In general, an artist's impression of an astronomical object is acceptable for inclusion in Wikipedia only if:
- it was distributed by a reliable source, and
- the first phrase of the caption is “An artist's impression of ...”.
If both criteria are fulfilled, but there is a more evidence-based image (such as a telescopic image or another artist's impression that depicts more known features and fewer speculative features) available, the artist's impression may still be included, but should not be the lead image.
When choosing images to illustrate astronomical objects, editors should select images with maximum potential to inform readers and minimum potential to misinform readers. Before illustrating an astronomical object with an artist's impression, editors should consider whether a figure, diagram, or telescopic image would strike a better balance of information vs. speculation.
For the purpose of this guideline, an artist's impression is defined as an image intended to represent the visual appearance of an astronomical object, that is not directly generated from collected data. Images depicting visual features of an astronomical object known from collected data, but that are not themselves directly generated from that data, are artist's impressions. Figures and diagrams that do not depict visual features of the astronomical object are not artist's impressions.
The definition of reliable source in this context should be interpreted strictly. Major national space agencies, astronomical observatories, and peer-reviewed scientific papers are reliable sources; amateur blogs and astronomical visualization software (e.g. Celestia) are not. Images from non-scientific print or online media should be treated with caution, because editors at these publications likely lack scientific expertise.
As with all guidelines, this guideline is not absolute and may be ignored according to common sense and discussion of individual cases. For example, a truly terrible artist's impression (sloppy artwork or blatant contradiction of known features) from a reliable source should not be included, nor should an excellent artist's impression (informative, minimal speculation, primarily depicting known features) be excluded because it is not from a reliable source.