Why do astronomers get "different looking" images of space objects in UV, IR, and Xray satellite telescopes ..

Think about how YOU look with different light:

hard x-rays : see your bones well and other tissue blurry

soft x-rays : see your skin right through your clothing

ultraviolet : see all your skin blemishes

visible : see the surface of your body

near infrared : see through your clothes

far infrared : see your body heat

microwaves : you're just a blur

The HST has been used to produce some excellent images of the four main gas giant planets of our Solar System. I've just spent a couple of minutes to do a Google search and found plenty. Neptune is the furthest of the gas giants and beyond this there is nothing of any major significance to justify aiming the HST at. The main purpose of the HST is, and always has been, to study the much more distant Universe of galaxies and galaxy clusters. All the instruments designed for use on the HST have been accordingly designed with this purpose in mind. Because there is such a huge difference in the brightness between the planets and distant galaxies, if you were to try and take an image of Jupiter say with a camera which is designed to take images of very faint and distant galaxies over a period of a few days, you would most like destroy the camera. With conventional telescopes such as those used by amateurs, we can see both brighter and much dimmer objects. Professional telescopes on the other hand, and in particular telescopes in orbit are much more specialised and the cameras used with them are designed to image much more specialised targets. Even in amateur astronomy, when imaging objects you have to used the most appropriate type of telescope and camera to suit the brightness and size of the object you want to image.

Different wavelengths of light trace different processes.

There are two different ways things can emit light too.

In the case of solids and high density gases they essentially emit like blackbodies, and so they emit a borad range of wavelengths, but a hot body will emit more high energy photons (per unit surface area) than a cool body.

For low density gas that hot, they emit according to the electronic transitions - and that gets more complex to analyze.

If you are interested in dust, it is not hot enough to emit in the Visible or higher energy photons, so we use IR wavelength.

If you are interested in hot bodies, you use UV or higher energy photons.

If, for instance I look at a Planetary Nebula (which has nothing to do with planets - its a long story), the central star might be as hot as 100000K - so it emits UV and X-rays; while the gas around it glows like a neon light due to electronic transitions, and this can be investigated at all wavelengths. The dust around it will only be seen at IR wavelengths.

Taking images at lots of different wavelengths is how we determine the structure, composition and relevant physical processes.

Consider it this way:

If I were to hold a highly radioactive isotope in my hand, I wouldn't KNOW that it were radioactive. I can't SEE the radiation.

If, on the other hand, I had a Geiger counter, I could easily determine that the substance was radioactive, and I probably wouldn't pick it up.

Our eyes can't see very much, in terms of the different types of radiant energy. We use different telescopes because something that looks the same in one wavelength (visible light) might look very different in another wavelength.

Because UV,IR, X-RAY etc, are all different kinds of light. We see in one light wavelength the visible light for our eyes. Those different telescopes are eyes to see different wavelengths which show their own vision of the universe.

A body emits the entire spectrum of electromagnetic radiation but in a bell curve like a black body. The peak of emittion, or the top of the bell curve, moves around depending on the temperature of the body. For our Sun, this is around 6000K and correlates to visible light. When you observe different spectrums, you are looking at the part of the object that is emitting that spectrum. It is going to look different.

different wavelengths (as already mentioned) give different images. there's the visible light that covers a relatively small band of the electromagnetic spectrum which, obviously; gives us our 'naked eye' images. longer wavelength include radio waves, microwaves and infra red light, while the shorter wavelengths include ultra-violet light, x-rays, gamma rays, etc.

when you see images like the eagle nebula taken from hubble, the gigantic cloud-like towers would not be visible to the naked eye as they're emitting radiation outside of the visible range of the electromagnetic spectrum.

only instruments capable of detecting these wavelengths can 'see' these images and convert them to the beautiful pictures we know and love.

Different wave lengths - different light source = different picture.