APOD: A Plutonian Landscape (2021 Jan 15)

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APOD: A Plutonian Landscape (2021 Jan 15)

Post by APOD Robot » Fri Jan 15, 2021 5:08 am

Image A Plutonian Landscape

Explanation: This shadowy landscape of majestic mountains and icy plains stretches toward the horizon on a small, distant world. It was captured from a range of about 18,000 kilometers when New Horizons looked back toward Pluto, 15 minutes after the spacecraft's closest approach on July 14. The dramatic, low-angle, near-twilight scene follows rugged mountains formally known as Norgay Montes from foreground left, and Hillary Montes along the horizon, giving way to smooth Sputnik Planum at right. Layers of Pluto's tenuous atmosphere are also revealed in the backlit view. With a strangely familiar appearance, the frigid terrain likely includes ices of nitrogen and carbon monoxide with water-ice mountains rising up to 3,500 meters (11,000 feet). That's comparable in height to the majestic mountains of planet Earth. The Plutonian landscape is 380 kilometers (230 miles) across.

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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by Chris Peterson » Fri Jan 15, 2021 5:21 am

APOD Robot wrote:
Fri Jan 15, 2021 5:08 am
It was captured from a range of about 18,000 kilometers when New Horizons looked back toward Pluto, 15 minutes after the spacecraft's closest approach on July 14.
July 14, 2015.
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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by Alex515 » Fri Jan 15, 2021 8:30 am

A world shaped by sublimation and deposition. Incredible.

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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by madtom1999 » Fri Jan 15, 2021 9:35 am

When I first saw Sputnik Planum I thought 'Ooh that looks a lot like a meteorite crater. Those mountains to the left look like they were one of the debris lobes thrown out from the impact. Or it could have been some gaseous bulge that rose up and then collapsed as stuff leaked out the sides.
If it is an impact it needs to be a slow one - is it possible Pluto had a moon whose orbit slowly collapsed and then was further slowed by the atmosphere (possibly throwing off a large part of it) before splashing down to create this large puddle?

Adrian2021

Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by Adrian2021 » Fri Jan 15, 2021 11:22 am

It is amazing that we can get such a picture of Pluto! Astonishing feat!
Question though: was the light in the picture enhanced or is that the natural amount of light on Pluto?

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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by orin stepanek » Fri Jan 15, 2021 1:31 pm

Pluto-Mountains-Plains9-17-15_1024.jpg

Ahh! My little world! A little planet with a sky; sea; mountains; and full of mysteries! :D :mrgreen:
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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by bls0326 » Fri Jan 15, 2021 1:59 pm

3D Solar System view of the planets' orbits on July 14, 2015, looking down. Looks like Pluto is about as close to the Sun as it gets in its orbit. Summertime! Still long ways from the Sun.



SolarSystem_Pluto_20150714.jpg
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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by johnnydeep » Fri Jan 15, 2021 3:00 pm

APOD Robot wrote:
Fri Jan 15, 2021 5:08 am
Image A Plutonian Landscape

Explanation: This shadowy landscape of majestic mountains and icy plains stretches toward the horizon on a small, distant world. It was captured from a range of about 18,000 kilometers when New Horizons looked back toward Pluto, 15 minutes after the spacecraft's closest approach on July 14. The dramatic, low-angle, near-twilight scene follows rugged mountains formally known as Norgay Montes from foreground left, and Hillary Montes along the horizon, giving way to smooth Sputnik Planum at right. Layers of Pluto's tenuous atmosphere are also revealed in the backlit view. With a strangely familiar appearance, the frigid terrain likely includes ices of nitrogen and carbon monoxide with water-ice mountains rising up to 3,500 meters (11,000 feet). That's comparable in height to the majestic mountains of planet Earth. The Plutonian landscape is 380 kilometers (230 miles) across.
A truly awe-inspiring image. Note that this is a crop of a much larger wide field image shown at the "New Horizons looked back toward Pluto" link in the description, which somehow mutes the wow factor that I get from the cropped image.
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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by johnnydeep » Fri Jan 15, 2021 3:05 pm

madtom1999 wrote:
Fri Jan 15, 2021 9:35 am
When I first saw Sputnik Planum I thought 'Ooh that looks a lot like a meteorite crater. Those mountains to the left look like they were one of the debris lobes thrown out from the impact. Or it could have been some gaseous bulge that rose up and then collapsed as stuff leaked out the sides.
If it is an impact it needs to be a slow one - is it possible Pluto had a moon whose orbit slowly collapsed and then was further slowed by the atmosphere (possibly throwing off a large part of it) before splashing down to create this large puddle?
Sputnik Planum doesn't look much like the remnants of an impact crater to me, but I'm no expert. Do you still feel the same way after viewing the full image at New Horizons looked back toward Pluto?
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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by XgeoX » Fri Jan 15, 2021 3:10 pm

