Shadow is the darkness formed when any opaque objects hit the light ray. Both the terms penumbra and umbra are different parts of shadow. These terms are used for the shadow formed by heavenly objects or celestial objects.
Different types of shadow are observed during different eclipses. These are 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 the penumbra and the umbra.
Key Takeaways
- Umbra is the darkest part of a shadow cast by an opaque object, while Penumbra is the partial shadow region surrounding the umbra.
- The umbra is formed when a light source is completely blocked, while the Penumbra is formed when the light source is only partially blocked.
- In an eclipse, the umbra is where the sun is completely obscured, while the region where the sun is partially obscured is the Penumbra.
Penumbra vs Umbra
Penumbra is a type of shadow whose color density is light. Penumbra can be seen when half of the moon is covered with the sun. Penumbra is not visible in a full lunar eclipse. It appears on the perimeters. Umbra is a shadow whose color density is high. The position of the umbra shadow is always centred. It becomes small during an eclipse.
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 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 centre of the portion. It is considered a part of the penumbra. It is also formed parallel with the 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 umbra completely covers the moon, and the penumbra part becomes invisible.
Comparison Table
| 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 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 used in astronomy to make one understand the logic of 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; at that time, the penumbra is observed. So it is also called the penumbra lunar eclipse.
This term is also applicable to paintings. There it is used to make a painter understand shading. It is the outer portion of the shadow formed by an opaque object. This portion’s shading is lighter than the shadow’s interior portion near the object.
What is Umbra?
Umbra is the darkest portion of the shadow formed. It is mostly formed in the centre of the portion. It is considered a part of the penumbra. It is also formed parallel with the 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, which 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 the 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 towards the light portion, the shadow becomes lighter and 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; 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 centre near the object. That’s why it is the darkest portion.
- During an eclipse, an observer will observe that the penumbra and the umbra become smaller over time.
Last Updated : 21 June, 2023
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.
I had heard about umbra and penumbra before and wanted to know the difference between them, finally I got it, incredible explanation.
The author hit the nail on the head, Walsh Alexandra.
Incredible article! Gave me a clear understanding of penumbra and umbra, never knew the difference between them before!
These are my thoughts exactly, Walsh.
I agree, Walsh.