New research involving University of Hawaii astronomers suggests that our solar system is a bit, well, odd.
After completing what astronomers are calling the most comprehensive direct imaging survey ever, the Gemini Observatory’s Planet-Finding Campaign found that the distant backyards of many solar systems are largely devoid of planets like Uranus and Neptune.
The great orbital distances of those so-called "gas giants" seem to be the exception rather than the rule. Neptune is about 2.8 billion miles from the sun — more than 31 times farther than Earth.
Typically, gas giants "are like clinging offspring," Michael Liu from the University of Hawaii’s Institute for Astronomy said in an announcement June 27.
That includes Jupiter, which astronomers consider relatively near at 383 million miles from the sun, or about four times the Earth-sun distance, called an astronomical unit.
"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," said Eric Nielsen of the University of Hawaii. "We found that this lack of gas-giant planets in more distant orbits is typical for nearby stars over a wide range of masses."
The findings will help astronomers understand the formation of gas giants, said Liu, who is also the leader of the Gemini Planet-Finding Campaign.
Liu’s project was conducted at the Gemini South telescope in Chile, with funding from the National Science Foundation and NASA, the Gemini news release said. The observations were made using a novel instrument called the Near-Infrared Coronagraphic Imager.
Some gas-giant exoplanets meander extremely far from their star.
Research in 2008 at the Gemini North telescope and the Keck Observatory on Mauna Kea found planets around the star HR 8799 with orbits of 25 to 70 astronomical units.
That led scientists to believe that such planets might be common, but now it seems such orbital distances for gas giants are rare.
Our solar system is strange in another respect, astronomers have noticed.
According to NASA’s space-based Kepler planetary survey, most of the hundreds of planets found so far around other stars have a diameter between that of Earth and Neptune. In our solar system, there is nothing in that range.
So the most typical "exoplanet" around other stars is completely unrepresented in our own solar system.
