APOD: Pluto at Night (2024 Nov 16)

[APOD Robot]

Pluto at Night

Explanation: The night side of Pluto spans this shadowy scene. In the stunning spacebased perspective the Sun is 4.9 billion kilometers (almost 4.5 light-hours) behind the dim and distant world. It was captured by far flung New Horizons in July of 2015 when the spacecraft was at a range of some 21,000 kilometers from Pluto, about 19 minutes after its closest approach. A denizen of the Kuiper Belt in dramatic silhouette, the image also reveals Pluto's tenuous, surprisingly complex layers of hazy atmosphere. Near the top of the frame the crescent twilight landscape includes southern areas of nitrogen ice plains now formally known as Sputnik Planitia and rugged mountains of water-ice in the Norgay Montes.

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[RocketRon]

Pluto -
'Discovered' (by Earthlings) in 1930
Imaged from the far side in 2015.
Technology has come a very long way in those intervening years....

Nitrogen freezing point −210 °C (−346 °F; 63 K)
Brrrrr !!!
Ski fields only for the very well rugged up.
And prepared to travel.

Interesting atmosphere.
And that it is visible in such an image ?

[Ann]

The great thing about today's APOD is that it actually shows us some surface details on Pluto below the little planet's layered atmosphere.

Pluto at Night. Image Credit: NASA, Johns Hopkins Univ./APL, Southwest Research Institute

---

A gorgeous high-resolution image really shows surface details of Pluto below the hazy atmosphere, including Sputnik Planitia, the large light-colored "heart" of Pluto:

Haze with multiple layers in the atmosphere of Pluto. Part of the plain Sputnik Planitia with nearby mountains is seen below. Photo by New Horizons, taken 15 min after the closest approach to Pluto. Credit: NASA/JHUAPL/SwRI

---

Doesn't it look amazing?

Talking of Pluto's Sputnik Planitia, we've really got to look at the day side of Pluto, to see its huge nitrogen flood plain heart!

Enhanced color view of Pluto. Lightly peach-colored Sputnik Planitia is front and center. Credit: NASA/JHUAPL/SwRI

---

But since I am the Color Commentator - or, more precisely, since I call myself the Color Commentator - I feel compelled to show you that Pluto's atmosphere is blue!

The blue bands of Pluto's atmospheric haze, captured in high resolution by New Horizons' Long Range Reconnaissance Imager (LORRI), with additional data from the Ralph/Multispectral Visible Imaging Camera (MVIC). (Image credit: NASA/JHUAPL/SwRI)

---

Pluto's blue sky: Pluto’s haze layer shows its blue color in this picture taken by the New Horizons Ralph/Multispectral Visible Imaging Camera (MVIC). The high-altitude haze is thought to be similar in nature to that seen at Saturn’s moon Titan. This image was generated by software that combines information from blue, red and near-infrared images to replicate the color a human eye would perceive as closely as possible. Credit: NASA/JHUAPL/SwRI

---

Since Wikipedia compared the atmosphere of Pluto with the upper haze layer of Titan, let's look at the atmosphere of Titan:

This natural color image shows Titan's upper atmosphere -- an active place where methane molecules are being broken apart by solar ultraviolet light and the byproducts combine to form compounds like ethane and acetylene. The haze preferentially scatters blue and ultraviolet wavelengths of light, making its complex layered structure more easily visible at the shorter wavelengths used in this image. A movie sequence of images, taken around the same time as this color view, shows movement of the haze layers over the course of a few hours (see PIA06223). Lower down in the atmosphere, the haze turns into a globe-enshrouding smog of complex organic molecules. This thick, orange-colored haze absorbs visible sunlight, allowing only perhaps 10 percent of the light to reach the surface. The thick haze is also inefficient at holding in and then re-radiating infrared (thermal) energy back down to the surface. Thus, despite the fact that Titan has a thicker atmosphere than Earth, the thick global haze causes the greenhouse effect there to be somewhat weaker than it is on Earth.

