XPoSat: ISRO’s Groundbreaking Venture Explained

ISRO has sent shockwaves through the scientific community with the launch of XPoSat at the start of the new year on January 1st, an unprecedented venture and the world’s second satellite-based mission solely devoted to unravelling the secrets of celestial bodies. The satellite achieved a precise orbit of 650 km after a 21-minute flight. The indigenously designed and fabricated mission is designated for observation from low earth orbit.

This groundbreaking endeavour, equipped with meticulously crafted technology, marks a pivotal leap in X-ray polarimetry, promising to delve deep into the enigmatic realm of X-ray emissions.

Here’s everything you need to know about the pioneering space mission by ISRO.

Unveiling XPoSat: Unraveling X-ray Polarimetry

XPoSat, or the X-ray Polarimeter Satellite, represents India's debut mission focused on studying how X-rays from celestial bodies are oriented or polarized within a specific energy range. To carry out this detailed investigation, the satellite is furnished with two crucial instruments created within the country—POLIX and XSPECT—crafted by the Raman Research Institute and UR Rao Satellite Centre in Bengaluru.

Imagine POLIX as a specialized tool that works within a specific range of X-ray energy. It's designed to catch and analyze X-rays from bright celestial sources like magnetars or black holes. Picture it as a highly sensitive 'filter' that sieves through these X-rays to reveal their polarization details—how these X-rays are aligned or organized in their path.

POLIX operates in the energy band of 8 to 30-kilo electron Volts (keV), boasting a collimator and four X-ray proportional counter detectors to filter and capture light from prominent sources in its field of view.

On the other hand, XSPECT is like a high-tech stopwatch combined with a powerful analyzer. It focuses on studying softer X-rays emitted by various celestial sources. These sources could be anything from pulsars (spinning neutron stars) to active galactic nuclei or regions around black holes. XSPECT's job is to precisely time and analyze these softer X-rays, capturing crucial data about their behaviour and characteristics. 

XSPECT specializes in fast timing and high-resolution spectroscopy in the soft X-ray energy band (0.8-15 keV)

So, these two instruments, POLIX and XSPECT, act as specialized 'eyes' and 'analyzers,' working together to scrutinize X-rays from different celestial sources—providing a deeper understanding of how these X-rays behave and what they reveal about the fascinating cosmic phenomena they originate from.

Deciphering X-rays: Understanding the Complexity

Think of X-rays as energetic siblings of visible light, both being forms of electromagnetic waves produced when electric charges move and interact with electric and magnetic fields. However, while visible light is like a gentle breeze, X-rays are more like a powerful gust of wind due to their higher energy levels.

Now, imagine playing with a skipping rope. When you move one end up and down, it creates waves along the rope. These waves travel in a specific direction, just like visible light waves. But, if you were to shake the rope vigorously and fast, the waves created would be more forceful and directional, resembling the behaviour of X-rays compared to visible light.

So, X-rays, with their intense energy, behave somewhat differently from ordinary light waves. Their 'fluctuations' or movements in the electric field depend on how electric charges move around, much like the forceful and directional waves on a vigorously shaken skipping rope compared to the gentle waves created by a casual shake.

Significance of XPoSat Mission

XPoSat is venturing into uncharted territory by diving into X-ray polarization within the medium energy band, a realm between 8 to 30 keV. This leap represents a seismic shift from conventional observations using optical or radio telescopes. Now, the focus is on a narrower slice of the electromagnetic spectrum, allowing XPoSat to delve into celestial phenomena previously untouched by polarization measurements.

In this unexplored energy range, XPoSat is poised to uncover the intricacies of cosmic entities, from those that maintain a consistent presence (termed 'persistent sources') to those that transiently appear and vanish. Among these enigmatic celestial beings are pulsars, emitting rapid pulses of radiation; active galactic nuclei, the powerhouse centres of galaxies emitting vast amounts of energy; and magnetars, celestial bodies boasting intense magnetic fields.

Through its examination of this specific energy band, XPoSat seeks to unveil the nuances of these cosmic phenomena. By scrutinizing the polarization of X-rays from these sources, it aims to unlock the secrets hidden within their emissions and unravel the distinct characteristics that define their presence in the cosmic landscape. This mission stands as a pioneering endeavour, aiming to shed unprecedented light on the nature and behaviour of these captivating celestial entities within the medium energy band of the X-ray spectrum.

Unveiling the Secrets of X-ray Polarization

In the vast expanse of space, X-rays encounter various celestial elements that cause their polarization—a phenomenon where the direction of the X-ray waves becomes aligned due to specific interactions. Imagine these X-rays as beams of light encountering different obstacles in space, like powerful magnetic fields or dense materials swirling around black holes. As these X-rays interact with these elements, their waves become organized, aligning themselves in a specific direction.

Scientists are particularly intrigued by polarized X-rays because they carry crucial information about their origins and the intricate processes governing their creation. It's akin to deciphering a message hidden within the light—each polarization pattern holds clues about the cosmic objects that emitted these X-rays and the conditions they encountered on their cosmic journey.

For instance, when X-rays pass through intense magnetic fields, their polarization changes in response to the magnetic forces they encounter. Similarly, when they interact with the swirling matter around black holes, their polarization alters due to these encounters.

By meticulously studying the polarization of these X-rays, scientists can decode the nature of the radiation, providing insights into the cosmic environments, the materials they traverse, and the physical processes responsible for generating these high-energy emissions. It's like reading the fingerprints of cosmic events encoded within the behaviour of polarized X-rays, offering a unique window into the otherwise hidden aspects of celestial objects and the complex cosmic phenomena shaping our universe.

Comparing XPoSat Globally

Prior missions in X-ray polarimetry have been limited. Notable attempts include balloon-based experiments like HX-POL and XL-Calibur by NASA and collaborators. Indian astronomers, through AstroSat, conducted X-ray source spectroscopy but lacked polarization studies.

NASA’s 2021 launch of the Imaging X-ray Polarimetry Explorer (IXPE) ventured into soft X-ray polarimetry (2 to 8 keV energy band), while XPoSat’s POLIX payload extends into the medium X-ray band (8 to 30 keV), offering an expanded observational energy band and complementing IXPE’s efforts.

XPoSat’s voyage into X-ray polarimetry holds the promise of unravelling cosmic enigmas, shedding light on the nature of celestial bodies, magnetic fields, and the intricate processes governing their emissions. With its trajectory set and instruments ready, XPoSat stands at the forefront of decoding the profound mysteries hidden within the vast expanse of the universe.