Stuti Jain | November 18, 2022
The origin of the universe has baffled astronomers, physicists and evolutionary scientists for decades. Despite the newest slew of stunning pictures from the James Webb telescope, scientists are really no closer to answering the basic question that drives evolutionary space research: how do stars really form?
Given its scope, understanding the universe as a whole is a strenuous, if not an impossible, task. Therefore, focusing on the evolution of its individual components is perhaps the best way to further our overall comprehension.
Professor Keivan Stassun of Vanderbilt University has used this broken-down approach to explore our universe. He, along with a team of astronomers, recently made an astonishing discovery: a rare binary star system.
What is a binary star system?
Let’s start from the basics. Stellar clusters are large groups of stars which are important benchmarks for study because they allow scientists to test and refine their theories of stellar structure, or the internal structure of stars. Stellar clusters often share many characteristics, such as distance, chemical composition, approximate age, etc. These characteristics can be used to create models that describe physical mechanisms and other observed characteristics of all star cluster members.
However, individual stars exhibit variability in their rotations, surface conditions, pulsations, eclipsing habits, etc. Through collective modeling, individual star clusters can be used to enhance existing models and create novel ones as well. Due to differing characteristics, individual stars provide more information that could add onto the current theory of stellar structure and evolution.
A binary star system is a special kind of stellar cluster that consists of two stars orbiting a common center of mass. The brighter star of the pair is labeled as the primary star.
Stassun’s new binary star system is unique
Binary systems are not uncommon in the cosmos, but the one discovered by Stassun and his team is unique because of its orientation. The two stars in this system eclipse each other when viewed from Earth, allowing researchers to more easily calculate each one’s respective mass and luminosity.
Stars undergo a process known as pulsation, where the outlier of the star expands and contracts, causing a change in its size and luminosity. When pulsation happens, astronomers may get a view of a star’s interior. However, the phenomenon itself is very rare, and of the two types of pulsations that exist, stars that pulsate usually only do one kind. One of the stars in Stassun’s new binary star system—to add on to its uniqueness—exhibits a hybrid of both pulsation types, which is entirely unprecedented.
Additionally, this hybrid pulsing star exerts a strong magnetic field, which is extremely uncommon for a pulsating star. Massive stars and/or pulsating stars tend to not have magnetic fields because they do not have the continuous, convective zones on their outer layers that are necessary for maintaining magnetic fields.
This lack of a magnetic field is what Stassun believes to be a key missing piece of the puzzle in understanding the stages of star formation. According to current research on pulsating and massive stars, any magnetic field at the surface would have to come from a past phase of magnetic activity. Thus, the star would have had to evolve from an older star that had the capabilities of maintaining a stronger magnetic field.
Overall, Stassun and his team’s discovery can be a key to solving the age-old mystery of star formation. As the team continues to investigate, the answer to that question is slowly but steadily developing.
Sources:
Farkas S. Why are magnetic fields rare in massive stars and in close pairs? as. Astronomy.com. 2016 Oct 17 [accessed 2022 Nov 4]. https://astronomy.com/magazine/ask-astro/2016/10/magnetic-fields-in-close-pairs
Flick A. Vanderbilt astronomers discover exceedingly rare star. Evolution@Vanderbilt. 2022 May 2 [accessed 2022 Nov 4]. https://www.vanderbilt.edu/evolution/vanderbilt-astronomers-discover-exceedingly-rare-star/
Pulsating stars. Encyclopædia Britannica. [accessed 2022 Nov 4]. https://www.britannica.com/science/star-astronomy/Pulsating-stars
Staff SS. Binary star systems: Classification and evolution. Space.com. 2018 Jan 17 [accessed 2022 Oct 20]. https://www.space.com/22509-binary-stars.html
Stassun KG, Torres G, Johnston C, Stevens DJ, Feliz DL, Kounkel M, Bouma LG. Discovery and characterization of a rare magnetic hybrid β Cephei slowly pulsating B-type star in an eclipsing binary in the young open cluster NGC 6193. The Astrophysical Journal. 2021;910(2):133. doi:10.3847/1538-4357/abe5a8