Rare White Dwarf Pulsar Found in Our Solar System’s Back Yard – Only 773 Light Years Away

Posted by Guy Pirro 06/24/2023 12:09AM

This is an artist's impression of a white dwarf pulsar. In this binary star system, a rapidly spinning white dwarf (right) accelerates electrons to nearly the speed of light. These high-energy particles produce bursts of radiation that strike the accompanying red dwarf star (left), causing the entire system to pulsate from the radio to the X-ray range. The discovery of a rare type of white dwarf pulsar system in two independent studies by the University of Warwick and the Leibniz Institute for Astrophysics Potsdam (AIP) provides new insights into the dynamo model’s predictions for stellar evolution. The new white dwarf pulsar, an extremely close binary system of a white dwarf star and a red dwarf star that together would fit inside the Sun, is only the second known of its kind. (Image Credit: M. Garlick, University of Warwick, ESO)

Rare White Dwarf Pulsar Found in Our Solar System’s Back Yard – Only 773 Light Years Away

A rare type of white dwarf pulsar has been found for only the second time in history in research led by the University of Warwick in the UK and independently by the Leibniz Institute for Astrophysics Potsdam (AIP) in Germany. To the great surprise of the scientific community, this odd pulsar phenomenon in a white dwarf was only observed for the first time in 2016. Only 773 light years away from Earth and spinning 300 times faster than our planet, the white dwarf pulsar has a size similar to the Earth, but a mass at least as large as the Sun. This means that a teaspoon of white dwarf material would weigh around 15 tons. A white dwarf pulsar consists of a rapidly spinning, burnt-out stellar remnant that lashes its neighbor – a red dwarf – with powerful beams of electrical particles and radiation, causing the entire system to brighten and fade dramatically over regular intervals. This is due to strong magnetic fields, but scientists are unsure what causes them.

Typical white dwarfs are small dense stars roughly the size of a planet. They are formed when a star of low mass has burnt all its fuel and loses its outer layers. Sometimes referred to as “stellar fossils,” white dwarfs offer insight into different aspects of star formation and evolution.

Pulsars, on the other hand, have been known since the 1960s and more than 3000 have been found. They are rapidly rotating, strongly magnetic neutron stars in which charged particles are torn from the surface by ultra-strong electric fields and then accelerated to almost the speed of light. As a result, they emit radiation, i.e. light, in the radio to the X-ray or even gamma range. Due to the fast rotation of the stars, short pulses of radiation arrive at the Earth, which is the reason for their name – pulsar.

A key theory which explains the strong magnetic fields is the “dynamo model” – that white dwarfs have dynamos (electrical generators) in their core, as does the Earth, but much more powerful. But for this theory to be tested, scientists needed to search for other white dwarf pulsars to see if their predictions held true.

Researchers funded by the UK Science and Technology Facilities Council (STFC) have just announced the detection of a very rare white dwarf pulsar, J191213.72-441045.1 (J1912-4410 for short). It is only the second time such a star system has been found, following the discovery of AR Scorpii (AR Sco) in 2016.

White dwarfs begin their lives at extremely hot temperatures before cooling down over billions of years, and the low temperature of J1912−4410 points to an advanced age.

Dr Ingrid Pelisoli, University of Warwick’s Department of Physics, said: “The origin of magnetic fields is a big open question in many fields of astronomy, and this is particularly true for white dwarf stars. The magnetic fields in white dwarfs can be more than a million times stronger than the magnetic field of the Sun, and the dynamo model helps to explain why. The discovery of J1912−4410 provided a critical step forward in this field.

“We used data from a few different surveys to find candidates, focusing on systems that had similar characteristics to AR Sco. We followed up any candidates with ULTRACAM, which detects the very fast light variations expected of white dwarf pulsars. After observing a couple dozen candidates, we found one that showed very similar light variations to AR Sco. Our follow-up campaign with other telescopes revealed that every five minutes or so, this system sent a radio and X-ray signal in our direction.

“This confirmed that there are more white dwarf pulsars out there, as predicted by previous models. There were other predictions made by the dynamo model, which were confirmed by the discovery of J1912−4410. Due to their old age, the white dwarfs in the pulsar system should be cool. Their companions should be close enough that the gravitational pull of the white dwarf was in the past strong enough to capture mass from the companion, and this causes them to be fast spinning. All of those predictions hold for the new pulsar found: the white dwarf is cooler than 13,000K, spins on its axis once every five minutes, and the gravitational pull of the white dwarf has a strong effect in the companion.

“This research is an excellent demonstration that science works – we can make predictions and put them to test, and that is how any science progresses.”

Axel Schwope, Leibniz Institute for Astrophysics Potsdam (AIP), who is leading a complementary study published as a letter in Astronomy and Astrophysics, added: "We are excited to have independently found the object in the X-ray all-sky survey performed with SRG/eROSITA. The follow-up investigation with the ESA satellite XMM-Newton revealed the pulsations in the high-energy X-ray regime, thus confirming the unusual nature of the new object and firmly establishing the white dwarf pulsars as a new class.”

For more information:

https://warwick.ac.uk/newsandevents/pressreleases?newsItem=8a17841a8895e8e30188bf9533d5041e

https://www.aip.de/en/news/white-dwarf-pulsar/

https://astromart.com/news/show/exotic-pulsar-and-white-dwarf-binary-pair-help-prove-that-einstein-was-right

https://astromart.com/news/show/newly-found-pulsar-helps-astronomers-explore-milky-ways-mysterious-core

https://astromart.com/news/show/white-dwarfs-have-solid-crystalline-cores-made-of-oxygen-and-carbon

https://astromart.com/news/show/pulsars-the-most-extraordinary-physics-laboratories-in-the-universe

https://astromart.com/news/show/space-warping-white-dwarfs-produce-gravitational-waves

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