Two theories for the gamma-ray burst detected on Christmas 2010

The gamma-ray burst interpreted as the merger of a neutron star and a red giant (Image NASA/Goddard Space Flight Center)
The gamma-ray burst interpreted as the merger of a neutron star and a red giant (Image NASA/Goddard Space Flight Center)

On Christmas Day of 2010, NASA’s orbital observatory Swift detected a gamma-ray burst which lasted at least half an hour and was formally labeled as GRB 101225A. Gamma-ray bursts are the brightest explosions in the universe because in seconds more energy is emitted than the Sun will produce in the course of its entire life.

Astronomers believe that gamma-ray bursts are generated when a high-mass star turns into a neutron star or a black hole. Short gamma-ray bursts lasting less than two seconds may be emitted in the case of a coalescence of two merging neutron stars.

The GRB 101225A gamma-ray burst was abnormally long because for such events lasting a few minutes is already extraordinary, so it has stimulated astronomers for their research. However, when the Hubble space telescope was pointed in that direction it wasn’t possible to determine the distance of the source of this gamma-ray burst. As a result, nearly a year after the event there are two different theories to explain it.

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According to astronomer Christina Thoen of the Institute of Astrophysics of Andalusia in Grenada, Spain, the anomalous gamma-ray burst occurred in another galaxy in a binary system consisting of a neutron star and a star that has just become a red giant and is rich in helium.

The expansion of a star that is becoming a red giant is remarkable so in this case it’s possible that the neutron star was literally enveloped by the outer layers of its companion. This alteration of the balance between the two stars was so strong that it might have led to their merging, which would have resulted in a weak supernova.

Subsequently, the new star would’ve become a black hole or a magnetar, a neutron star with a very strong magnetic field, causing such a long gamma-ray burst in the process.

The gamma-ray burst interpreted as the collision of a comet with a neutron star (Image NASA/Goddard Space Flight Center)
The gamma-ray burst interpreted as the collision of a comet with a neutron star (Image NASA/Goddard Space Flight Center)

Astrophysicist Sergio Campana of the Astronomical Observatory of Brera, in Merate, Italy, conducted a study of this phenomenon and together with his team came up with another explanation. According to their theory the Christmas 2010 gamma-ray burst was generated by the collision of an object that could be a large comet with a neutron star about ten thousand light years away from us, which means that it would be in our galaxy.

This object might have had a mass of about half the dwarf planet Ceres, an object like many in the Kuiper Belt of our solar system, far enough to survive the death of a star, even though it becomes a supernova.

The object might have passed at a distance of about 5,000 km (3,000 miles) of the neutron star, it was torn to pieces by the powerful gravity of the star and the remaining debris fell on it at enormous speeds causing the violent and prolonged release of energy in the form of a gamma-ray burst.

To understand which of the two theories is the most likely it’s first necessary to determine the distance of the gamma-ray burst source. Further observations with the Hubble Space Telescope and by other observatories should be decisive.

Gamma rays have very intense energies and for this reason they are used for sterilization, for example of medical equipment because they can easily kill all bacteria. A gamma-ray burst directed at the Earth could sterilize the entire planet from many light years away. Therefore, studying these phenomena not only satisfies a scientific curiosity but also serves to evaluate a potential danger for us.

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