Gas Giants Found Clinging to Parent Stars in New Study

Gas giant planets rarely venture far away from their parent stars, scientists recently discovered - a realization that could have significant impacts on theories of planetary formation.

The find came out of Gemini Observatory's recently completed Planet-Finding Campaign, which marks the most extensive direct imaging survey to date, and was true for many types of stars.

"It seems that gas-giant exoplanets are like clinging offspring," Michael Liu of the University of Hawaii's Institute for Astronomy and leader of the Gemini Planet-Finding Campaign said in a press release.

Throughout the search, Liu further explained, the researchers were unable to locate gas giants with orbital distances that corresponded to those of Uranus and Neptune.

Conducted with funding support from the National Science Foundation and NASA, the results, the researchers believe, will help scientists everywhere better understand how gas giants are formed due to the fact that orbital distances of planets are a key signature used to test exoplanet formation theories.

According to the University of Hawaii's Eric Nielsen, who is currently overseeing a new paper about the Campaign's search for planets around stars more massive than the Sun, the study's implications reach beyond the specific stars imaged by the team.

"The two largest planets in our Solar System, Jupiter and Saturn, are huddled close to our Sun, within 10 times the distance between the Earth and Sun," he explained. "We found that this lack of gas-giant planets in more distant orbits is typical for nearby stars over a wide range of masses."

Two additional papers based on the Campaign scheduled to be published soon reveal similar tendencies around other classes of stars.

However, this does not mean that this proximity is true in all cases.

In 2008, for example, astronomers using the Gemini North telescope and the W.M. Keck Observatory on Hawaii's Mauna Kea took the first-ever direct images of a family of planets around the star HR 8799, only to find gas giants at orbital separations ranging between 35 to 70 times the distance between the Earth and the Sun.

Because this discovery happened so quickly (the researchers had only examined a few stars), the belief that such large separations were not uncommon for gas giants was developed - a theory that the latest, more thorough Gemini results directly contradict.

One reason for the discrepancy, Liu explains, lies partly in technological advancements.

"We've known for nearly 20 years that gas-giant planets exist around other stars, at least orbiting close-in. Thanks to leaps in direct imaging methods, we can now learn how far away planets can typically reside. The answer is that they usually avoid significant areas of real estate around their host stars. The early findings, like HR 8799, probably skewed our perceptions.