Scientists for first time saw eclipses of binary star shed light on orbiting exoplanets

A team of researchers at the Raman Research Institute in Bengaluru and the University of Delhi reported that they have discovered indications of a massive planet orbiting a low mass X-ray binary star system, the first-ever discovery of its kind.

The discovery was made through a new technique, X-ray observations, which is a new way of detecting exoplanets. The results of the study have been published in the monthly notices of the Royal Astronomical Society.

Key Highlights

• The star system in question-MXB 1658-298 is an X-ray binary, which was discovered in 1976.

• It is a part of the constellation Ophiuchus (serpent bearer) and is located nearly 30,000 light years away.

• The newly discovered exo-planet is expected to be nearly 8,000 times as massive as the earth.

• The X-ray binaries consist of a pair of stars orbiting each other of which one is a compact one, similar to a black hole or a neutron star.

• In this case, it is a neutron star.  A neutron star draws matter from its less massive companion and generates X-rays that are detected by the detectors in satellites orbiting in space.

• The system is so far and faint that it can be observed only when it shows an outburst of X-rays. The recent discovery too was aided by such an outburst.

According to Chetana Jain, an Assistant Professor at Hansraj College Delhi, who is also the first author of the published paper, the outburst provided them with an excellent opportunity to try and trace the orbital evolution of the system.

However, while generally in X-ray binaries, the time in-between eclipses of the source can increase, decrease and show abrupt changes, in this particular system - MXB 1658-298- the time between the eclipses was seen to increase and decrease periodically.

Elaborating more on the system’s unusual behaviour, Biswajit Paul, the lead researcher in the study, stated that the eclipse first time arrived about ten seconds earlier, after a year it arrived about ten seconds later than expected.

This periodic variation in the eclipses led the researchers to believe that there was a third body orbiting the system.