In space, the primary means by which we observe distant objects is through the detection of electromagnetic radiation, including visible light and other forms of radiation such as radio waves, X-rays, and gamma rays. While it is true that space itself is mostly empty and devoid of matter, it is not entirely devoid of light.
Visible light and other forms of electromagnetic radiation are emitted by various celestial objects and travel through space. These emissions can originate from stars, galaxies, nebulae, and other astrophysical phenomena. When these emissions reach Earth or our space-based observatories, they can be detected and recorded, allowing us to study and observe the distant objects.
Even in seemingly dark regions of space, there can be sources of light. For example, stars emit visible light that can travel vast distances before reaching our telescopes. Additionally, various celestial objects and processes can emit electromagnetic radiation across different wavelengths, such as infrared or radio waves, which can also be detected and observed.
Furthermore, advanced telescopes and detectors are designed to collect and amplify the faint signals from distant objects. These instruments can capture and analyze electromagnetic radiation, providing us with valuable information about the composition, temperature, movement, and other properties of the observed objects.
It's important to note that while visible light is just one part of the electromagnetic spectrum, astronomers have developed techniques and instruments that allow them to observe and analyze different forms of electromagnetic radiation. By studying these various wavelengths, scientists can gain a more comprehensive understanding of the universe, even in the absence of direct visible light.