Nav: Home

Some planetary systems just aren't into heavy metal

October 24, 2018

New Haven, Conn. - Small planetary systems with multiple planets are not fans of heavy metal -- think iron, not Iron Maiden -- according to a new Yale University study.

Researchers at Yale and the Flatiron Institute have discovered that compact, multiple-planet systems are more likely to form around stars that have lower amounts of heavy elements than our own Sun. This runs counter to a good deal of current research, which has focused on stars with higher metallicity.

The research team looked at 700 stars and their surrounding planets for the study, which appears in The Astrophysical Journal Letters. The researchers considered any element heavier than helium -- including iron, silicon, magnesium, and carbon -- as a heavy metal.

"We used iron as a proxy," said lead author John Michael Brewer, a postdoctoral researcher at Yale who works with astronomy professor Debra Fischer. "These are all elements that make up the rocks in small, rocky planets."

Brewer said an abundance of compact, multi-planet systems around low-metallicity stars suggests several things.

First, he said, it may indicate that there are many more of these systems than previously assumed. Until recently, research instruments have not had the necessary precision to detect smaller planets and instead focused on detecting larger planets. Now, with the advent of technology such as the Extreme Precision Spectrometer (EXPRES) developed by Fischer's team at Yale, researchers will be able to find smaller planets.

In addition, Brewer said, the new study suggests that small planetary systems may be the earliest type of planetary system, making them an ideal place to search for life on other planets. "Low-metallicity stars have been around a lot longer," Brewer said. "That's where we'll find the first planets that formed."

Fischer, who is a co-author of the study, demonstrated in 2005 that higher metallicity in stars increased the probability of forming large, Jupiter-like planets. This provided strong support to the core-accretion model for gas giant planet formation and established this as the leading mechanism for planet formation.

Understanding the formation of smaller planets has been more elusive.

"Our surprising result, that compact systems of multiple, small planets are more likely around lower metallicity stars suggests a new, important clue in understanding the most common type of planetary system in our galaxy," said co-author Songhu Wang, a 51 Pegasi b Fellow at Yale.

Another tantalizing possibility to explore, according to the researchers, is the connection between iron and silicon in the birth of planets. The new study shows a high silicon-to-iron ratio in stars with lower metallicity.

"Silicon could be the secret ingredient," Fischer said. "The ratio of silicon to iron is acting as a thermostat for planet formation. As the ratio increases, nature is dialing up the formation of small, rocky planets."
-end-
The National Science Foundation helped support the research. Wang's fellowship is supported by the Heising-Simons Foundation.

Yale University

Related Planets Articles:

How planets may form after dust sticks together
Scientists may have figured out how dust particles can stick together to form planets, according to a Rutgers co-authored study that may also help to improve industrial processes.
Planets around a black hole?
Theoreticians in two different fields defied the common knowledge that planets orbit stars like the Sun.
The rare molecule weighing in on the birth of planets
Astronomers using one of the most advanced radio telescopes have discovered a rare molecule in the dust and gas disc around a young star -- and it may provide an answer to one of the conundrums facing astronomers.
How many Earth-like planets are around sun-like stars?
A new study provides the most accurate estimate of the frequency that planets that are similar to Earth in size and in distance from their host star occur around stars similar to our Sun.
Dead planets can 'broadcast' for up to a billion years
Astronomers are planning to hunt for cores of exoplanets around white dwarf stars by 'tuning in' to the radio waves that they emit.
The sun follows the rhythm of the planets
One of the big questions in solar physics is why the sun's activity follows a regular cycle of 11 years.
Five planets revealed after 20 years of observation
To confirm the presence of a planet, it is necessary to wait until it has made one or more revolutions around its star.
Icy giant planets in the laboratory
Giant planets like Neptune may contain much less free hydrogen than previously assumed.
New NASA mission could find more than 1,000 planets
A NASA telescope that will give humans the largest, deepest, clearest picture of the universe since the Hubble Space Telescope could find as many as 1,400 new planets outside Earth's solar system, new research suggests.
Giant planets around young star raise questions about how planets form
Researchers have identified a young star with four Jupiter and Saturn-sized planets in orbit around it, the first time that so many massive planets have been detected in such a young system.
More Planets News and Planets Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Teaching For Better Humans 2.0
More than test scores or good grades–what do kids need for the future? This hour, TED speakers explore how to help children grow into better humans, both during and after this time of crisis. Guests include educators Richard Culatta and Liz Kleinrock, psychologist Thomas Curran, and writer Jacqueline Woodson.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

Space
One of the most consistent questions we get at the show is from parents who want to know which episodes are kid-friendly and which aren't. So today, we're releasing a separate feed, Radiolab for Kids. To kick it off, we're rerunning an all-time favorite episode: Space. In the 60's, space exploration was an American obsession. This hour, we chart the path from romance to increasing cynicism. We begin with Ann Druyan, widow of Carl Sagan, with a story about the Voyager expedition, true love, and a golden record that travels through space. And astrophysicist Neil de Grasse Tyson explains the Coepernican Principle, and just how insignificant we are. Support Radiolab today at Radiolab.org/donate.