From NASA
January 8, 2021
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In 2020, astronomers added a new member to an exclusive family of exotic objects with the discovery of a magnetar. New observations from NASA’s Chandra X-ray Observatory support the idea that it is also a pulsar, meaning it emits regular pulses of light.
Magnetars are a type of neutron star, an incredibly dense object made up primarily of tightly packed neutrons that are formed from the collapsed core of a massive star during a supernova.
What sets magnetars apart from other neutron stars is that they also have the strongest known magnetic fields in the universe. For context, the strength of our planet’s magnetic field is roughly one gauss, while a fridge magnet is roughly 100 gauss. Magnetars, on the other hand, have magnetic fields of around one million billion Gauss. If a magnetar was one-sixth of the way to the moon (about 40,000 miles) it would erase the data from all credit cards on earth.
On March 12, 2020, astronomers discovered a new magnetar with NASA’s Neil Gehrels Swift Telescope. This is only the 31st known magnetar among the approximately 3,000 known neutron stars.
After making subsequent observations, the researchers found that this object, named J1818.0-1607, was special for other reasons. First, it is possibly the youngest known magnetar, with an estimated age of around 500 years. This is based on how quickly the rate of rotation is slowing down and assuming it was born and spinning much faster. Second, it also spins faster than any previously discovered magnetar, spinning once every 1.4 seconds.
Chandra’s observations of J1818.0-1607, obtained less than a month after its discovery with Swift, gave astronomers the first high-resolution X-ray view of this object. The Chandra data showed a point source where the magnetar was located, surrounded by diffuse X-ray emission, likely caused by X-rays reflected from dust nearby. (Some of this diffuse X-ray emission can also come from winds blowing away from the neutron star.)
Harsha Blumer of West Virginia University and Samar Safi-Harb of the University of Manitoba, Canada recently published results of the Chandra observations from J1818.0-1607 in The Astrophysical Journal Letters.
This composite image contains a wide infrared field of view from two NASA missions, the Spitzer Space Telescope and the Far-Field Infrared Survey Explorer (WISE), captured prior to the magnetar’s discovery. X-rays from Chandra show the magnetar in purple. The magnetar is located near the plane of the Milky Way, about 21,000 light years from Earth.
Other astronomers have also observed J1818.0-1607 using radio telescopes such as the NSF’s Karl Jansky Very Large Array (VLA) and found that it emits radio waves. This implies that it also has properties similar to a typical “rotation-driven pulsar,” a type of neutron star that emits radiation beams that are captured as repetitive emission pulses as it rotates and slows down. It has been recorded that only five magnetars, including this one, also act like pulsars, making up less than 0.2% of the known neutron star population.
The Chandra observations can also support this general idea. Safi-Harb and Blumer studied how efficiently J1818.0-1607 converts energy from its decreasing spin rate into X-rays. They concluded that this efficiency is less than that typical of magnetars and probably within the range found for other rotationally driven pulsars.
It is to be expected that the explosion that created a magnetar of this age left behind a detectable debris field. To search for this supernova remnant, Safi-Harb and Blumer looked at the X-rays from Chandra, infrared data from Spitzer, and the radio data from the VLA. Based on the Spitzer and VLA data, they found possible evidence of a residue, but at a relatively large distance from the magnetar. To cover this distance, the Magnetar would have to travel at speeds that are well above those of the fastest known neutron stars, even if it is much older than expected, which would allow more travel time.
A preprint of the Astrophysical Journal Letters paper by Blumer and Safi-Harb describing these results is available online.
NASA’s Marshall Space Flight Center administers the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science from Cambridge, Massachusetts and flight operations from Burlington, Massachusetts.
Photo credit: Röntgen: NASA / CXC / Univ. from West Virginia / H. Blumer; Infrared (Spitzer and Wise): NASA / JPL-CalTech / Spitzer
Read more from NASA’s Chandra X-ray Observatory.
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http://www.nasa.gov/chandra
Last updated: January 8, 2021 Publisher: Lee Mohon
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