Shadow is the darkness formed when the light ray is hit by any opaque objects. Both the terms penumbra and umbra are different parts of shadow. These terms are usually used for the shadow formed by heavenly objects or celestial objects. Different types of shadow are observed during different eclipses. These are often formed during eclipses or sunspots. To know the details about the parts of the shadow, it is important to know the difference between them. So here are some differences between penumbra and umbra.
Penumbra vs Umbra
The main difference between penumbra and umbra is that they are different parts of a shadow having different densities of darkness. Penumbra is the shadow that forms in the perimeters of the umbra. It is light in color density. Umbra is the shadow formed in the center. It is the darkest having a high density of black color.
Penumbra is the light part of a shadow. It is formed in the perimeter of the umbra. Penumbra is the term given to the shadow formed by the heavenly objects. Penumbra is derived from the Latin word paene, meaning almost or nearly. Penumbra is normally formed and observed during the eclipse. The penumbra is observed during the partial or half eclipse, as the moon is partially covered by the sun, and the penumbra portion is observed.
Umbra is the darkest portion of the shadow formed. It is mostly formed in the center of the portion. It is considered a part of the penumbra. It is also formed parallel with penumbra. During the eclipse, the umbra starts to become smaller. During the eclipse, an observer within the area of the umbra always experiences a full eclipse. During the full lunar eclipse, the moon is completely covered with the umbra, and the penumbra part becomes invisible.
Comparison Table Between Penumbra and Umbra
| Parameters of Comparison | Penumbra | Umbra |
| First used in | 1604 | 1950 |
| Meaning | Nearly a shadow or almost a shadow | Shadow |
| Color of shadow | Lighter in color than the umbra | Darkest portion of the shadow |
| Position | On the perimeters of the shadow area | At the center of the whole shadow portion |
| During eclipse | Becomes larger | Becomes smaller |
What is Penumbra?
Penumbra is the light part of a shadow. It is formed in the perimeter of the umbra. Penumbra is the term given to the shadow formed by the heavenly objects. Penumbra is derived from the Latin word paene, meaning almost or nearly. Penumbra is normally formed and observed during the eclipse.
Penumbra was first observed in 1604. At that that the whole shadow is called the penumbra. The different parts of shadow were unknown at that time. The term penumbra is often used in astronomy to make one understand the logic of the eclipses. This term is normally used for celestial bodies.
When a full lunar eclipse occurs, the shadow of the inner earth completely covers the moon. This means that the umbra covers the moon completely. But during half lunar eclipse or partial lunar eclipse, the umbra partially covers the moon, and at that time, the penumbra is observed. So it is also called the penumbra lunar eclipse.
This term is also applicable in paintings. There it is used to make a painter understand shading. It is the outer portion of the shadow formed by an opaque object. The shading in this portion is lighter compared to the interior portion of the shadow near the object.
What is Umbra?
Umbra is the darkest portion of the shadow formed. It is mostly formed in the center of the portion. It is considered a part of the penumbra. It is also formed parallel with penumbra. During the eclipse, the umbra starts to become smaller. During the eclipse, an observer within the area of the umbra always experiences a full eclipse.
Umbra was first observed in 1950. Before that, the shadow was not segregated into different parts. It was considered as one penumbra. During these recent years, another two parts of the shadow were discovered that are umbra and antumbra.
The name umbra is derived from a Latin word meaning shadow. It is the darkest portion of a shadow. The color density of the umbra is the highest among the three parts of a shadow. It is darkest in color. It is situated in the middle of the whole shadow portion. Umbra is considered a part of the penumbra.
In painting, the shading part has the concept of the umbra. When we are shading a picture of an object, the inner portion of the nearest interior portion of an object is the darkest. It is called the umbra portion. As the shading moves forward towards the light portion, the shadow starts becoming lighter and then disappears.
Main Differences Between Penumbra and Umbra
- The idea of penumbra was first developed in 1604, but the umbra was observed recently in 1950.
- The meaning of penumbra is nearly a shadow, and on the other hand, the meaning of umbra is shadow.
- The color or the darkness density of the umbra is higher than the penumbra. So as a result, the penumbra appears light in color, and the umbra is dark.
- The position of the penumbra is on the parameters of the umbra, and the umbra is always in the center near the object. That’s why it is the darkest portion.
- During an eclipse, an observer will observe that the penumbra becomes larger and the umbra becomes smaller over time.
Conclusion
Penumbra and umbra are different parts of a shadow. The concept of umbra is discovered in recent times. Before that, the shadow does not have any fragments or parts. Umbra is the darkest portion, and penumbra is the lightest portion of the shadow. It is observed mainly during lunar eclipses, but shadow always has these parts, whether it is of a vase or a celestial body. During an eclipse, it is observed that the penumbra of the celestial body becomes larger, and the umbra becomes smaller with passing the time. Penumbra is observed during partial lunar eclipses as the moon is partially covered.
References
- https://europepmc.org/article/med/8173671
- https://europepmc.org/article/med/8703672