5 Theories (1 Aliens)

Comets, solar power stations, or a nebula? Astronomers have five theories, which each explain the apparently random dimmings.

COMETS PASS IN FRONT OF STAR

Clusters of comets – and their very long tails – could block out the light of the star at irregular intervals. The comets must orbit far away from the star, as the water vapour of the tails would otherwise be heated and emit infrared heat radiation. PROBLEM: The theory does not explain the general dimming of the star's light over the past 100 years.

A NEBULA DIMS THE LIGHT

A dark nebula of dust and gas, which is located in empty space between Earth and the star, could dim the light of the star at irregular intervals. The turbulent motions in the nebula would compress the dust and the gases in different places of the nebula. PROBLEM: A dark nebula would also dim the light of the neighbouring stars, and that is not the case.

THE LIGHT PASSES THE DISC SURROUNDING A BLACK HOLE

Black holes are surrounded by a disc of dust and gases, which is spinning around the hole. Such a disc of varying thickness could dim the light from the star at irregular intervals. PROBLEM: The disc must be larger than any disc ever observed to have dimmed the light for 100 years.

SOLAR POWER PLANTS SURROUND STAR

According to some scientists, the reduction of the star's brightness over the past 100 years and the irregular dimmings could be due to alien civilisations constructing huge clusters of solar power plants around the star. PROBLEM: This would be the first alien civilisation ever discovered. It seems hard to believe.

STAR SWALLOWED A PLANET

In the past 10,000 years, the star might have swallowed a planet, first increasing brightness, which would secondly be reduced to the normal level. If the planet had moons which came close to the star, they could melt into clouds of dust and gas to dim the light. PROBLEM: Both planet remains and clouds should emit infrared heat radiation, but none have been detected.