Need to Know if Star Light is Coherent?

[sadegh4137]

for visible interference, we should have coherent source.

if we want to take spectrum of star, need coherent light.

i don't know that star's light coherent or not!

 

[nasu]

for visible interference, we should have coherent source.

if we want to take spectrum of star, need coherent light.

i don't know that star's light coherent or not!

If by coherent source you mean something like a laser, then no.
To obtain the spectrum of the starlight you don't need any interference.
You can just use dispersion through a prism. This is how the spectrometers used to work.
Modern ones use diffraction gratings. Still don't need intrinsically coherent source, same as you don't need it in classical Young experiment or diffraction.

 

[Andy Resnick]

for visible interference, we should have coherent source.

if we want to take spectrum of star, need coherent light.

i don't know that star's light coherent or not!

There are two limiting cases of the general optical coherence function: spatial and temporal. Temporal coherence refers to the spectral width of the light, while spatial coherence is a measure of the size of the source. Temporal coherence is measured using (for example) a Michaelson interferometer, while spatial coherence can be measured using a Young double-slit interferometer.

Laser light, for example, has a very narrow spectrum (long temporal coherence), but the spatial coherence is low (speckle is visible). Starlight, by contrast, has a short coherence time (broad spectrum), but is highly spatially coherent. Just as temporal coherence can be increased by spectrally filtering the light, spatial coherence can be increased by spatially filtering the light (through a pinhole or single-mode fiber, for example).

Measuring the spectrum of a distant star is fairly easy since the spatial coherence is much larger than the entrance slit of a spectrometer.

 

[y33t]

There are two limiting cases of the general optical coherence function: spatial and temporal. Temporal coherence refers to the spectral width of the light, while spatial coherence is a measure of the size of the source. Temporal coherence is measured using (for example) a Michaelson interferometer, while spatial coherence can be measured using a Young double-slit interferometer.

Laser light, for example, has a very narrow spectrum (long temporal coherence), but the spatial coherence is low (speckle is visible). Starlight, by contrast, has a short coherence time (broad spectrum), but is highly spatially coherent. Just as temporal coherence can be increased by spectrally filtering the light, spatial coherence can be increased by spatially filtering the light (through a pinhole or single-mode fiber, for example).

Measuring the spectrum of a distant star is fairly easy since the spatial coherence is much larger than the entrance slit of a spectrometer.

Fields radiating from a star is all over the spectrum and they are prone to various effect (doppler etc) on their way as well. It doesn't make sense to me to talk about 'coherence of a star'.

 

[sardar]

I can provide some insights on the concept of coherent light and how it applies to starlight. Coherent light refers to light waves that have the same frequency and maintain a constant phase relationship with each other. This allows for constructive interference, resulting in a bright and well-defined pattern. In contrast, incoherent light has varying frequencies and phases, leading to a diffuse and less defined pattern.

In order to observe visible interference, a coherent light source is indeed necessary. This is because the interference pattern is only visible when the light waves are in phase with each other. Therefore, if we want to take a spectrum of a star, which involves analyzing the different frequencies of light, a coherent light source is needed to produce a clear and distinguishable pattern.

However, it is currently unknown if starlight is coherent or not. This is because the light from stars undergoes various interactions and distortions as it travels through space, making it difficult to determine its coherence. Additionally, the size and distance of stars also play a role in determining the coherence of their light.

In conclusion, while a coherent light source is necessary for visible interference and spectroscopy, the coherence of starlight remains a topic of ongoing research in the scientific community.