APOD: LHS 475 b: Earth-Sized Exoplanet (2023 Jan 24)

[APOD Robot]

LHS 475 b: Earth-Sized Exoplanet

Explanation: If you could stand on exoplanet LHS 475 b, what might you see? No one knows for sure but pictured here is an interesting guess made by an Earth-based artificial intelligence (AI) engine. The existence of the exoplanet was indicated in data taken by the Earth-orbiting TESS satellite but confirmed and further investigated only this year by the near-Earth Sun-orbiting James Webb Space Telescope. What is known for sure is that LHS 475 b has a mass very similar to our Earth and closely orbits a small red star about 40 light years away. The featured AI-illustrated guess depicts a plausibly rugged Earth-like landscape replete with molten lava and with the central red star rising in the distance. Webb data does not as yet reveal, however, whether LHS 475 b has an atmosphere. One of Webb’s science objectives is to follow up previous discoveries of distant exoplanets to better discern their potential for developing life.

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[Ann]

Saturn as seen from Titan. Painting by Chesley Bonestell in 1944.

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View of red dwarf star LHS 475 from its Earth-sized planet LHS 475b. Illustration Credit: DeepAI's Fantasy World Generator

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I guess AI may have seen a picture or two by Chesley Bonestell.

Ann

[alex555]

Even with a red star you couldn't see the stars in daylight. Well spotted, AI.

[FLPhotoCatcher]

Here's what Stable Diffusion 2.1 came up with after I added the keywords, "exoplanet, red dwarf, lava mountain rocks sunset".
The red dwarf looks to be in front of one of the mountains. The caption does say that it's a "small red star."

[rstevenson]

When I saw this image a few minutes ago, my initial reaction was that the star was much too small in the sky.

Our Sun appears to be about 1/2° in diameter, if memory serves. We are, by definition, 1 AU away from our Sun which is 1 M☉ in radius. The equivalent figures for this exoplanet are 0.0206 AU and 0.2789±0.0014 R☉. A more knowledgeable person than I can probably use those figures to calculate how many degrees wide the star would be in the sky of the exoplanet. I gave it a try, taking the inverse of each of those figures (since I am comparing them to 1 AU and 1 M☉) and multiplying by 1/2°, …
(1/0.0206) (1/0.2789) (1/2°) = 1.52°
If that’s the right way to do it, then the star should appear to be about 3 times the size of our Sun, given an equivalent viewing angle on each planet. So now I think the AI illustrated the star much too large, as opposed to my initial reaction. But I’ve no idea if that calculation I just did is correct. Can someone check that for me, please?
—————- a few minutes pass —————
ACK! Found a mistake already. The answer 1.52 is in radians, not degrees. It should be 87°, according to Wolfram Alpha (which knows a great deal more than I about how to calculate.) Of course, garbage in, garbage out, so it remains to see if what I calculated makes sense. If it does, then the star should be much larger in the sky.

Rob

[De58te]

Something puzzles me. If the Earth-like planet LHS 475 b is orbiting its red star at a distance of 40 light years from the red star, than why does its sun look bigger in the sky than our Sun does to us which I believe is much closer to the Earth than even 1 light year away??

[rstevenson]

Something puzzles me. If the Earth-like planet LHS 475 b is orbiting its red star at a distance of 40 light years from the red star, than why does its sun look bigger in the sky than our Sun does to us which I believe is much closer to the Earth than even 1 light year away??

The star and planet are both 40 ly from Earth. The planet is far closer to its star than Earth is to Sol. See my post just above this.

