MAY 16, 2022 2:00 PM PDT

A Strange 'Black Widow' Pulsar Candidate in Our Galaxy

WRITTEN BY: Amanpreet Kaur

Pulsars are remnants of dead stars that die by the process of supernova explosion. These explosions often leave either a black hole or a neutron star as the final remnant. If this remnant is a neutron star, and it is spinning and highly magnetized, it emits radiation out of its poles and is called a pulsar. Dr. Jocelyn Bell, who discovered the first pulsar in 1967, was a graduate student at that time. These pulsars spin fast, particularly the ones called millisecond pulsars. They spin about 1000 times per second! Now, let us add a living star next to this millisecond pulsar such that they orbit around each other. The jets from these pulsars destroy the material on its companion, or in a way slowly devour them. Therefore, the name “black widow” was given to such binary systems. During this phase, a lot of X-rays and gamma-rays are emitted from this phenomenon which is often caught by our telescopes in space. The first such system was discovered in 1988 and the orbital period of this was 9.2 hours, i.e., it takes about 9.2 hours for them to complete one orbit around each other. 

On 4th May 2022, an international team of researchers published the discovery of the strangest black widow pulsar ever found in the journal Nature. The binary system, also known as ZTF J1406+1222, was found via an optical telescope (Zwicky Transient Facility). In optical data, astronomers usually see a periodic rise and dip in the brightness of the system because of the rotation which sometimes brings the cooler side of the companion star in front of us and other times the one which is facing the wrath of the pulsar. These authors found that the orbital period of this system is merely 62 minutes, which is rather fast for such binaries.

Moreover, the next obvious step for them was to search for gamma-ray and X-ray data because these are often discovered in these regimes, but surprisingly they did not find any, which makes it a bit strange. Another factor that adds to its strangeness is that it is not a binary system. There is a third star that is in a wide orbit with this pulsar and its nearby companion star. The orbital period of this star is approximate 10000 light-years in contrast to 62 minutes of the nearby companion. This finding poses a new theoretical challenge to the astronomers in terms of the formation and existence of such systems. 



About the Author
Doctorate (PhD)
Aman (she/her) is a scientific writer at labroots and an astrophysics researcher at Penn State University. She works in the field of high-energy astrophysics such as black holes, gamma-rays, etc., and collects data from various space telescopes to conduct her research. She received her doctorate from Clemson University in Physics. On a personal note, she loves spending time out in nature; camping or hiking. If given a choice, she will decorate her house only with plants, did she say she likes plants? :D
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