I am curious to know whether the James Webb Space Telescope will be able to take pictures of our own planets like Jupiter / Saturn like Hubble did.

If yes, then how different are these images expected to look from those of Hubble, as Webb is optimized for infrared?

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    $\begingroup$ From Wikipedia: "Relatively cool objects (temperatures less than several thousand degrees} emit their radiation primarily in the infrared, as described by Planck's law. As a result, most objects that are cooler than stars are better studied in the infrared. This includes the clouds of interstellar medium, brown dwarfs, planets both in our own and other solar systems,...". What do you mean exactly with "how different it will look" ? $\endgroup$
    – Cornelis
    Dec 30, 2021 at 11:15
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    $\begingroup$ @uhoh "many of the target chemical compounds, such as water, carbon dioxide, and methane, also exist in the Earth's atmosphere, vastly complicating analysis ", also from wiki. $\endgroup$
    – Cornelis
    Dec 30, 2021 at 11:25
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    $\begingroup$ @Cornelis since when have astronomers been afraid of vastly complicated things? $\endgroup$
    – uhoh
    Dec 30, 2021 at 12:26
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    $\begingroup$ @uhoh Maybe a better writing would be ¨vastly limiting analysis ? Another thing, would you think they let JWST observe Venus so close to the Sun, even at 40⁰ from it ? $\endgroup$
    – Cornelis
    Dec 30, 2021 at 12:47
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    $\begingroup$ @Cornelis no, but there are some planets which are not named Venus :-) Seriously thought that's certainly a good point, JWST is not going to be seeing Venus no matter what. $\endgroup$
    – uhoh
    Dec 30, 2021 at 12:52

3 Answers 3


JWST must forever be oriented to remain in the shadow of its own sun shield, so that it remains cool and sensitive to the low temperatures of deep space, limiting what can be observed. Notably, it cannot look inwards in our solar system towards the sun or inner planets, nor can it orient to look directly away from the sun, but outer solar system objects will be observable some of the time. Details about what JWST can look at are disclosed in the Technical FAQ Specifically On Solar System Observations

Some things in our outer solar system that JWST may observe are listed in detail at SOLAR SYSTEM PROGRAM INFORMATION. Included there are:

  • Martian Atmosphere
  • Periodic Comets
  • Bright Comets, Targets of Opportunity (ToO)
  • Icy Dwarf Planets
  • Solar System Ice Giants: Uranus & Neptune
  • Giant Planet Satellites
  • Kuiper Belt Objects
  • Main-Belt Asteroids

As for how JWST is different from Hubble, consider reading Webb vs Hubble. You've already identified it sees further into the infrared range of the spectrum, and less of the visible spectrum. So its images of objects in our solar system will necessarily be presented to us with false-colour.

Electromagnetic Spectrum Comparison (source)

JWST has superior ability to sense temperature and chemical structure, and as such it will do a good job of telling us what things are made of and will provide insight into their chemical processes.

For example, regarding observations of Uranus and Neptune:

“The key thing that Webb can do that is very, very difficult to accomplish from any other facility is map their atmospheric temperature and chemical structure,” ... Crucially, Webb can distinguish one chemical from another. [source]

Therefore, I expect the majority of false-colour images of planets in our solar system to be colourized in a way that calls attention to different chemicals (e.g. assigning individual colours to oxygen, hydrogen, ammonia etc.). This example below shows how three near-infrared wavelengths of 756 nm, 727 nm, and 889 nm (methane) are combined into a false-colour image as compared to visible spectrum. This shows methane as blue.

A Jovian Hotspot in True and False Colors (source)

Hubble's vision extends to 2500 nm, whereas JWST sees wavelengths as long as 28500 nm.

It's hard to imagine how different the images will look until we see them (we're all as excited as you!), and each image will be different depending on the science being done, because there's no default way to map IR wavelengths to visible wavelengths for the purposes of general presentation. Images posted in galleries may be processed just to give them visual appeal. There's a certain amount of artistry involved here. But to give you an idea how how intense the contrast can be at certain wavelengths, here's an infrared terrestrial view (from Hawaii) of Jupiter at just 4680 nm. Predominantly this image is giving us a sense of temperature, something JWST will excel at.

