Scientists have potentially discovered an exoplanet by observing unexpected shifts in another planet's orbit

The hot Jupiter TOI-2818b exhibited unexpected timing variations, suggesting the presence of a hidden companion. This challenges the conventional belief that hot Jupiter typically exist alone. After ruling out alternative explanations, researchers are now employing advanced telescopes to verify the characteristics of the potential second planet.

Figure 1. Hidden Exoplanet.

Detecting Planets Using Transit Timing Variations (TTV)

Researchers from UNSW Sydney have found evidence of a potential exoplanet — a planet orbiting a star outside our solar system — using a method known as transit timing variation (TTV). FiIn a study published on March 4 in The Astrophysical Journal, Scientia Senior Lecturer Dr. Ben Montet and PhD candidate Brendan McKee analyzed irregular shifts in the transit timing of a known exoplanet. These subtle changes suggested the gravitational influence of an unseen companion planet.gure 1 hidden exoplanet.

The team focused on TOI-2818b, a "hot Jupiter" exoplanet, whose transit data showed unexpected variations. Through computer simulations, they concluded that these timing anomalies likely indicate the presence of a smaller planet orbiting the same star.

The potential exoplanet is estimated to be 10 to 16 times the size of Earth, with an orbital period of less than 16 days.“Hot Jupiters rarely have nearby companion planets,” said Dr. Montet. “This discovery challenges our understanding of how hot Jupiters form and could provide new insights into the evolution of planetary systems.”

Searching for Exoplanets

An exoplanet refers to any planet that exists outside our solar system. Just like planets in our solar system orbit the Sun, most exoplanets revolve around their own host stars.

According to NASA, over 5,500 exoplanets have been confirmed so far, with predictions suggesting that trillions more may exist within the Milky Way galaxy [1]. Among these discovered exoplanets, around 500 are classified as "hot Jupiters" — large, gas giant planets that orbit very close to their stars, resulting in extremely high surface temperatures.

Even rarer than hot Jupiters are their companion planets — smaller planets that share the same star. The discovery of such companions is significant, as it challenges current understandings of planetary formation and system dynamics, opening new possibilities for studying complex exoplanetary systems.

Uncovering Hidden Worlds Through Planetary Shadows

A widely used technique for discovering exoplanets is called Transit Timing Variation (TTV), which relies on observing changes in a star’s brightness caused by orbiting planets.

“When a planet passes in front of its star from our perspective on Earth, it’s similar to an eclipse, temporarily blocking some of the star’s light,” explains Mr. McKee. “As the planet moves across, we record a brief dip in brightness lasting a few hours, and this dip repeats with each orbit.”

Dr. Montet further illustrates it as “the planet casting a shadow on the star, making it appear slightly dimmer.” If the timing or duration of these dips fluctuates, it can indicate the gravitational influence of another hidden planet, providing astronomers a pathway to uncover unseen worlds.

Planets as Celestial Timekeepers

Planets can serve as reliable cosmic clocks, as their orbits around stars typically remain stable, ensuring consistent intervals between transits. However, when multiple planets exist in a system, their gravitational pull on one another can slightly alter their orbital speeds.

“If there’s more than one planet, their gravitational interactions cause small changes in their orbits, making one planet speed up or slow down slightly,” explains Dr. Montet. “As a result, the transit may occur a bit earlier or later than expected, and these timing shifts can indicate the presence of another hidden planet.”

Simulating Planetary Orbits

TOI-2818b, a hot Jupiter over 1000 light-years away in the constellation Puppis, showed unusual transit timing shifts after its discovery. PhD candidate Brendan McKee noticed that its transits were occurring slightly earlier, hinting at an irregular orbit.Initially, researchers considered tidal forces from the star, similar to the Moon’s influence on Earth, as a possible cause. However, simulations ruled out these scenarios.

“The only plausible explanation is that another unseen planet is gravitationally affecting TOI-2818b's orbit,” explained Dr. Montet. Further observations are needed to confirm the companion planet’s existence.

Insights Into Planet Formation

Since the first exoplanets were discovered in the mid-1990s, astronomers have made remarkable progress in exploring planets beyond our solar system [2]. Although no Earth-like exoplanet capable of supporting life has been found yet, scientists have identified several Earth-sized rocky exoplanets, some of which lie within their star’s habitable zone — a region where liquid water could potentially exist on the planet's surface.

“There are still many unanswered questions about exoplanets,” says Dr. Montet. “Every time we discover a new planet; it raises fresh questions about how they form. Hot Jupiters, for example, remain a fascinating mystery. Despite being the first type of exoplanets we detected; we still don’t fully understand their formation or why they exist in such close orbits around their stars.”

Exploring Hot Jupiter Formation and Future Research

Scientists propose two main theories for how hot Jupiters form. One, known as dynamical excitation, involves chaotic interactions that may eject other planets from the system. The other, called cold migration, suggests a gradual inward drift of the planet. “If hot Jupiters often have companion planets, it supports cold migration. But if they are usually isolated, chaotic scattering is likely more common,” explains Dr. Montet.

The unusual transit of TOI-2818b suggests the presence of a companion planet, but further observations are needed. Instruments like ESPRESSO on the Very Large Telescope (VLT) will help confirm its existence by eliminating other possibilities, such as a brown dwarf.

Dr. Montet emphasizes that ongoing collaboration, from major observatories to citizen scientists, will drive future discoveries. “As new missions and advanced techniques emerge, we’ll continue uncovering surprising planetary systems unlike our own,” he says.

Reference:

1. https://scitechdaily.com/this-planets-orbit-made-no-sense-until-scientists-discovered-a-hidden-world/
2. https://edition.cnn.com/2024/11/04/science/planet-nine-kuiper-belt-latest-evidence/index.html

Cite this article:

Keerthana S (2025), This Planet’s Orbit Made No Sense – Until Scientists Discovered a Hidden World, AnaTechMaz,pp.241