Protostar

The recent discovery by a team at IIST, Thiruvananthapuram of circular polarization in radio emissions from a massive, young protostar is a remarkable breakthrough in astrophysics.

What is a Protostar?

A protostar represents the early stage of a star’s life cycle, during which a giant molecular cloud in the interstellar medium begins to collapse under its own gravity. This process leads to the formation of a dense core that heats up as the cloud contracts.

Key stages of protostar evolution:

• Formation: The collapse of a molecular cloud results in a protostar, a hot, dense mass of gas and dust.

• Duration: The protostar phase lasts anywhere from 100,000 to 10 million years, depending on the star's mass.

• Ending: The protostar phase transitions into the pre-main-sequence stage, where the star is known as a T-Tauri star if it's of similar mass to the Sun.

• Main Sequence: The protostar eventually ignites hydrogen fusion in its core, marking the transition to a main sequence star.

However, because protostars are surrounded by dense dust, they are difficult to observe in visible light, which makes radio observations a valuable tool for studying them.

Circular Polarization in Radio Emissions

Circular polarization occurs when the electric and magnetic vectors of radio waves rotate around the wave's direction of travel. This special property of the radio emission helps scientists probe the magnetic fields near the protostar.

Why is this important?

1. Magnetic Fields: Measuring circular polarization provides insights into the magnetic fields surrounding the protostar, which is crucial for understanding how stars like this one form. The magnetic fields can also influence the formation of protostellar jets.

2. New Observations: This study marks the first direct measurement of a magnetic field near a massive protostar (specifically, IRAS 18162-2048), revealing a field that is about 100 times stronger than Earth's. This is a breakthrough, as magnetic fields in massive protostars had been difficult to measure until now.

3. Protostellar Jets: The magnetic fields are thought to play a key role in the formation of bipolar jets of high-velocity material that are ejected from the protostar. These jets are crucial in shaping the environment around a protostar and contribute to the overall dynamics of star formation.

Conclusion

This discovery is a crucial step forward in our understanding of the star formation process, especially for massive stars, which are much harder to study than lower-mass stars like the Sun. The ability to measure magnetic fields and observe protostellar jets through radio polarization opens up new possibilities for astronomers to explore how stars, planets, and other cosmic objects evolve.