APOD: The Space Station Crosses a Spotless Sun (2019 Jul 15)

[APOD Robot]

The Space Station Crosses a Spotless Sun

Explanation: That's no sunspot. It's the International Space Station (ISS) caught passing in front of the Sun. Sunspots, individually, have a dark central umbra, a lighter surrounding penumbra, and no solar panels. By contrast, the ISS is a complex and multi-spired mechanism, one of the largest and most sophisticated machines ever created by humanity. Also, sunspots occur on the Sun, whereas the ISS orbits the Earth. Transiting the Sun is not very unusual for the ISS, which orbits the Earth about every 90 minutes, but getting one's timing and equipment just right for a great image is rare. Strangely, besides that fake spot, in this recent two-image composite, the Sun lacked any real sunspots. The featured picture combines two images -- one capturing the space station transiting the Sun -- and another taken consecutively capturing details of the Sun's surface. Sunspots have been rare on the Sun since the dawn of the current Solar Minimum, a period of low solar activity. For reasons not yet fully understood, the number of sunspots occurring during both the previous and current solar minima have been unusually low.

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[starsurfer]

And this is the Ninth and Last Sign: You will hear of a dwelling-place in the heavens, above the earth, that shall fall with a great crash. It will appear as a blue star. Very soon after this, the ceremonies of my people will cease.

I wonder if this Hopi prophecy refers to the ISS?

[orin stepanek]

I am not upset with the solar minimum!

[neufer]

In Cyrano de Bergerac's (1619-1655) science-fiction novel _A Voyage to the Moon: with Some Account of the Solar World_, [the hero Dyrcona (an anagram of "cyrano D")] uses a flying machine in the form of an icosahedron to escape from prison in a tower and to land on a sunspot... an icosahedron with a unit length edge has a volume of 5φ⁵/6

• - p.70 _The Golden Ratio: The Story of PHI [φ], the World's Most Astonishing Number_ by Mario Livio

The speed of light is ~100,000 φ nautical miles per second;
(where φ is the Golden Ratio).

[Chris Peterson]

I am not upset with the solar minimum! :mrgreen:

I'm giving a talk tomorrow at our local library on the Sun. I'm setting up three telescopes. I don't think they're going to see any spots or any prominences. Just a white disc, a red disc, and a projected white disc. Oh well. By the time interesting stuff starts showing up again, most of these kids will be in high school.

[neufer]

I'm giving a talk tomorrow at our local library on the Sun.

• They have libraries on the Sun

misplaced modifier: a phrase or clause placed awkwardly in a sentence
so that it appears to modify or refer to an unintended word.

[TheZuke!]

That's no Space Station, that's a Tie Fighter!
"Quick! Chewie, jam its transmissions!"

[Chris Peterson]

I'm giving a talk tomorrow at our local library on the Sun.

• They have libraries on the Sun :?: :!:

misplaced modifier: a phrase or clause placed awkwardly in a sentence
so that it appears to modify or refer to an unintended word.

It's not misplaced. I live on the Sun, and that's where I'm giving the talk.

[NCTom]

I love APOD and its discussion page!

[neufer]

I'm giving a talk tomorrow at our local library on the Sun.

• They have libraries on the Sun

misplaced modifier: a phrase or clause placed awkwardly in a sentence
so that it appears to modify or refer to an unintended word.

It's not misplaced. I live on the Sun, and that's where I'm giving the talk.

The Colorado Sun
110 16th Street
Suite 1300
Denver, CO 80202

<<Colorado Sun is an online news outlet launched on September 10, 2018 to provide long-form in depth coverage of news from all around Colorado. Eight former employees of the Denver Post started Colorado Sun in response to multiple layoffs at the Denver Post after the Post's acquisition by the private equity firm Alden Global Capital. Colorado Sun is one of a few digital news organizations that are pioneering the use of a new platform for journalism called Civil. Civil is an Ethereum-based blockchain platform on which journalists can independently found and run newsrooms.

Of the fifth Platonic solid, the dodecahedron, Plato obscurely remarks, "...the god used [it] for arranging the constellations on the whole heaven". Aristotle added a fifth element, aithēr (aether in Latin, "ether" in English) and postulated that the heavens were made of this element.>>

[FLPhotoCatcher]

The photo of the sun looks like a (colored) negative. The sun should look darker around the edges.

[neufer]

---

The photo of the sun looks like a (colored) negative.

The sun should look darker around the edges.

The photosphere should, indeed,
look darker around the edges in the visible.

However, this resembles an image of the chromosphere in
the extreme ultraviolet (i.e., in the 304 angstrom He II line).

An active Sun photographed at 304 angstroms by the Atmospheric Imaging Assembly (AIA 304) of NASA's Solar Dynamics Observatory (SDO). This is a false-color image of the Sun observed in the extreme ultraviolet region of the spectrum.

[MarkBour]

Sunspots are a bit surprising to me. A sunspot is a region on the Sun that is cooler and is emitting less light in the visible part of the spectrum. And I believe (ala blackbody radiation), it is emitting less radiation throughout the spectrum.

