A recently discovered solar system with six confirmed exoplanets and a possible seventh is boosting astronomers’ knowledge of planet formation and evolution. Counting on a globe-spanning arsenal of observatories and instruments, a team led by researchers on the University of California, Irvine has compiled essentially the most precise measurements yet of the exoplanets’ masses, orbital properties and atmospheric characteristics.
In a paper published today in The Astronomical Journal, the researchers share the outcomes of the TESS-Keck Survey, providing a radical description of the exoplanets orbiting TOI-1136, a dwarf star within the Milky Way galaxy greater than 270 light years from Earth. The study is a follow-up to the team’s initial commentary of the star and exoplanets in 2019 using data from the Transiting Exoplanet Survey Satellite. That project provided the primary estimate of the exoplanets’ masses by clocking transit timing variations, a measure of the gravitational pull that orbiting planets exert on each other.
For essentially the most recent study, the researchers joined TTV data with a radial velocity evaluation of the star. Using the Automated Planet Finder telescope on the Lick Observatory on California’s Mount Hamilton and the High-Resolution Echelle Spectrometer on the W.M. Keck Observatory on Hawaii’s Mauna Kea, they might 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 acquire such exact information on the planets on this solar system, the team built computer models using lots of of radial velocity measurements layered over TTV data. Lead writer Corey Beard, a UCI Ph.D. candidate in physics, said that combining these two sorts of readings yielded more knowledge concerning the system than ever before.
“It took lots of trial and error, but we were really glad with our results after developing one of the complicated planetary system models in exoplanet literature up to now,” Beard said.
The big variety of planets is one factor that inspired the astronomy team to conduct further research, in accordance with 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 are able to control for the results of planet evolution that rely upon the host star, and that helps us concentrate on individual physical mechanisms that led to those planets having the properties that they do,” he said.
Robertson added that when astronomers try to match planets in separate solar systems, there are a lot of variables that may differ based on the distinct properties of the celebrities and their locations in disparate parts of the galaxy. He said that taking a look at exoplanets in the identical system enables the study of planets which have experienced an identical history.
By stellar standards, TOI-1136 is young, a mere 700 million years old, one other feature that has attracted exoplanet hunters. Robertson said that juvenile stars are each “difficult and special” to work with because they’re so lively. 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 greater than twice the radius of Earth, and others are as much as 4 times Earth’s radius, comparable to the sizes of Uranus and Neptune.
All these planets orbit TOI-1136 in lower than the 88 days it takes Mercury to go around Earth’s sun, in accordance with the study. “We’re packing a whole solar system right into a region across the star so small that our entire planetary system here can be outside of it,” Robertson said.
“They’re weird planets to us because we haven’t got anything exactly like them in our solar system,” said co-author Rae Holcomb, a UCI Ph.D. candidate in physics. “However the more we study other planet systems, it looks as if they could be the most typical variety of planet within the galaxy.”
One other odd component to this solar system is the possible yet unconfirmed presence of a seventh planet. The researchers have detected some evidence of one other resonant force within the system. Robertson explained that when planets are orbiting close to at least one one other, they’ll pull on one another gravitationally.
“Whenever you hear a chord played on a piano and it sounds good to you, it’s because there may be resonance, and even spacing, between the notes that you just’re hearing,” he said. “The orbital periods of those planets are spaced similarly. When the exoplanets are in resonance, the tugs are in the identical direction each time. This will have a destabilizing effect, or in special cases, it might probably serve to make the orbits more stable.”
Robertson noted that removed from answering all his team’s questions on the exoplanets in this technique, the survey has made the researchers need to pursue additional knowledge, particularly concerning the composition of planetary atmospheres. That line of inquiry can be best approached through the advanced spectroscopy capabilities of NASA’s James Webb Space Telescope, he said.
“I’m proud that each UCO’s Lick Observatory and the Keck Observatories were involved within the characterization of a extremely essential system,” said Matthew Shetrone, deputy director of UC Observatories. “Having so many moderate-sized planets in the identical system really lets us test formation scenarios. I actually need to know more about these planets! Might we discover a molten rock world, a water world and an ice world all in the identical solar system? It almost looks like science fiction.”
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 Technology; Maryland’s Johns Hopkins University; Spain’s University of La Laguna; Sweden’s Lund University; Poland’s Nicolaus Copernicus University; Recent Jersey’s 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, Berkeley; the University of California, Los Angeles; the University of California, Riverside; the University of Hawaii; the University of Chicago; the University of Kansas; Indiana’s University of Notre Dame; Australia’s University of Southern Queensland; and Connecticut’s Yale University. Funding was provided by the W.M. Keck Foundation, NASA and the National Science Foundation.
