18 new planets 'discovered'
Astronomers claim to have discovered 18 new planets said to be the largest collection of confirmed heavenly bodies around stars more massive than sun.
An international team, led by California Institute of Technology, has described its findings in 'The Astrophysical Journal Supplement Series'.
"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 team leader John Johnson.
Using the Keck Observatory in Hawaii -- with follow-up observations using the McDonald and Fairborn Observatories in Texas and Arizona, respectively -- the astronomers surveyed about 300 stars.
They focused on those dubbed "retired" A-type stars that are more than one and a half times more massive than the sun. These stars are just past the main stage of their life, hence, "retired" and are now puffing up into a "subgiant star".
By searching the wobbly stars' spectra for Doppler shifts -- the lengthening and contracting of wavelengths due to motion away from and toward the observer -- the team found 18 planets with masses similar to Jupiter's.
This new bounty marks a 50 percent increase in the number of known planets orbiting massive stars and, according to Johnson, provides an invaluable population of planetary systems for understanding how planets -- and our own solar system -- might form.
The astronomers say that the findings also lend further support to the theory that planets grow from seed particles accumulating gas and dust in disk surrounding a newborn star.
"It's nice to see all these converging lines of evidence pointing toward one class of formation mechanisms," Johnson said.
