Astronomers Spot Rare Exoplanet System with Rapidly Changing Orbits

Astronomers Spot Rare Exoplanet System with Rapidly Changing Orbits
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Astronomers have discovered a highly unusual planetary system around the star TOI‑201, located about 370 light‑years from Earth, where the orbits of its planets are evolving swiftly — a phenomenon rarely seen in real time.

The finding was made using data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and follow‑up observations from the Antarctic Search for Transiting ExoPlanets (ASTEP) at Antarctica’s Concordia Station.

The star TOI‑201 is slightly larger and more massive than the Sun, with about 1.3 times the Sun’s mass and diameter. Researchers identified three distinct worlds orbiting the star, namely:

TOI‑201 d: a rocky “super‑Earth” roughly six times the mass of Earth, completing an orbit every 5.85 days.
TOI‑201 b: a “warm Jupiter” gas giant with about half the mass of Jupiter on a 53‑day orbit.
TOI‑201 c: a massive companion with about 16 times the mass of Jupiter — technically a brown dwarf — on a ~7.9‑year orbit.

What makes TOI‑201 extraordinary is how the outer body’s highly elongated and tilted orbit strongly influences the inner planets. Its gravitational pull causes measurable changes in the timing of planetary transits and in the shapes of the orbits — alterations astronomers can observe over decades rather than millions of years, as is typical in most systems.

In the study, published in the journal Science, researchers noted that the changing dynamics mean that the planets’ transits may no longer align as seen from Earth in about 200 years. This makes TOI‑201 one of the few known systems where orbital evolution is observable on human timescales, offering a unique laboratory for studying how planetary systems form and change.