Adrian2021 wrote:
Fri Jan 15, 2021 11:22 am
It is amazing that we can get such a picture of Pluto! Astonishing feat!
Question though: was the light in the picture enhanced or is that the natural amount of light on Pluto?
If by “enhanced” you mean was it processed to give a rough (emphasis on “rough”) idea on what it would like to a human eye? Yes, the images in this mosaic which is the APOD were taken with exposures of 1/100 of a second. If you look at the unprocessed images they are quite dark but with skilled processing the image comes out beautifully. Regardless though with such a short exposure the area was pretty bright to begin with.

Just how bright? NASA has said...
The sun would be approximately 1,000 times dimmer than it is here on Earth.
Sounds pretty dark eh? Well have no fear as the full moon is 400,000 times dimmer!
So there is actually quite a bit of light to work with, at noon, the sunlight would be strong enough for you to read a book.
The Sun’s magnitude would be -18.7 even though when this photo was taken the Sun could still, barely, be able to be discerned as a disc by the naked eye. A diameter of 58.3 arc seconds to be precise, so you would need sharp eyesight to do it. As small as it is it would still be painful to look at.
At a magnitude of -18.7 you would get about 85 lux at noon, much more than enough to have full color vision as well!
A poster at StackExchange put that in perspective...
“ Might be worth pointing out how wide-ranging is the human perception of brightness: From 100 Klux in bright sunlight to ~1 lux for full Moon. That's five orders of magnitude. 85 Lux is plenty of light.”
So yeah the photo was enhanced but nothing drastic as NH had plenty of light to work with!

Eric

https://astronomy.stackexchange.com/que ... of-the-day

https://www.discovermagazine.com/the-sc ... from-pluto

https://en.wikipedia.org/wiki/Extraterr ... and_Charon

http://pluto.jhuapl.edu/soc/Pluto-Encou ... n&page=125

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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by XgeoX » Fri Jan 15, 2021 3:17 pm

“This image really makes you feel you are there, at Pluto, surveying the landscape for yourself,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute, Boulder, Colorado. “But this image is also a scientific bonanza, revealing new details about Pluto’s atmosphere, mountains, glaciers and plains.””

https://www.nasa.gov/feature/pluto-wows ... t-panorama

I got to meet Dr. Stern after he gave an incredible talk on the mission. Nothing beats seeing Pluto on an IMAX screen! Breathtaking!
He was a very nice, very intelligent and very interesting man.

Eric

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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by Chris Peterson » Fri Jan 15, 2021 3:29 pm

Adrian2021 wrote:
Fri Jan 15, 2021 11:22 am
It is amazing that we can get such a picture of Pluto! Astonishing feat!
Question though: was the light in the picture enhanced or is that the natural amount of light on Pluto?
Virtually every photograph, even of ordinary terrestrial things like flowers, is adjusted so that the brightest areas map to white and the darkest to black. Because that's what our eyes do naturally. We observe landscapes over several orders of magnitude different lighting conditions, and our brain normalizes the scene to that standard range. (The Moon, for instance, is the color of freshly laid black asphalt... but we certainly don't see it that way.)

The light at Pluto is much dimmer than at Earth, of course. But if you were there, your eyes would adjust to that low light, and you'd see the scene in a similar way to what this image shows, despite the fact that the actual light level is similar to early twilight or to a very deeply overcast day on Earth.
Chris

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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by orin stepanek » Fri Jan 15, 2021 3:40 pm

XgeoX wrote:
Fri Jan 15, 2021 3:10 pm
Adrian2021 wrote:
Fri Jan 15, 2021 11:22 am
It is amazing that we can get such a picture of Pluto! Astonishing feat!
Question though: was the light in the picture enhanced or is that the natural amount of light on Pluto?
If by “enhanced” you mean was it processed to give a rough (emphasis on “rough”) idea on what it would like to a human eye? Yes, the images in this mosaic which is the APOD were taken with exposures of 1/100 of a second. If you look at the unprocessed images they are quite dark but with skilled processing the image comes out beautifully. Regardless though with such a short exposure the area was pretty bright to begin with.

