Do Stars Flicker Colour & Intensity in the Night Sky?

[dacruick]

Hi,

Do stars flicker colour and intensity in the night sky?

I was in an argument with a friend of mine, and he told me stars can flicker 300nm in wavelength at 15Hz. I told him that I thought his eyes were just confusing change in intensity with colour.

Was I wrong?

Thanks

 

[phinds]

Hi,

Do stars flicker colour and intensity in the night sky?

I was in an argument with a friend of mine, and he told me stars can flicker 300nm in wavelength at 15Hz. I told him that I thought his eyes were just confusing change in intensity with colour.

Was I wrong?

Thanks

Since the flicker has nothing to do with the stars themselves, but rather is an artifact of diffraction of the light by our atmosphere before it reaches your eye, it seems reasonable to assume that some of the flickering is a prismatic effect by tiny moisture drops that would cause some apparent shift in color but I wouldn't know how to quantize that in wavelengths. Probably could be determined experimentally but I doubt the human eye is a sensitive enough instrument for that.

 

[dacruick]

Since the flicker has nothing to do with the stars themselves, but rather is an artifact of diffraction of the light by our atmosphere before it reaches your eye, it seems reasonable to assume that some of the flickering is a prismatic effect by tiny moisture drops that would cause some apparent shift in color but I wouldn't know how to quantize that in wavelengths. Probably could be determined experimentally but I doubt the human eye is a sensitive enough instrument for that.

You're saying the flickering couldn't be caused by an asteroid or something of that sort? At any point in time, what is the probability that something is obstructing the optical path between our eye and the star?
Also, when you say that your eye isn't a sensitive enough instrument you are saying that you highly doubt the quoted 300 nm wavelength difference?

 

[phinds]

You're saying the flickering couldn't be caused by an asteroid or something of that sort? At any point in time, what is the probability that something is obstructing the optical path between our eye and the star?
Also, when you say that your eye isn't a sensitive enough instrument you are saying that you highly doubt the quoted 300 nm wavelength difference?

The stars, as observed outside the Earth's atmosphere are essentially unwavering points of light. I'm sure there must be a fair amount of disruption of the light beams in an absolute sense but I think it's likely a small amount proportionally. That is, the small variations in intensity are nothing like the flickering that we see due to the atmospheric effects. In fact, adaptive optics can remove most of the flickering BECAUSE it is almost entirely an atmospheric effect. If the flickering were happening outside the atomsphere, adaptive optics wouldn't work.

I was not making any comment on wavelenghts, just on the ability of the human eye to make that kind of fine-tuned distinctions in intensity and wavelengths. THIS point is pretty much speculation on my part and I could be quite wrong. Certainly some humans can make astoundingly precise distinctions among colors, which are of course just different wavelenghts. The paragraph above this is not speculation.

 

[turbo]

Stars are very distant and are point-sources, as seen from Earth. Stars are very large bodies and they cannot "flicker" (short-term variations) because they are so very large. The fire in your stove might flicker, but you cannot expect a huge fusing mass like a star to vary in a way that could be described as a flicker.

Sharp drops in luminosity could theoretically be cause by occlusion (asteroid eclipse or such), but such events would be so very rare as to be vanishingly insignificant. Searches for MACHOS have turned up empty. You can draw your own conclusions.

 

[russ_watters]

You're saying the flickering couldn't be caused by an asteroid or something of that sort? At any point in time, what is the probability that something is obstructing the optical path between our eye and the star?

Extrordinarily unlikely. As someone who often has a telescope pointed at the night sky, I can tell you that you most often see an extraneous satellite or airplane go across your field of view and may see a handful a night.

Also, when you say that your eye isn't a sensitive enough instrument you are saying that you highly doubt the quoted 300 nm wavelength difference?

He's just saying you can't measure specific wavelengths with your eyes.