New Planet System Challenges Planet Formation Theories | NASA Discovery

An ‘Inside-Out’ Solar System Challenges Planet Formation Theories

More than 100 light-years from Earth, a planetary system is puzzling astronomers and may force science to reconsider established concepts about world formation. Observations made with telescopes from NASA and the European Space Agency (ESA) have revealed an unusual architecture around the star LHS 1903, a red dwarf – the most common type of star in the Universe.

A Peculiar Planetary Arrangement

Four planets orbit LHS 1903, but their arrangement defies the known pattern. The innermost planet is rocky; the next two are gaseous; and the outermost, unexpectedly, is also rocky. This configuration contradicts the model observed in our own Solar System, where rocky planets occupy the inner orbits and gas giants concentrate in the outer regions.

How Planets Typically Form

The traditional model posits that planets form from a disk of gas and dust around young stars. In the hotter, inner regions close to the star, only heat-resistant materials like iron and silicates can clump together, forming rocky bodies. Beyond the “snow line,” where temperatures allow water and other compounds to condense, planetary cores grow rapidly and can capture large amounts of hydrogen and helium, forming gas giants.

A First-of-Its-Kind Discovery

According to Thomas Wilson, assistant professor at the University of Warwick and lead author of the study published in Science, this is the first time a rocky planet has been observed so far from its host star, situated beyond gaseous worlds. The outermost object, classified as a “Super-Earth,” is approximately 1.7 times the radius of Earth.

Possible Explanations and Ongoing Research

The team tested hypotheses such as planet collisions or the loss of atmosphere from a gas giant, but simulations failed to replicate the observed system. The most plausible explanation, according to researchers, is a formation mechanism with a progressive scarcity of gas. In this scenario, the planets would have emerged one after another, from the innermost to the outermost. When the last planet began to form, the disk was already poor in gas and dust, favoring the emergence of a predominantly rocky body.

The system was initially identified by NASA’s TESS satellite and subsequently analyzed with ESA’s CHEOPS, along with complementary data from ground-based observatories.

Implications for Planet Formation Around Red Dwarfs

Sara Seager, from the Massachusetts Institute of Technology and a co-author of the study, suggests the discovery may represent one of the first pieces of evidence that planet formation around red dwarfs follows distinct paths from those observed around stars like our Sun. However, experts emphasize that the debate remains open.

Heather Knutson, from the California Institute of Technology, highlighted that the outermost planet may be cold enough to allow water to condense, and future observations with the James Webb Space Telescope could reveal details about its atmosphere.

The case of LHS 1903 adds an unexpected data point to current models and should stimulate new simulations in the coming years. In a field still in consolidation, the system serves as a reminder that the diversity of planetary architectures may be greater – and more complex – than previously imagined.

Future Trends: The Search for More ‘Inside-Out’ Systems

The discovery of LHS 1903 is likely to spur a focused search for similar systems. Astronomers will be analyzing data from TESS and CHEOPS, as well as from ground-based observatories, looking for other instances of rocky planets orbiting beyond gas giants. This will require refining existing planet detection algorithms to better identify these unusual configurations.

The James Webb Space Telescope will play a crucial role in characterizing the atmospheres of planets in these systems. By analyzing the light that passes through their atmospheres, scientists can determine their composition and gain insights into their formation history.

FAQ

• What makes the LHS 1903 system unusual? The planets are arranged in an order that contradicts typical planet formation models – rocky, gaseous, gaseous, rocky.
• What is a red dwarf star? It’s a small, cool star that is the most common type in the universe.
• How was this system discovered? Initially by NASA’s TESS satellite, then confirmed and analyzed with ESA’s CHEOPS and ground-based telescopes.
• What is the “snow line”? It’s the distance from a star where temperatures are low enough for volatile compounds like water to condense into ice.

Pro Tip: Red dwarf stars are smaller and cooler than our Sun, meaning their habitable zones are much closer in. This makes detecting planets around them more challenging, but also increases the chances of finding potentially habitable worlds.

Did you know? The planets in the LHS 1903 system all orbit in less than 30 days, making for a very compact system!

Want to learn more about exoplanet discoveries? Explore our other articles on the latest advancements in space exploration and the search for life beyond Earth.