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Titan is, of course, the largest moon of Saturn. Titan is surprisingly dark compared with the haze-covered yellow cloudtops of Saturn. Titan's blue haze layers are invisible when the moon is seen in front of the face of Saturn. But we do see hints of a blue haze layer on Saturn:

Larger than the planet Mercury, Huge moon Titan is seen here as it orbits Saturn. Below Titan are the shadows cast by Saturn’s rings. This natural color view was created by combining six images captured by NASA’s Cassini spacecraft on May 6, 2012. Credits: NASA/JPL-Caltech/Space Science Institute

---

But since the APOD is about Pluto, not about Titan or Saturn, let's look at a picture of Pluto and its (comparatively) huge moon, Charon, to appreciate the brightness or rather reflectivity (albedo) difference between them!

A composite of enhanced color images of Charon (upper left) and Pluto (lower right), taken by NASA's New Horizons spacecraft on its 2015 flyby. (Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

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I note that one thing the the Earth, Pluto and Titan have in common is that our atmospheres are mostly composed of nitrogen. All in all, I'm happy that I get to breathe the atmosphere of the Earth rather than the atmosphere of Pluto or Titan!

Clouds and blue layers of the atmosphere of the Earth. Credit: I don't know.

---

Ann

P.S. I've got to show you this!

NASA astronaut Matthew Dominick photographs a crescent moon over so-called noctilucent clouds from the International Space Station on July 4, 2024. Credit: Matthew Dominick / Earth Science and Remote Sensing Unit / NASA Johnson Space Center

---

Can you believe it? This picture was taken from the ISS by astronaut Matthew Dominick. You can see the thin crescent of the Moon above the Earth's atmosphere, and our planet's upper atmosphere is rippling with noctilucent clouds. Doesn't it look amazing?

[Christian G.]

What I like about this image of Pluto and Charon which Ann posted is to think that these two are mutually tidally locked in their slow dance, forever facing one another, never turning their backs. Almost romantic! (although Pluto hides its heart...)

[Jim Armstrong]

A literally awesome APOD, so much to think about.
One of the best ever.
Thanks.

[JimT]

Clarfication, just for the record:

Tenzing Montes
Feature type Mountain range
Location Western Sputnik Planitia, Pluto
Discoverer New Horizons
Eponym Tenzing Norgay

"The Tenzing Montes /ˈtɛnzɪŋ ˈmɒntiːz/ (formerly Norgay Montes) are a range of icy mountains on Pluto, bordering the southwest region of Sputnik Planitia and the nearby Hillary Montes...

The mountains, first viewed by the New Horizons spacecraft on 14 July 2015, and announced by NASA on 15 July 2015, are named after the Nepalese mountaineer Tenzing Norgay...The mountains were informally called Norgay Montes by the New Horizons team, but that name was later changed from Norgay to Tenzing. On 7 September 2017..."

— Wikipedia

[JimT]

Clarification, just for the record:

Tenzing Montes
Feature type Mountain range
Location Western Sputnik Planitia, Pluto
Discoverer New Horizons
Eponym Tenzing Norgay

"The Tenzing Montes /ˈtɛnzɪŋ ˈmɒntiːz/ (formerly Norgay Montes) are a range of icy mountains on Pluto, bordering the southwest region of Sputnik Planitia and the nearby Hillary Montes...

The mountains, first viewed by the New Horizons spacecraft on 14 July 2015, and announced by NASA on 15 July 2015, are named after the Nepalese mountaineer Tenzing Norgay...The mountains were informally called Norgay Montes by the New Horizons team, but that name was later changed from Norgay to Tenzing. On 7 September 2017..."

— Wikipedia

Astonishing image in any case, especially to one who was a teenager in 1957, and can well remember the excitement when Sputnik I was launched in October of that year.

[AVAO]

Clarification, just for the record:

Tenzing Montes
Feature type Mountain range
Location Western Sputnik Planitia, Pluto
Discoverer New Horizons
Eponym Tenzing Norgay

"The Tenzing Montes /ˈtɛnzɪŋ ˈmɒntiːz/ (formerly Norgay Montes) are a range of icy mountains on Pluto, bordering the southwest region of Sputnik Planitia and the nearby Hillary Montes...

