Astronomers have discovered two ultra-short-period (USP) planets that are disintegrating due to intense heat and radiation from their host stars. As these planets spiral toward their demise, they leave behind debris trails similar to those of comets, offering scientists a rare and unprecedented opportunity to study the interiors of distant planets, according to Science Alert magazine.
USPs are characterized by their incredibly short orbital periods, with some completing a full orbit in only a few hours. Positioned very close to their host stars, they are subjected to extreme heat, stellar radiation, and powerful gravitational forces.
These planets, which orbit their stars extremely rapidly, are among a rare class of USPs that lack the mass to retain their material, making them unique subjects of study.
Most USPs are tidally locked to their stars, meaning one side of the planet is perpetually facing the star, transforming it into a furnace. Typically, these planets are no larger than twice Earth’s radius, and astronomers estimate that approximately one in every 200 Sun-like stars has such a planet. USPs were only recently discovered, challenging our understanding of planetary systems.
The formation mechanisms of USPs remain unclear, but astronomers believe they likely migrated toward their current positions rather than forming there. Their proximity to their stars makes them difficult to observe, posing significant challenges for researchers seeking to understand their structures and evolution.
Fortunately, two separate American-based teams of astronomers have recently observed the disintegration of two USPs, allowing them to gather data about the planets’ compositions. This groundbreaking research has been published in two separate studies.
The first study, led by Marc Hon, a postdoctoral researcher at MIT’s TESS Science Office, describes the disintegration of the planet BD+054868Ab, which orbits a bright K-dwarf star every 1.27 days. The planet was discovered by the TESS spacecraft, and its unique features include variable transit depths and asymmetric transit profiles, indicative of dust tails being ejected from the planet.
The dust forms two distinct tails, one on the leading edge and the other on the trailing edge, with the leading tail consisting of larger dust particles and the trailing tail made of finer grains. These tails stretch out to approximately 9 million kilometers, encircling over half of the planet’s orbit every 30.5 hours.
The researchers estimate that the planet is losing material at a rate of 10 Earth masses per billion years, and given the planet’s small size, similar to Earth’s Moon, it will likely be completely destroyed within a few million years. This process is described as “cataclysmic” by researcher Hon, who expressed excitement about witnessing the final stages of this planet’s life.
The second study, led by Nick Tusay, a PhD student at Penn State, focuses on K2-22b, a disintegrating planet discovered during the Kepler mission’s extended K2 phase. This planet orbits its M-dwarf star every 9.1 hours and also exhibits dramatic variability in its light curve, which is a signature of dust being sublimated from the planet’s surface.
Using the James Webb Space Telescope (JWST), the team observed that the material emanating from K2-22b is likely composed of magnesium silicate minerals, which suggests that the planet is shedding mantle material rather than core material. This discovery provides scientists with a rare opportunity to study the composition of a planet’s interior by analyzing the debris it sheds into space.
Interestingly, some of the material observed by JWST showed features typically associated with icy bodies like comets, such as nitrogen oxide (NO) and carbon dioxide (CO2). These unexpected findings have prompted the researchers to consider multiple possible sources for the observed material and plan further observations to refine their understanding.
The unique characteristics of these disintegrating planets are not only exciting for astronomers studying planetary interiors but also demonstrate the capabilities of the JWST in investigating exoplanetary systems. According to Avi Shporer, a research scientist at MIT and co-author of the first study, the bright host star of BD+054868Ab makes it an excellent target for further observations, as its brightness will allow JWST to capture even more detailed data.
Both studies highlight the exciting potential for future research into the composition and structure of disintegrating planets. As astronomers continue to observe these planets with advanced telescopes like the JWST, they hope to uncover more about the processes that shape planets and the fate of those that fall victim to the extreme conditions around their stars.
The findings from these studies represent a significant step forward in our understanding of planetary evolution, providing a unique glimpse into the inner workings of planets that are “literally spilling their guts into space,” lead author Tusay said. The data gathered from these disintegrating worlds could help refine models of planetary formation, structure, and the forces that lead to their destruction.