Just how bright? NASA has said...
The sun would be approximately 1,000 times dimmer than it is here on Earth.
Sounds pretty dark eh? Well have no fear as the full moon is 400,000 times dimmer!
So there is actually quite a bit of light to work with, at noon, the sunlight would be strong enough for you to read a book.
The Sun’s magnitude would be -18.7 even though when this photo was taken the Sun could still, barely, be able to be discerned as a disc by the naked eye. A diameter of 58.3 arc seconds to be precise, so you would need sharp eyesight to do it. As small as it is it would still be painful to look at.
At a magnitude of -18.7 you would get about 85 lux at noon, much more than enough to have full color vision as well!
A poster at StackExchange put that in perspective...
“ Might be worth pointing out how wide-ranging is the human perception of brightness: From 100 Klux in bright sunlight to ~1 lux for full Moon. That's five orders of magnitude. 85 Lux is plenty of light.”
So yeah the photo was enhanced but nothing drastic as NH had plenty of light to work with!

Eric

https://astronomy.stackexchange.com/que ... of-the-day

https://www.discovermagazine.com/the-sc ... from-pluto

https://en.wikipedia.org/wiki/Extraterr ... and_Charon

http://pluto.jhuapl.edu/soc/Pluto-Encou ... n&page=125

Thanks Eric ! I liked your post! 8-)
Orin

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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by neufer » Fri Jan 15, 2021 3:53 pm

https://www.youtube.com/watch?v=skzxLaYkiGQ
Alex515 wrote:
Fri Jan 15, 2021 8:30 am

A world shaped by sublimation and deposition. Incredible.
  • Just sublimation and deposition :?:
https://en.wikipedia.org/wiki/Pluto#Surface wrote: <<The plains on Pluto's surface are composed of more than 98 percent nitrogen ice, with traces of methane and carbon monoxide. Nitrogen and carbon monoxide are most abundant on the anti-Charon face of Pluto (around 180° longitude, where Tombaugh Regio's western lobe, Sputnik Planitia, is located), whereas methane is most abundant near 300° east. The mountains are made of water ice. Pluto's surface is quite varied, with large differences in both brightness and color. Pluto is one of the most contrastive bodies in the Solar System, with as much contrast as Saturn's moon Iapetus. The color varies from charcoal black, to dark orange and white. Pluto's color is more similar to that of Io with slightly more orange and significantly less red than Mars. Notable geographical features include Tombaugh Regio, or the "Heart" (a large bright area on the side opposite Charon), Cthulhu Macula, or the "Whale" (a large dark area on the trailing hemisphere), and the "Brass Knuckles" (a series of equatorial dark areas on the leading hemisphere).

Sputnik Planitia, the western lobe of the "Heart", is a 1,000 km-wide basin of frozen nitrogen and carbon monoxide ices, divided into polygonal cells, which are interpreted as convection cells that carry floating blocks of water ice crust and sublimation pits towards their margins; there are obvious signs of glacial flows both into and out of the basin. It has no craters that were visible to New Horizons, indicating that its surface is less than 10 million years old. Latest studies have shown that the surface has an age of 180000 years. The New Horizons science team summarized initial findings as "Pluto displays a surprisingly wide variety of geological landforms, including those resulting from glaciological and surface–atmosphere interactions as well as impact, tectonic, possible cryovolcanic, and mass-wasting processes."

In Western parts of Sputnik Planitia there are fields of transverse dunes formed by the winds blowing from the center of Sputnik Planitia in the direction of surrounding mountains. The dune wavelengths are in the range of 0.4–1 km and they are likely consists of methane particles 200–300 μm in size.>>
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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by johnnydeep » Fri Jan 15, 2021 4:38 pm

Chris Peterson wrote:
Fri Jan 15, 2021 3:29 pm
Adrian2021 wrote:
Fri Jan 15, 2021 11:22 am
It is amazing that we can get such a picture of Pluto! Astonishing feat!
Question though: was the light in the picture enhanced or is that the natural amount of light on Pluto?
Virtually every photograph, even of ordinary terrestrial things like flowers, is adjusted so that the brightest areas map to white and the darkest to black. Because that's what our eyes do naturally. We observe landscapes over several orders of magnitude different lighting conditions, and our brain normalizes the scene to that standard range. (The Moon, for instance, is the color of freshly laid black asphalt... but we certainly don't see it that way.)

