![A composite image of a pulsar wind nebula, which strongly resembles a ghostly purple hand with sparkling fingertips. (Credit: X-ray: NASA/CXC/Stanford Univ./R. Romani et al. [Chandra]; NASA/MSFC [IXPE]; Infrared: NASA/JPL-Caltech/DECaPS; Image Processing: NASA/CXC/SAO/J. Schmidt)](https://s.w-x.co/util/image/w/in-hand%20cosmic.jpg?crop=16:9&width=480&format=pjpg&auto=webp&quality=60)
From religious motifs to legendary football goals, the title ‘Hand of God’ has been attributed to many remarkable occurrences. But now, thanks to the combined powers of two of NASA's X-ray space telescopes, we may have just encountered the most fitting bearer of this title: a celestial ‘cosmic hand’ from the depths of space.
To understand this cosmic marvel, we must journey back some 1,500 years when a massive star in our galaxy exhausted its nuclear fuel. In its final act, the star imploded, giving birth to an incredibly dense entity known as a neutron star.
These rotating neutron stars, also known as pulsars, are extraordinary laboratories for extreme physics. Young pulsars have the power to generate streams of matter and antimatter radiating from their poles, accompanied by fierce stellar winds. This dynamic interplay results in what scientists call a “pulsar wind nebula”.
In 2001, NASA's Chandra X-ray Observatory first set its sights on one such pulsar dubbed PSR B1509-58, only to find something unbelievable: a pulsar wind nebula that bore a striking resemblance to a human hand! Referred to as MSH 15-52, it is located a staggering 16,000 light-years from Earth.
Fast forward to the present, where NASA's latest X-ray telescope, the Imaging X-ray Polarimetry Explorer (IXPE), has been meticulously observing MSH 15-52 for an astounding 17 days. It's a record duration, unparalleled since the telescope's launch in December 2021.
Roger Romani, leading the charge from Stanford University in California, notes: “The IXPE data gives us the first map of the magnetic field in the ‘hand’. The charged particles producing the X-rays travel along the magnetic field, determining the basic shape of the nebula like the bones do in a person’s hand.”
IXPE boasts a unique capability of divulging critical information regarding the orientation of electric fields in X-rays. This orientation, in turn, hinges on the magnetic field of the X-ray source, a phenomenon termed ‘X-ray polarisation’.
The results from MSH 15-52's X-ray polarisation are nothing short of fascinating. In vast regions of the cosmic hand, the degree of polarisation reaches remarkable levels, matching theoretical predictions. This strength signifies that the magnetic field within these regions is remarkably uniform and devoid of turbulence, akin to calm waters.
A highlight of MSH 15-52 is a radiant X-ray jet emanating from the pulsar towards the ‘wrist’ at the cosmic hand's base. This polarisation at the jet's inception is quite low, suggesting a turbulent, intricate magnetic field as the source of high-energy particles. However, as the jet nears the wrist, the magnetic field lines appear to straighten, becoming far more consistent. This transition leads to a remarkable surge in polarisation.
These observations hold profound implications, hinting that particles are energised in the complex and turbulent realm near the pulsar, found at the ‘palm’ of the celestial hand. These particles then flow towards regions where the magnetic field aligns smoothly along the wrist, fingers and thumb, forming a mesmerizing cosmic creation in the depths of space.
“We’ve uncovered the life history of super energetic matter and antimatter particles around the pulsar,” said co-author Niccolò Di Lalla, also of Stanford. “This teaches us about how pulsars can act as particle accelerators.”
These results are published in a new paper in The Astrophysical Journal and can be accessed here.
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