Yes, stars can appear to flash red and green, but this is not due to changes in the star itself.
The phenomenon of stars appearing to flash red and green is caused by Earth's atmosphere.
How Atmospheric Refraction Creates the Illusion
The Earth's atmosphere acts like a prism, splitting the light from stars into different colors. This process is called refraction. When starlight passes through our atmosphere, it bends, and different colors of light bend by slightly different amounts. As a result, we might perceive a star's light flashing red and green.
Refraction of Light: Just as a prism splits sunlight, the atmosphere can split starlight.
Color Separation: Different colors of light (like red and green) bend at slightly different angles when passing through the atmosphere.
Perceived Flashing: This can cause us to see the star’s light briefly shift to red and then green.
Example: Capella
The star Capella is a great example where people often report seeing red and green flashes. According to the reference, these flashes are not originating from Capella, but are caused by the refraction of its light in the Earth's atmosphere.
Why Stars Don't Actually Change Color
Stars have a consistent color based on their temperature. A star's color doesn't rapidly switch between red and green like a traffic light. The perceived red and green flashes are atmospheric effects, not actual changes in the star's color.
In Summary
While we may see stars flash red and green, this phenomenon is not intrinsic to the star itself. It's an optical illusion created by the way our atmosphere bends and separates light. The next time you see a star exhibiting these colors, remember it's Earth's atmosphere putting on a light show!
