Investigating the statistical possibility of triple star systems containing exoplanets

An example of a triple star system. Credit: Caltech/R. Hart (Infrared Processing Analysis Center, or IPAC)
Why is it important to look for exoplanets in triple star systems? And how many planets can we find there? That’s what a recent study accepted in Astrophysics & Space Science seeks to address, after investigating the statistical possibility of a triple star system in which This study has the potential to help researchers better understand the formation and evolution of triple star systems, and whether they are suitable for supporting life as we know it.
The research will be published on the arXiv preprint server.
Here, Universe Today speaks with Dr. Manfred Kunz, professor of physics at the University of Texas at Arlington and lead author of this study, about this amazing study, the motivation behind the study, the most important results, and more. Discuss the importance of triple research. The possibility of finding extrasolar life in star systems and triple star systems.
What is the motivation for your research?
Dr Kuntz told Universe Today: “Age and metallicity (i.e. heavy elements = elements other than hydrogen and helium) are fundamental properties of stars, and this is true for all stars. Most (with the exception of the Sun) Given that they are members of higher-order star systems, the study of stars in triple star systems is a natural extension of studies focused on single stars.
For this study, the researchers conducted a statistical analysis of both the age and metallicity of a triple star system containing a total of 27 exoplanets identified based on previous studies. The number of exoplanets in each system ranges from 1 to 5. Within margin of error, the age of the triple star system was between 20 million and 7.2 billion years. By the way, our sun is estimated to be just over 4.6 billion years old.
The metallicity of a star system ranges from -0.59 to +0.56, within error, and is often calculated based on the iron to hydrogen ratio (Fe/H). It is also calculated using the equation: X + Y + Z. =1, where X is the percentage of hydrogen, Y is the percentage of helium, and Z is everything else (i.e. carbon, oxygen, silicon, iron, etc.).
These values range from -4.5 to +1.0, with stars indicating 0, -1, greater than 0, and less than 0, indicating that the star has the same iron abundance as the Sun and 10% of the Sun’s iron abundance. Indicates that it is one minute or more. They have more metal content than the Sun and less metal content than the Sun, respectively.
What are the most important findings from this study?
“We identified two very important results,” Dr. Kuntz told Universe Today. “First, stars in triple star systems are, on average, significantly younger than stars in the Sun’s neighborhood. The most plausible explanation is that the stars that host the planets in these systems have relatively large masses (dwelling times (shorter), a possible double selection effect.” (more on the main sequence than low-mass stars), planets in triple star systems may have long-term orbital instability.
“The stellar metallicity of these stars is on average similar to that of the Sun, but due to the limited amount of data, this result reflects a relatively broad estimated metallicity distribution.”
Distances to each triple star system range from 4.3 to 1,870 light-years from Earth, but only six of the 27 triple star systems are within 100 light-years. These six triple star systems include Alpha Centauri (4.3 light-years), Epsilon Indi (11.9 light-years), LTT 1445 (22.4 light-years), Gliese 667 (23.6 light-years), and 94 Cetus (73.6 light-years). Contains. , and Psi1 Draconis (74.5 light-years), and the total number of exoplanets in each system (exoplanet candidates are shown in parentheses) is 3 (2), 1, 1, 2 (1), and 1, respectively. , and 1.
For comparison, as of September 2024, the total number of confirmed exoplanet systems in our universe is over 4,300, including approximately 5,800 exoplanets.
Despite the small number of triple star systems that host exoplanets, what is the importance of studying triple star systems?
“Most stars (with the exception of the Sun) are members of higher-order systems, especially binary systems, and rarely triple-star systems or even higher-order systems,” Kuntz told Universe Today.
“The study of planets hosted by triple star systems is therefore a natural extension of the standard approach that focuses on planets around single stars. The current study explores some of the properties of stars in triple star systems. The focus is on: a) planets – a relatively rare environment; the importance of the current study is to expand our general understanding of star-planet systems;
In the case of Alpha Centauri, the exoplanet Proxima Centauri b is terrestrial (rocky), approximately the same size as Earth in both radius and mass, and is a habitat for one of its constituent stars, Proxima Centauri. It has been confirmed that it is orbiting within the Bull Zone (HZ). Alpha Centauri triple star system.
The only other terrestrial exoplanet orbiting within its star’s HZ is Gliese 667 Cc, whose mass and radius are larger than Earth’s, making it a super-Earth.
Given the small number of triple star systems with exoplanets, and the even lower number of triple star systems that host terrestrial exoplanets orbiting within their HZs, extrasolar life can be found in triple star systems. What are the chances?
“Earth is the only planet where we know for sure that life exists,” Kuntz told Universe Today. “However, through decades of intense research, both observational and theoretical, scientists are convinced that extraterrestrial life almost certainly exists. This statement also applies to planets in triple star systems. That should apply.”
“However, these planets are typically subject to relatively variable environmental forcings (such as fluctuations in the amount of radiation received by stellar components), which we expect to reduce the likelihood of advanced life emerging.” However, the survival of microorganisms, especially extremophiles, should still be allowed.
As the number of confirmed exoplanets continues to increase, the number of confirmed triple star systems hosting exoplanets should also increase. When science fiction fans read about multi-star systems, they immediately think of the iconic scene in Star Wars: A New Hope, where Luke Skywalker watches two stars set on the horizon.
Tatooine is habitable for humans and other interesting life forms, as Proxima Centauri b is currently the only Earth-like exoplanet orbiting the HZ within 100 light years of Earth. As such, it may not apply to the real world.
So what constraints should scientists place on discovering life in triple star systems? In the movie Avatar, a semi-habitable satellite orbiting a much larger exoplanet in the Alpha Centauri star system Should we study their moons instead, like Pandora was depicted? Are triple star systems containing exoplanets as rare as today’s statistics suggest?
“The search for life beyond Earth continues to be an interesting topic,” Dr. Kuntz tells Universe Today. “We appreciate the political and societal support for ongoing and future space missions. As scientists, we are grateful for the continued support of taxpayers around the world, but especially here in the United States. I am especially grateful.”
Further information: Manfred Cuntz et al., On the age and metallicity of planet-hosting triple star systems, arXiv (2024). DOI: 10.48550/arxiv.2408.09268
Magazine information: arXiv
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