Gemini North Infrared View of Jupiter (source)

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    $\begingroup$ Why can't JWST look directly away from the Sun? $\endgroup$
    – kristianp
    Jan 1 at 0:58
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    $\begingroup$ @kristianp excellent question! If you think of the sunshield on the bottom (radially inward toward the sun), and the mirrors facing forward (orbitally prograde) then if it pitches "down" too far to look at inner solar system objects, the "front" gets exposed to direct sunlight. Similarly if it pitches "up" too far to look directly anti-sun, the back gets exposed to direct sunlight. Here's a diagram. Or should I update my answer? $\endgroup$
    – Wyck
    Jan 1 at 5:10
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    $\begingroup$ @kristianp, actually this video explains the observing constraints better than any diagram I could make for you. $\endgroup$
    – Wyck
    Jan 1 at 5:15
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    $\begingroup$ The key point from that video is that the telescope is fixed, and almost perpendicular to the sun-shield (@kristianp). That was stated and shown a few seconds before the timestamp you linked. (At least that was the point I didn't know; everything else followed from that pretty obviously.) I would have linked 00:26 in the same video: youtu.be/y0bOi3kVIBs?t=26. The time you linked is just stating the consequence of that reason, and jumping into the middle of some complex images and dialogue. (That's why I linked 00:26 instead of 27, to give the view a second to get their bearings $\endgroup$ Jan 1 at 13:16
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    $\begingroup$ @Vikki: I think that's a terminology problem (probably on my part). I was looking at the dish as shown in the video as a tall thin thing which is sticking up out of the back of the sunshield (nearly perpendicularly). i.e. looking across the diameter of the dish. But now that you mention it, the normal (see what I did there...) way to describe a telescope mounting is to say which direction it can look. $\endgroup$ Jan 12 at 1:57

Here's NASA's site with an overview of already approved Solar System science missions for JWST: https://www.stsci.edu/jwst/science-execution/approved-programs/cycle-1-go

If you click on the red number to the left of each table entry, you can read an executive summary of what is intended to be done.

I'm myself surprised by how much Solar System science it will do! Okay, I don't see anything about Jupiter or Saturn in the first batch. Those are too easy for JWST. It will put its eye on Uranus, Neptune and Pluto!

And the link above is only the first "cycle". There's more and more, and yet more will come.

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    $\begingroup$ Note however that it can’t look at Venus or Mercury, or anything else closer to the sun than we are, because it has to point away from the sun at all times. $\endgroup$
    – Mike Scott
    Dec 30, 2021 at 14:18
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    $\begingroup$ "It will put its eye on Uranus". I can't wait for 2060, when they get tired of that stupid joke. $\endgroup$
    – RonJohn
    Dec 31, 2021 at 3:18
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    $\begingroup$ @RonJohn see comment on "Why was Neptune rather than Uranus chosen as an archetype?" and now I can't even read these titles without laughing: Could Neptune be viewed with the naked eye from Uranus? and What is the underlying nature of the dark spot found on Uranus? $\endgroup$
    – uhoh
    Dec 31, 2021 at 20:23
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    $\begingroup$ @uhoh: huh, I always thought the joke pronunciation was incorrect, but according to melmagazine.com/en-us/story/… that was the accepted pronunciation even among astronomers until the 1980s (when news anchors didn't want to be saying it that way in the same sentence as "deep space probe" for weeks). I guess that me I can enjoy Uranus puns more without thinking they're based on an ignorant mis-pronunciation. (Not that that would have ruled out choosing Neptune first; the old pronunciation is still widely known and laughed about.) $\endgroup$ Jan 1 at 13:31


10. Can Webb observe objects in our Solar System?

Yes. Webb is designed to be able to observe solar system objects having an apparent angular rate of motion of 0.030 arc seconds per second or less. This rate capability includes Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, their satellites, and comets, asteroids and minor planets at or beyond the orbit of Mars. Webb has the near-IR and mid-IR sensitivity to be able to observe and study virtually all known Kuiper Belt Objects. The very large infrared brightnesses of Mars, Jupiter, and Saturn may limit Webb observations of these planets to a subset of the instrument modes.

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    $\begingroup$ Saturn too bright to observe? Hehehe, they've gotta be kidding. $\endgroup$
    – LocalFluff
    Dec 30, 2021 at 19:53
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    $\begingroup$ @Local Why's that? Don't the gas giants radiate a ton of heat? $\endgroup$
    – wjandrea
    Dec 30, 2021 at 23:46
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    $\begingroup$ @LocalFluff Too bright in IR for some instruments designed to look for single photons coming from billions of light years away, yes. $\endgroup$
    – ceejayoz
    Dec 31, 2021 at 4:39

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