Jeddah astronomy society: 'false eclipse' term scientifically inaccurate

The Jeddah Astronomy Society has clarified that some astronomical sources have used the term "false eclipse" to refer to a penumbral lunar eclipse. While this phrase may seem linguistically understandable—since this type of eclipse is so faint that it is difficult for observers to notice any change in the Moon’s brightness—the use of "false eclipse" is not scientifically accurate.

The society explained on its X (formerly Twitter) account that the correct term is "penumbral lunar eclipse," as it accurately reflects the phenomenon and how it occurs. A lunar eclipse happens when the Earth is positioned between the Sun and the Moon during a full moon, causing the Moon to pass through the shadow cast by Earth into space. This shadow consists of two main parts: the umbra (central shadow) and the penumbra, which is the lighter, outer region.

Society president Majed Abu Zahra stated that a penumbral eclipse occurs when the Moon passes wholly or partially through Earth's penumbra without entering the umbra, resulting in only a slight dimming of the Moon’s brightness. As a result, the change may not be noticeable to the naked eye, especially during weaker eclipses.

Abu Zahra added that the faint visual effect does not mean the phenomenon is not real. The penumbral eclipse is a genuine astronomical event with a specific geometry, and its timing can be calculated precisely. It is considered one of the main types of lunar eclipses, alongside partial and total eclipses.

He noted that describing the phenomenon as "false" could mislead the public, as it suggests the event is not a real eclipse. In contrast, the term "penumbral eclipse" directly indicates the region of the shadow the Moon passes through and explains why the change in brightness is limited. He stressed the importance of using precise scientific terminology in astronomy content, especially given the rapid spread of information on social media.

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