In a stark deviation from what astronomers once believed about planetary systems, researchers have discovered that planets larger than Earth but smaller than Neptune are surprisingly common in the far reaches of alien solar systems.
A new study published in the journal Science on April 24 reveals these “super Earths” frequently orbit their stars at distances comparable to or greater than Jupiter’s position in our own solar system – a finding that challenges longstanding assumptions about planetary formation.
“We found a ‘super Earth’ — meaning it’s bigger than our home planet but smaller than Neptune — in a place where only planets thousands or hundreds of times more massive than Earth were found before,” said Weicheng Zang, a Fellow at the Center for Astrophysics | Harvard & Smithsonian (CfA) and lead author of the paper.
The international research team identified a planet approximately twice Earth’s size orbiting its star at a distance greater than Saturn’s position in our solar system. This discovery stems from the largest microlensing study of its kind, analyzing about three times more planets than previous samples and including planets roughly eight times smaller than those found in earlier microlensing surveys.
Microlensing occurs when light from distant stars is amplified by an intervening body such as a planet. The technique excels at detecting planets at substantial distances from their host stars – comparable to the region between Earth’s and Saturn’s orbits.
The researchers utilized data from the Korea Microlensing Telescope Network (KMTNet), which consists of three telescopes strategically positioned in Chile, South Africa, and Australia. This global arrangement allows for continuous monitoring of the night sky.
“This measurement of the planet population from planets somewhat larger than Earth all the way to the size of Jupiter and beyond shows us that planets, and especially super-Earths, in orbits outside the Earth’s orbit are abundant in the Galaxy,” noted co-author Jennifer Yee of the Smithsonian Astrophysical Observatory.
Our solar system features a relatively neat arrangement – four small rocky planets close to the Sun, followed by four large gaseous planets in the outer system. Previous exoplanet studies using transit and radial velocity methods already demonstrated that many systems contain a variety of planet sizes in orbits closer than Earth’s. This new research extends that understanding to the outer regions of planetary systems.
“This result suggests that in Jupiter-like orbits, most planetary systems may not mirror our Solar System,” explained co-author Youn Kil Jung of the Korea Astronomy and Space Science Institute.
The findings also indicate there are at least as many super-Earth planets as Neptune-sized planets in these distant orbits, providing crucial data about planetary population distributions.
“The current data provided a hint of how cold planets form,” said Professor Shude Mao of Tsinghua University and Westlake University, China. “In the next few years, the sample will be a factor of four larger, and thus we can constrain how these planets form and evolve even more stringently with KMTNet data.”
As astronomers continue to expand their catalog of exoplanets, the evidence increasingly suggests our solar system’s arrangement may be more exception than rule – a humbling reminder that the architecture of planetary systems throughout the galaxy follows diverse evolutionary paths.
If our reporting has informed or inspired you, please consider making a donation. Every contribution, no matter the size, empowers us to continue delivering accurate, engaging, and trustworthy science and medical news. Independent journalism requires time, effort, and resources—your support ensures we can keep uncovering the stories that matter most to you.
Join us in making knowledge accessible and impactful. Thank you for standing with us!