A city-sized collapsed star, pulsar PSR J2030+4415 – the ancient remains of exploded stars so dense its gravity warps nearby space-time – has generated an X-ray filament of matter and antimatter (image above) that stretches for trillions of miles as revealed by NASA’s Chandra X-ray Observatory. This discovery could help explain the presence of positrons (the antimatter positively charged counterparts to electrons) detected throughout the Milky Way galaxy and here on Earth.
This image below from NASA’s Chandra X-ray Observatory and ground-based optical telescopes shows an extremely long beam of matter and antimatter extending from a relatively tiny pulsar. The panel on the left displays about one third the length of the beam from the pulsar known as PSR J2030+4415 (J2030 for short), which is located about 1,600 light years from Earth.
J2030 is a dense, city-sized object that formed from the collapse of a massive star and currently spins about three times per second. X-rays from Chandra (blue) show where particles flowing from the pulsar along magnetic field lines are moving at about a third the speed of light. A close-up view of the pulsar in the right panel shows the X-rays created by particles flying around the pulsar itself. As the pulsar moves through space at about a million miles an hour, some of these particles escape and create the long filament. In both panels, optical light data from the Gemini telescope on Mauna Kea in Hawaii have been used and appear red, brown, and black. The full length of the filament is shown in a separate image. (X-ray Credit: NASA/CXC/Stanford Univ./M. de Vries)
Although the vast majority of the Universe consists of ordinary matter rather than antimatter, scientists continue to find evidence for relatively large numbers of positrons in detectors on Earth.
Pulsars –Are they the Source of the Antimatter?
What are possible sources of this antimatter? The researchers in the new Chandra study of J2030 think that pulsars like it may be one answer. The combination of two extremes — fast rotation and high magnetic fields of pulsars — lead to particle acceleration and high energy radiation that creates electron and positron pairs.
Einstein’s E = mc^2 Equation is Reversed
The usual process of converting mass into energy famously determined by Einstein’s E = mc^2 equation is reversed, and energy is converted into mass. The extreme magnetic fields also help to separate the negatively charged electrons and positively charged positrons from annihilating each other.
A paper by astronomers Martjin de Vries and Roger Romani of Stanford University explains that pulsars generate winds of charged particles that are usually confined within their powerful magnetic fields.
Triggers a Particle Leak
The pulsar, according to the paper, is traveling through interstellar space at about half a million miles per hour, with the wind trailing behind it. A bow shock of gas moves along in front of the pulsar, similar to the pile-up of water in front of a moving boat. However, about 20 to 30 years ago the bow shock’s motion appears to have stalled and the pulsar caught up to it, resulting in a collision that likely triggered a particle leak, where the pulsar wind’s magnetic field linked up with the interstellar magnetic field.
Forms a “Nozzle”
As a result, the authors explain, the high-energy electrons and positrons could have squirted out through a “nozzle” formed by connection into the Milky Way Galaxy. The strong magnetic fields from the pulsar can collimate the subatomic particles into a narrow, high-density, relativistic jet that allow the positrons to escape to large, interstellar distances. The magnetic field lines from the pulsar then reconnect with the ambient magnetic fields permeating our Milky Way Galaxy, providing a conduit for positrons to travel extreme distances within our galaxy at a third of the speed of light
Think of it as like a dam that can (partially) open to let some water through.
“The ‘nozzle’ should not be thought of literally,” Martijn Nicolaas De Vries told The Daily Galaxy. “Rather,” he says, “it’s a way to illustrate that only a small fraction of the electrons and positrons (the most energetic ones) leak out into the interstellar medium. The most important factor here is the distance between the pulsar and the apex of the bow shock, which is called the standoff distance. The smaller that is, the more particles escape. Magnetic reconnection makes this process easier on one side of shock specifically, so that the particles leak out on one side but not the other. An alternative way to think of it as like a dam that can (partially) open to let some water through. For J2030, the dam was closed most of the time. But because it hit this wall of density a few decades ago, the standoff distance decreased. And because of that, for a time (maybe 10 years or so) the dam opened a bit and some of the water (i.e. the electrons/positrons) got out.”
Previously, astronomers have observed large halos around nearby pulsars in gamma-ray light that imply energetic positrons generally have difficulty leaking out into the Galaxy. This undercut the idea that pulsars explain the positron excess that scientists detect. However, pulsar filaments that have recently been discovered, like J2030, show that particles actually can escape into interstellar space, and eventually could reach Earth.