Astronomers have discovered a doomed world slowly being destroyed by its star. It has a huge comet-like tail.

The discovery was announced at the 245th meeting of the American Astronomical Society. It was carried out by TESS, which tracks the light curves of stars in order to search for “dips” caused by transits of exoplanets. Over the years, it has discovered many extrasolar worlds, including those orbiting at extremely short distances from their stars. But the exoplanet, designated BD+05 4868 Ab, stands out even against their background.
BD+05 4868 Ab orbits an orange dwarf, part of a double star system located 140 light-years from Earth. The exoplanet orbits at a distance of just 0.02 a.u. (3 million kilometers) from its parent star. It makes one orbit around it in 30.5 hours.

The astronomers’ attention was attracted by the unusual shape of the dips in the star’s light curve illustration, which were not similar to typical transits. The star’s brilliance decreased sharply, after which it only gradually returned to full brightness. Scientists have concluded that it’s all about the large dust clouds surrounding BD+05 4868 Ab, which block about 1% of the star’s light during each transit. Their source is the exoplanet itself. The powerful radiation from the orange dwarf literally destroys it, vaporizing its rocky surface.
When the team analyzed the shape of the light curve in more detail, they found that the exoplanet has two tails — a longer rear tail and a shorter front tail. The rear tail extends for 9 million kilometers. By modeling how the star’s radiation scatters the particles, the scientists concluded that larger particles, about the size of a grain of sand, cluster around the leading tail, while smaller grains, about the size of soot particles, accumulate along the rear tail.

This led to the calculation of mass loss. For every million years BD+05 4868 Ab loses mass equivalent to that of the Moon. If an exoplanet is small and comparable to Mercury or Venus, this mass loss is catastrophic for it. The smaller the exoplanet gets, the faster it will decay. Researchers predict BD+05 4868 Ab will cease to exist in a few million years, which by astronomical standards is literally one instant.
In the future, astronomers hope to study the spectrum of the dying exoplanet with the James Webb Telescope to learn more about its internal structure. As for the immediate cause of the demise, a second component of the system may be to blame. The gravitational interaction between the two stars may well have put BD+05 4868 Ab into a “death orbit”.
Earlier we reported on another extrasolar world with a comet-like tail as well.
According to Sky & Telescope