Indian astronomers have discovered a new way to study the atmospheres of extra solar planets. They demonstrated that planets orbiting stars other than the Sun can be researched by researching polarisation fingerprints and detecting light polarisation. Existing technologies can detect these polarisation signals or fluctuations in light scattering strength, allowing for the research of planets outside the solar system to grow.
Astronomers have recently revealed that many other stars, like our solar system, have planets around them. So far, approximately 5000 such exoplanets have been discovered so far. Sujan Sengupta, a scientist at the Indian Institute of Astrophysics (IIA), Bangalore, an autonomous institute of the Department of Science and Technology (DST), Government of India, proposed a few decades ago that the thermal radiation of hot young planets and the reflected light of planets orbiting other stars, known as extra-solar planets or exoplanets, would both be polarised, and that measuring the polarisation could reveal the chemical composition and other properties of these planets The discovery of polarisation in several Brown Dwarfs, a kind of failed star with an atmosphere very similar to Jupiter’s, encouraged researchers all over the globe to develop very sensitive polarimeters and utilise polarimetric techniques to explore exoplanetary environments, confirming the prediction.
Aritra Chakrabarty, a postdoctoral researcher at IIA who collaborated with Sujan Sengupta, has devised a sophisticated three-dimensional numerical approach for simulating exoplanet polarisation. Because of their fast spin rotation, exoplanets, like solar planets, are somewhat oblate.Furthermore, depending on its orbit around the star, the starlight illuminates just a portion of the planetary disc. Non-zero polarisation is caused by the asymmetry of the light-emitting area.
The authors built a Python-based computational algorithm that integrates a state-of-the-art planetary atmosphere model and uses all such asymmetries of an exoplanet circling the parent star at varying inclination angles in their study published in “The Astrophysical Journal.” They averaged the amount of polarisation at various latitudes and longitudes of the lighted and rotation-induced oblate planetary surface defined with respect to the disc centre. If the starlight is obstructed, the polarisation at various wavelengths is sufficiently high to be observed even by a basic polarimeter. It aids in the research of exoplanet atmospheres and their chemical composition.
Even if we can’t photograph the planet directly and allow unpolarized starlight to mingle with the planet’s polarised reflected light, the quantity should be a few ten parts of a million, which can still be identified by some of the current high-end equipment like HIPPI, POLISH, PlanetPol, and others.” The findings will assist in the development of tools that are sensitive enough to direct observers, according to Aritra Chakrabarty.
Unlike traditional and popular methods such as Transit Photometry and Radial Velocity, which can only detect planets seen virtually edge-on, this polarimetric approach may discover and study exoplanets orbiting with a wide range of orbital inclination degrees.As a result, polarimetric approaches will open up a new window for the study of exoplanets in the near future, allowing us to overcome many of the constraints of previous techniques.
Source: Press Information Bureau