Far-off planets now in sight

8220;It8217;s the tip of the iceberg,8221; said Christian Marois of the Herzberg Institute of Astrophysics in Victoria, British Columbia. 8220;Now that we know they are there, there is going to be an explosion.8221;

Marois is the leader of a team that recorded three planets circling a star known as HR 8799 that is 130 light-years away in the constellation Pegasus. The other team, led by Paul Kalas of the University of California, found a planet orbiting the star Fomalhaut, only 25 light-years from Earth, in the constellation Piscis Austrinus.

In an interview by e-mail, Kalas said that when he finally confirmed his discovery last May, 8220;I nearly had a heart attack8221;.

In scratchy telescope pictures released on Thursday in Science Express, the online version of the journal Science, the planets appear as fuzzy dots that move slightly around their star from exposure to exposure. Astronomers who have seen the new images agreed that these looked like the real thing.

8220;I think Kepler himself would recognise these as planets orbiting a star following his laws of orbital motion,8221; Mark S Marley of the Ames Research Center in Mountain View, California, wrote in an e-mail message.

More than 300 so-called extrasolar planets have been found circling distant stars, making their discovery the hottest and fastest growing field in astronomy. But the observations have been made mostly indirectly, by dips in starlight as planets cross in front of their home star or by wobbles they induce going by it.

8220;Every extrasolar planet detected so far has been a wobble on a graph,8221; said Bruce Macintosh, an astrophysicist from Lawrence Livermore National Laboratory in California and a member of Marois8217; team. 8220;These are the first pictures of an entire system.8221;

The new planetary systems are anchored by young bright stars more massive than our own Sun and swaddled in large disks of dust, the raw material of worlds.

The three planets orbiting HR 8799 are roughly 10, nine and six times the mass of Jupiter, and orbit their star in periods of 450, 180 and 100 years respectively, all counterclockwise.

The Fomalhaut planet is about three times as massive as Jupiter, according to Kalas8217; calculations, and is on the inner edge of a huge band of dust, taking roughly 872 years to complete a revolution of its star.

Both systems appear to be scaled-up versions of our own solar system, with giant planets in the outer reaches, leaving plenty of room for smaller planets to lurk undetected in the warmer inner regions. Dust rings lie even farther out, like the Kuiper belt of icy debris extending beyond the orbit of Neptune.

Sara Seager, a planetary theorist at the Massachusetts Institute of Technology, said it was significant that the planets in both cases seemed to be associated with disks of dust, particularly Fomalhaut, one of the brightest and closest stars known to be host to a massive disk.

8220;Fomalhaut is like a Hollywood star to astronomers, so we have some personal excitement here,8221; Seager said. 8220;It feels like finding out that one of your four closest friends just won the lottery big time8221;.

Fomalhaut is also a young star, about 200 million years old, and its dust ring extends 11 billion to 20 billion miles from its planet, Kalas said. In order not to disturb or roil the dust ring, Fomalhaut8217;s planet must be less than three Jupiter masses, well within regulation planet size, Kalas and his collaborators calculated.