The falling temperature of the photosphere with height is responsible for the effect known as limb darkening. The Sun is not equally bright all over the disc. When we observe the Sun towards the limbs, it appears to get darker. Light from the photosphere travels through an absorptive medium. Therefore, one can see only so far into the photosphere. This is the optical depth (Fig. 1). The line of sight at the center sees deeper into the Sun to an optical depth of about 2/3 into the photosphere. In other words, photons that escape from a smaller radius of the photosphere have originated in a hotter region; therefore, they will have a higher intensity. Photons that originate from a larger radius come from a cooler part of the photosphere; therefore, this results in lower intensity. This effect is known as solar limb darkening. In addition, the solar photosphere displays various phenomena that can easily be observed in images obtained with small telescopes, such as sunspots, faculae, and granulation. Limb darkening results from the fact that we are looking into hot gas when we look at the Sun and, as a consequence of this, the brightness of the Sun decreases as one looks from the center of the disc (where we see deeper inside the Sun) towards the limb (where we will not see as deeply into the solar atmosphere because we are looking at a slant through the photospheric material).
Skip Nav Destination
Article navigation
April 2021
PAPERS|
April 01 2021
Observing Solar Limb Darkening in the Classroom
S.S.R. Inbanathan;
S.S.R. Inbanathan
Post Graduate and Research Department of Physics, The American College
, Madurai, India
Search for other works by this author on:
K. Moorthy;
K. Moorthy
Post Graduate and Research Department of Physics, The American College
, Madurai, India
Search for other works by this author on:
Ashok Kumar S
Ashok Kumar S
Post Graduate and Research Department of Physics, The American College
, Madurai, India
Search for other works by this author on:
Phys. Teach. 59, 292–293 (2021)
Citation
S.S.R. Inbanathan, K. Moorthy, Ashok Kumar S; Observing Solar Limb Darkening in the Classroom. Phys. Teach. 1 April 2021; 59 (4): 292–293. https://doi.org/10.1119/10.0004162
Download citation file:
Sign in
Don't already have an account? Register
Sign In
You could not be signed in. Please check your credentials and make sure you have an active account and try again.
Pay-Per-View Access
$40.00
Citing articles via
Quark/Gluon Plasma: When Protons Melt
Don Lincoln
Theoretical and Experimental Analysis of Tethered Buoys
Hans C. Mayer
A Simple and Cost-Effective Fluid Dynamics Apparatus to Engage Students in the Classroom and Laboratory
David James Horne, Lily Zheng, et al.
Related Content
Wavelength-Dependent Solar Limb Darkening with Smartphones, Solar Projection, and SalsaJ
Phys. Teach. (December 2022)
Rocket Propulsion with Sparklers
The Physics Teacher (September 2006)
The Opaque Projector: The Inverse of the Camera Obscura
The Physics Teacher (April 2011)
Probeware Modification of a Spectrometer
The Physics Teacher (September 2006)
Lecture Demonstration of Electron Diffraction
American Journal of Physics (December 1962)