Planet With Largest Solid Core Ever Discovered

Jul 01, 2005
Planet With Largest Solid Core Ever Discovered

NASA researchers recently discovered the largest solid core ever found in an extrasolar planet, and their discovery confirms a planet formation theory.
"For theorists, the discovery of a planet with such a large core is as important as the discovery of the first extrasolar planet around the star 51 Pegasi in 1995," said Shigeru Ida, theorist from the Tokyo Institute of Technology, Japan.

When a consortium of American, Japanese and Chilean astronomers first looked at this planet, they expected one similar to Jupiter.

"None of our models predicted that nature could make a planet like the one we are studying," said Bun'ei Sato, consortium member and postdoctoral fellow at Okayama Astrophysical Observatory, Japan.

Scientists have rarely had opportunities like this to collect such solid evidence about planet formation. More than 150 extrasolar planets have been discovered by observing changes in the speed of a star, as it moves toward and away from Earth. The changes in speed are caused by the gravitational pull of planets.

This planet also passes in front of its star and dims the starlight.

"When that happens, we are able to calculate the physical size of the planet, whether it has a solid core, and even what its atmosphere is like," said Debra Fischer. She is consortium team leader and professor of astronomy at San Francisco State University, Calif.

The planet, orbiting the sun-like star HD 149026, is roughly equal in mass to Saturn, but it is significantly smaller in diameter.

It takes just 2.87 days to circle its star, and the upper atmosphere temperature is approximately 2,000 degrees Fahrenheit. Modeling of the planet's structure shows it has a solid core approximately 70 times Earth's mass.

This is the first observational evidence that proves the "core accretion" theory about how planets are formed. Scientists have two competing but viable theories about planet formation.

In the "gravitational instability" theory, planets form during a rapid collapse of a dense cloud.

With the "core accretion" theory, planets start as small rock-ice cores that grow as they gravitationally acquire additional mass. Scientists believe the large, rocky core of this planet could not have formed by cloud collapse. They think it must have grown a core first, and then acquired gas.

"This is a confirmation of the core accretion theory for planet formation and evidence that planets of this kind should exist in abundance," said Greg Henry, an astronomer at Tennessee State University, Nashville. He detected the dimming of the star by the planet with his robotic telescopes at Fairborn Observatory in Mount Hopkins, Arizona.

Support for this research came from NASA, the National Astronomical Observatory of Japan and the National Science Foundation.

A paper about this discovery was accepted for publication in the Astrophysical Journal.

Source: NASA

Explore further: Spacewalking astronauts finish extensive, tricky cable job

add to favorites email to friend print save as pdf

Related Stories

Could the Milky Way become a quasar?

Feb 27, 2015

A quasar is what you get when a supermassive black hole is actively feeding on material at the core of a galaxy. The region around the black hole gets really hot and blasts out radiation that we can see billions ...

What is Mars made of?

Feb 26, 2015

For thousands of years, human beings have stared up at the sky and wondered about the Red Planet. Easily seen from Earth with the naked eye, ancient astronomers have charted its course across the heavens ...

Astrophysicist explores star formation in Orion's belt

Feb 26, 2015

U.S. Naval Research Laboratory (NRL) astrophysicist Dr. T.L. Wilson is part of a multi-national research team that has discovered an outburst in the infrared from a deeply embedded protostar. The Herschel ...

A recipe for returning Pluto to full planethood

Feb 20, 2015

A storm is brewing, a battle of words and a war of the worlds. The Earth is not at risk. It is mostly a civil dispute, but it has the potential to influence the path of careers. In 2014, a Harvard led debate ...

Recommended for you

NASA spacecraft nears historic dwarf planet arrival

9 hours ago

NASA's Dawn spacecraft has returned new images captured on approach to its historic orbit insertion at the dwarf planet Ceres. Dawn will be the first mission to successfully visit a dwarf planet when it enters ...

An old-looking galaxy in a young universe

12 hours ago

A team of astronomers, led by Darach Watson, from the University of Copenhagen used the Very Large Telescope's X-shooter instrument along with the Atacama Large Millimeter/submillimeter Array (ALMA) to observe ...

Giant methane storms on Uranus

14 hours ago

Most of the times we have looked at Uranus, it has seemed to be a relatively calm place. Well, yes its atmosphere is the coldest place in the solar system. But, when we picture the seventh planet in our ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.