Nevertheless, the more sunspot activity on the Sun, the greater the amount of radiation reaching the Earth. And so, a Solar minimum is associated with cooling on the Earth, a Solar maximum with warming. (The effect is not large ... even at the famous Maunder Minimum, only about 0.25% , an amount that is dwarfed by the amount of global warming that human activity is causing.)

https://en.wikipedia.org/wiki/Solar_cycle
TSI [Total Solar Irradiance] is higher at solar maximum, even though sunspots are darker (cooler) than the average photosphere. This is caused by magnetized structures other than sunspots during solar maxima, such as faculae and active elements of the "bright" network, that are brighter (hotter) than the average photosphere. They collectively overcompensate for the irradiance deficit associated with the cooler, but less numerous sunspots. The primary driver of TSI changes on solar rotational and sunspot cycle timescales is the varying photospheric coverage of these radiatively active solar magnetic structures.[citation needed]

[Donald Pelletier]

ISS looks like the Canadian flag on this picture!

[neufer]

Sunspots are a bit surprising to me. A sunspot is a region on the Sun that is cooler and is emitting less light in the visible part of the spectrum. And I believe (ala blackbody radiation), it is emitting less radiation throughout the spectrum. Nevertheless, the more sunspot activity on the Sun, the greater the amount of radiation reaching the Earth. And so, a Solar minimum is associated with cooling on the Earth, a Solar maximum with warming. (The effect is not large ... even at the famous Maunder Minimum, only about 0.25% , an amount that is dwarfed by the amount of global warming that human activity is causing.)

<<TSI [Total Solar Irradiance] is higher at solar maximum, even though sunspots are darker (cooler) than the average photosphere. This is caused by magnetized structures other than sunspots during solar maxima, such as faculae and active elements of the "bright" network, that are brighter (hotter) than the average photosphere. They collectively overcompensate for the irradiance deficit associated with the cooler, but less numerous sunspots. The primary driver of TSI changes on solar rotational and sunspot cycle timescales is the varying photospheric coverage of these radiatively active solar magnetic structures.>>

• TSI is higher at solar maximum ... but this isn't really observed at ground level (i.e., reaching the "earth").

---

This image, courtesy of Dr. Judith Lean at the US Naval Research Laboratory, shows the spectrum of solar radiation from 10 to 100,000 nm (dark blue), its variability betwen Solar Maximum and Solar Minimum (green) and the relative transparency of Earth's atmosphere at sea level (light blue). At wavelengths shorter than about 300 nm, there is a relatively large variation in the Sun's extreme UV and x-ray output (greater than 1%), but the Earth's atmosphere is nearly opaque at those wavelengths. For Earth-dwelling beach-goers there is no significant difference between Solar Max and solar minimum.

[Guest]

For about a minute I thought the sillouetted space station was a Canadian flag. Now how did that get there?

[MarkBour]

• TSI is higher at solar maximum ... but this isn't really observed at ground level (i.e., reaching the "earth").

That's okay. The energy must be absorbed by the atmosphere then, so there should be warming at solar max.

[neufer]

• TSI is higher at solar maximum ... but this isn't really observed at ground level (i.e., reaching the "earth").

That's okay. The energy must be absorbed by the atmosphere then, so there should be warming at solar max.

The energy would mostly be absorbed by stratospheric ozone resulting in a warmer (and dynamically modified) stratosphere.

[TheOtherBruce]

That's okay. The energy must be absorbed by the atmosphere then, so there should be warming at solar max.

The energy would mostly be absorbed by stratospheric ozone resulting in a warmer (and dynamically modified) stratosphere.

Isn't this the cause of the expansion of the upper atmosphere that took down Skylab? ISTR the proposed shuttle-launched rescue mission might have been tried if it hadn't happened. Although delays to the first launch didn't help.

[neufer]

The energy must be absorbed by the atmosphere then, so there should be warming at solar max.

The energy would mostly be absorbed by stratospheric ozone resulting in a warmer (and dynamically modified) stratosphere.

Isn't this the cause of the expansion of the upper atmosphere that took down Skylab? ISTR the proposed shuttle-launched rescue mission might have been tried if it hadn't happened. Although delays to the first launch didn't help.

Skylab view of the Sun

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Activity cycles 21, 22 and 23

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<<British mathematician Desmond King-Hele of the Royal Aircraft Establishment predicted in 1973 that Skylab would de-orbit and crash to Earth in 1979, sooner than NASA's forecast, because of increased solar activity. Greater-than-expected solar activity heated the outer layers of Earth's atmosphere and increased drag on Skylab. By late 1977, NORAD also forecast a reentry in mid-1979; a National Oceanic and Atmospheric Administration (NOAA) scientist criticized NASA for using an inaccurate model for the second most-intense sunspot cycle in a century, and for ignoring NOAA predictions published in 1976.

The reentry of the USSR's nuclear powered Cosmos 954 in January 1978, and the resulting radioactive debris fall in northern Canada, drew more attention to Skylab's orbit. Although Skylab did not contain radioactive materials, the State Department warned NASA about the potential diplomatic repercussions of station debris. Battelle Memorial Institute forecast that up to 25 tons of metal debris could land in 500 pieces over an area 4,000 miles long and 1,000 miles wide. The lead-lined film vault, for example, might land intact at 400 feet per second.

Although NASA worked on plans to reboost Skylab with the Space Shuttle through 1978 and the TRS was almost complete, the agency gave up in December when it became clear that the shuttle would not be ready in time; its first flight, STS-1, did not occur until April 1981. Also rejected were proposals to launch the TRS using one or two uncrewed rockets or to attempt to destroy the station with missiles.>>