The IXPE (Imaging X Ray Polarimetry Explorer) satellite launched in 2021 from the Kennedy Space Center, Florida, USA, is keeping its promises: the high expectations of the astrophysical community are totally fulfilled.
IXPE was born as a NASA mission for the SMEX (Small Explorer Program) and it was developed with a strong Italian contribution coordinated and funded by ASI – Agenzia Spaziale Italiana,
OHB Italia, as unique industrial partner, realized fundamental parts of the satellite: the Detector Unit Electronics (BEE), the so-called Filter and Calibration Wheel Mechanism and the Detector Service Unit (DSU) which controls the Detector Units and provides a variety of functions as thermal control of detector, collecting scientific data and also interfaces to the rest of the spacecraft.
This new space explorer with three telescopes on board, is observing the universe at high energies, measuring the polarisation in X-rays emitted by large cosmic sources and analysing celestial objects with extreme magnetic-gravitational fields with a detail never seen before.
The release of gravitational energy in binary systems is among the most powerful physical processes in the Universe. X-ray-emitting consists of a compact object (a black hole or a neutron star) and a buddy-star from which gas is withdrawn. Since the early 1970s, the Cygnus X-3 binary system was famous to become very bright in the radio band, to fade then in a few days, for this reason it was defined as “Cygnus X-3 astronomical puzzle”: the science needed IXPE to solve this issue!
The satellite discovered that the compact object is surrounded by an envelope of dense, opaque matter. The light observed is a reflection from the inner walls of a ‘funnel’ similar to a ‘cup’ with a mirror-like interior, allowing to observe for the first time ever the polarisation, i.e. the degree of order of the X-rays it was emitting.
The measured value cannot be explained by any applicable model but it was needed to develop a new one specifically. This is based on the assumption that we do not observe directly emitted light, but light that reaches the Earth after being reflected by a ‘wall’ formed by matter falling into the black hole.
This discovery led to the classification of Cygnus X-3 as an ultra-bright X-ray source (ULXs): the source is able to swallow so much gas so quickly that some of it is not captured by the black hole, but is instead ejected from the system itself.
Due to the enormous distances of these sources, they appear relatively faint to X-ray telescopes. Our discovery has now revealed an extremely bright counterpart of these distant ULXs even within our own Galaxy.
X-ray astronomy is really taking with IXPE an innovative, amazing, huge and strong step forward.
