Based on planet formation in our solar system, ice and rock cores that are about ten times as massive as Earth begin to form into gas giants.
However, judging from the absence of Jupiterlike planets in the newly found planet's vicinity, its solar system may have lacked the gas necessary to make gas planets.
"In the disks orbiting low-mass stars, the cores generally do not have enough time to grow to the requisite size to accrete gas before the gas disappears, and the cores are left stranded as Neptune-mass [smaller] planets," said Gregory Laughlin, an astronomy professor at University of California, Santa Cruz.
Scientists believe that smaller planets may form more easily around low-mass stars than larger planets do. Since researchers have found that most stars in our galaxy are red dwarfs (much smaller and dimmer than our sun), solar systems dominated by super-Earths may be more common in our galaxy than those with gas giants.
"[This discovery] is very exciting, because it strongly suggests that Neptune-mass planets are common around low-mass stars, in stark contrast to Jupiter-mass [giant] planets, which appear to be quite rare in orbit around low-mass stars," said Laughlin.
Probing New Frontiers
Until a decade ago scientists didn't know what other solar systems were like. Since then around 170 planets have been discovered. Most of them have been gas giants.
Only a handful of smaller, Neptune-mass planets have been detected, and only two of those were found in the outer regions of their solar systems.
The only technique sensitive enough to detect these types of planets is microlensing. Scientists say the method allows them to probe a new domain of space.
"I think we'll be seeing a lot more detections in the coming years with the microlensing technique," Laughlin said.
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