Mystery Solved: How Planets Reflect Light?

Vrinda Gupta
Vrinda Gupta
Mystery Solved: How Planets Reflect Light?

The Mystery

In 1916, an American astronomer named Henry Norris Russell came across the problem of calculating reflected light from the planets. This problem was posed in a widely circulated research paper. Although, Russell mentioned that the percentage of sunlight reflected by the planet and the phase curves did tell about their properties. He could not find out a general solution that could apply to all bodies. However, he derived important information through photometric observations on the sun, the moon and the planets.

The Solution By Researchers

In the year 1981, another astronomer, Bruce Hapke also tried to solve this problem. Although, he tried to provide an analytical solution. He also didn’t succeed in finding a closed- function solution. His solution did not express the relationship between the percentage of sunlight reflected by a planet and the phase curves.

An astrophysicist from the University of Bern, Switzerland has solved the century-old mystery of how planets reflect light. He has discovered closed-form solutions, solvable in finite steps using the relationship between the reflectivity of the planet and its phase curve. The phase curve determines the brightness of the planet as the function of the phase angle. The phase angle is the angle between sunlight falling on the planet and reflected light from the planet on Earth.

This research is produced by Heng in collaboration with two other scientists. It has been published in Nature Astronomy on August 30.  In a statement, Heng said ‘ The ground-breaking aspect of these solutions is that they are valid for any law of reflection, which means they can be used in very general ways”.

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In Conclusion

The trailblazing solutions provided by Heng and his team of researchers will surely provide a wider perspective to astronomers.

These solutions will also offer a multitude of benefits that will continue to foster the world of Astronomy. It will help astronomers in efficiently analyzing decades of data that is available. Subsequently,  it will assist us in knowing more about the planets just by observing the sunlight they reflect.





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