Astronomers discover 18 new Jupiter-size alien planets

Pasadena - A team of of scientists led by Caltech astronomers have announced discovery of 18 new Jupiter-size gas planets in an alien planetary system. The discovery was published in the December issue of The Astrophysical Journal Supplement Series.

According to John Johnson, assistant professor of astronomy at Caltech, "Its the largest single announcement of planets aside from discoveries made by the Kepler mission." PhysOrg.com reports the team of astronomers worked at the Keck Observatory in Hawaii, surveying about 300 stars, focusing on the so-called "retired" A-type stars that are more than one and half times the mass of the sun. "Retired" stars are those that are just past the main stage of their life cycle and are growing into subgiant stars. The astronomers found the new planets by looking for stars that "wobble" under gravitational tug of an orbiting planet.The 18 Jupiter-size planets were found by searching the "wobbling" stars' spectra for Doppler shifts which are lengthening and contracting of wavelengths due to motion away or toward the observer. The new finds, according to the researchers, represent a 50 percent increase in the number of planets that have been found in the orbit of massive stars. The finds are important because they aid understanding of how planets form. The researchers also say the new findings support the core accretion theory that planets arise from seed particles that clump gas and dust in disks surrounding newborn stars. The core accretion theory predicts that stellar mass will have a relationship to planet size and number in a planetary system According to Space.com, the competing theory to the core accretion theory is the gravitational collapse theory which posits that planets form when big clouds of gas and dust in the disk spontaneously collapse into clumps and become planets. This theory predicts that stellar mass should have no relationship to planet size and number. In their recent discoveries, astronomers have found that stellar mass is an important factor in the prevalence of giant planets. This discovery lends support to the accretion theory of planetary system formation. Johnson says:

"It's nice to see all these converging lines of evidence pointing toward one class of formation mechanisms...Not only do we find Jupiter-like planets more frequently around massive stars, but we find them in wider orbits. If you took a sample of 18 planets around sunlike stars, half of them would orbit close to their stars. But in the cases of the new planets, all are farther away, at least 0.7 astronomical units from their stars."