Doomed Exoplanet TOI-2109b’s Three Possible Fates

Doomed Exoplanet TOI-2109b: A Cosmic Death Spiral

Astronomers have observed the ultrahot gas giant TOI-2109b, a planet five times the mass of Jupiter, spiraling towards its host star. Located 870 light-years away, this exoplanet is caught in a perilous orbit, completing a full revolution in a mere 16 hours – the shortest orbit known for any ultrahot Jupiter. The intense heat from the star is causing its atmosphere to boil away as it inexorably inches closer to its demise. This celestial dance of destruction has captivated scientists, leading them to contemplate the possible fates awaiting this doomed world.

Observing the Inevitable Spiral

Data from NASA’s TESS (Transiting Exoplanet Survey Satellite) and ESA’s Cheops (CHaracterising ExOPlanet Satellite) missions have provided crucial insights into TOI-2109b’s decaying orbit. These observations confirm that the planet is indeed spiraling inward, a process that will continue over thousands of Earth years. The rate of decay, measured at approximately 10 seconds over three Earth years, serves as a stark reminder of the relentless forces at play in this cosmic drama.

The Ultrahot Jupiter Phenomenon

TOI-2109b belongs to a class of exoplanets known as ultrahot Jupiters. These gas giants orbit extremely close to their stars, resulting in scorching atmospheric temperatures that can reach thousands of degrees Celsius. The proximity to the star also exposes them to intense tidal forces and radiation, making them ideal candidates for studying planetary evolution and destruction.

Three Possible Fates for TOI-2109b

The ultimate destiny of TOI-2109b remains uncertain, with three distinct scenarios proposed by researchers:

• The Fiery Plunge: In this dramatic scenario, the exoplanet’s decaying orbit will eventually lead it to plunge directly into its host star. This collision would generate a spectacular luminous flare, similar to the event known as ZTF SLRN-2020, a transient astronomical event.
• Tidal Disruption: The immense tidal forces exerted by the star could permanently warp and ultimately rip the planet apart. This process, known as tidal disruption, would result in the formation of a debris disk around the star, a telltale sign of a planetary demise. The Roche limit, a critical distance from a celestial body within which a second celestial body will disintegrate due to tidal forces exceeding the second body’s own gravitational self-attraction, plays a crucial role in this scenario. If the planet spirals within its Roche limit, destruction is all but certain.
• Planetary Rebirth: A less tragic, yet still transformative, possibility involves photoevaporation. The strong radiation from the host star could strip away TOI-2109b’s gaseous envelope, potentially revealing its rocky core. If this process occurs rapidly enough, the planet might shrink sufficiently to avoid complete destruction. It could then settle into a stable orbit as a super-Earth or a Neptune-sized “blow-up” hard relic. This outcome would provide a rare opportunity to observe the evolution of a gas giant into a smaller, rocky planet.

Photoevaporation Explained

Photoevaporation is a process where high-energy photons from a star heat the atmosphere of a planet, causing the gas to escape into space. This process is more effective for planets that are close to their star and have low gravity. The rate of photoevaporation depends on several factors, including the star’s luminosity, the planet’s mass and radius, and the composition of its atmosphere.

Witnessing Planetary Evolution

Regardless of its ultimate fate, TOI-2109b presents a unique opportunity to study the processes that shape and destroy exoplanets. By observing its death spiral, astronomers can gain valuable insights into the dynamics of planetary systems and the diverse range of outcomes that can occur. The study of ultrahot Jupiters like TOI-2109b contributes significantly to our understanding of planetary evolution and the conditions that may lead to the formation of habitable worlds. Further observations and theoretical modeling will be crucial to unraveling the mysteries surrounding this doomed exoplanet.

The Role of Space Telescopes

The discovery and ongoing study of TOI-2109b have been made possible by the remarkable capabilities of space telescopes like TESS and Cheops. These instruments allow astronomers to observe exoplanets with unprecedented precision, measuring their sizes, masses, and orbital parameters. The data collected by these telescopes provide crucial evidence for understanding the processes that govern planetary evolution and the diverse range of exoplanets that exist in our galaxy.

TESS: Surveying the Sky for Exoplanets

TESS is designed to survey the entire sky, searching for exoplanets that transit their host stars. When a planet passes in front of its star, it causes a slight dip in the star’s brightness. By measuring these dips, TESS can detect the presence of exoplanets and determine their orbital periods.

Cheops: Characterizing Exoplanets

Cheops is designed to precisely measure the sizes of exoplanets that have already been discovered by other telescopes. By combining the size measurements from Cheops with the mass measurements from other telescopes, astronomers can determine the density of exoplanets and gain insights into their composition.

Implications for Exoplanet Research

The study of TOI-2109b has significant implications for exoplanet research. It provides valuable insights into the processes that can lead to the destruction of planets, as well as the conditions that may allow them to survive. By studying extreme cases like TOI-2109b, astronomers can develop a better understanding of the diversity of exoplanets and the factors that influence their evolution.