The white dwarf that led to the historic Tycho supernova died in a violent explosion, but its legacy resembles a fluffy pink cotton ball.
The last picture released (opens in new tab) on February 28 it shows Tycho supernova remnant (Tychos supernova or Tycho) as a neon pink cloud edged by a thin red line. In new research, astronomers have mapped in unprecedented detail the geometry of the magnetic fields near the shock wave, which is where they say charged particles are accelerated to light-like speeds before streaming out as cosmic rays which eventually rains down on the earth.
The first direct evidence (opens in new tab) for this process can be traced to 2011, then Chandra X-Ray Observatory captured a pattern of X-ray streaks in Tycho’s outer edge. At the time, astronomers said the stripes are spots where magnetic fields are entangled, trapping electrons that then spiral into the fields to higher energies and emit X-rays.
So while astronomers have long known that supernova remnants rapidly tore up charged particles to extremely high energies, the details of exactly how they were accelerated were poorly understood.
Related: Supernova anniversary: The famous Tycho star flared up 450 years ago this month
Read more: Tycho Brahe Biography
Now scientists have studied some highly excited electrons near where they are accelerated to light-like speeds in Tycho, whose explosion released as much energy as the sun would release in 10 billion years. Scientists say the latest findings bring them one step closer to learning how supernova remnants like Tycho become giant cosmic particle accelerators.
The process “involves a delicate dance between order and chaos,” said Patrick Slane, senior astrophysicist at the Harvard–Smithsonian Center for Astrophysics and co-author of the latest study, in a statement (opens in new tab).
Slane’s team used data from NASA’s Imaging X-ray Polarimetry Explorer (IXPE) space observatory. The three identical X-ray telescopes aboard IXPE studied Tycho twice in 2022: From late June to early July and from December 21 to 25, according to the study.
From the data collected, the team was able to study X-rays produced by high-energy electrons near Tycho’s edge as they slide across magnetic fields. Scientists explain that the red edge – the place where Tycho accelerates particles to light-like speeds – is very thin because electrons emitting X-rays lose their energy very quickly. So when they move any appreciable distance from this edge, “they’ve lost so much energy that they’re not producing X-rays anymore,” Slane told Space.com in an email.
Before the IXPE data came in, Slane and his team weren’t sure what they were going to find, he added. To finally map out the geometry of the magnetic field, the team looked for signals which showed how polarized the radiation from X-rays is.
However, such signals are sensitive to how entangled the magnetic fields are: When the turbulence in these fields is high, the radiation is less directed and less intense, which means that IXPE cannot detect the polarization signals as strongly. The team’s simulations had previously shown that the signals they hoped to detect might be too small, which would mean the magnetic field is very messy.
“It would be important,” Slane told Space.com in an email, “but it’s kind of sad to say, ‘I didn’t see anything, and it’s really important!'”
When the IXPE data came in, the team found that the magnetic fields are definitely messy — they have high turbulence, “but not so high that we couldn’t detect the polarization,” he added.
So they measured the polarization of the X-rays and found it to be 9% in the center of the rest and a higher 12% at its edge. This is a much higher measure of polarization than the team’s previous goals, Cassiopeia Ashowing that Tycho’s magnetic field is more ordered, researchers say.
“These observations are the first ever to truly probe the polarization of emissions from the most energetic electrons in these cosmic particle accelerators,” Slane told Space.com in an email.
Once they knew the angle or degree of polarization, Slane’s team could map the geometry of the magnetic field, which they saw was stretched in an outward, or radial, direction.
Scientists already knew this from previous radio observations, so the finding wasn’t a total surprise. They say the IXPE space observatory helped them map the field in much more detail than previous observations, on scales smaller than a parsec — 3.26 light years or 19 trillion miles (31 trillion km).
They learned that for Tycho to accelerate its charged particles near light-like speeds requires “strong and turbulent magnetic fields,” Slane said in the same statement, “but IXPE shows us that there is a large-scale uniformity, or coherence, involved as well, extending right down to the places where the acceleration takes place.”
Using this data, the team found that the radial structure remains intact all the way to the acceleration sites, which they did not know before. They say this insight will shed light on how Tycho accelerates charged particles to energies at least a hundred times higher than even most powerful particle accelerators on earth.
The research is described in a paper (opens in new tab) published in the latest issue of The Astrophysical Journal.
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