The mountains, first viewed by the New Horizons spacecraft on 14 July 2015, and announced by NASA on 15 July 2015, are named after the Nepalese mountaineer Tenzing Norgay...The mountains were informally called Norgay Montes by the New Horizons team, but that name was later changed from Norgay to Tenzing. On 7 September 2017..."

— Wikipedia

Astonishing image in any case, especially to one who was a teenager in 1957, and can well remember the excitement when Sputnik I was launched in October of that year.

"Reasons Why Pluto Is a Dwarf Planet

Pluto orbits the Sun and meets the second criterion, which is a nearly round shape. However, it has difficulty with the other criteria for planethood.

It resides in the Kuiper Belt, a region of small icy bodies, signifying that it has not cleared its neighborhood of other objects. But, clearing an orbit is about mass and not just about location. Pluto is about two-thirds the size of Earth’s moon, but only one-sixth of its mass. It contains a larger proportion of ice to rock than a typical planet and just doesn’t pull in the debris it encounters on its journey around the Sun.

The other issues concern Pluto’s moon, Charon. Pluto has at least five moons, but Charon is special because it’s about half the size of Pluto. It is so massive that the center of mass (barycenter) of the Pluto-Charon system doesn’t actually reside within Pluto, but in the space between the two bodies. Due to this unique characteristic, some argue that Pluto and Charon are a binary (dwarf) planet system. In other words, Pluto and Charon are essentially satellites of each other. However, the IAU has yet to officially recognize binary dwarf planets as a separate category."

Source: https://sciencenotes.org/is-pluto-a-planet/

[Chris Peterson]

Clarification, just for the record:

Tenzing Montes
Feature type Mountain range
Location Western Sputnik Planitia, Pluto
Discoverer New Horizons
Eponym Tenzing Norgay

"The Tenzing Montes /ˈtɛnzɪŋ ˈmɒntiːz/ (formerly Norgay Montes) are a range of icy mountains on Pluto, bordering the southwest region of Sputnik Planitia and the nearby Hillary Montes...

The mountains, first viewed by the New Horizons spacecraft on 14 July 2015, and announced by NASA on 15 July 2015, are named after the Nepalese mountaineer Tenzing Norgay...The mountains were informally called Norgay Montes by the New Horizons team, but that name was later changed from Norgay to Tenzing. On 7 September 2017..."

— Wikipedia

Astonishing image in any case, especially to one who was a teenager in 1957, and can well remember the excitement when Sputnik I was launched in October of that year.

"Reasons Why Pluto Is a Dwarf Planet

Pluto orbits the Sun and meets the second criterion, which is a nearly round shape. However, it has difficulty with the other criteria for planethood.

It resides in the Kuiper Belt, a region of small icy bodies, signifying that it has not cleared its neighborhood of other objects. But, clearing an orbit is about mass and not just about location. Pluto is about two-thirds the size of Earth’s moon, but only one-sixth of its mass. It contains a larger proportion of ice to rock than a typical planet and just doesn’t pull in the debris it encounters on its journey around the Sun.

The other issues concern Pluto’s moon, Charon. Pluto has at least five moons, but Charon is special because it’s about half the size of Pluto. It is so massive that the center of mass (barycenter) of the Pluto-Charon system doesn’t actually reside within Pluto, but in the space between the two bodies. Due to this unique characteristic, some argue that Pluto and Charon are a binary (dwarf) planet system. In other words, Pluto and Charon are essentially satellites of each other. However, the IAU has yet to officially recognize binary dwarf planets as a separate category."

Source: https://sciencenotes.org/is-pluto-a-planet/

I consider everything that orbits the Sun to be a planet, and beyond that it's just the class of planet. Pluto is as much a planet as Jupiter. Or an asteroid. The IAU definition doesn't change reality, it's just a usage convention for those who write academic papers.

[AVAO]

.

size comparison Earth Pluto:

Click to view full size image

P.S. I like whirl-poles ...especially these ones from today

https://earth.google.com/web/@-80.28285 ... _____wEQAA

https://earth.nullschool.net/#current/w ... 88,-66.049

[AVAO]

Astonishing image in any case, especially to one who was a teenager in 1957, and can well remember the excitement when Sputnik I was launched in October of that year.

