The term “illustration” generally refers to a visual representation that is created to convey a concept or idea, rather than to document a specific reality or object. Depictions of distant planets, such as those we see in scientific publications, textbooks, or popular media, are typically illustrations rather than images because they are not based on direct observations or photographs of the planets themselves.
In most cases, depictions of distant planets are based on scientific models and simulations that take into account various physical and astronomical factors, such as the planet's size, composition, atmospheric conditions, and distance from its star. Scientists use this information to create computer-generated images or artistic renderings that aim to convey what the planet might look like based on our current understanding of its properties
However, since we cannot directly observe these planets with our current technology, the images we see are not actual photographs or representations of what the planet really looks like. Instead, they are artistic interpretations that are meant to help us visualize and understand the characteristics of these distant worlds.
So, while these depictions can be incredibly detailed and informative, they are still illustrations rather than images, since they are not based on direct observations or photographs of the planets themselves.
NASA’s Exoplanet Exploration website notes that most of the images we have of exoplanets are “artist's impressions” or “conceptual illustrations.” These images are created by artists and scientists based on the available data and scientific models, rather than being direct observations.
Similarly, in a 2015 article published in the scientific journal Nature (@nature), researchers noted that most of the exoplanet images we have are “computer-generated artistic representations” that are intended to help us visualize the properties and characteristics of these distant worlds.
Overall, while there may be some actual photographs of planets that are relatively close to us, most depictions of distant planets are likely to be artistic renderings based on scientific models and simulations, rather than actual images.
As of writing, there are 5,338 exoplanets confirmed and this number is constantly increasing as new planets are being discovered by astronomers using various detection methods, such as the transit method, radial velocity method, and gravitational microlensing method.
The study of exoplanets is an active field of research, and scientists are continually learning more about these distant worlds and their potential to support life.
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