Planet Thought to Have Been Engulfed by Sun Still Exists, Astronomers Find

This artist's rendering provided by NASA and JPL-Caltech shows the Juno spacecraft above the planet Jupiter. Five years after its launch from Earth, Juno is scheduled to go into orbit around the gas giant on Monday, July 4, 2016. NASA/JPL-Caltech via AP

An international team of astronomers from the University of Sydney, Australia, and the University of Hawaii Institute for Astronomy have discovered that a planet that was thought to have long ago disappeared actually still exists.

Using two Maunakea Observatories on Hawaii Island—W. M. Keck Observatory and Canada-France-Hawaii Telescope (CFHT)—the team of researchers, led by Marc Hon, a NASA Hubble Fellow at the University, found the Jupiter-like planet 8 UMi b, nicknamed Hala after the highest mountain in South Korea, is still very much alive.

The planet was initially discovered in 2015 by South Korean astronomers and is located in the Ursa Minor constellation, also known as “Little Bear” approximately 530 light years away from planet Earth.

It is 1.3 times heavier and 1.22 times larger than Jupiter and mostly comprised of gaseous material, according to NASA. Hala orbits within close proximity (0.49 AU, astronomical unit) of its red giant star Baekdu (8 UMi) which is much larger than our sun, according to the agency.

Astronomers believed the planet would have suffered a demise at the hands of its sun which was thought to have exploded, a common occurrence in other solar systems.

However, they were instead left pleasantly surprised after using observations of Baekdu’s stellar oscillations from NASA’s Transiting Exoplanet Survey Satellite (TESS) and finding that the star is burning helium in its core, suggesting that it had already expanded enormously into a red giant star once before.

Typically, this would have caused nearby planets to be completely destroyed, but Hala somehow survived.

“Engulfment by a star normally has catastrophic consequences for close orbiting planets. When we realized that Halla had managed to survive in the immediate vicinity of its giant star, it was a complete surprise,” said study coauthor Dr. Dan Huber, Australian Research Council Future Fellow at the University of Sydney and associate professor at the Institute for Astronomy of the University of Hawaii at Manoa, in a press release.

Possible Reasons for Hala’s Survival

“As it exhausted its core hydrogen fuel, the star would have inflated up to 1.5 times the planet’s current orbital distance—engulfing it completely in the process—before shrinking to its current size,” Huber added.

The researcher’s findings were published in the journal Nature on June 28. They believe that Hala’s survival may be down to three possibilities.

One they suggested is that the planet never faced any real threat of engulfment because the host star, Baekdu, may have originally been two stars, meaning that a merger between two stars would have prevented either one of them from expanding to a size large enough to engulf the planet.

Another possibility is that the gas giant began its life orbiting much further away from the star before migrating inward after it expanded and shrunk, although researchers believe the chances of that happening are relatively slim.

The third possibility is that Halla is a “relative newborn” created from a gas cloud caused by a violent collision, making it what researchers call a “second generation” planet.

“Planetary engulfment has catastrophic consequences for either the planet or the star itself, or both. The fact that Halla has managed to persist in the immediate vicinity of a giant star that would have otherwise engulfed it highlights the planet as an extraordinary survivor,” said Hon, the lead author of the study,  from the University of Hawaii.

“Most stars are in binary systems, but we don’t yet fully grasp how planets may form around them. Therefore, it’s plausible that more planets may actually exist around highly evolved stars thanks to binary interactions,” explained Hon.

Researchers said they now plan to use their findings to examine whether other planets in the solar system have also escaped destruction like Halla.

“Together, these observations confirmed the existence of Halla, leaving us with the compelling question of how the planet survived,” Hon added.