Seeing Is Believing: Researchers Capture Images of New Planets

First optical images of an extrasolar planet orbiting a star 25 light years from Earth. Fomalhaut b is 100 million times fainter than the star and sits just inside a vast dust belt circling the star. The discovery was made by blocking the glare from the bright star Fomalhaut using special instrumentation aboard the Hubble Space Telescope.

[Image courtesy of Paul Kalas, University of California, Berkeley]

Scientists have produced the first-ever image of multiple planets orbiting a star other than our own Sun. And, in related news, another research team has directly detected a planet orbiting the star Fomalhaut, which is one of the brightest in the sky and just 25 light years from Earth.

The journal Science published these findings today at the Science Express Web site.

Researchers typically infer a planet's presence—usually through its gravitational influence on a star. But a research team led by Christian Marois of the NRC Herzberg Institute of Astrophysics in British Columbia and the Lawrence Livermore National Laboratory and University of California, Berkeley, imaged three planets directly using the Keck and Gemini telescopes.

The star, HR 8799, is a "main sequence star," in the prime of its life, fueled by nuclear reactions within its core, and it occurs 128 light years from Earth. The planets traveling around it have masses between five and 13 times that of Jupiter, with the smallest planet closest to its sun and the largest the farthest away.

This size relationship, which is generally similar to that of the outer planets in our own solar system, supports a scenario in which the planets formed as through the accretion of particles in a disk of gas and dust whirling around the star. The system resembles a scaled-up version of the outer portion of our solar system, according to the authors, who estimate that if HR 8799 had been as faint as the Sun, its planets would be at distances similar to those of Saturn, Uranus and Neptune.

In another study, Paul Kalas of the University of California, Berkeley and colleagues used the Hubble Space Telescope to image a planet they call Fomalhaut b, orbiting its star, within a large dust belt. The researchers estimate that the planet's mass is no greater than several times that of Jupiter. If their findings are confirmed, this object will be the coolest and lowest-mass body imaged outside of our solar system.

Kathleen Wren

13 November 2008