In 2018 the first Very Large Array sky survey detected an object, VT 1137-0337, that appears to be a supernova remnant in a galaxy 395 million light-years away. Further investigation has revealed two features that make this stand out from the usual such discoveries. The first is the extraordinary brightness of the pulsar in question, far beyond what is normal for pulsars. The second is that a survey of the same region conducted in 1998 did not pick up this pulsar, yet it has been seen in four subsequent surveys, suggesting this may be the youngest object of its type ever seen.
In 1054, a new star was recorded by Chinese, Japanese and Islamic astronomers. We now know it was a supernova, and its remnants – known as the Crab Nebula – have become one of the most studied objects in the sky. The nebula seen in optical telescopes is an 11-light-years-wide cloud of gas thrown off by the explosion, and at the center is a neutron star whose rapid spin causes a beam of radiation to sweep across the sky 30 times a second.
Being astronomically young and just 6,500 light-years from Earth, the Crab Nebula pulsar is the brightest persistent gamma-ray source in Earth's sky. At the American Astronomical Society meeting in Pasadena this week, however, Dillon Dong a graduate student at Caltech reported VT 1137-0337 is intrinsically 10,000 times brighter.
However, Dong and his supervisor Professor Gregg Hallinan think VT 1137-0337 and the Crab belong to the same category.
"What we're most likely seeing is a pulsar wind nebula," Dong said in a statement. Pulsar wind nebulae occur when the magnetic field from a pulsar accelerates charged particles in the material thrown off by the supernova explosion to close to the speed of light. Most of what we know about them comes from studying the Crab.
"[VT 1137-0337] appears to be approximately 10,000 times more energetic than the Crab, with a stronger magnetic field," Dong said. "It likely is an emerging 'super Crab'."
The Crab Nebula is less than 1,000 years old, very young by astronomical standards, but it's ancient compared to VT 1137-0337.
"Based on its characteristics, this is a very young pulsar – possibly as young as only 14 years, but no older than 60 to 80 years," Hallinan said. The reason it's even possible VT 1137-0337 is more than 24 years old is its cloud may have been too dense in 1998 for the VLA to spot it. The rapid expansion of gas clouds decreases their density, probably making VT 1137-0337 visible some time around the Millennium.
Pulsars fade with time, and VT 1137-0337 is losing around 5 percent of its power a year, so it won't be so powerful for long.
To be a pulsar wind nebula, VT 1137-0337 must have a very strong magnetic field, and its magnetism may even be so strong it qualifies as a magnetar – a rare form of hyper-magnetized neutron star. "In that case, this would be the first magnetar caught in the act of appearing, and that, too, is extremely exciting," Dong said.
Magnetars are one of the favored explanations for Fast Radio Bursts (FRBs), huge flashes of light that last just a fraction of a millisecond, currently among the leading astronomical mysteries. Dong and Hallinan raise the possibility pulsar wind nebulae are the sources of at least some FRBs.
VT 1137-0337's host galaxy is interesting in itself. Despite being a dwarf galaxy with a mass similar to the Small Magellanic Cloud, it is forming stars a hundred times faster than our near galactic neighbor.
