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: Precise ages of largest number of stars hosting planets ever measured

Related Stories

Can planets be rejuvenated around dead stars?

Jun 26, 2015

For a planet, this would be like a day at the spa. After years of growing old, a massive planet could, in theory, brighten up with a radiant, youthful glow. Rejuvenated planets, as they are nicknamed, are ...

What is the biggest planet in the solar system?

Jun 25, 2015

Ever since the invention of the telescope four hundred years ago, astronomers have been fascinated by the gas giant of Jupiter. Between it's constant, swirling clouds, its many, many moons, and its Giant ...

What is the Kuiper Belt?

Jun 17, 2015

Dr. Mike Brown is a professor of planetary astronomy at Caltech. He's best known as the man who killed Pluto, thanks to his team's discovery of Eris and other Kuiper Belt Objects. We asked him to help us ...

A conversation with astronomer Dimitri Mawet

May 18, 2015

Associate Professor of Astronomy Dimitri Mawet has joined Caltech from the Paranal Observatory in Chile, where he was a staff astronomer for the Very Large Telescope. After earning his PhD at the University ...

Drawing the line between stars and brown dwarfs

Dec 10, 2013

(Phys.org) —Stars come in a tremendous size range, from many tens of times bigger than the Sun to a tiny fraction of its size. But the answer to just how small an astronomical body can be, and still be ...

Recommended for you

The discovery of the molecule Si-C-Si in space

12 hours ago

The space between stars is not empty—it contains a vast reservoir of diffuse material with about 5-10% of the total mass of our Milky Way galaxy. Most of the material is gas, but about 1% of this mass (quite ...

Hubble view of a nitrogen-rich nebula

12 hours ago

This NASA/ESA Hubble Space Telescope image shows a planetary nebula named NGC 6153, located about 4,000 light-years away in the southern constellation of Scorpius (The Scorpion).

Is the universe ringing like a crystal glass?

Jun 26, 2015

Many know the phrase "the big bang theory." There's even a top television comedy series with that as its title. According to scientists, the universe began with the "big bang" and expanded to the size it ...

Improved sensors help navigate gravity waves

Jun 26, 2015

Efforts to detect gravitational waves—which were first predicted by Albert Einstein nearly 100 years ago—are advancing with international researchers including UWA researchers boosting the sensitivity ...

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.