Indian astronomers have found a new method to understand the atmosphere of a planet beyond our solar system by observing the polarization of light. In our quest for life beyond Earth, science has taken us to more than 5,000 exoplanets in the Milky Way galaxy, rich in water and atmospheric compositions, some larger than Earth, others still larger than Jupiter.
Astronomers at the Indian Institute of Astrophysics have now devised a method to study the atmosphere of these planets by observing polarization signatures or variations in the intensity of light scattering using radars and radars. ground observatories. It has been discovered that exoplanets revolve around a star, just as the planets in our solar system revolve around the Sun.
The reflected light from the planets orbiting these stars would be polarized and reveal the chemical composition and other properties of the exoplanetary atmosphere. In an article published in The Astrophysical Journal, Aritra Chakrabarty and Sujan Sengupta detail a three-dimensional digital method and simulate the polarization of exoplanets.
The two astronomers in the article say that, just like the planets in our solar system, exoplanets are slightly flattened due to their rapid rotation. In addition, depending on its position around the star, only part of the planetary disk is illuminated by starlight. This asymmetry of the light-emitting region gives rise to a non-zero polarization.
They developed a digital code based on Python (programming language) that incorporates a state-of-the-art model of the planetary atmosphere and used all of these asymmetries of an exoplanet orbiting the parent star at different angles. tilt and calculated the amount of polarization at different latitudes. and longitudes.
The polarization at different wavelengths is high enough and can therefore be detected even by a simple polarimeter if starlight is blocked. It makes it possible to study the atmosphere of exoplanets as well as their chemical composition.
Aritra Chakrabarty, postdoctoral researcher at IIA and co-author of the study, said: âEven though we cannot image the planet directly and unpolarized starlight is allowed to mix with polarized reflected light planet, the amount should be a few tens of parts of a million, but can still be detected by some of the existing high-end instruments such as HIPPI, POLISH, PlanetPol. The research will help design instruments with appropriate sensitivity and guide observers. “
Astronomers widely use the transit method to detect distant planets in other systems. A transit occurs when a planet passes between a star and its observer.
According to NASA, the transits reveal an exoplanet not because we see it directly many light years away, but because the planet passing in front of its star dims its light very slightly. This gradation can be seen in light curve graphs showing the light received over a period of time. As the exoplanet passes in front of the star, the light curve will show a drop in brightness. If this process is repeated on a pattern, it confirms that a planet-like object orbiting the star on a path.
The Department of Science and Technology said in a statement that the polarimetric method can detect and probe orbiting exoplanets with a wide range of orbital tilt angles.