New investigation was conducted using the ALMA telescope

Apr 13, 2012 08:48 GMT  ·  By
This artist's impression shows how the Fomalhaut star system may be set up, according to the new ALMA data
   This artist's impression shows how the Fomalhaut star system may be set up, according to the new ALMA data

Taking advantage of the capabilities provided by the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope – currently under construction in Chile – astronomers were able to gain a deeper understanding of how a nearby planetary system is set up.

The research team was able to provide additional evidence that two extrasolar planets revolve around the star Fomalhaut, just 25 light-years away from Earth. The work could offer more insight into how these stellar systems form and evolve.

ALMA is not yet complete. The massive radio observatory only has a few antennas at this point, but it was already opened for science some time ago. Even at reduced capacity, the installation is still capable of collecting invaluable scientific data.

The most important conclusion in the research was that the two planets originally hypothesized to exist around the nearby star are, in fact, smaller than originally predicted. The paper describing the findings is the first to be released by experts working at ALMA.

The sizes of the two exoplanets were analyzed indirectly, by studying a dust disk that revolves around the Fomalhaut. Astronomers used the radio observatory to analyze the edges of the disk, and found them to be very sharp.

By combining these readings with a series of computer models of the star and its surroundings, experts were able to determine that the disk is most likely held together by the gravitational influence of the two, “shepherding” planets.

Investigators believe that one of them orbits Fomalhaut on the inside of the disc, while the other moves around its parent star just outside the boundaries of the disc. The two worlds are most likely larger than Mars, but no larger than a few times the size of Earth.

“Combining ALMA observations of the ring's shape with computer models, we can place very tight limits on the mass and orbit of any planet near the ring. The masses of these planets must be small; otherwise the planets would destroy the ring,” study leader, Aaron Boley, explains.

The researcher holds an appointment as a Sagan Fellow at the University of Florida, in the US. He explains that infrared telescopes could not detect these two exoplanets simply because they are too small.

“ALMA may be still under construction, but it is already the most powerful telescope of its kind. This is just the beginning of an exciting new era in the study of discs and planet formation around other stars,” explains Bill Dent, an astronomer with the European Southern Observatory (ESO).