Astronomy

Where do the stars go in the day?

A starry nightA starry night The stars are still there in the sky during the day. You just cannot see them because the sky is so bright. In fact, there is one star you can see during the day—although you should NEVER look at it directly: the Sun, our local star. During the day, the Sun's rays overpower the faint light we see from all the other stars. At night, when the Sun is shining on the other side of the Earth, it becomes possible to see the stars that were there in the sky all along. If you watch the sunset on a clear night, as the Sun's rays become dimmer and dimmer, the brightest stars start to become visible, beginning with those farthest away from the setting Sun.

Speeded-up video of a sunsetSpeeded-up video of a sunsetClick to play video

During the day, when our part of the Earth is facing the Sun, the blue light that radiates from the Sun (although sunlight looks white, it is really made up of several different colours—the colours of the rainbow) scatters through the atmosphere, which is what causes the sky to look blue. This light is so bright that the faint light from very much more distant stars is blocked. If the Earth had no atmosphere, the stars would be visible in daylight, just as they are from the Moon’s surface even while the Sun is shining.

Sirius, the brightest star in the night sky, would have to shine at five times its normal intensity if it were to become visible during the day.

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