The light at Pluto is much dimmer than at Earth, of course. But if you were there, your eyes would adjust to that low light, and you'd see the scene in a similar way to what this image shows, despite the fact that the actual light level is similar to early twilight or to a very deeply overcast day on Earth.
Whoa there! So, are you saying that if the moon were entirely paved over with a layer of freshly laid black asphalt, a full moon would look as bright to us as it currently does? If so, that might be the most surprising thing I've heard about space in a long long time! But, since the maria and non-maria areas appear to have different brightnesses, which is it that would have the same brightness as black ashpalt?
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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by Chris Peterson » Fri Jan 15, 2021 5:00 pm

johnnydeep wrote:
Fri Jan 15, 2021 4:38 pm
Chris Peterson wrote:
Fri Jan 15, 2021 3:29 pm
Adrian2021 wrote:
Fri Jan 15, 2021 11:22 am
It is amazing that we can get such a picture of Pluto! Astonishing feat!
Question though: was the light in the picture enhanced or is that the natural amount of light on Pluto?
Virtually every photograph, even of ordinary terrestrial things like flowers, is adjusted so that the brightest areas map to white and the darkest to black. Because that's what our eyes do naturally. We observe landscapes over several orders of magnitude different lighting conditions, and our brain normalizes the scene to that standard range. (The Moon, for instance, is the color of freshly laid black asphalt... but we certainly don't see it that way.)

The light at Pluto is much dimmer than at Earth, of course. But if you were there, your eyes would adjust to that low light, and you'd see the scene in a similar way to what this image shows, despite the fact that the actual light level is similar to early twilight or to a very deeply overcast day on Earth.
Whoa there! So, are you saying that if the moon were entirely paved over with a layer of freshly laid black asphalt, a full moon would look as bright to us as it currently does? If so, that might be the most surprising thing I've heard about space in a long long time! But, since the maria and non-maria areas appear to have different brightnesses, which is it that would have the same brightness as black ashpalt?
Yup. The average albedo of the Moon is 15%, the same as fresh asphalt. (Of course, that's just the average; there is some variation, which is why we see features.) If we actually paved over the entire Moon, it would appear to us in the sky at night as a featureless white circle.
Chris

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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by heehaw » Fri Jan 15, 2021 6:35 pm

In the far ultraviolet (~1500 Å) the seas are brighter than the mountains, the opposite to what we see in the visible: it's like looking at a negative. (My colleagues and I discovered this with our UV spectrometer on the Apollo 17 orbiter).

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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by neufer » Fri Jan 15, 2021 7:13 pm

Chris Peterson wrote:
Fri Jan 15, 2021 5:00 pm
johnnydeep wrote:
Fri Jan 15, 2021 4:38 pm
Chris Peterson wrote:
Fri Jan 15, 2021 3:29 pm

Virtually every photograph, even of ordinary terrestrial things like flowers, is adjusted so that the brightest areas map to white and the darkest to black. Because that's what our eyes do naturally. We observe landscapes over several orders of magnitude different lighting conditions, and our brain normalizes the scene to that standard range. (The Moon, for instance, is the color of freshly laid black asphalt... but we certainly don't see it that way.)
Whoa there! So, are you saying that if the moon were entirely paved over with a layer of freshly laid black asphalt, a full moon would look as bright to us as it currently does? If so, that might be the most surprising thing I've heard about space in a long long time! But, since the maria and non-maria areas appear to have different brightnesses, which is it that would have the same brightness as black ashpalt?
Yup. The average albedo of the Moon is 15%, the same as fresh asphalt. (Of course, that's just the average; there is some variation, which is why we see features.) If we actually paved over the entire Moon, it would appear to us in the sky at night as a featureless white circle.
  • Paving over the entire Moon was scheduled to be part of Trump's 2021 Infrastructure Week :!:
https://en.wikipedia.org/wiki/Pitch_drop_experiment wrote:
<<Asphalt, also known as bitumen, is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used. The word is derived from the Ancient Greek ἄσφαλτος ásphaltos. The largest natural deposit of asphalt in the world, estimated to contain 10 million tons, is the Pitch Lake located in La Brea in southwest Trinidad, within the Siparia Regional Corporation.

A pitch drop experiment is a long-term experiment which measures the flow of a piece of pitch over many years. 'Pitch' is the name for any of a number of highly viscous liquids which appear solid, most commonly bitumen. At room temperature, tar pitch flows at a very low rate, taking several years to form a single drop.

