Around the pulsar Geminga maybe a system is being reborn from its ashes

The area around the pulsar Geminga (Image Jane Greaves / JCMT / EAO)
The area around the pulsar Geminga (Image Jane Greaves / JCMT / EAO)

An article published in the journal “Monthly Notices of the Royal Astronomical Society” describes a research for possible planets in formation orbiting the pulsar Geminga. The astronomers Jane Greaves and Wayne Holland used the James Clerk Maxwell Telescope (JCMT) in Hawaii to conduct observations at submillimetric wavelengths and understand the mechanisms of planet formation in a system after a supernova.

The first exoplanets were discovered not orbiting a star in its main sequence but orbiting a pulsar, a type of neutron star originated from what remains of a massive star after its explosion in a supernova. Their existence remained a mystery because a supernova emits a quantity of materials with such high energies to destroy a system’s planets.

The hypothesis is that such systems were literally born from their ashes, using the materials emitted by the supernova and later attracted back towards the neutron star. The problem was to detect them because they seem to be very rare the use of very powerful instruments is needed to capture the alterations of the arrival times of the radio pulses from the pulsar they cause with their force of gravity.

The pulsar Geminga (Gemini gamma-ray source) was discovered in 1972 by astrophysicist Giovanni Bignami and already in 1997 a team of astronomers thought they had found a planet orbiting it but subsequently that was debunked because of some glitches discovered in its rotation. Much later, Jane Greaves studied that data to build an image of the neutron star and the surrounding area.

Most of the collected data, however, come from observations made with the JCMT and specifically with its SCUBA and SCUBA-2 (Submillimeter Common-User Bolometer Array) cameras. The pictures taken show a signal towards the pulsar and an arc around it. Jane Greaves compared it to a bow-wave that is formed at the bow of a ship while it’s moving.

The pulsar Geminga is moving at a much higher speed than sound in the interstellar gas so it’s possible that the materials get captured by that bow-wave and that some particles drift towards the neutron star. Over time, these materials accumulate and could even form new planets.

In the image the pulsar Geminga is indicated in the black circle and is moving to the upper-left. The dashed orange arc and cylinder show the bow-wave. The included region is about 1.3 light years across but probably the bow-wave extends even further and was only partially photographed due to the two SCUBAs’ limits.

Jane Greaves and Wayne Holland’s conclusions are not yet definitive. Their goal is to conduct new observations with the ALMA radio telescope, currently the most powerful in the world, which also has a considerable sensitivity at submillimetric wavelengths. More details will allow to test the models proposed by the two astronomers.

If the mystery of planet formation around neutron stars has been resolved, it would be interesting to try to understand what kind of conditions there might be on their surface. They are totally inhospitable to life forms comparable to the Earth’s ones but some “hard” science fiction writers might think of very exotic life forms.

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