Smashing young stars leave dwarfs in their wake

Jun 09, 2006
Smashing young stars leave dwarfs in their wake
Visualizations of brown dwarf simulations completed by Sijing Shen for her Master's Thesis (May 2006) under the supervision of James Wadsley.

Astronomers have discovered that the large disks of gas and dust around young stars will fragment if two young stars pass close to each other and form smaller brown dwarfs stars with disks of their own.

The news was announced this week at the Canadian Astronomical Society in Calgary, Alta, by James Wadsley, assistant professor of Physics & Astronomy at McMaster University, and his student Sijing Shen.

"This is an exciting discovery because it may be the dominant way brown dwarfs are made," says Wadsley. "The challenge to theorists was to explain not only the origin of brown dwarfs but also the details telescopes are seeing: brown dwarfs with disks and the systems of many dwarfs orbiting a single regular star. We've done that."

Brown dwarf stars are as common in number as large stars but are no more than 8 percent of the mass of the Sun. Their low mass prevents nuclear fusion in their core so they don't shine like regular stars. Regular stars form from cold dense cores in giant molecular gas clouds. The natural mass of a core is expected to be large, closer to that of a regular star than a brown dwarf so something extra was required to understand the origin of brown dwarfs.

Using SHARCNET (Shared Hierarchical Academic Research Computing Network) parallel computing facilities at McMaster, Shen and Wadsley simulated several encounters between young stars with disks at unprecedented resolution, seeing gas pile-ups, drawn-out tidal arms and huge masses of gas driven closer to the stars. Amid this chaos several small objects were seen to form, from Jupiter-sized objects up to brown dwarfs. Reports from lower resolution simulations by other groups had shown no indication of disks. However, in every case, the new objects had disks with sizes ranging up to 18 astronomical units (the size of Saturn's orbit). As these rapidly spinning disks evolve they should produce jets of gas and even result in the formation of planets orbiting the brown dwarfs. Both these things have been observed in nature.

"We had no idea the simulated results would be so beautiful and complex, and then we found out that observations were revealing brown dwarfs with disks that matched what we were seeing, " said Shen, who is studying for her PhD in Physics & Astronomy at McMaster.

The simulated objects would either leave the stars on their own or in groups, or remain as multiple brown dwarf companions to a star. Telescopes have detected up to three brown dwarfs orbiting a regular star. Thus the brown dwarfs and planets in the simulations are remarkably similar to what is observed. However, it remains to be determined exactly how often such encounters occur in nature and what fraction of those encounters reliably produce brown dwarfs. For this, Shen and Wadsley are planning a much larger set of encounter simulations using SHARCNET's new supercomputers.

Source: McMaster University

Explore further: A sharp eye on Southern binary stars

add to favorites email to friend print save as pdf

Related Stories

Planet X myth debunked

Mar 16, 2014

It was an elusive planet that for 200 years appeared to explain Uranus's wobbly orbit. And there was the sister sun theorized to be near our solar system that caused asteroids to swerve toward Earth.

Could Jupiter become a star?

Feb 21, 2014

NASA's Galileo spacecraft arrived at Jupiter on December 7, 1995, and proceeded to study the giant planet for almost 8 years. It sent back a tremendous amount of scientific information that revolutionized ...

Recommended for you

A sharp eye on Southern binary stars

12 hours ago

Unlike our sun, with its retinue of orbiting planets, many stars in the sky orbit around a second star. These binary stars, with orbital periods ranging from days to centuries, have long been the primary ...

Hubble image: A cross-section of the universe

12 hours ago

An image of a galaxy cluster taken by the NASA/ESA Hubble Space Telescope gives a remarkable cross-section of the Universe, showing objects at different distances and stages in cosmic history. They range ...

Cosmologists weigh cosmic filaments and voids

16 hours ago

(Phys.org) —Cosmologists have established that much of the stuff of the universe is made of dark matter, a mysterious, invisible substance that can't be directly detected but which exerts a gravitational ...

User comments : 0

More news stories

Cosmologists weigh cosmic filaments and voids

(Phys.org) —Cosmologists have established that much of the stuff of the universe is made of dark matter, a mysterious, invisible substance that can't be directly detected but which exerts a gravitational ...

Hubble image: A cross-section of the universe

An image of a galaxy cluster taken by the NASA/ESA Hubble Space Telescope gives a remarkable cross-section of the Universe, showing objects at different distances and stages in cosmic history. They range ...

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...

Deadly human pathogen Cryptococcus fully sequenced

Within each strand of DNA lies the blueprint for building an organism, along with the keys to its evolution and survival. These genetic instructions can give valuable insight into why pathogens like Cryptococcus ne ...