"Reasons Why Pluto Is a Dwarf Planet

Pluto orbits the Sun and meets the second criterion, which is a nearly round shape. However, it has difficulty with the other criteria for planethood.

It resides in the Kuiper Belt, a region of small icy bodies, signifying that it has not cleared its neighborhood of other objects. But, clearing an orbit is about mass and not just about location. Pluto is about two-thirds the size of Earth’s moon, but only one-sixth of its mass. It contains a larger proportion of ice to rock than a typical planet and just doesn’t pull in the debris it encounters on its journey around the Sun.

The other issues concern Pluto’s moon, Charon. Pluto has at least five moons, but Charon is special because it’s about half the size of Pluto. It is so massive that the center of mass (barycenter) of the Pluto-Charon system doesn’t actually reside within Pluto, but in the space between the two bodies. Due to this unique characteristic, some argue that Pluto and Charon are a binary (dwarf) planet system. In other words, Pluto and Charon are essentially satellites of each other. However, the IAU has yet to officially recognize binary dwarf planets as a separate category."

Source: https://sciencenotes.org/is-pluto-a-planet/

I consider everything that orbits the Sun to be a planet, and beyond that it's just the class of planet. Pluto is as much a planet as Jupiter. Or an asteroid. The IAU definition doesn't change reality, it's just a usage convention for those who write academic papers.

I agree with you. Rule 3 was only introduced by the IAU so that the number of planets in the solar system remains manageable, i.e. it is, as you say, a pure convention.

[Ann]

"Reasons Why Pluto Is a Dwarf Planet

Pluto orbits the Sun and meets the second criterion, which is a nearly round shape. However, it has difficulty with the other criteria for planethood.

It resides in the Kuiper Belt, a region of small icy bodies, signifying that it has not cleared its neighborhood of other objects. But, clearing an orbit is about mass and not just about location. Pluto is about two-thirds the size of Earth’s moon, but only one-sixth of its mass. It contains a larger proportion of ice to rock than a typical planet and just doesn’t pull in the debris it encounters on its journey around the Sun.

The other issues concern Pluto’s moon, Charon. Pluto has at least five moons, but Charon is special because it’s about half the size of Pluto. It is so massive that the center of mass (barycenter) of the Pluto-Charon system doesn’t actually reside within Pluto, but in the space between the two bodies. Due to this unique characteristic, some argue that Pluto and Charon are a binary (dwarf) planet system. In other words, Pluto and Charon are essentially satellites of each other. However, the IAU has yet to officially recognize binary dwarf planets as a separate category."

Source: https://sciencenotes.org/is-pluto-a-planet/

Is it important if Pluto is called a planet or a dwarf planet? Brian Cox doesn't think so.

"It's a beautiful world", he says.

https://youtu.be/cO87BJbwes4?t=447

Ann

[AVAO]

"Reasons Why Pluto Is a Dwarf Planet

Pluto orbits the Sun and meets the second criterion, which is a nearly round shape. However, it has difficulty with the other criteria for planethood.

It resides in the Kuiper Belt, a region of small icy bodies, signifying that it has not cleared its neighborhood of other objects. But, clearing an orbit is about mass and not just about location. Pluto is about two-thirds the size of Earth’s moon, but only one-sixth of its mass. It contains a larger proportion of ice to rock than a typical planet and just doesn’t pull in the debris it encounters on its journey around the Sun.

The other issues concern Pluto’s moon, Charon. Pluto has at least five moons, but Charon is special because it’s about half the size of Pluto. It is so massive that the center of mass (barycenter) of the Pluto-Charon system doesn’t actually reside within Pluto, but in the space between the two bodies. Due to this unique characteristic, some argue that Pluto and Charon are a binary (dwarf) planet system. In other words, Pluto and Charon are essentially satellites of each other. However, the IAU has yet to officially recognize binary dwarf planets as a separate category."

Source: https://sciencenotes.org/is-pluto-a-planet/

Is it important if Pluto is called a planet or a dwarf planet? Brian Cox doesn't think so.

"It's a beautiful world", he says.

https://youtu.be/cO87BJbwes4?t=447

Ann

It's a beautiful AND mysterious world.
...also exciting when rivers first flow down the crater wall, but then flow back up again...