Terrestrial Planets Could Be More Common Than Gas Giants

[LongTomH]

The mysteries of how extra-solar planets form is getting more interesting. From Universe Today

As acclaimed astronomer Carl Sagan once famously noted, “We are all made of star-stuff.” So are the multitudes of extra-solar planets that are currently being discovered at a breathtaking pace. What Sagan meant was that all of the elements heavier than hydrogen and helium, commonly known as “metals” to astrophysicists, must be created in the interior furnaces of stars. But it takes time for stars to create these heavier elements, and since they are needed to start planets those time spans could have a major impact on solar system formation.

New research led by the University of Copenhagen with help from the Harvard-Smithsonian Center for Astrophysics sheds some light on those time spans. In a paper recently presented at a meeting of the American Astronomical Society, Lars Buchhave and his team selected more than 150 stars with known planetary systems that were cataloged by NASA’s Kepler mission. They then studied these star’s metal content and the size of the planets in their solar systems. What they found was that gas giant planets were more likely to form around metal rich stars, whereas terrestrial planets were equally likely to form around metal rich or metal poor stars.

As the team explains, the reason for this fits neatly into the “core accretion” model of planetary formation. Each gas giant has a metal core which hydrogen and helium accumulate around. However, if there is no core to collect around, the lighter elements will be blown away by stellar winds while the star is still relatively young. If a star has a high enough metal content, its potential planets might be able to form a large metallic core quickly, before the winds do their work. The core will then gravitationally attract the remaining gas to itself and a new gas giant is born.

Read more: http://www.universetoday.com/95832/terrestrial-planets-could-be-more-common-than-gas-giants/

[longship]

1. Helping nail down another factor of the Drake Equation

Which means that we now know that there are more ETs than before this finding.

Keep listening, Dr. Shostak.