Tue, Dec 16, 2008 - Page 2 News List

Taiwanese in star-dwarf research

RESEARCH FINDING Scientists have been trying to determine if brown dwarfs form like stars from the collapse of gas clouds, or like planets by the accumulation of material

STAFF WRITER, WITH CNA

A Taiwan-US astronomical research project has discovered the first ever direct evidence that brown dwarfs, sub-stellar object form in the same way as other stars, a finding that may settle the argument on whether brown dwarfs form like stars or like planets.

Academia Sinica said a brown dwarf is an astronomical object with a mass larger than a planet but smaller than a star — generally 15 times to 75 times larger than Jupiter.

The paper, which will be published in Saturday’s edition of the Astrophysical Journal Letters, stated that a brown dwarf dubbed “ISO-Oph 102” was observed developing an accretion disk and two outflow jets in opposite directions — the unique phenomena of star formation.

However, it is not clear whether brown dwarfs — sometimes called “failed stars” — form like stars, from the gravitational collapse of gas clouds, or form like planets, agglomerating rocky material until they grow massive enough to draw in nearby gas.

Another surprising aspect of the scientists’ findings is that the observation was made with an older generation telescope, the Submillimeter Array — a collaborative project of the Smithsonian Astrophysical Observatory in the US and Academia Sinica.

“As brown dwarfs tend to have less mass and weaker outflows, we thought only a next-generation telescope like ALMA could make the observation,” said Phan Bao-ngoc, a visiting scholar at the Institute of Astronomy and Astrophysics of Academia Sinica.

Compared with the outflow from a typical star, the ISO-Oph 102’s outflow contains 1,000 times less mass and the outflow rate is also one-hundredth that of star, the scientists said.

“In all respects, the molecular outflow of ISO-Oph 102 is a scaled-down version of the outflow process seen in young stars,” they said.

The Atacama Large Millimeter Array (ALMA) is a collaborative project conducted by Europe, Japan, the US and Taiwan.

ALMA employs 66 antennas of various sizes to form the largest ground-based radio telescope that is being constructed in the 5,000m high foothills of the Andes Mountains in Chile.

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