A newly formed planet is shown in this illustration amid the gas and dust surrounding its star. NASA / JPL-Caltech
— Astronomers found 18 Jupiter-sized planets orbiting distant stars.
— The discovery boosts the number of known alien worlds to well past 700.
— The finding also sheds light on how planets form around stars.
A new haul of 18 Jupiter-sized gas giant planets have been detected orbiting stars bigger than our sun, according to a release by scientists at the California Institute of Technology (Caltech).
The find boosts the number of known planets circling huge stars by 50 percent. Studying the newly found planets could also help astronomers better understand how planets — including ones in our own solar system — form and grow.
The new batch of alien worlds was announced on the heels of another recent discovery of 50 newly found planets from another team of astronomers, bringing the list of identified alien planets well past 700.
"It's the largest single announcement of planets in orbit around stars more massive than the sun, aside from the discoveries made by the Kepler mission," said John Johnson, assistant professor of astronomy at Caltech, in the release. Findings on the discovery were published in the December issue of The Astrophysical Journal Supplement Series.
The Kepler space telescope has so far identified more than 1,200 possible planets, though most of those have not yet been confirmed.
Using the Keck Observatory in Hawaii — with follow-up observations using the McDonald and Fairborn Observatories in Texas and Arizona, — the researchers surveyed about 300 stars.
They zeroed-in on stars that are more than one and a half times more massive than the sun.
To detect planets, the astronomers looked for stars that wobble, which can be caused by the gravitational tug of an orbiting planet. By searching for the signature wobble in the distant stars, the team found 18 planets with masses similar to Jupiter's.
The researchers say that the findings lend further support to the theory that planets grow from seed particles that accumulate gas and dust in a disk surrounding a newborn star.
According to this theory, tiny particles start to clump together, eventually snowballing into a planet. If this theory is accurate, the characteristics of the resulting planetary system — such as the number and size of the planets, or their shapes — depends on the mass of the star.
A more massive star would create a bigger disk, which in turn would offer up more material to produce a greater number of giant planets.
"It's nice to see all these converging lines of evidence pointing toward one class of formation mechanisms," Johnson said in the release.
In another twist, the new batch of planets appear to have orbits that are mostly circular, while planets around sun-like stars span a wide range of circular to elliptical paths. Johnson said he's now trying to find an explanation.