Asteroid belts, like the one we have in our Solar System, may form around other stars. A ring of orbiting debris may be formed sometimes due to a host star transformation (i.e. supernova explosion), and separate bodies like asteroids may migrate inwards closer to a recently formed pulsar, down to the point where interactions with the pulsar’s magnetosphere starts to manifest. In other words, these asteroids could eventually fall onto the surface of that pulsar.

One possible example of such even has been evidenced recently by an international team of astronomers from the United Kingdom, South Africa and Australia. The scientists used data from long-term monitoring data of pulsar PSR J0738-4042 obtained from Hartebeesthoek Radio Astronomy Observatory (HartRAO) in South Africa and Parkes radio telescope in Australia. They tried to analyze pulse shape variations of this object and, in fact, succeded to detect an abrupt change of the star’s torque (related to a derivative of the rotational period), which has been registered in September 2005. The results of this study have been published at the arXiv.org.

Since pulsars are regarded as a very high-precision astrophysical clocks, it is possible to register even slightest changes in average shape of the radio pulses they emit. Their rotational frequency gradually decreases with time due to the loss of energy from magnetic dipole radiation. However, any abrupt changes in the spin-down rate typically indicate some major astronomical event.

Material in-fall is a possible source for such pulse profile and spin-down rate disturbances. This phenomenon has been probably studied previously, with some studies referencing the examples of planetary and disk systems around neutron stars, such as the planets around PSR B1257+12 (Wolszczan & Frail, 1992) and PSR B1620-26 (Thorsett et al., 1999), as well as the dust disk around magnetar 4U 0142+61 (Wang et al., 2006) and some others.

A 24-year set of radioastronomical data has been analyzed In the current study; the data had been collected from September 1988 to September 2012. The authors note, that the detected perturbation – dramatic change in pulse shape and torque – coincides with the emergence of a new component in the average pulse profile of the pulsar, thus confirming the results of a similar study conducted in 2011.

The scientists performed numerical simulations of such perturbations and analyzed resulting changes in star periodicity parameters to verify the hypothesis about the possible encounter between the pulsar and an asteroid. They concluded, that change in star’s pulse profile could not be caused by events of periodic nature, such as disruptions of surrounding material debris by some larger body such as orbiting planet with mass greater than 6×1025 kg. A planet of smaller mass may exist, although in such case it could not introduce any significant impact on the timing of this pulsar.

Thus, encounter between the asteroid and the pulsar currently remains the most probable scenario according to the authors of the study. In any case, the team also plans to investigate alternative interpretations of the observed phenomenon in the future.

By Alius Noreika, Source: www.technology.org