The best known version of the experiment was started in 1927 by Professor Thomas Parnell of the University of Queensland in Brisbane, Australia, to demonstrate to students that some substances which appear solid are actually highly viscous fluids. Parnell poured a heated sample of pitch into a sealed funnel and allowed it to settle for three years. In 1930, the seal at the neck of the funnel was cut, allowing the pitch to start flowing. A glass dome covers the funnel and it is placed on display outside a lecture theatre. Large droplets form and fall over a period of about a decade. The eighth drop fell on 28 November 2000, allowing experimenters to calculate the pitch as having a viscosity of approximately 2.3×1011 times that of water.

Code: Select all

Substance 	Viscosity (mPa·s)
..........................................
Benzene 	0.604
Water	 	1.000
Mercury 	1.526
Whole milk 	2.12
Dark beer 	2.53
Olive oil 	56.2
Honey	 	2,000–10,000
Ketchup 	5,000–20,000
Peanut butter	10,000–1,000,000
This experiment is recorded in Guinness World Records as the 'world's longest continuously running laboratory experiment', and it is expected there is enough pitch in the funnel to allow it to continue for at least another hundred years. This experiment is predated by two other (still-active) scientific devices; the Oxford Electric Bell (1840) and the Beverly Clock (1864), but each of these has experienced brief interruptions since 1937.

The experiment was not originally carried out under any special controlled atmospheric conditions, meaning the viscosity could vary throughout the year with fluctuations in temperature. Some time after the seventh drop fell (1988), air conditioning was added to the location where the experiment takes place. The lower average temperature has lengthened each drop's stretch before it separates from the rest of the pitch in the funnel.

In October 2005, John Mainstone and the late Thomas Parnell were awarded the Ig Nobel Prize in physics for the pitch drop experiment. Professor Mainstone subsequently commented: I am sure that Thomas Parnell would have been flattered to know that Mark Henderson considers him worthy to become a recipient of an Ig Nobel prize. Professor Parnell's award citation would of course have to applaud the new record he had thereby established for the longest lead-time between performance of a seminal scientific experiment and the conferral of such an award, be it a Nobel or an Ig Nobel prize.

The experiment is monitored by a webcam but technical problems prevented the November 2000 drop from being recorded. The pitch drop experiment is on public display on Level 2 of Parnell building in the School of mathematics and physics at the St Lucia campus of the University of Queensland. Hundreds of thousands of Internet users check the live stream each year.

The ninth drop touched the eighth drop on 17 April 2014. However, it was still attached to the funnel. On 24 April 2014, Professor White decided to replace the beaker holding the previous eight drops before the ninth drop fused to them. While the bell jar was being lifted, the wooden base wobbled and the ninth drop snapped away from the funnel.>>
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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by neufer » Fri Jan 15, 2021 8:32 pm

heehaw wrote:
Fri Jan 15, 2021 6:35 pm

In the far ultraviolet (~1500 Å) the seas are brighter than the mountains, the opposite to what we see in the visible: it's like looking at a negative. (My colleagues and I discovered this with our UV spectrometer on the Apollo 17 orbiter).
  • Do you have a reference :?:
https://iopscience.iop.org/article/10.1086/309771/fulltext/ wrote:
THE ASTROPHYSICAL JOURNAL, 454:L69–L72, 1995 November 20
© 1995. The American Astronomical Society. All rights reserved. Printed in U.S.A.
Ultraviolet Albedo of the Moon with the Hopkins Ultraviolet Telescope
Richard C. Henry, 1 Paul D. Feldman, Jeffrey W. Kruk, Arthur F. Davidsen, and Samuel T. Durrance 2

Center for Astrophysical Sciences, Department of Physics and Astronomy, Johns Hopkins University, Charles and 34th Streets, Baltimore, MD 21218-2695
Received 1995 July 24; accepted 1995 September 7

ABSTRACT: During the 1995 March flight of the Hopkins Ultraviolet Telescope, as part of the Astro-2 Space Shuttle mission, we observed the Moon over the wavelength range 820–1840 Å, with a resolution of 3–4 Å. The FUV albedo of the Moon has been measured over the spectral range 1250–1800 Å, and an albedo of 0.038 ± 0.0038 at 1700 Å obtained, with the albedo showing a gentle increase to shorter wavelengths that is in qualitative accord with previous measurements of both lunar fines and the Moon itself. The FUV albedo shows no evidence of an opposition effect. The present measurement is probably the most accurate yet made and is at a level of accuracy such that our result is dominated by place-to-place variations in lunar albedo rather than by measurement errors.
https://www.universetoday.com/117625/moonlight-is-a-many-splendored-thing/ wrote:
Moonlight Is a Many-Splendored Thing
Posted on December 31, 2014 by Bob King

