Astronomers Have Discovered The Youngest Pulsar In The Milky Way

The pulsar wind nebula of Kes 75 is in blue in this composite image. X-ray: NASA/CXC/NCSU/S. Reynolds; Optical: PanSTARRS

Pulsars are one of the extreme objects that can be produced during a supernova, the moment a star ends its life in an explosive and spectacular fashion. They are extremely dense neutron stars that spin on their axis quickly emitting beams of particles, like a lighthouse. Over 2,000 of these pulsars have been discovered since Jocelyn Bell Burnell spotted the first one in the 1960s. And now researchers have discovered the youngest among them.

As reported in the Astrophysical Journal, the light we see from pulsar Kes 75 comes from when it was just 500 years old, so this is the youngest we have ever seen a pulsar. But Kes 75 is located 19,000 light-years away, so it is currently 19,500 years old. The data collected by NASA's Chandra X-ray Observatory in the last two decades were used to work out how the object is changing and with that astronomers were able to work backward to its formation.

The pulsar emits a lot of particles, both matter and antimatter, which move away from the degenerate star at almost the speed of light. These particles form pulsar wind which in turn creates a region around the pulsar known as the pulsar wind nebula. This is a magnetized bubble of high-energy particles.

The expansion rate of a pulsar wind nebula tells the astronomers how long it has been going for. The team used Chandra observations from 2000, 2006, 2009, and 2016 to establish that the nebula is expanding at about 1 million meters per second, which is more than 2 million miles per hour.

The high speed might be due to a low-density environment surrounding the pulsar. It is possible that it’s expanding in a bubble of radioactive nickel that was produced in the supernova. As the nickel decayed into iron, it contributed to the light emission of the system. The heavier elements in the periodic table are produced in supernovae, and this research allows scientists to understand the formation of elements in more detail.

Over the last two decades, the brightness of the pulsar wind nebula has decreased by about 10 percent, with changes concentrated in the northern region of the nebula. These rapid changes and the peculiar shape fail to find an explanation in the current models, and the team notes the need for more sophisticated ones to truly understand what is going on in Kes 75.

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