Rob

[RJN]

It should be 87°

Thanks, Rob! Interesting point. However, the angular diameter across the entire frame was not given. It is common in astrophotography, as you know, to zoom in or zoom out of objects to make them appear angularly big or small compared to the angular size of the frame. This APOD (https://apod.nasa.gov/apod/ap200802.html) shows an example involving the Sun being made to look small, while this APOD. (https://apod.nasa.gov/apod/ap200322.html) depicts Earth's Moon as looking unusually big. It seems to me that if we allow astrophotographers this freedom, we should allow astro-artists the same freedom, even if they are AI. - RJN

[rstevenson]

It should be 87°

Thanks, Rob! Interesting point. However, the angular diameter across the entire frame was not given. It is common in astrophotography, as you know, to zoom in or zoom out of objects to make them appear angularly big or small compared to the angular size of the frame. This APOD (https://apod.nasa.gov/apod/ap200802.html) shows an example involving the Sun being made to look small, while this APOD. (https://apod.nasa.gov/apod/ap200322.html) depicts Earth's Moon as looking unusually big. It seems to me that if we allow astrophotographers this freedom, we should allow astro-artists the same freedom, even if they are AI. - RJN

True, of course. That's why I was mainly trying to figure out the angular diameter of the star itself rather than the entire frame. For example, we often mention that the Moon is 1/2° "wide" in our sky. That remains true whether we take a photo of it using a telephoto lens or a wide angle lens. Lacking the angular diameter information of the frame of that illustration does put the kibosh on any sort of comparison, as you say. But I think a human illustrator would have tried to show that much larger appearance in a realistic way. If I were doing it I would have started with the field of view of a 50mm lens on a 35mm camera, since that is often described as being about the same sort of perspective our eyes give us (though some say a 35mm lens is closer.) The AI seems not to have had a sense of how we humans would see it and feel it, so didn't consider that in its illustration. But unlike many humans, it can be trained.

Rob

[orin stepanek]

ws8MosQggVDs2RuK8Rs2oH-1200-80.jpg (18.93 KiB) Viewed 14159 times

Kitty looking for inteligent life!

Changing subject; Earth sized planet in habitable zone! Is there
intelligent life out there; Probably; but too far out to visit or
communiate!

[Chris Peterson]

When I saw this image a few minutes ago, my initial reaction was that the star was much too small in the sky.

Our Sun appears to be about 1/2° in diameter, if memory serves. We are, by definition, 1 AU away from our Sun which is 1 M☉ in radius. The equivalent figures for this exoplanet are 0.0206 AU and 0.2789±0.0014 R☉. A more knowledgeable person than I can probably use those figures to calculate how many degrees wide the star would be in the sky of the exoplanet. I gave it a try, taking the inverse of each of those figures (since I am comparing them to 1 AU and 1 M☉) and multiplying by 1/2°, …
(1/0.0206) (1/0.2789) (1/2°) = 1.52°
If that’s the right way to do it, then the star should appear to be about 3 times the size of our Sun, given an equivalent viewing angle on each planet. So now I think the AI illustrated the star much too large, as opposed to my initial reaction. But I’ve no idea if that calculation I just did is correct. Can someone check that for me, please?
—————- a few minutes pass —————
ACK! Found a mistake already. The answer 1.52 is in radians, not degrees. It should be 87°, according to Wolfram Alpha (which knows a great deal more than I about how to calculate.) Of course, garbage in, garbage out, so it remains to see if what I calculated makes sense. If it does, then the star should be much larger in the sky.

Rob

How large a star or moon appears in an image is entirely a product of the focal length of the imaging system and the relative distances between foreground objects. Without knowing that there is no way of knowing how this scene would look to our eyes.

[rstevenson]

How large a star or moon appears in an image is entirely a product of the focal length of the imaging system and the relative distances between foreground objects. Without knowing that there is no way of knowing how this scene would look to our eyes.

True. But see my reply to RJN just above Orin's kitties.

Rob

[Cousin Ricky]

Do AIs know that “red” is relative, and that red dwarfs are more or less the color of incandescent light bulbs? Well, I guess not, if they’re learning from human artists. I have seen very, very few red or yellow stars depicted realistically by human space illustrators.

I understand that some artistic license is required to cope with the dynamic range (stars are very bright!), but space illustrators don’t even seem to be working from a realistic baseline.

[Chris Peterson]

Do AIs know that “red” is relative, and that red dwarfs are more or less the color of incandescent light bulbs? Well, I guess not, if they’re learning from human artists. I have seen very, very few red or yellow stars depicted realistically by human space illustrators.

I understand that some artistic license is required to cope with the dynamic range (stars are very bright!), but space illustrators don’t even seem to be working from a realistic baseline.

