These exoplanets are teetering on the verge of destruction

Exoplanets, or planets outside our solar system, are a hot topic in astronomy research right now. Recently, a team of astronomers has discovered some very hot exoplanets indeed – ones that are orbiting so close to their stars that they are soon to be gobbled up by them.

A team using the High-Resolution Echelle Spectrometer (HIRES) instrument at the W. M. Keck Observatory located on Maunakea, Hawaiʻi, have investigated three exoplanets and found they are teetering on the verge of destruction. Planets TOI-2337b, TOI-4329b, and TOI-2669b are what are called short-period planets, meaning they orbit close to their stars, and are some of the shortest period planets yet discovered around stars of this type.

The closest planet to destruction is TOI-2337b, which will be consumed within the next one million years. That might sound like a long time, but it's a blink of an eye in astronomical terms, making it the planet soonest to face extinction that we've discovered.

The stars which host these doomed planets are giant or subgiant stars, meaning they are bright and are either currently or developing into larger stars than main sequence stars like our sun. Over time, planets that orbit very close to their stars will spiral toward them, making the planets hotter and hotter. This makes the planets' atmospheres puff up, and even brings a danger that other planets in the system will also be drawn in and collide with each other.

That means that studying the planets can show researchers about the development of planetary systems through time. "These discoveries are crucial to understanding a new frontier in exoplanet studies: how planetary systems evolve over time," explained Samuel Grunblatt, lead author of the study soon to be published in The Astronomical Journal (via Keck Observatory). "These observations offer new windows into planets nearing the end of their lives, before their host stars swallow them up."

The three planets were first discovered by NASA's TESS (Transiting Exoplanet Survey Satellite), a space-based planet-hunting telescope, in 2018 and 2019. Then the researchers used the HIRES instrument to learn more about them. They found the three planets are comparable to Jupiter, with masses from 0.5 times to 1.7 times that of the gas giant, and sizes from just under the size of Jupiter to 1.6 times its size.

That means the planets have very different densities, ranging from what Keck Observatory describes as "styrofoam-like" to three times the density of water. This range of densities suggests the planets formed in different ways and could have formed from collisions of other planets.

To learn more, researchers will continue observing the planets with TESS to see if they can spot the planets beginning their inward spirals toward eventual destruction.