NASA and the Italian Space Agency are scheduled to launch an X-ray-observing mission on Thursday that should give astronomers an important new tool for studying energetic objects across the universe.
The will ride into orbit on a SpaceX Falcon 9 rocket from Cape Canaveral, Florida, and will measure the polarisation of the X-ray light coming from objects including neutron stars, black holes and the glowing leftovers of exploded stars, known as supernovae remnants.
Polarisation can be thought of as a collective orientation of the electromagnetic waves that make up light. Studying the polarisation in the glow from astronomical bodies can help researchers refine their models of the physics at work in those objects.
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“Each [theoretical] model of any of these [X-ray] sources has a peculiar expected signature in polarisation and measuring it would allow us to [identify] the correct model,” explains at Italy’s National Institute for Astrophysics, who works on the IXPE project.
Polarisation data can also provide clues about the physical characteristics of distant objects. For example, it can reveal if an X-ray-emitting object has an asymmetrical shape – such as a swirling disc of superheated material around a black hole or neutron star.
“Measurements of polarisation give us the opportunity to study the asymmetry of the system even when the source is too far, or too small, to be resolved with our telescopes,” says Muleri.
One enigma that scientists hope the mission will be able to shed light on is the immense “relativistic” jets of matter blasted out from black holes at close to the speed of light. The IXPE observations should give researchers a detailed insight into the magnetic fields and particles within these jets, says at University College London.
“This information will be extremely important in understanding the genesis and structural composition of relativistic jets, as well as helping to clarify more precisely how black holes power and launch these [jets] across such vast distances,” he says.
Supernovae remnants are another type of object that the IXPE will investigate. Astronomers think these glowing clouds of material – permeated by violent shockwaves from the detonation of a star – are responsible for producing high-energy particles called cosmic rays.
“These are believed to be important to heating up gas in the cosmos,” says at Cardiff University in the UK. “Polarisation imaging in the X-ray wavelengths will capture exactly how the particles are accelerated in supernova remnants.”
Ahead of the mission’s launch into orbit 540 kilometres above Earth, there is a feeling of “cautious optimism” on the team, according to the project’s principal investigator, at the Marshall Space Flight Center in Alabama. “Everything has to work and we won’t know [if it does] until we complete the 40-day commissioning phase,” he says.
For some, the prospect of starting to resolve enduring mysteries is already generating excitement. “IXPE will provide us [with] a new observational window on the astronomical objects that shine in X-rays, making possible measurements that have been pursued but precluded to us for 50 years,” says Muleri. “Over such a long period, we accumulated many expectations based on our current knowledge that we now will be able to confirm or disprove.”
