First glimpses of a stars weather

Astronomers have for the first time observed the weather, caused by the same forces as on Earth, on a star.

London, June 26 : Astronomers have for the first time observed the weather, caused by the same forces as on Earth, on a star.

Previously, astronomers had thought that any structures on stars were caused by magnetic fields. Sunspots, for example, are relatively cool regions on the Sun where strong magnetic fields prevent energy from flowing outwards.

But now, seven years of painstaking observations of Alpha Andromedae has shown that stars do not need magnetic fields to form clouds after all.

Lying about 100 light years away, Alpha Andromedae is one of a class of stars unusually rich in mercury and manganese. Earlier observations of similar stars had revealed uneven distributions of mercury, but all of them had strong magnetic fields.

Scientists say, as relatively massive stars do not mix gases in their atmospheres, which less massive stars, like the Sun, do, so the balance between the pull of gravity and the push of radiation pressure concentrates some heavy elements at certain atmospheric levels.

At that point, it was believed, their magnetic fields continued the separation process, sequestering some chemicals in particular regions.

But now Oleg Kochukhov of Uppsala University in Sweden and his team have found that this last step is not necessary to create chemical clouds on a star.

They observed that the mercury concentration in Alpha Andromedae varied by as much as a factor of 10,000 across its surface, and the pattern of concentration changed as well.

The researchers are, however, not sure as to what causes the clouds to change over time.

They believe the changes "may have the same underlying physics as the weather patterns on terrestrial and giant planets".

The findings appear in the journal Nature Physics, reports New Scientist.

ANI