NASA launched the Imaging X-ray Polarimetry Explorer (IXPE) on December 9, 2021 onboard SpaceX’s Falcon 9 rocket the Kennedy Space Center in Florida. The IXPE observatory is a joint effort of NASA and the Italian Space Agency. According to NASA, the mission will study “the most extreme and mysterious objects in the universe–supernova remnants, supermassive black holes, and dozens of other high-energy objects.” The mission complements other X-ray telescopes such as the Chandra X-ray Observatory and the XMM-Newton of the European Space Agency.
The mission is expected to last for two years with the observatory orbiting over the Earth’s equator at 600 km altitude. In its first year in space, the IXPE is expected to study about 40 celestial objects.
The spacecraft carries three state-of-the-art identical space telescopes. Each of the telescopes has a light-weight X-ray mirror and a detector unit which will help observe polarised X-rays from neutron stars and supermassive black holes. Polarisation is a way of looking at how X-ray is oriented as it travels through space. The polarisation of light contains clues to the environment where the light originated. Measuring the polarisation of these X-rays would help in the study of where the light came from and in understanding the geometry and inner workings of the light source.
According to NASA, the polarisation measurements will help scientists answer questions about how black holes spin, if the black hole at the centre of the Milky Way is actively feeding on surrounding material in the past, how pulsars shine so brightly in X-rays, and what gives the power to the jets of energetic particles that are ejected from the region around the supermassive black holes at the centres of galaxies.
The first imaging data received from IXPE are of the supernova remnant Cassiopeia A (Cas A). The object exploded in the 17th century and sent shock waves, heating the surrounding gas to high temperatures and accelerating cosmic ray particles to make a cloud that glows in X-ray light. Cas A has been studied by other telescopes, including Chandra, but IXPE will allow researchers to examine it in a new perspective.
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