(Near?) Ultraviolet Imaging Telescope on the Space Shuttle Endeavour in March 1995.: Similar to the view in visible light but with a lower resolution. The brightest areas probably correspond to regions where the most recent resurfacing due to impacts has occurred. Once again, the bright rayed crater Tycho stands out in this regard. The photo was made with the Ultraviolet Imaging Telescope flown aboard the Space Shuttle Endeavour in March 1995.

..........................................................

Visible light: The iron-rich composition of the lavas that formed the lunar “seas” give them a darker color compared to the ancient lunar highlands, which are composed mostly of a lighter volcanic rock called anorthosite.
https://archive.stsci.edu/uit/project/Astro2/Astro2_pictures.html wrote: :arrow: <<A Photo of the full Moon at ultraviolet (UV) wavelengths (only observable from space) on the left is compared with a visible photograph (from a ground-based observatory) on the right. The brightest UV areas probably correspond with regions where the most recent resurfacing has occurred---such as in the vicinity of the bright-rayed impact crater Tycho near the lunar south pole. This UV photograph was made with the Ultraviolet Imaging Telescope (built by Ted Stecher and colleagues at NASA's Goddard Space Flight Center in Greenbelt, Maryland), part of the Astro-2 payload flown aboard the Space Shuttle Endeavour in March, 1995. This material was presented to the American Astronomical Society meeting in Pittsburgh, Pennsylvania on June 12, 1995.>>
Art Neuendorffer

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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by Ann » Fri Jan 15, 2021 9:33 pm

The APOD is a great picture. The mighty ice structure at right looks like the remnant of a semi-liquid, molten lava stream that inexorably flowed across the Plutopian(?) landscape until it froze "in its tracks" and came to a sudden stop.

Magnificent.

Ann
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heehaw

Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by heehaw » Fri Jan 15, 2021 11:09 pm

neufer wrote:
Fri Jan 15, 2021 8:32 pm
heehaw wrote:
Fri Jan 15, 2021 6:35 pm

In the far ultraviolet (~1500 Å) the seas are brighter than the mountains, the opposite to what we see in the visible: it's like looking at a negative. (My colleagues and I discovered this with our UV spectrometer on the Apollo 17 orbiter).
  • Do you have a reference :?:
https://www.researchgate.net/publicatio ... _Telescope

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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by Cousin Ricky » Sat Jan 16, 2021 3:57 am

johnnydeep wrote:
Fri Jan 15, 2021 4:38 pm
Whoa there! So, are you saying that if the moon were entirely paved over with a layer of freshly laid black asphalt, a full moon would look as bright to us as it currently does? If so, that might be the most surprising thing I've heard about space in a long long time! But, since the maria and non-maria areas appear to have different brightnesses, which is it that would have the same brightness as black ashpalt?
Ever look at black asphalt in bright sunlight immediately after walking out of a dark building?

At nighttime, the Moon (and planets, if any) are the only objects in direct sunlight, while your eyes are adjusted to seeing things in the dark.

During the daytime, the Moon looks a little brighter than asphalt, because only the lighter lunar highlands are visible through the atmosphere.

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XgeoX
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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by XgeoX » Sat Jan 16, 2021 12:12 pm

orin stepanek wrote:
Fri Jan 15, 2021 3:40 pm
XgeoX wrote:
Fri Jan 15, 2021 3:10 pm
Adrian2021 wrote:
Fri Jan 15, 2021 11:22 am
It is amazing that we can get such a picture of Pluto! Astonishing feat!
Question though: was the light in the picture enhanced or is that the natural amount of light on Pluto?
If by “enhanced” you mean was it processed to give a rough (emphasis on “rough”) idea on what it would like to a human eye? Yes, the images in this mosaic which is the APOD were taken with exposures of 1/100 of a second. If you look at the unprocessed images they are quite dark but with skilled processing the image comes out beautifully. Regardless though with such a short exposure the area was pretty bright to begin with.

