The spectrum of sunlight closely resembles that of a blackbody because the sun acts as a good approximation of one. The distribution of photons emitted by the sun aligns with the Planck distribution, primarily due to its high temperature and size. Most of the sun's emission is continuous spectrum radiation generated in the photosphere, where photons are absorbed and reemitted in equilibrium. This process results in minimal absorption or emission lines, leading to a spectrum that is predominantly blackbody-like. Overall, the sun's characteristics contribute to its similar spectral output.
#1
wenty
20
0
Why is the spectrum of sunligt similar to that of a blackbody?
Because the observed wavelength (or frequency) distribution of photons from the Sun is the same as that of a blackbody, to the zeroth order (using total energy as the measure).
Because the sun is a big, hot thing, and the Planck distributed radiation swamps the line and band emissions.
Jerry Abbott
#5
Tyger
388
0
A little more detailed explanation is that most of the emmision from the sun is continuous spectrum radiation produced deeper in the photosphere where the photons are absorbed and reemitted about equally, so that the two processes are in equilibrium, which is what occurs in a blackbody. Very little of the radiation is absorbed (fraunhofer lines) or added to produce emission lines.
Partial solar eclipse from Twizel, South Isl., New Zealand ...
almost missed it due to cloud, didnt see max at 0710 NZST as it went back into cloud.
20250922, 0701NZST
Canon 6D II 70-200mm @200mm,
F4, 100th sec, 1600ISO
Makeshift solar filter made out of solar eclipse sunglasses
3I/ATLAS, also known as C/2025 N1 (ATLAS) and formerly designated as A11pl3Z, is an iinterstellar comet. It was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) station at Río Hurtado, Chile on 1 July 2025.
Note: it was mentioned (as A11pl3Z) by DaveE in a new member's introductory thread.
https://www.physicsforums.com/threads/brian-cox-lead-me-here.1081670/post-7274146
https://earthsky.org/space/new-interstellar-object-candidate-heading-toward-the-sun-a11pl3z/
One...
Is a homemade radio telescope realistic?
There seems to be a confluence of multiple technologies that makes the situation better than when I was a wee lad: software-defined radio (SDR), the easy availability of satellite dishes, surveillance drives, and fast CPUs.
Let's take a step back - it is trivial to see the sun in radio. An old analog TV, a set of "rabbit ears" antenna, and you're good to go. Point the antenna at the sun (i.e. the ears are perpendicular to it) and there is...