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Astronomers discover planetary system that resembles Tatooine from Star Wars

An unprecedented multi-planetary system discovery by an international team of astronomers has ignited new interest in the fascinating field of space science. 

This team has announced the discovery of the second multiplanetary circumbinary system ever found. This system, which is not your everyday planetary system, features planets orbiting not one, but two stars at its core, in stark contrast to the single-star orbit we see in our own Solar System.

Researchers name the system BEBOP-1c

Published in today’s issue of the journal Nature Astronomy, the discovery is the result of rigorous research by the team at the University of Birmingham. The researchers have named their new discovery as BEBOP-1c, echoing the project that produced the data, called BEBOP, which stands for Binaries Escorted By Orbiting Planets. The system is also referred to as TOI-1338.

This planetary system is not entirely new to us. It’s the same system where, back in 2020, astronomers detected a circumbinary planet, TOI-1338b, using data from NASA’s TESS space telescope. The University of Birmingham team played a part in that discovery, too. 

Transit method vs. the Doppler method

The finding was possible through the transit method, which involves observing a planet passing in front of its host star. This particular planet happened to transit the brighter of the two stars in its system multiple times, catching the team’s attention.

“The transit method permitted us to measure the size of TOI-1338b, but not its mass which is the planet’s most fundamental parameter,” explained study lead author Dr. Matthew Standing, who earned his PhD at the University of Birmingham and is currently a researcher at The Open University.

As it turns out, the BEBOP team was already tracking this system, using a different detection method, known as the Doppler method. This method, which measures the velocity of stars, led to the first-ever detection of an exoplanet.

High-tech equipment used in the Atacama Desert

Using cutting-edge equipment installed on telescopes located in the Atacama Desert in Chile, the team set out to measure the mass of TOI-1338b. Despite years of hard work and dedication, the team was unable to accomplish this. But instead, they found a second planet, BEBOP-1c, and were able to measure its mass.

David Martin, a Sagan Fellow and astronomer at Ohio State University, points out that “only 12 circumbinary systems are known so far, and this is only the second that hosts more than one planet.”

“BEBOP-1c has an orbital period of 215 days, and a mass 65 times larger than Earth, which is about five times less than Jupiter’s mass,” said Dr. Standing.

The detection of this system posed numerous challenges, including a six-month-long interruption due to the COVID pandemic when the Chilean telescopes were forced to close down. The critical part of the planet’s orbit only became observable again last year, which allowed the team to finalize their detection.

More planets may be found in BEBOP-1c

This multiplanetary circumbinary system, TOI-1338/BEBOP-1, currently known to host two planets, may hold more surprises in the future. The researchers are hopeful that further observations could reveal additional planetary bodies.

Despite their scarcity, circumbinary planets play a significant role in enhancing our understanding of planetary formation. Dr. Lalitha Sairam is a researcher at the University of Birmingham and second author of the study. She noted that planets are born in a disc of matter surrounding a young star, where mass progressively gathers into planets.

How circumbinary systems work

When it comes to circumbinary systems, the disc of matter encompasses both stars. As the stars orbit each other, their gravitational forces interact with the disc, like a massive paddle stirring up the surrounding matter. 

This disrupts the disc close to the stars, preventing planet formation except in quiet regions that are distant from the binary system. “It is easier to pinpoint the location and conditions of planet formation in circumbinary systems compared to single stars like the Sun,” said Dr. Sairam.

The next phase of the study

The research team still has work to do with BEBOP-1c. While they have determined its mass, the size of the planet remains a mystery. In an effort to solve this, the researchers are planning to use the transit method to measure its dimensions.

During their attempts to detect the inner planet, TOI-1338b, the team managed to place a stringent upper limit on its mass. This boundary has revealed that the planet has a lower density than a Victoria Sponge cake, a trait that sets it apart as a particularly unique celestial body. 

As such, it becomes an ideal candidate for further investigation with the James Webb space telescope. Future observations may shed light on the chemical environment in which this rare circumbinary planet formed.

This exciting find marks yet another leap forward in our understanding of the cosmos. It challenges us to broaden our conceptions of planetary systems and offers invaluable insights into the processes that shape them. The ongoing study of circumbinary planets may well hold the key to unlocking more of the universe’s many secrets.

More about circumbinary systems

Circumbinary systems, as the name suggests, are astronomical systems featuring two stars at the center with planets orbiting both stars. The term “circumbinary” is derived from Latin, with “circum” meaning around and “binary” referring to a system of two stars.

The concept of a planet in a stable orbit around two stars, also known as a binary star system, challenges our traditional perspective of a solar system like ours, where planets orbit a single star.

The existence of circumbinary planets was purely theoretical until the first such planet was detected in 1993. This planet, called PSR B1620-26 b, was discovered orbiting a pair of stars: a pulsar and a white dwarf. However, this discovery was an unusual case because the planet is thought to have originally formed around the pulsar before it became a neutron star.

Kepler spacecraft found the first one

The first detection of a circumbinary planet formed in a protoplanetary disc, like how planets form in our Solar System, occurred in 2011 with the discovery of Kepler-16b by NASA’s Kepler spacecraft. The planet, located about 200 light-years away, orbits two stars that are also orbiting each other.

Observing and studying circumbinary systems can be more challenging than single-star systems. For instance, the gravitational dynamics in these systems are more complex due to the interaction of the two stars and their planets. Additionally, these planets follow a more complicated path, and the gravitational forces they experience can vary significantly as the distance between the two stars changes.

Many questions remain about circumbinary systems

The discovery of circumbinary systems has significant implications for our understanding of planetary formation. For example, the existence of circumbinary planets challenges the classical model of planet formation, suggesting that planet formation processes are more flexible and diverse than previously assumed.

There are roughly a dozen known circumbinary systems. However, scientists anticipate discovering more as observational technology and techniques continue to improve. Despite their rarity, these systems are of considerable interest to scientists, as they provide a unique perspective on the processes of star and planet formation.

Image Credit: NASA


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