In solar astronomy, what is the name of the outermost layer of the Sun that forms its extended atmosphere?

Introduction / Context:
This question deals with basic solar structure in astronomy. The Sun has several layers, each with different properties. Knowing the names and order of these layers is a common part of general science curricula, especially when eclipses and solar observations are discussed.

Given Data / Assumptions:

• The Sun has inner and outer layers such as core, radiative zone, convective zone, photosphere, chromosphere, and corona.
• We are asked about the outermost layer.
• The options list corona, photosphere, chromosphere, and granule.

Concept / Approach:
The photosphere is the visible surface of the Sun that we normally see. Above it lies the chromosphere, and beyond that is the corona, which extends millions of kilometres into space as a very hot, thin atmosphere. The corona is usually not visible to the naked eye except during a total solar eclipse, when the bright photosphere is blocked. Therefore the outermost layer in the list is the corona.

Step-by-Step Solution:

Verification / Alternative check:
Images of total solar eclipses show a faint, pearly white, crown like structure surrounding the dark disk of the Moon. This glowing region is the solar corona. Textbooks and diagrams explicitly label it as the outermost part of the solar atmosphere, confirming the reasoning above.

Why Other Options Are Wrong:

• Photosphere is wrong because it is the visible surface below the chromosphere and corona.
• Chromosphere is wrong because it is a middle layer above the photosphere but still below the corona.
• Granule is wrong because it refers to convection cells within the photosphere, not a large scale external layer.

Common Pitfalls:
Students sometimes confuse photosphere and corona because the photosphere is the brightest and most obvious layer, while the corona is usually not visible without special conditions. Remember that brightness does not mean outermost. The term corona itself means crown, which can help you recall it as the extended outer atmosphere seen like a crown around the Sun during eclipses.

Final Answer:
Corona