Observations from NASA’s Spitzer Space Telescope show that gas giants either form within the first 10 million years of a sun-like star’s life, or not at all. The study offers new evidence that gas-giant planets must form early in a star’s history. The lifespan of sun-like stars is about 10 billion years. Ilaria Pascucci of the University of Arizona Steward Observatory in Tucson led a team of astronomers who conducted the most comprehensive search for gas around 15 different sun-like stars, most with ages ranging from 3 million to 30 million years. The scientists used Spitzer’s heat-seeking infrared eyes to search for warm gas in the inner portions of star systems, an area comparable to the zone between Earth and Jupiter in our own solar system. In addition, team member Michael Meyer of the UA Steward Observatory and their colleagues probed for cold gas in the outer regions of these star systems with the Arizona Radio Observatory’s 10-meter Submillimeter Telescope (SMT) on Mount Graham, Arizona. The outer zones of these star systems are analogous to the region around Saturn’s orbit and beyond in our own solar system. All of the stars in the study – including those as young as a few million years – have less than 10 percent of Jupiter’s mass in gas swirling around them. This indicates that gas giant planets like Jupiter and Saturn have already formed in these young solar system analogs – or they never will.

https://news.arizona.edu/story/gas-giants-jump-planet-formation-early

https://www.spitzer.caltech.edu/news/ssc2007-02-gas-giants-form-quickly