Astronomers have detected faint, rhythmic radio emissions from a neutron star previously thought to be silent, a discovery that could fundamentally reshape our understanding of the pulsar population. According to research published June 25 in Nature Astronomy, a team led by Zhang Lei of the National Astronomical Observatories of the Chinese Academy of Sciences identified these pulses from 1E 1207.4-5209, a central compact object (CCO) located 10,000 light-years away.
Why are some neutron stars silent?
For decades, astronomers have tuned into neutron stars at the center of supernova remnants, finding only radio silence. The prevailing theory, according to the research team, was that CCOs possessed magnetic fields too weak to generate detectable radio jets. The discovery of 1E 1207.4-5209—dubbed the “Blue Eye Pulsar” by Li Di, a professor of astronomy at Tsinghua University—challenges the assumption that these objects are inherently silent.
Did you know? The “Blue Eye Pulsar” nickname comes from the fact that when the faint radio emission is combined with X-ray images that show the neutron star shining brightly, it looks like a blue eye.
How did researchers detect the “Blue Eye”?
The team utilized the MeerKAT radio telescope in South Africa to monitor 1E 1207.4-5209, identifying a pulse every 424 milliseconds. This timing matches the known spin period of the pulsar. The researchers suggest that a “spin glitch”—a small increase in rotation of a neutron star probably caused by some kind of disruption or shifting of material within the neutron star’s dense interior observed in 2015—may have acted as a trigger. This event likely strengthened or reoriented the pulsar’s magnetic field, allowing the radio emissions to become detectable. As the star’s rotation rate gradually slows back down to its original rate, the team notes that these radio signals may eventually fade back into silence.
What does this mean for the “missing” pulsars?
This finding offers a potential solution to the mystery of why some supernova remnants seem to be missing pulsars. A prominent example is the expanding cloud of debris formed from the explosion of supernova 1987A in the Large Magellanic Cloud, where indirect evidence suggests a neutron star exists, yet no radio emissions have been confirmed. If the Blue Eye Pulsar is representative of a larger class of “feeble” emitters, it implies that there is a large population of very feeble pulsars that remain undetected in the galaxy. Astronomers may have been misidentifying some of these pulsars as being old when they could in fact be relatively young but softly radio emitting.
Pro Tip: Continued monitoring of the Blue Eye Pulsar is essential. If the radio emissions cease, it could answer the question of whether the pulsar’s radio emission switches back off.
Frequently Asked Questions
What is a Central Compact Object (CCO)?
A CCO is a neutron star found at the center of a supernova remnant that has been dead quiet in radio waves.
Why is the 1E 1207.4-5209 discovery significant?
It is the first time faint radio emissions have been detected coming from one such object. This raises the prospect that there could be many more pulsars in our galaxy than we thought.
Could other “dead” pulsars start pulsing again?
The research suggests that internal physical changes, such as spin glitches, may have strengthened or reoriented the magnetic field sufficiently to trigger radio emissions. This implies a larger, undetected population of faint pulsars exists.
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