Space

June 13, 2012

Small planets don’t need stars with heavy metal content to form

The formation of small worlds like Earth previously was thought to occur mostly around stars rich in heavy elements such as iron and silicon.

However, new ground-based observations, combined with data collected by NASA’s Kepler space telescope, shows small planets form around stars with a wide range of heavy element content and suggests they may be widespread in our galaxy.

A research team led by Lars A. Buchhave, an astrophysicist at the Niels Bohr Institute and the Centre for Star and Planet Formation at the University of Copenhagen, studied the elemental composition of more than 150 stars harboring 226 planet candidates smaller than Neptune.

“I wanted to investigate whether small planets needed a special environment in order to form, like the giant gas planets, which we know preferentially develop in environments with a high content of heavy elements,” said Buchhave. “This study shows that small planets do not discriminate and form around stars with a wide range of heavy metal content, including stars with only 25 percent of the sun’s metallicity.”

Astronomers refer to all chemical elements heavier than hydrogen and helium as metals. They define metallicity is the metal content of heavier elements in a star. Stars with a higher fraction of heavy elements than the sun are considered metal-rich. Stars with a lower fraction of heavy elements are considered metal-poor.

Planets are created disks of gas and dust around new stars. Planets like Earth are composed almost entirely of elements such as iron, oxygen, silicon and magnesium.

The metallicity of a star mirrors the metal content of the planet-forming disk. Astronomers have hypothesized that large quantities of heavy elements in the disk would lead to more efficient planet formation. It has long been noted that giant planets with short orbital periods tend to be associated with metal-rich stars.

Unlike gas giants, the occurrence of smaller planets is not strongly dependent on the heavy element content of their host stars. Planets up to four times the size of Earth can form around stars with a wide range of heavy element content, including stars with a lower metallicity than the sun. The findings are described in a new study published in the journal Nature.

“Kepler has identified thousands of planet candidates, making it possible to study big-picture questions like the one posed by Lars. Does nature require special environments to form Earth-size planets?” said Natalie Batalha, Kepler mission scientist at NASA’s Ames Research Center at Moffett Field, Calif. “The data suggest that small planets may form around stars with a wide range of metallicities – that nature is opportunistic and prolific, finding pathways we might otherwise have thought difficult.”

The ground-based spectroscopic observations for this study were made at the Nordic Optical Telescope on La Palma in the Canary Islands; Fred Lawrence Whipple Observatory on Mt. Hopkins in Ariz.; McDonald Observatory at the University of Texas at Austin; and W.M. Keck Observatory atop Mauna Kea in Hawaii.

Launched in March 2009, Kepler searches for planets by continuously monitoring more than 150,000 stars, looking for telltale dips in their brightness caused by passing, or transiting, planets. At least three transits are required to verify a signal as a planet. Follow-up observations from ground-based telescopes are also needed to confirm a candidate as a planet.

Ames manages Kepler’s ground system development, mission operations and science data analysis. NASA’s Jet Propulsion Laboratory in Pasadena, Calif., managed the Kepler mission development.

Ball Aerospace & Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

The Space Telescope Science Institute in Baltimore archives hosts and distributes Kepler science data. Kepler is NASA’s 10th Discovery Mission and is funded by NASA’s Science Mission Directorate at the agency’s headquarters in Washington.




All of this week's top headlines to your email every Friday.


 
 

 

Headlines July 23, 2014

News: Israel’s Iron Dome defense in line for tripled U.S. spending - Israel’s iron Dome missile defense system may end up getting triple the U.S. funding that the Defense Department sought for it in March. Ukraine asked U.S. for systems to counter Russian missiles - A month before the United States says a Russian missile likely brought...
 
 

News Briefs July 23, 2014

U.S. military deaths in Afghanistan at 2,194 As of July 22, 2014, at least 2,194 members of the U.S. military had died in Afghanistan as a result of the U.S.-led invasion of Afghanistan in late 2001, according to an Associated Press count. The AP count is three less than the Defense Department’s tally. At least...
 
 
Raytheon photograph

Raytheon completes key Air, Missile Defense Radar reviews

Raytheon photograph Partially-populated, full-sized Air and Missile Defense Radar array. Raytheon has completed two critical program reviews for the new Air and Missile Defense Radar, the U.S. Navy’s next generation integ...
 

 
Insitu photograph

Insitu demonstrates long endurance capabilities of Integrator unmanned aircraft

Insitu photograph Insitu’s Integrator unmanned aircraft recovers via SkyHook; the aircraft recently completed a 24-hour endurance flight. Insitu announced July 22 the successful 24-hour flight of its Integrator unmanned a...
 
 

NASA partners punctuate summer with spacecraft development advances

Spacecraft and rocket development is on pace this summer for NASA’s aerospace industry partners for the agency’s Commercial Crew Program as they progress through systems testing, review boards and quarterly sessions under their† Space Act Agreements with the agency. NASA engineers and specialists continue their review of the progress as the agency and partners move...
 
 

U.S. Navy selects Northrop Grumman for ship self-defense system

The U.S. Navy has awarded Northrop Grumman a $12 million task order for a full range of engineering services to continue modernizing the Ship Self-Defense System Mark 2. The contract has a potential value of $61 million over five years, if all options are exercised. SSDS MK2 is a combat system designed for anti-air defense...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>