Astronomers have recently discovered a small rocky exoplanet with an orbit very close to its host star. What’s particularly fascinating is that its surface is being evaporated by the heat from the star, creating a comet-like mineral dust tail extending about 5.6 million miles (9 million kilometers) behind it.
According to a report by Reuters, since the 1990s, approximately 5,800 exoplanets have been discovered outside our solar system. Among these planets, only four have been observed disintegrating on their orbits, with this exoplanet being one of them. It is also one of the four planets closest to our solar system, offering scientists a rare opportunity to study these planets destined for destruction.
Researchers have observed that the planet named BD+05 4868 Ab releases material equivalent to the mass of Mount Everest each time it orbits the star, with the dust tail trailing around the star for half a circumference.
This planet is estimated to be between the smallest planet in our solar system, Mercury, and Earth’s moon in size. It is located in the Pegasus constellation about 140 light-years away from Earth.
Its parent star is an orange dwarf star with lower temperature and dimmer brightness compared to the Sun, with a mass and diameter about 70% of the Sun’s and a brightness of only around 20%. This planet orbits the star every 30.5 hours at a distance about 1/20 of Mercury’s distance from the Sun.
Due to its proximity to the star, the surface temperature of this planet is estimated to be around 3,000 degrees Fahrenheit (approximately 1,600 degrees Celsius). As a result, the surface of the planet may have turned into magma – lava.
Dr. Marc Hon, a postdoctoral researcher at the Kavli Institute for Astrophysics and Space Research at MIT and the lead author of the study, stated, “We expect this planet to disintegrate into dust in about a million years.” He further added, “In cosmic time scales, this is extremely rapid. Disintegration is an uncontrolled process. As more material on the planet turns into dust, the disintegration process will accelerate.”
Once in space, the evaporated material will cool down, forming mineral dust streaming out of the planet. Hon mentioned, “We know that the dust grains in the tail range in size from large cigarette ash particles to fine sand grains. The mineral composition of the tail is still unclear.”
This planet was discovered through NASA’s Transiting Exoplanet Survey Satellite (TESS) space telescope. Researchers used the transit method to observe the decrease in the star’s brightness every time BD+05 4868 Ab passes in front of its parent star.
As for how this planet’s close-in orbit was formed, it remains uncertain. Hon suggested, “It is possible that this planet was originally formed in a more distant location and altered its original orbit due to the influence of external bodies, causing it to be sent closer to the star.”
This might have been caused by the gravitational effects of another planet or other celestial bodies.
Researchers plan to conduct further observations in the coming months using NASA’s James Webb Space Telescope to study the composition of the tail material, which could provide clues about the composition of rocky exoplanets.
The search for life in other solar systems often focuses on rocky exoplanets orbiting in the “habitable zone” of stars. This distance makes the presence of liquid water on the planet’s surface a possibility, with water being a key ingredient for life.
“The tail is expected to contain minerals evaporated from the disintegrating planet’s surface or interior. Therefore, this may include the crust, mantle, or even the planet’s core. Understanding the internal structure of planets is highly challenging, even for planets within our solar system. But BD+05 4868 Ab will allow us to directly measure the mineral composition of Earth-like exoplanets beyond our solar system,” Hon remarked.
“This is undoubtedly a special opportunity for exoplanetary geology, enabling us to understand the diversity and potential habitability of rocky worlds beyond our solar system.”