In 2020, astronomers added a new member to an exclusive family of exotic objects with the discovery of a magnet. The new observations from NASA’s Chandra X-ray Observatory help support the idea that it is also a pulsar, which means it emits regular pulses of light.
Magnets are a type of neutron star, an incredibly dense object made up mainly of tight neutrons, which form from the collapsed nucleus of a massive star during a supernova.
What differentiates magnets 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 has a value of about one Gauss, while a refrigerator magnet measures about 100 Gauss. Magnetists, on the other hand, have magnetic fields of about one billion billion Gauss. If a magnet were located one-sixth of the way to the moon (about 40,000 miles), it would erase data from all credit cards on Earth.
On March 12, 2020, astronomers detected a new magnet with NASA’s Neil Gehrels Swift telescope. This is only the 31st known magnet, out of the approximately 3,000 known neutron stars.
After further observations, the researchers determined that this object, nicknamed J1818.0-1607, was special for other reasons. First, it may be the youngest known magnet, with an estimated age of about 500 years. This is based on how fast the rotation rate slows down and on the assumption that it was born spinning much faster. Second, it rotates faster than any previously discovered magnet, rotating once every 1.4 seconds.
Chandra’s observations of J1818.0-1607 obtained less than a month after the discovery with Swift gave astronomers the first high-resolution view of this object in X-rays. Chandra’s data revealed a point source in which the magnet, which is surrounded by diffuse X-ray emissions, probably caused by X-rays reflecting dust in its vicinity. (Part of this diffuse X-ray emission may also be from winds blowing away from the neutron star.)
Harsha Blumer of West Virginia University and Samar Safi-Harb of the University of Manitoba in Canada recently published the results of Chandra’s 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 WISE Infrared Exploration Explorer (WISE), made before the discovery of the magnet. Chandra’s X-rays show the magnet in purple. The magnet is located close to the plane of the Milky Way galaxy about 21,000 light-years from Earth.
Other astronomers have also observed J1818.0-1607 with radio telescopes, such as the NSF’s Karl Jansky Very Large Array (VLA), and have determined that it emits radio waves. This implies that it also has properties similar to those of a typical “rotating powered pulsar”, a type of neutron star that emits beams of radiation that are detected as repeated pulses of emission as it rotates and slows down. Only five magnets have been recorded, including this one, which also acts as pulsars, constituting less than 0.2% of the known population of neutron stars.
Chandra’s comments can also provide support for this general idea. Safi-Harb and Blumer studied how efficiently J1818.0-1607 converts energy from its rate of decrease in X-ray rotation. They concluded that this efficiency is lower than that commonly found for magnets and probably in the range found for other rotating pulses.
The explosion that created a magnet from this era would have waited to leave behind a detectable field of debris. To search for this supernova remnant, Safi-Harb and Blumer analyzed X-rays from Chandra, infrared data from Spitzer, and radio data from VLA. Based on Spitzer and VLA data, they found possible evidence for a remnant, but at a relatively large distance from the magnet. To cover this distance, the magnet would have to travel at speeds well in excess of the fastest known neutron stars, even assuming it is much older than expected, which would allow more travel time.
The observations reveal the dynamic magnetosphere of the Swift J1818.0−1607 magnet
Harsha Blumer et al. Chandra Observations of the Newly Discovered Magnetar Swift J1818.0–1607, The astrophysics journal (2020). DOI: 10.3847 / 2041-8213 / abc6a2
Provided by the Harvard-Smithsonian Center for Astrophysics
Citation: Chandra’s remarks reveal an extraordinary magnet (2021, January 8) retrieved on January 8, 2021 from https://phys.org/news/2021-01-chandra-reveal-extraordinary-magnetar.html
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