These newly discovered worlds are hot and gassy, and don’t seem to be comfortable places to visit. Their cozy orbits around their parent stars place them well inside what astrobiologists consider the planetary system’s “habitable zone.” The quest for Earth 2.0 continues.
But what makes these planets unusual, in addition to their large numbers, is that they resonate with each other as they orbit their stars. For example, one planet will draw exactly 3 of its orbits, but a neighboring planet will draw 2 of its orbits.
“Such resonance chains are extremely rare in nature,” lead author Rafael Luque of the University of Chicago said in a webinar with reporters on Tuesday.
This striking reminder that mathematics rules the universe also has another meaning. That means these six planets have followed a stable and predictable two-by-three orbital pattern since they formed at least 4 billion years ago. Most planetary systems, including our own, do not.
The resonant orbits of these planets are consistent with the idea that the system has not experienced any major disturbance (for example, a catastrophic collision or approach by another star) for billions of years. In this scenario, the planet formed from a cloud of gas and dust with its parent star and found a resonant orbit relatively quickly. And nothing interesting happened to change that.
This unusual orbital pattern is highlighted by the new paper’s fancy title: “A sub-Neptunian resonance sextuplet passing through the bright star HD 110067.”
“Every once in a while, nature unearths an absolute gem,” Sarah Seeger, a professor of planetary science at the Massachusetts Institute of Technology and co-author of the paper, said in an email. She said: “HD 110067 is an immediate astronomical Rosetta Stone, providing an important system that will help unravel the mysteries of planet formation and evolution.”
How to find planets hidden in starlight
This new paper, written by more than 150 scientists from 12 countries, describes Earth’s planetary system. HD 110067, a star in the galaxy. It is located in the constellation Coma, It is not visible to the naked eye.
Still, it’s only 100 light years away, which means it’s on the outskirts of our neighborhood, the Milky Way. Because of its proximity to Earth, Earth is bright compared to many other stars previously known to have planetary systems. For example, it is 10,000 times brighter than Trappist 1, a red dwarf star with an equally interesting swarm of rocky planets.
Starlight is a valuable currency for astronomers, who can study it for clues to the existence of planets invisible in the glare of stars. When a planet passes over the surface of a star, as seen through a telescope (a phenomenon known as a transit), the star’s light dims depending on the size of the planet.
Astronomers can then use the second technique to look for periodic wobbles in the star’s light as the orbiting planet and star interact with their gravity. By combining these methods, astronomers can obtain estimates of the planet’s size and density. Further investigation could detect the molecular composition of the atmosphere, if it exists.
Astronomers discovered the first few planets orbiting HD 110067 in 2020 using NASA’s Transiting Exoplanet Survey Satellite (TESS). TESS scans the entire sky looking for subtle planetary signals. The planetary roster was filled out in 2022 during another series of observations by TESS and a European Space Agency satellite known as CHEOPS (short for “CHARacterising ExOPlanets Satellite”), which allows for more targeted observations.
The new planet is called “subneptunian” because it is larger than the rocky worlds closer to our solar system, such as Earth and Venus, but not as large as the ice giants Neptune and Uranus. Its range is two to three times the diameter of the Earth. The innermost planet orbits the star in just 9 days, while the outermost planet orbits it in 54 days. There may be other planets in this system that have not yet been detected.
For some reason, there are planets smaller than Neptune in the universe, which is one reason the new system is so interesting to astronomers.
“There are six major planets, and their structures are interesting,” Knicole Colon, a NASA astrophysicist and exoplanet expert, said in an email. “All of these planets are probably too warm and too large to support life. But the whole sub-Neptunian angle is still the interesting part. [because] We still don’t know why our solar system lacks it. ”
It is an open question whether the universe simply prefers planets of this size or whether our detection methods are skewing the results. It’s hard to find a small, rocky world like ours orbiting a comfortable distance from an old, gentle star like our Sun. As seen from Earth, it is unlikely to pass through the star’s surface, and the influence of gravity on the star’s motion is minimal.
The discoverers of the new planets said there is evidence that these planets have atmospheres, based on their density. But Luque said: I don’t know what they are made of. ”
We may find out more soon. The new planetary system will be closely observed from NASA’s James Webb Space Telescope, which orbits the sun about 1 million miles from Earth and is designed to gather information about exoplanets’ atmospheres. .