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James Webb Telescope

Lennart Hyland said:
Yes, atleast thats how Nature.com explains it:
The star symbol marks the exoplanet HIP 65426 b’s star, which Webb has blocked from the image
https://www.nature.com/articles/d41586-022-02807-4
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Thank you. Now I understand what I'm seeing. :D

Anyway, if I understand correctly, the imaging sensor has individual shutters for each pixel, which is how it can effectively block out the light of that nearby star so that we can see the much dimmer exoplanet that orbits the star.
RecoveringYuppy said:
But I'm still not sure what that would mean in this context.
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What I'm trying to say is, look at the image in the Nature article, the one that says "Digitized Sky Survey" in the top right. Where it has a caption "Star HP 65426", there are two oblique lines going down and left, and down and right, respectively. At the bottom are four rectangular boxes which show the exoplanet. What I meant by "zoomed in" is that those rectangles are enlargements of the area around "Star HP 65426".

My confusion was that I wasn't sure that it was even possible to see an exoplanet so clearly. I thought it must be drowned out by the light of the much brighter star around which it orbits.
HIP 65426 b orbits its star at roughly twice the distance that Pluto orbits the Sun.
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That probably helps too. It's far enough away from its star that you can block the star without blocking the planet.

More info:

https://en.wikipedia.org/wiki/HIP_65426_b
 
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Puppycow said:
My confusion was that I wasn't sure that it was even possible to see an exoplanet so clearly. I thought it must be drowned out by the light of the much brighter star around which it orbits.
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Well, that is, of course, one of the best images but the general technique of finding planets by blocking out the light of the nearby star has been used for quite a while now.

https://en.wikipedia.org/wiki/List_of_directly_imaged_exoplanets

HIP 65426 b orbits its star at roughly twice the distance that Pluto orbits the Sun.
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Puppycow said:
That probably helps too. It's far enough away from its star that you can block the star without blocking the planet.
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I don't think we need anywhere near that big a gap to make this technique work. If it's correct that the star icon is marking the position of the star and the blob of pixels is the planet then the gap between them is nowhere near twice the radius of Pluto's orbit. That gap is not much larger than the planet itself but Pluto's orbit is much much larger than even a super Jupiter.

So if we're making correct assumptions about what that image is showing then I think the planet must be nearly directly in front of or behind it's parent star.

Something still seems off though, I can't make that work out numerically.
 
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RecoveringYuppy said:
I don't think we need anywhere near that big a gap to make this technique work. If it's correct that the star icon is marking the position of the star and the blob of pixels is the planet then the gap between them is nowhere near twice the radius of Pluto's orbit. That gap is not much larger than the planet itself but Pluto's orbit is much much larger than even a super Jupiter.

So if we're making correct assumptions about what that image is showing then I think the planet must be nearly directly in front of or behind it's parent star.

Something still seems off though, I can't make that work out numerically.
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The Wikipedia article I linked above has a photo with a circle representing the orbit of Neptune (30 AU) superimposed for scale. Pluto's orbit is more eccentric but the semi-major axis is at 39 AU. Whereas the semi-major axis for HIP 65426 b is 87 AU

https://en.wikipedia.org/wiki/HIP_65426_b

The only information I can't seem to find is what angle the plane of the orbit is at from our perspective. It looks to be perpendicular, but I'm not sur whether that's actually the case. However, if the image in Wikipedia is correct, it looks to be at near maximum angular distance.



https://en.wikipedia.org/wiki/HIP_65426_b
 
OK. So I think there must be some source of aberration or other distortion I'm not accounting for. Could be as simple as me not accounting for how close this object is.
 
I am not disputing that the planet is as far as they say. I'm assuming that's correct*. I am asking what direction it is from the star so that I can break that distance down in to radial and perpendicular components.

And that is so that I can understand what valid information about size, distance, and other things can be obtained from this.

* BTW I said that to keep things simple. At the moment I can't rule out that the distance cited is the radial distance and the absolute distance may not be stated or even known.
 
Puppycow said:
https://en.wikipedia.org/wiki/HIP_65426_b

The only information I can't seem to find is what angle the plane of the orbit is at from our perspective. It looks to be perpendicular, but I'm not sur whether that's actually the case. However, if the image in Wikipedia is correct, it looks to be at near maximum angular distance.
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I think I figured out this part too. The Wikipedia article gives the inclination as 100 degrees, (+15/-6), so very nearly perpendicular from our perspective.

The temperature of the planet is also very hot, around 1500 1667 kelvins (for comparison Venus is only 737 kelvins). I think that makes it hot enough that it would glow orange as a black body. So the light we are seeing is mostly due to its temperature, not reflected light.
 
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RecoveringYuppy said:
This link might be helpful:

https://en.wikipedia.org/wiki/Orbital_inclination
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Ah, thanks. That does clarify it. I guess it's actually closer to edge-on to our line of sight in that case.

Exoplanets and multiple star systems
The inclination of exoplanets or members of multiple stars is the angle of the plane of the orbit relative to the plane perpendicular to the line of sight from Earth to the object.[5]

  • An inclination of 0° is a face-on orbit, meaning the plane of the exoplanet's orbit is perpendicular to the line of sight with Earth.
  • An inclination of 90° is an edge-on orbit, meaning the plane of the exoplanet's orbit is parallel to the line of sight with Earth.
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If we take the sensational language out of the Scientific American article, which (I remind readers) is a journalistic article and not a scientific paper, it appears that there are aspects of some observations that cosmologists have been struggling to explain.

Shocking? Or exciting? Certainly surprising.

The article goes on to state that there are potentially ways to explain the observations within our current cosmological theories, so physics may not be "broken" after all. Regardless, this is exciting science and exactly what the JWST was designed and built for.
 
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