Astronomers in the United States have observed a small, rocky exoplanet orbiting perilously close to its star, disintegrating as its surface vaporizes due to extreme temperatures. This process leaves behind a comet-like tail of mineral dust stretching approximately 9 million kilometers.
Since the 1990s, around 5,800 planets outside our solar system, known as exoplanets, have been discovered. Among these, only four have been observed disintegrating in orbit, like this one. This particular planet is the closest of the four to our solar system, providing scientists with a unique opportunity to understand the fate of these doomed worlds.
Researchers observed the planet BD+05 4868 Ab as it gradually turns to dust, shedding an amount of material with each orbit equal to the volume of Mount Everest. The dust trail it leaves behind spans a semi-circle around its star.
Size of the Exoplanet
The planet is estimated to be between the size of Mercury and our Moon. Located in the constellation Pegasus, it is approximately 140 light years away from Earth. A light year is the distance light travels in one year, equating to about 9.5 trillion kilometers.
BD+05 4868 Ab orbits an orange dwarf star, which is smaller, cooler, and less bright than our Sun, having about 70% of the Sun’s mass and diameter, and roughly 20% of its luminosity. The planet completes a full orbit every 30.5 hours, at a distance around 20 times closer than Mercury is to the Sun.
Surface temperatures on the planet are estimated to reach 1,600 degrees Celsius due to its proximity to the star, resulting in its surface being transformed into magma and molten rock.
“We expect this planet will become completely dust within the next million years or so,” said Mark Hon, a postdoctoral researcher at the Kavli Institute for Astrophysics and Space Research at MIT. Hon is the lead author of the study published today in the Astrophysical Journal Letters.
The ‘Galloping’ Disintegration Process
“In cosmic timescales, this period is considered catastrophically short. The disintegration is a galloping process; the more material coalesces, the quicker the breakdown happens,” he explained.
The vaporized material, once in space, solidifies to form dust particles of various sizes that drift away from the planet. Hon noted that scientists still do not know the chemical composition of the “tail.”
The researchers discovered BD+05 4868 with NASA’s TESS telescope, designed for exoplanet observations.
It remains unclear how this planet ended up orbiting so closely to its star. It’s possible that it originally occupied a different orbit that changed due to the gravitational influence of another body, possibly another planet, Hon explained.
The researchers plan to continue monitoring the planet in the coming months using NASA’s James Webb Telescope, aiming to study the composition of the tail material, which could provide insights into the chemical makeup of rocky exoplanets.
The Search for Life on Other Planets
In the quest for life in other solar systems, scientists focus on rocky exoplanets that orbit within the so-called “Goldilocks Zone” or habitable zone—distances where liquid water could potentially exist on their surfaces.
“The tail is expected to contain minerals that have vaporized from the planet’s surface or interior. It could even include material from its core. Understanding the interior of planets is a significant challenge.
This is difficult even for planets within our own solar system. However, BD+05 4868 Ab allows us to directly assess the makeup of a planet similar to Earth outside our solar system.
This certainly presents a remarkable opportunity to learn about the geology of exoplanets and to understand the diversity and potential habitability of rocky worlds beyond our solar system,” said Hon.
