Why do telescopes observing the night sky in different wavelengths yield different results?
Astronomers have long used telescopes operating in different wavelengths to observe celestial objects: from high-energy gamma rays and X-rays to ultraviolet, visible, and infrared light, and finally to radio waves. This is because celestial objects emit radiation across multiple wavelengths, and astronomers can use telescopes in different wavelengths to observe different aspects of the same object.
On a moonless summer night, the Milky Way appears exceptionally bright, and we can clearly see patches of dark areas in it, which are thick dust clouds that block the starlight behind them. Although they appear black in the visible light wavelength, if we use an infrared telescope or a radio telescope, we will find that these dust clouds become very bright. Are the dust clouds also emitting light? Indeed, most celestial objects "emit light," but just in different wavelengths. Cold interstellar dust clouds are mainly composed of molecules and dust particles, which mainly emit longer-wavelength radio waves and infrared light, so they cannot be seen with telescopes in other wavelengths.
There are also phenomena in the universe that are difficult to observe with visible light telescopes. For example, there is a particularly bright celestial object called a "quasar", which is suspected to have a supermassive black hole at its center. In the optical wavelength, quasars are often just an indistinguishable point, but astronomers have observed "jets" emitted from the center of quasars using X-ray and gamma-ray telescopes, and they can also see even more extensive giant radio "lobes" using radio telescopes.
Because a celestial object often emits electromagnetic waves in various wavelengths, if astronomers only observe it in one wavelength, it's like "the blind man feeling an elephant", only able to understand one aspect of the celestial object. Only by observing in multiple wavelengths can we comprehensively understand the celestial object.