Just how bright? NASA has said...
The sun would be approximately 1,000 times dimmer than it is here on Earth.
Sounds pretty dark eh? Well have no fear as the full moon is 400,000 times dimmer!
So there is actually quite a bit of light to work with, at noon, the sunlight would be strong enough for you to read a book.
The Sun’s magnitude would be -18.7 even though when this photo was taken the Sun could still, barely, be able to be discerned as a disc by the naked eye. A diameter of 58.3 arc seconds to be precise, so you would need sharp eyesight to do it. As small as it is it would still be painful to look at.
At a magnitude of -18.7 you would get about 85 lux at noon, much more than enough to have full color vision as well!
A poster at StackExchange put that in perspective...
“ Might be worth pointing out how wide-ranging is the human perception of brightness: From 100 Klux in bright sunlight to ~1 lux for full Moon. That's five orders of magnitude. 85 Lux is plenty of light.”
So yeah the photo was enhanced but nothing drastic as NH had plenty of light to work with!

Eric

https://astronomy.stackexchange.com/que ... of-the-day

https://www.discovermagazine.com/the-sc ... from-pluto

https://en.wikipedia.org/wiki/Extraterr ... and_Charon

http://pluto.jhuapl.edu/soc/Pluto-Encou ... n&page=125

Thanks Eric ! I liked your post! 8-)
You’re very welcome!

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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by johnnydeep » Sat Jan 16, 2021 3:10 pm

Cousin Ricky wrote:
Sat Jan 16, 2021 3:57 am
johnnydeep wrote:
Fri Jan 15, 2021 4:38 pm
Whoa there! So, are you saying that if the moon were entirely paved over with a layer of freshly laid black asphalt, a full moon would look as bright to us as it currently does? If so, that might be the most surprising thing I've heard about space in a long long time! But, since the maria and non-maria areas appear to have different brightnesses, which is it that would have the same brightness as black ashpalt?
Ever look at black asphalt in bright sunlight immediately after walking out of a dark building?

At nighttime, the Moon (and planets, if any) are the only objects in direct sunlight, while your eyes are adjusted to seeing things in the dark.

During the daytime, the Moon looks a little brighter than asphalt, because only the lighter lunar highlands are visible through the atmosphere.
Oh boy, I'm still finding this "the moon is a dark as asphalt" fact very hard to fathom, now even more so after you mentioning the moon in daytime. Here's a typical(?) picture of how I remember the moon appearing in daylight, in a blue sky:
The light areas on the moon sure look lighter than what I would think asphalt would look like in the moon's place. The dark areas look about the same as the blue sky, but sill brighter than asphalt. I suppose it must be a type of optical illusion.
"To Boldly Go......Beyond The Fields We Know."

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Chris Peterson
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Re: APOD: A Plutonian Landscape (2021 Jan 15)

Post by Chris Peterson » Sat Jan 16, 2021 3:16 pm

johnnydeep wrote:
Sat Jan 16, 2021 3:10 pm
Cousin Ricky wrote:
Sat Jan 16, 2021 3:57 am
johnnydeep wrote:
Fri Jan 15, 2021 4:38 pm
Whoa there! So, are you saying that if the moon were entirely paved over with a layer of freshly laid black asphalt, a full moon would look as bright to us as it currently does? If so, that might be the most surprising thing I've heard about space in a long long time! But, since the maria and non-maria areas appear to have different brightnesses, which is it that would have the same brightness as black ashpalt?
Ever look at black asphalt in bright sunlight immediately after walking out of a dark building?

At nighttime, the Moon (and planets, if any) are the only objects in direct sunlight, while your eyes are adjusted to seeing things in the dark.

During the daytime, the Moon looks a little brighter than asphalt, because only the lighter lunar highlands are visible through the atmosphere.
Oh boy, I'm still finding this "the moon is a dark as asphalt" fact very hard to fathom, now even more so after you mentioning the moon in daytime. Here's a typical(?) picture of how I remember the moon appearing in daylight, in a blue sky:
The light areas on the moon sure look lighter than what I would think asphalt would look like in the moon's place. The dark areas look about the same as the blue sky, but sill brighter than asphalt. I suppose it must be a type of optical illusion.
You need to be very cautious comparing a photograph to what your eye sees. Again, photos are normalized to span the range from black to white, i.e. from the minimum to the maximum value that a pixel can have. Your eyes/brain dynamically process a very wide dynamic range and build a perceptual image that is not accurately representative of actual intensities.
Chris

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