GS PAPER III: Science and Technology- developments and their applications and effects in everyday life.

Context: Polar-Areas Stellar-Imaging in Polarisation High-Accuracy Experiment (PASIPHAE) will help to understand the mysteries surrounding the origin of the universe.

• This vital instrument will be used in upcoming sky surveys to study stars, is being led by an Indian astronomer.
• The project has been funded by the world’s leading institutions, signalling India’s growing expertise in building complex astronomical instruments.

What is PASIPHAE?

• Polar-Areas Stellar-Imaging in Polarisation High-Accuracy Experiment (PASIPHAE) is an international collaborative sky surveying project.
• Scientists aim to study the polarisation in the light coming from millions of stars.
• The survey will use two high-tech optical polarimeters to observe the northern and southern skies, simultaneously.
• It will focus on capturing starlight polarisation of very faint stars that are so far away that polarisation signals from there have not been systematically studied.
• The distances to these stars will be obtained from measurements of the GAIA satellite.
• By combining these data, astronomers will perform a maiden magnetic field tomography mapping of the interstellar medium of very large areas of the sky using a novel polarimeter instrument known as WALOP (Wide Area Linear Optical Polarimeter).

Why is PASIPHAE important?

• Since its birth about 14 billion years ago, the universe has been constantly expanding, as evidenced by the presence of Cosmic Microwave Background (CMB) radiation, which fills the universe.
• Immediately after its birth, the universe went through a short inflationary phase during which it expanded at a very high rate, before it slowed down and reached the current rate. However, so far, there have only been theories and indirect evidence of inflation associated with the early universe.
• A definitive consequence of the inflationary phase is that a tiny fraction of the CMB radiation should have its imprints in the form of a specific kind of polarisation (known scientifically as B-mode signal).
• All previous attempts to detect this signal met with failure mainly due to the difficulty posed by our galaxy, the Milky Way, which emits copious amounts of polarised radiation.
• Besides, it contains a lot of dust clouds that are present in the form of clusters. When starlight passes through these dust clouds, they get scattered and polarised.
• The PASIPHAE survey will measure starlight polarisation over large areas of the sky.
• This data along with GAIA distances to the stars will help create a 3-Dimensional model of the distribution of the dust and magnetic field structure of the galaxy.
• Such data can help remove the galactic polarised foreground light and enable astronomers to look for the elusive B-mode signal.

What is WALOP?

• Wide Area Linear Optical Polarimeter (WALOP) is an instrument, when mounted on two small optical telescopes, that will be used to detect polarised light signals emerging from the stars along high galactic latitudes.
• A WALOP each will be mounted on the 1.3-metre Skinakas Observatory, Crete, and on the 1-metre telescope of the South African Astronomical Observatory located in Sutherland.
• WALOP will operate on the principle that at any given time, the data from a portion of the sky under observation will be split into four different channels.
• Depending on the manner in which light passes through the four channels, the polarisation value from the star is obtained.
• That is, each star will have four corresponding images which when stitched together will help calculate the desired polarisation value of a star.
• As the survey will focus on sky areas where very low polarisation values (<0.5 per cent) are expected to emerge, a polarimeter with high sensitivity and accuracy clubbed with a large field of view was needed, so WALOP was planned sometime in 2013.
• A major limitation while using large optical telescopes is that they cover a relatively smaller area of the sky, defeating the overall purpose of PASIPHAE.
• The attempt to press-in the 1-metre-class telescopes is also to demonstrate that breakthrough science and challenging experiments can be undertaken using smaller telescopes, even in the era of large and extremely large telescopes.

https://indianexpress.com/article/explained/explained-how-pasiphae-will-peep-into-the-unknown-regions-of-the-sky-7357628/

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