ISRO lights up the new year with XPoSat launch to study black holes

Ushering in the new year, the Indian Space Research Organisation (Isro) on Monday successfully launched XPoSat  (X-ray Polarimeter Satellite) to study black holes and neutron stars.

Alongside ten other satellites, the XPoSat soared skyward aboard the PSLV-C58 rocket from Sriharikota. The satellite achieved its planned 650 km circular low earth orbit after a flawless 21-minute flight. 

India’s first polarimetry mission, XPoSat is an observatory satellite that aims to investigate the polarization of X-ray emissions from celestial sources in the medium frequency band, including black holes, to gain new insights into their behavior and properties. 

XPoSat’s five-year mission targets celestial sources emitting polarized X-rays, with prime observations occurring during earth’s shadow-casting eclipses of highly magnetic magnetars and neutron stars.

With this launch, India becomes only the second nation to have an X-ray polarimetry mission after Nasa’s Imaging X-ray Polarimetry Explorer (IXPE). 

Isro shared the news on X (formerly Twitter) on Monday morning. 

PSLV-C58/XPoSat Mission:
Lift-off normal 🙂

🛰️XPoSat satellite is launched successfully.

🚀PSLV-C58 vehicle placed the satellite precisely into the intended orbit of 650 km with 6-degree inclination🎯.

The POEM-3 is being scripted …#XPoSat

— ISRO (@isro) January 1, 2024

Prime Minister Narendra Modi also took to X to congratulate the Indian space body. 

“A great start to 2024 thanks to our scientists! This launch is wonderful news for the space sector and will enhance India’s prowess in this field. Best wishes to our scientists at Isro and the entire space fraternity in taking India to unprecedented heights,” he said. 

A great start to 2024 thanks to our scientists! This launch is wonderful news for the space sector and will enhance India’s prowess in this field. Best wishes to our scientists at @isro and the entire space fraternity in taking India to unprecedented heights. https://t.co/4O4F6kRpEX

— Narendra Modi (@narendramodi) January 1, 2024

Building upon Nasa’s IXPE mission which launched in 2021, India’s XPoSat pushes the boundaries of X-ray polarimetry further. Unlike IXEP, which focuses on the 2-8 keV range, XPoSat will explore the 8-50 keV energy range, offering a new perspective on cosmic phenomena. 

XPoSat packs two scientific payloads: POLIX, the Indian X-ray Polarimeter, and XSPECT, the X-ray Spectroscopy and Timing instrument, crafted by Bengaluru’s Raman Research Institute (RRI) and UR Rao Satellite Centre respectively. 

Objectives of this mission are to measure the polarization of X-rays in the energy band 8-30keV emanating from about 50 potential cosmic sources through Thomson Scattering by POLIX payload; to carry out long-term spectral and temporal studies of cosmic X-ray sources in the energy band 0.8-15keV by XSPECT payload; and to carry out polarisation and spectroscopic measurements of X-ray emissions from cosmic sources by POLIX and XSPECT payloads respectively in the common energy band.

POLIX will operate in the medium frequency band (8-30 keV). This novel instrument incorporates a collimator for targeted observations and utilizes four X-ray proportional counter detectors for sensitive polarization measurements. Designed and built by RRI, it will focus on a few tens of carefully chosen astronomical sources.

Meanwhile, XSPECT will provide high-resolution spectra and rapid timing data in the 0.8-15 keV band. This versatile instrument allows for in-depth studies of diverse cosmic objects, including X-ray pulsars, black hole binaries, neutron stars, active galactic nuclei, and magnetars.

Along with the expanded observational window and combined with its focus on 50 prominent galactic sources, the mission promises to revolutionize our understanding of the universe.

Traditionally, astronomical observations relied on data like spectroscopic, imaging and timing–based data from a range of telescopes, from optical to radio frequencies. Investigating the polarization of celestial objects was limited to these same bands. XPoSat marks a breakthrough by enabling X-ray polarization measurements for bright sources, specifically in the unexplored medium frequency band (8-30 keV).