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Scientists find
possible birth of tiniest known solar system
Nov. 30,
2005
Courtesy Penn State University
and World Science staff
Scientists say they have discovered a tiny “failed star” possibly in the process of forming a solar system a hundredth the size of our own.
The researchers used a combination of ground-based and orbiting telescopes to make the find.
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This artist's conception compares a hypothetical solar system centered around a tiny "sun" (top) to a known solar system centered around a star about the same size as our Sun called 55 Cancri.
(Credit: NASA/JPL-Caltech)
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They said the “failed star,” less than one-hundredth the weight of the Sun, is the smallest known star-like object to harbor what seems to be a surrounding disk of debris. This material could evolve into tiny planets.
A team led by Kevin Luhman of Penn State University in University Park, Penn, plans to describe the finding in the December 10 issue of the research journal
Astrophysical Journal Letters.
The found object, called a brown dwarf, is described as a failed star because it is not massive enough to start burning nuclear fuel to shine the way our Sun does. The object is only eight times more massive than the planet Jupiter, the researchers said.
The fact that a brown dwarf this small could be creating a solar system challenges the very definition of star, planet, moon and solar system, they added.
“Our goal is to determine the smallest ‘sun’ with evidence for planet formation,” said Luhman. “Here we have a sun that is so small it is the size of a planet. The question then becomes, what do we call any little bodies that might be born from this disk: planets or moons?”
If this disk of debris and gas, called a protoplanetary disk, does form into planets, the whole system would be a miniaturized version of our solar system—with the central “sun,” the planets, and their orbits all roughly 100 times smaller, he added.
Luhman’s team said they detected the brown dwarf, called Cha 110913-773444, using six telescopes.
Brown dwarfs are born like stars, condensing out of thick clouds of gas and dust. They remain relatively cool objects that give off lower-energy forms of light such as infrared.
A protoplanetary disk is a flat disk made up of dust and gas that is thought to clump together to form planets. Our solar system was formed from such a disk about five billion years ago.
The science team spotted Cha 110913-773444 about 500 light years away in the constellation Chamaeleon. This brown dwarf is young, only about 2 million years old, they said.
In the past decade, advances in astronomy have led to the detection of small brown dwarfs and massive extra-solar planets, which has brought about a quandary in how to classify both.
“There are two camps when it comes to defining planets versus brown dwarfs,” said team member Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics. “Some go by size, and others go by how the object formed. For instance, this new object would be called a planet based on its size, but a brown dwarf based on how it formed.”
If one were to call the object a planet, Fazio said, then Spitzer may have discovered its first “moon-forming” disk.
No matter what the final label may be, one thing is clear: The universe produces some strange solar systems very different from our own, he added.
Other members of the team are Lucia Adame and Paola D’Alessio of the National Autonomous University of Mexico and Nuria Calvet and Lee Hartmann of the University of Michigan.
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