Exoplanet Evolution Unveiled in a Distant Solar System

Researchers have unveiled a solar system with up to seven exoplanets around TOI-1136, employing advanced methodologies for precise measurements of their characteristics, which could significantly influence theories on planet formation.

A recently discovered solar system with six confirmed exoplanets and a possible seventh is boosting astronomers’ knowledge of planet formation and evolution. Relying on a globe-spanning arsenal of observatories and instruments, a team led by researchers at the University of California, Irvine has compiled the most precise measurements yet of the exoplanets’ masses, orbital properties, and atmospheric characteristics.

In a paper published on January 29 in The Astronomical Journal, the researchers share the results of the TESSLaunched on April 18, 2018, aboard a SpaceX Falcon 9 rocket, NASA’s Transiting Exoplanet Survey Satellite (TESS) is a space telescope mission to search nearby stars for undiscovered worlds with a goal of discovering thousands of exoplanets around nearby bright stars.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>TESS-Keck Survey, providing a thorough description of the exoplanets orbiting TOI-1136, a dwarf star in the Milky WayThe Milky Way is the galaxy that contains our Solar System and is part of the Local Group of galaxies. It is a barred spiral galaxy that contains an estimated 100-400 billion stars and has a diameter between 150,000 and 200,000 light-years. The name "Milky Way" comes from the appearance of the galaxy from Earth as a faint band of light that stretches across the night sky, resembling spilled milk.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Milky Way galaxy more than 270 light-years from Earth. The study is a follow-up to the team’s initial observation of the star and exoplanets in 2019 using data from the NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>NASA’s Transiting Exoplanet Survey Satellite (TESS). That project provided the first estimate of the exoplanets’ masses by clocking transit timing variations, a measure of the gravitational pull that orbiting planets exert on one another.

Advanced Techniques for Exoplanet Analysis

For the most recent study, the researchers joined TTV data with a radial velocity analysis of the star. Using the Automated Planet Finder telescope at the Lick Observatory on California’s Mount Hamilton and the High-Resolution Echelle Spectrometer at the W.M. Keck Observatory on Hawaii’s Mauna Kea, they could detect slight variations in stellar motion via the redshift and blueshift of the Doppler effect – which helped them determine planetary mass readings of unprecedented precision.

To obtain such exact information on the planets in this solar system, the team built computer models using hundreds of radial velocity measurements layered over TTV data. Lead author Corey Beard, a UCI Ph.D. candidate in physics, said that combining these two types of readings yielded more knowledge about the system than ever before.

“It took a lot of trial and error, but we were really happy with our results after developing one of the most complicated planetary system models in exoplanetAn exoplanet (or extrasolar planet) is a planet that is located outside our Solar System, orbiting around a star other than the Sun. The first suspected scientific detection of an exoplanet occurred in 1988, with the first confirmation of detection coming in 1992.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>exoplanet literature to date,” Beard said.

Insights and Future Research Directions

The large number of planets is one factor that inspired the astronomy team to conduct further research, according to co-author Paul Robertson, UCI associate professor of physics & astronomy.

“We viewed TOI-1136 as being highly advantageous from a research standpoint, because when a system has multiple exoplanets, we can control for the effects of planet evolution that depend on the host star, and that helps us focus on individual physical mechanisms that led to these planets having the properties that they do,” he said.

Robertson added that when astronomers try to compare planets in separate solar systems, there are many variables that can differ based on the distinct properties of the stars and their locations in disparate parts of the galaxy. He said that looking at exoplanets in the same system enables the study of planets that have experienced a similar history.

Artist rendering of the TOI-1136 system and its young star flaring. Credit: Rae Holcomb/Paul Robertson/UCI

By stellar standards, TOI-1136 is young, a mere 700 million years old, another feature that has attracted exoplanet hunters. Robertson said that juvenile stars are both “difficult and special” to work with because they’re so active. Magnetism, sunspots and solar flares are more prevalent and intense during this stage of a star’s development, and the resulting radiation blasts and sculpts planets, affecting their atmospheres.

TOI-1136’s confirmed exoplanets, TOI-1136 b through TOI-1136 g, are categorized as “sub-Neptunes” by the experts. Robertson said the smallest one is more than twice the radius of Earth, and others are up to four times Earth’s radius, comparable to the sizes of UranusUranus is the seventh farthest planet from the sun. It has the third-largest diameter and fourth-highest mass of planets in our solar system. It is classified as an "ice giant" like Neptune. Uranus' name comes from a Latinized version of the Greek god of the sky.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Uranus and NeptuneNeptune is the farthest planet from the sun. In our solar system, it is the fourth-largest planet by size, and third densest. It is named after the Roman god of the sea.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Neptune.

All these planets orbit TOI-1136 in less than the 88 days it takes Mercury to go around Earth’s sun, according to the study. “We’re packing an entire solar system into a region around the star so small that our entire planetary system here would be outside of it,” Robertson said.

“They’re weird planets to us because we don’t have anything exactly like them in our solar system,” said co-author Rae Holcomb, a UCI Ph.D. candidate in physics. “But the more we study other planet systems, it seems like they may be the most common type of planet in the galaxy.”

Another odd component to this solar system is the possible yet unconfirmed presence of a seventh planet. The researchers have detected some evidence of another resonant force in the system. Robertson explained that when planets are orbiting close to one another, they can pull on each other gravitationally.