The luminosity of this star is 1% of the Sun's. That is about what the Sun looks like through the darkest commercial sunglasses. To our eyes, painfully bright white.

[ddorn777]

There could also be the matter of atmospheric scattering of the light. No telling what might be in the "air" including dust.

[johnnydeep]

The Wikipedia article about red dwarfs has this to say:

Because low-mass red dwarfs are fully convective, helium does not accumulate at the core, and compared to larger stars such as the Sun, they can burn a larger proportion of their hydrogen before leaving the main sequence.

Why does helium NOT building up in the core prolong the period of hydrogen fusion?

[Fred the Cat]

The "How To" create a space image seems a lot easier than getting there. Plenty goes into the process but anyone can imagine their way into space.

Unless you want to go out on a limb?

[gvann]

The Wikipedia article about red dwarfs has this to say:

Because low-mass red dwarfs are fully convective, helium does not accumulate at the core, and compared to larger stars such as the Sun, they can burn a larger proportion of their hydrogen before leaving the main sequence.

Why does helium NOT building up in the core prolong the period of hydrogen fusion?

The Wikipedia page for stellar evolution gives more details about what happens: In a low-mass star, since convection continually brings hydrogen down into the core, where pressure and temperature are highest, hydrogen can continue to fuse and generate energy.

In contrast, a larger star will accumulate only helium (which is heavier than hydrogen) in its core, and hydrogen fusion will continue in a shell above the surface of the helium core. At some point, pressure and temperature in the accumulating helium core will become large enough to start helium fusion. That's when the star evolves into the red-giant stage and hydrogen fusion stops.

[Avalon]

What is the explanation for the apparent red disc belting the star in the AI generated rendering?

[Ann]

What is the explanation for the apparent red disc belting the star in the AI generated rendering?

The illustration was made by AI. AI learns by copying. While searching for space images to be inspired by, AI undoubtedly came across pictures of Saturn, among them certainly Chesley Bonestell's View of Saturn from Titan.

After seeing Chesley Bonestell's Saturn picture and other Saturn images, AI probably "thought" that it was a good idea to portray red dwarf star LHS 475 as a reddish orb with a disk crossing its face, in the same way that the rings of Saturn can be seen crossing the face of Saturn.

Ann

[MarkBour]

What is the explanation for the apparent red disc belting the star in the AI generated rendering?

The illustration was made by AI. AI learns by copying. While searching for space images to be inspired by, AI undoubtedly came across pictures of Saturn, among them certainly Chesley Bonestell's View of Saturn from Titan.

After seeing Chesley Bonestell's Saturn picture and other Saturn images, AI probably "thought" that it was a good idea to portray red dwarf star LHS 475 as a reddish orb with a disk crossing its face, in the same way that the rings of Saturn can be seen crossing the face of Saturn.

Ann

Your theory of the origin of the AI's image seems quite reasonable.
It was fascinating to read about Chesley Bonestell; I don't think I knew of him before (though I've seen some of his work without knowing its origin). An artist of great imagination and accomplishments, who was able to inspire many others.

And I will make the sacrifice and undertake the journey,
I will sit on top of a scarcely-tamed explosion,
Sealed in a cramped and silent metallic vessel,
I will suffer the loneliness of interminable nights,
All to stand and gaze out to the horizon on another world.

[johnnydeep]

The Wikipedia article about red dwarfs has this to say:

Because low-mass red dwarfs are fully convective, helium does not accumulate at the core, and compared to larger stars such as the Sun, they can burn a larger proportion of their hydrogen before leaving the main sequence.

Why does helium NOT building up in the core prolong the period of hydrogen fusion?

The Wikipedia page for stellar evolution gives more details about what happens: In a low-mass star, since convection continually brings hydrogen down into the core, where pressure and temperature are highest, hydrogen can continue to fuse and generate energy.

In contrast, a larger star will accumulate only helium (which is heavier than hydrogen) in its core, and hydrogen fusion will continue in a shell above the surface of the helium core. At some point, pressure and temperature in the accumulating helium core will become large enough to start helium fusion. That's when the star evolves into the red-giant stage and hydrogen fusion stops.

Thanks - makes sense!