London, Jan 9 (IANS): Scientists have found a star that is almost identical to the Sun except for the chemical composition -- which they believe is like a Rosetta Stone that can help shed light on sun's variability and its effect on Earth's climate.

The star is located 120 light-years away in the constellation of Cygnus and, on the surface, it looks just like the Sun. It has the same mass, radius and age -- but inside, the chemical composition of the star is very different.

It consists of around twice as many heavy elements as in the Sun. Heavy elements here means elements heavier than hydrogen and helium.

"The unique combination of a star almost identical to the Sun, except for the chemical composition, with a cycle that has been observed from both the Kepler spacecraft and from ground makes this star a Rosetta Stone for the study of stellar dynamos," said Christoffer Karoff from Aarhus University in Denmark.

The study can help understand how the irradiance of the Sun has changed over time, which is likely to have an effect on our climate.

For the study, detailed in the Astrophysical Journal, the team combined observations from the Kepler spacecraft with ground-based observations dating as far back as 1978, thereby reconstructing a 7.4 year cycle in this star.

By combining photometric, spectroscopic and asteroseismic data, the team collected the most detailed set of observations for a solar-like cycle in any star other than the Sun.

The solar cycle is driven by the solar dynamo, which is an interplay between magnetic fields, convection and rotation.

The observations revealed that the amplitude of the cycle seen in the star's magnetic field is more than twice as strong as what is seen on the Sun, and the cycle is even stronger in visible light.