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Researchers at MIT have made an intriguing discovery of a distant planet located approximately 140 light-years from Earth, which is undergoing rapid disintegration.
This planet, roughly the mass of Mercury, orbits its star at an extraordinarily close distance—around 20 times nearer than Mercury to the Sun—completing its orbit in just 30.5 hours. Due to the extreme heat from its proximity to the star, the planet is likely covered in scorching magma that is evaporating into space. As it makes its swift orbit, the planet is losing a substantial amount of surface minerals, effectively disintegrating.
The astronomers identified this celestial body using NASA’s Transiting Exoplanet Survey Satellite (TESS), a mission led by MIT that tracks nearby stars for signs of transiting exoplanets, marked by periodic dimming in starlight. The researchers were alerted to the planet by an unusual transit pattern, which displayed variable depths with each passage.
The evidence confirmed that this rocky planet is not only tightly bound to its star but is also trailing a significant, comet-like tail of debris.
Marc Hon, a postdoctoral researcher at MIT’s Kavli Institute for Astrophysics and Space Research, noted, “The tail is enormous, extending up to 9 million kilometers—roughly half the distance of the planet’s complete orbit.”
This planet is disintegrating at an alarming rate, losing material equal to the mass of Mount Everest with each orbit. Given its small mass, the researchers estimate that it could fully disintegrate within one to two million years.
According to Avi Shporer, a collaborator at the TESS Science Office, “We were fortunate to catch it during a critical phase of its decay—it’s akin to the planet’s last gasp.”
The findings will be detailed in an upcoming publication in the Astrophysical Journal Letters. The team includes numerous MIT co-authors, such as Saul Rappaport, Andrew Vanderburg, and Sara Seager, alongside collaborators from various institutions.
Disintegrating Under Intense Heat
The newly identified planet, designated as BD+05 4868 Ab, was discovered somewhat serendipitously.
Hon remarked, “Our initial focus wasn’t on this type of planet. During routine vetting, I came across this unusual signal.”
Typically, signals from orbiting exoplanets manifest as brief, regular dips in light intensity, indicating a smaller object obscuring part of the light from its host star. However, the signal detected from BD+05 4868 A, situated in the Pegasus constellation, diverged from this norm. Despite its 30.5-hour transit, the star’s brightness restored at a much slower pace, hinting at a lingering structure that continued to block light. Additionally, each dip’s depth varied, indicating that the object obscuring the light was not of uniform shape or density.
Hon explained, “The transit shape is consistent with that of a comet with a long tail. However, this tail likely lacks the volatile gases and ice typical of comets, as those substances wouldn’t survive the intense heat at such proximity to the star. Instead, the tail mainly consists of mineral grains evaporating from the planet’s surface, which can persist long enough to create a distinct tail.”
The team estimates that the planet is subjected to temperatures around 1,600 degrees Celsius (nearly 3,000 degrees Fahrenheit). The intense heat is causing any surface minerals to vaporize and escape, resulting in the formation of the elongated, dusty tail.
The planet’s dramatic disintegration is attributed to its low mass, which falls between that of Mercury and the Moon. More massive rocky planets, like Earth, possess a stronger gravitational force that allows them to retain their atmospheres. Researchers suggest that BD+05 4868 Ab’s weak gravity makes it hard to retain mass.
Shporer described the situation: “This tiny object has such weak gravity that it easily loses considerable mass, which in turn diminishes its gravity further, leading to even more mass loss. It’s a self-reinforcing cycle that continues to escalate.”
Catching a Glimpse of the Cosmic Trail
Among the nearly 6,000 exoplanets cataloged to date, only three other disintegrating planets have been documented outside our solar system, all identified more than a decade ago using NASA’s Kepler Space Telescope. Each of these planets exhibited similar comet-like tails, with BD+05 4868 Ab possessing the longest and most profound transits of the group.
Hon explained, “This indicates that its rate of evaporation is considerably greater, suggesting it will vanish much quicker than its counterparts.”
Due to its host star’s relative brightness and proximity, this system presents an excellent opportunity for detailed observations with NASA’s James Webb Space Telescope (JWST). The JWST could help elucidate the mineral composition of the dust tail by analyzing the infrared light absorption.
This upcoming summer, Hon and graduate student Nicholas Tusay from Penn State University will spearhead observations of BD+05 4868 Ab using JWST. “This is a unique chance to directly assess the internal composition of a rocky planet, which could provide valuable insights into the diversity and potential habitability of terrestrial planets beyond our solar system,” Hon stated.
The research team will also delve into TESS data to seek out additional disintegrating planets.
Shporer expressed enthusiasm for the prospect, saying, “As we find more of these peculiar objects, we hope to expand our search. The varying shapes of their signals pose challenges, but they also present intriguing avenues for exploration.”
This research received partial support from NASA.
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