“When you hear a chord played on a piano and it sounds good to you, it’s because there is resonance, or even spacing, between the notes that you’re hearing,” he said. “The orbital periods of these planets are spaced similarly. When the exoplanets are in resonance, the tugs are in the same direction every time. This can have a destabilizing effect, or in special cases, it can serve to make the orbits more stable.”

Robertson noted that far from answering all his team’s questions about the exoplanets in this system, the survey has made the researchers want to pursue additional knowledge, particularly about the composition of planetary atmospheres. That line of inquiry would be best approached through the advanced spectroscopy capabilities of NASA’s James Webb Space TelescopeThe James Webb Space Telescope (JWST or Webb) is an orbiting infrared observatory that will complement and extend the discoveries of the Hubble Space Telescope. It covers longer wavelengths of light, with greatly improved sensitivity, allowing it to see inside dust clouds where stars and planetary systems are forming today as well as looking further back in time to observe the first galaxies that formed in the early universe.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>James Webb Space Telescope, he said.

“I am proud that both UCO’s Lick Observatory and the Keck Observatories were involved in the characterization of a really important system,” said Matthew Shetrone, deputy director of UC Observatories. “Having so many moderate-sized planets in the same system really lets us test formation scenarios. I really want to know more about these planets! Might we find a molten rock world, a water world and an ice world all in the same solar system? It almost feels like science fiction.”

For more on this research, see Exoplanets Discovered Around a New Star Reveal Secrets of Planet Formation.

Reference: “The TESS-Keck Survey. XVII. Precise Mass Measurements in a Young, High-multiplicity Transiting Planet System Using Radial Velocities and Transit Timing Variations” by Corey Beard, Paul Robertson, Fei Dai, Rae Holcomb, Jack Lubin, Joseph M. Akana Murphy, Natalie M. Batalha, Sarah Blunt, Ian Crossfield, Courtney Dressing, Benjamin Fulton, Andrew W. Howard, Dan Huber, Howard Isaacson, Stephen R. Kane, Grzegorz Nowak, Erik A Petigura, Arpita Roy, Ryan A. Rubenzahl, Lauren M. Weiss, Rafael Barrena, Aida Behmard, Casey L. Brinkman, Ilaria Carleo, Ashley Chontos, Paul A. Dalba, Tara Fetherolf, Steven Giacalone, Michelle L. Hill, Kiyoe Kawauchi, Judith Korth, Rafael Luque, Mason G. MacDougall, Andrew W. Mayo, Teo Močnik, Giuseppe Morello, Felipe Murgas, Jaume Orell-Miquel, Enric Palle, Alex S. Polanski, Malena Rice, Nicholas Scarsdale, Dakotah Tyler and Judah Van Zandt, 29 January 2024, The Astronomical Journal.
DOI: 10.3847/1538-3881/ad1330

Joining Robertson and Beard on this study were researchers from Spain’s Astrophysics Institute of the Canary Islands; the California Institute of Technology; Sweden’s Chalmers University of TechnologyChalmers University of Technology is a <span class="st">research-intensive</span> university located in Gothenburg, Sweden that was founded in 1829 following a donation by William Chalmers, a director of the Swedish East India Company. It focuses on technology, science, architecture, and shipping.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Chalmers University of Technology; Maryland’s Johns Hopkins University; Spain’s University of La Laguna; Sweden’s Lund University; Poland’s Nicolaus Copernicus University; New Jersey’s Princeton UniversityFounded in 1746, Princeton University is a private Ivy League research university in Princeton, New Jersey and the fourth-oldest institution of higher education in the United States. It provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences, and engineering.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Princeton University; Japan’s Ritsumeikan University; California’s SETI Institute; Maryland’s Space Telescope Science Institute; the University of California, Santa Cruz; the University of California, BerkeleyLocated in Berkeley, California and founded in 1868, University of California, Berkeley is a public research university that also goes by UC Berkeley, Berkeley, California, or Cal. It maintains close relationships with three DOE National Laboratories: Lawrence Berkeley National Laboratory, Los Alamos National Laboratory, and Lawrence Livermore National Laboratory.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>University of California, Berkeley; the University of California, Los Angeles; the University of California, Riverside; the University of Hawaii; the University of ChicagoFounded in 1890, the University of Chicago (UChicago, U of C, or Chicago) is a private research university in Chicago, Illinois. Located on a 217-acre campus in Chicago's Hyde Park neighborhood, near Lake Michigan, the school holds top-ten positions in various national and international rankings. UChicago is also well known for its professional schools: Pritzker School of Medicine, Booth School of Business, Law School, School of Social Service Administration, Harris School of Public Policy Studies, Divinity School and the Graham School of Continuing Liberal and Professional Studies, and Pritzker School of Molecular Engineering.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>University of Chicago; the University of Kansas; Indiana’s University of Notre Dame; Australia’s University of Southern Queensland; and Connecticut’s Yale UniversityEstablished in 1701, Yale University is a private Ivy League research university in New Haven, Connecticut. It is the third-oldest institution of higher education in the United States and is organized into fourteen constituent schools: the original undergraduate college, the Yale Graduate School of Arts and Sciences and twelve professional schools. It is named after British East India Company governor Elihu Yale.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Yale University. Funding was provided by the W.M. Keck Foundation, NASA and the National Science Foundation.