Despite the high temperature, an observer or object will experience cold temperatures in the thermosphere, because the extremely low density of the gas (practically a hard vacuum) is insufficient for the molecules to conduct heat. A normal thermometer will read significantly below 0 °C, at least at night, because the energy lost by thermal radiation would exceed the energy acquired from the atmospheric gas by direct contact. In the anacoustic zone above 160 kilometres, the density is so low that molecular interactions are too infrequent to permit the transmission of sound.

The dynamics of the thermosphere are dominated by atmospheric tides, which are driven predominantly by diurnal heating. Atmospheric waves dissipate above this level because of collisions between the neutral gas and the ionospheric plasma.>>

[johnnydeep]

How accurate is it to describe a vehicle moving through Earth's atmosphere by essentially falling around the planet as a space station? That's equivalent to someone who jumps up being regarded as an astronaut.

Accurate enough. The ISS is orbiting at 400 km. By legal convention, space starts at 100 km, or 62 miles. From https://www.thoughtco.com/where-does-sp ... in-3071112 :

Legal Space
For purposes of law and record-keeping, most experts consider space to begin at an altitude of 100 km (62 miles), the von Kármán line. It's named after Theodore von Kármán, an engineer and physicist who worked heavily in aeronautics and astronautics. He was the first to determine that the atmosphere at this level is too thin to support aeronautical flight.

There are some very straightforward reasons why such a division exists. It reflects an environment where rockets are able to fly. In very practical terms, engineers who design spacecraft need to make sure they can handle the rigors of space. Defining space in terms of atmospheric drag, temperature, and pressure (or lack of one in a vacuum) is important since vehicles and satellites have to be constructed to withstand extreme environments.

[johnnydeep]

There is a strange dark red band in the upper left part of the dark sky, and some other artifacts left and right of it.
What are they?

Parts of the International Space Station! The octagonal shapes at the top are probably solar panels, or maybe sun shields. Not sure what the black things on the left are.

[DL MARTIN]

Thanks for the info on what constitutes Space.