It seems that the Andromeda constellation is full of surprises. It contains the Andromeda Galaxy and also the brightest star, Alpha Andromedae, or Alpheratz. Andromeda Galaxy and the Milky Way are approaching each other at a speed of 100 to 140 kilometers per second, but until and if they collide, astronomers are searching for new and impressive features of our neighbor.

For instance, after performing a seven-year study of Alpha Andromedae, they found some very interesting shifting blotches of mercury vapor around the star, which could mean that this element is being constantly agitated up and down in huge clouds.

The interesting part is the fact that this effect does not depend on magnetic fields, so this is the first observed weather pattern in a star, producing surface features that depend only on atmospheric effects.

No one has been able to find definite signatures of weather in stars before," says astrophysicist Saul Adelman of The Citadel in Charleston, S.C. "In most stars, what is seen is the result of magnetic activity."

Adelman had previously reported finding a few large, bright stars that lacked magnetic fields but were chemically blotchy anyway and recorded a fluctuating amount of mercury in the atmosphere of Alpha Andromedae.

This star is located 97 light years from Earth, about 30 times brighter than the Sun, twice as wide and has a surface temperature of about 13,000 kelvins. By scanning for mercury and mapping its concentration on the surface of the star, they found an undulating high-concentration band of mercury circles the star's equator.

The difference in thickness between various areas of the surface is sometimes as much as a hundredfold, which is most probably caused by stellar winds and variations in the star's rotational speed between the equator and poles, which in turn influence the rise and fall of the clouds.

Mercury made atmospheric changes easily observable on Alpha Andromedae, but these may exist on other stars too, only more difficult to observe.