How can a planet have a deadly eclipse-like "spotlight"?

A solar eclipse occurs when the moon passes between the Earth and the sun. The result is a giant shadow that sweeps across the Earth's surface.

This world has the opposite phenomenon. Instead of a giant shadow, this world has a giant deadly "spotlight" sweep across its surface.

Must achieve these effects:

1. Must produce enough thermal power to kill humans (who are not native) and some (or all) non-native animals efficiently enough that full exposure to the light is (near?) certain doom.
2. Should have easily-observed warning signs allowing vulnerable creatures roughly one minute to find shelter. None of the lifeforms on the planet have developed its meteorology well enough to predict them except by visual/thermal observation.
3. Must be natural/meteorological/astronomical in nature. (Nothing like a giant orbiting laser).
4. Most or all plants, fungi, etc (non-animals) should be able to survive.

These would be a plus:

1. The starlight should normally be white, but the spotlight should be red (best case), blue (next best) or orange (third best). Otherwise, just brighter.
2. Should occur a few times per week in at least one area on the planet.
3. Should not be precisely periodic. If two occurrences are 36 hours apart, the next one might be 34 hours after, or 50 hours after. There may be a complex pattern, but it shouldn't be plausible to figure out over the course of a couple of weeks.

A "spotlight" that covers part of the planet is preferred, but if being larger than the planet is easier, that may be acceptable.

Here are a few ideas I was toying with, but I'm not sure how realistic they are:

1. There are multiple small (or distant) stars in the system, each white in color, and multiple red moons surrounding the planet. The stars are clustered around the center of the system so there is still a day/night cycle (is this possible?) with a roughly Earthlike luminosity. The red moons reflect light on the surface more or less constantly but the intensity is relatively small compared to the normal light from the stars... Until enough moons reflect light from enough stars to the same spot on the planet's surface! I don't know if they can really reflect enough light for this to work though.
2. Because of chaotic atmospheric conditions, atmospheric refraction causes the (single) star's rays to focus on a small area. I don't know if the color objective can be accomplished this way though.
3. There is very thick cloud cover, but sometimes a hole opens that allows the full light of the star through onto part of the surface. Also not sure if the color objective can be accomplished.

posted over 5 years ago

Devsman‭

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