A Tour of J1818.0-1607

Narrator (April Jubett, CXC): In 2020, astronomers added a new member to an exclusive family of exotic stars, with the discovery of a magnetar.

Magnetars are a type of neutron star, which are incredibly dense objects mainly made up of densely packed neutrons. They form from the collapsed core of a massive star during a supernova. What sets magnetars apart from the rest of their intriguing stellar clan is that they also have the most powerful known magnetic fields in the universe.

On March 12, 2020, astronomers detected a new magnetar with NASA’s Neil Gehrels Swift Telescope. After follow-up observations, researchers determined that this object, dubbed Swift J1818.0-1607 or J1818 for short, was special for a couple more reasons.

First, it may be the youngest known magnetar with an age estimated to be about 500 years old. Secondly, it also spins faster than any previously discovered magnetar, rotating once around every 1.4 seconds.

Observations with NASA’s Chandra X-ray Observatory of J1818 less than a month after the discovery with Swift gave astronomers the first high-resolution view of this object in X-rays. The Chandra data revealed a point source where the magnetar was located. This is surrounded by diffuse X-ray emission, likely caused by X-rays reflecting off dust located in its vicinity.

Astronomers expect that the explosion that created a magnetar of this age would have left behind a debris field, known as a supernova remnant. To search for this supernova remnant, a team of researchers looked at the X-rays from Chandra, infrared data from Spitzer, and radio data from the NSF’s Karl Jansky Very Large Array, or VLA. They may have found evidence for part of the remnant with the Spitzer and VLA data, but it is a relatively large distance away from the magnetar. In order to cover this distance the magnetar would need to have traveled at speeds far exceeding those of the fastest known neutron stars, even assuming it is much older than expected, which would allow more travel time.

Regardless, J1818 is only the 31st known magnetar, out of the approximately 3,000 known neutron stars. This means astronomers will continue to study it and its fellow magnetars as they strive to learn more about these extraordinary members of the cosmic family.