Determining If Massive O-Class Stars Have Magnetic Fields

The fact that stars are capable of producing massive magnetic fields has been known for many years, but astrophysicists have been trying to determine whether a particular class of stars, called the O-class, indeed features the magnetic manifestations.

The Zeeman effect, which is generally used to determine the existence and intensity of the magnetic fields, cannot be applied to these particular stars, due to a number of reasons.

The effect measures the strength of a magnetic field by splitting spectral lines into two. This happens when the fields hit the quantum structure of atomic orbitals. But when insufficient atoms are available, the technique cannot be applied.

O-class stars have spectra that are mostly featureless in the visual portion of the electromagnetic spectrum, because they have insufficient number of atoms with electrons in the necessary orbitals to undergo transitions.

This means that they cannot produce visual spectra lines. As such, determining whether members of this class of massive stars are actually expressing magnetic fields has been a challenge for years.

But now investigators are using a new approach to conducting this research. A team of experts from the University of Amsterdam has turned to synchrotron radiation for reaching new conclusions in the field.

Expert Roald Schnerr is the leader of the research effort. He says that the this type of radiation appears when relativistic, charged particles move through a magnetic field. As this happens, light is produced.

This light exists in all portions of the electromagnetic spectrum, from radio to gamma rays, the expert adds, and it can be detected using conventional telescopes with only minor modifications.

Synchrotron radiation were first discovered in the jets of the galaxy M87, and has since been used to explain the emissions of supernova and planetary magnetospheres, as well as those of areas around pulsars and black holes, Universe Today reports.

Using this type of radiation, the research team attempted to discover O-class stars and study their emissions. However, our of five initial candidates, they could only analyze three, of which just one released synchrotron radiation.

As such, the case arguing for the existence of magnetic fields around these stars is becoming stronger, but research is still conducted on small numbers of stars.

Perhaps future investigations will take a more systematic look at these impressively-large stars, which can reach 15 and 90 times the mass of the Sun. Surface temperatures range between 30,000 and 52,000 degrees Kelvin, experts say, which makes them between 30,000 and 1 million times more luminous than our own star.

O-class stars are so rare that statistics estimate only 20,000 of them exist throughout the entire Milky Way. Our galaxy has a diameter of 100,000 light-years.