Exoplanet is rapidly disintegrating, leaving behind a trail of dust

An exoplanet is a planet that orbits a star outside of our solar system. One such dusty body, perched about 140 light-years away, appears to be wasting away at a startling speed.

NASA’s Transiting Exoplanet Survey Satellite (TESS) picked up unusual dips in the host star’s brightness that hinted at a dramatic event taking place. When astronomers took a closer look, they found a small exoplanet flinging off dust and debris each time it whipped around its star.

Exoplanet’s dust cloud is evolving

“The extent of the tail is gargantuan, stretching up to 9 million kilometers (5.6 million miles) long,” said Dr. Marc Hon from the Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology.

This crumbling orb, known as BD+05 4868 Ab, completes its entire orbit around its star in roughly 30 hours. Its close position to the star means it experiences searing temperatures that can melt rock on its surface.

Researchers say these punishing conditions make the planet shed its outer layers, which forms a tail that gives the planet the appearance of a dusty comet. That dust cloud changes over time, which explains the strange fluctuations in starlight recorded by TESS.

Such variability is no small matter because typical signals from an orbiting object remain fairly consistent. The shifting pattern here suggests ongoing changes in how much dust is released and how that debris spreads out around the planet.

The planet loses mass with each orbit

Rocky planets with greater gravitational fields can hold onto their minerals, so this type of disintegration rarely comes to light. Small worlds simply do not have the pulling power to keep matter from escaping once intense heat takes over.

BD+05 4868 Ab loses a chunk of mass equivalent to a mountain every time it orbits. If this meltdown continues, the planet might break down completely in a mere few million years.

“We got lucky with catching it exactly when it’s really going away,” said Avi Shporer from the TESS Science Office. These discoveries help scientists explore the extreme conditions that can tear planets apart.

Many factors play a role in such destruction, including the star’s temperature and the planet’s distance. Because BD+05 4868 Ab sits so close, it gets a direct blast of scorching radiation.

Rare exoplanet with a dust tail

Astronomers rely on transits to observe these events, which occur when a planet crosses in front of its star from our viewpoint. When the planet lugs a substantial dust cloud behind it, the star’s brightness dips for longer periods than usual, and with different intensities.

Scientists can measure how the dip varies and piece together what the dust might be composed of. For BD+05 4868 Ab, tiny grains linger in orbit and form a stretched-out tail that makes the planet appear like a comet.

This elongated structure indicates a constant stream of evaporated material leaving the planet. The presence of a dusty tail also suggests that surface minerals are boiling away on a regular basis.

The star itself is a K-dwarf, which is cooler than our Sun but still intense enough at close range to strip material from a vulnerable body. Studying such star-planet interactions deepens our understanding of how quickly certain worlds can vanish.

Rare example of exoplanet disintegration

Only a handful of exoplanets show signs of disintegration like this. Each new case is a reminder that cosmic environments vary in ways we never expected a few decades ago.

Since the first confirmed discovery of a planet in orbit around another star in 1992, scientists have cataloged thousands of these objects. Detailed observations reveal a wide range of forms and fates, from gas giants to small rocky spheres on paths of destruction.

BD+05 4868 Ab stands out because the star is brighter than those hosting other known shredding planets. That brightness allows for clearer observations and may provide more direct measurements of the dust’s composition.

By comparing data from different star systems, astronomers can piece together common factors in planetary evolution. This knowledge can also shed light on how similar or dissimilar our solar system might be compared to others.

Future research directions

“Sometimes with the food comes the appetite, and we are now trying to initiate the search for exactly these kinds of objects,” said Shporer. Future work will involve the use of the James Webb Space Telescope, which excels at capturing infrared signatures. 

Infrared analysis can identify the precise mineral makeup of the dust swirling around exoplanet BD+05 4868 Ab. Those findings might confirm theories about what lies under the crust of rocky planets far beyond our neighborhood.

Once researchers pin down these minerals, they can match them to known compounds in our solar system. If parallels are found, it may hint that some planetary interiors share a similar recipe despite forming around very different stars.

Although BD+05 4868 Ab is facing an imminent exit, its dramatic transformation offers a wealth of new ideas about planetary survival.

By examining these fleeting worlds, astronomers uncover how quickly certain orbits become lethal. Data from TESS and other telescopes bring our galaxy into sharper focus.

The study is published in The Astrophysical Journal Letters.

Image Credit: Jose-Luis Olivares, MIT

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