Young world: NASA telescope reveals clues to newborn planet.

Astronomers have found signs of what may be the youngest planet known, plus the first signs ever of organic compounds in a region of dust that could evolve into a planet-forming system.

By measuring infrared light, the Spitzer Space Telescope also located hundreds of" newborn stars, some with potentially planet-forming dust. "The number of potential Earthlike planets in the galaxy is greater than we previously imagined," says Michael W. Werner of NASA's Jet Propulsion Laboratory in Pasadena, Calif.

More sensitive than any previous infrared detector, Spitzer was launched in August 2003. Astronomers announced some of Spitzer's earliest results last week in a press conference at NASA headquarters in Washington, D.C.

The team detected a gap in a dusty disk swaddling the young star CoKu Tau 4, which suggests that a large, Jupiterlike planet could be sweeping around the star. An asteroid, an unseen companion star, or the heat and light from CoKu Tau 4 itself could have caused the gap, the researchers acknowledge. But "the planetary explanation is the most likely explanation," said Alan B. Boss, an astronomer at the Carnegie Institute in Washington. Boss was not a member of the discovery team but spoke at the briefing.

CoKu Tan 4, about 420 light-years from Earth and in the constellation Taurus, is only 1 million years old, a cosmic baby. The researchers deduced the age of the star by its color and luminosity and inferred that a planet circling CoKu Tau 4 would be even younger.

The presumed planet's youth challenges the conventional model of planetary formation, in which dust around a star gathers into ever-larger rocks that crash together and eventually accrete into planets. This long process created the inner planets in our solar system, including Earth, but can't explain gas giants such as Jupiter and the possible planet circling CoKu Tau 4.

Instead, these planets might have formed after two arms of a rotating disk of dust and gas crossed each other. The resulting region of high-density gas could collapse into a planet in only 1,000 years, said Boss, who first proposed this planet-building mechanism a decade ago. The new findings are "one step in the right direction to understanding how gas giants form," says Boss.

At the NASA press conference, Dan M. Watson of the University of Rochester in New York also announced the discovery of organic molecules in frozen dust in another potentially planet-forming region of Tanrus. Such dust is the progenitor of asteroids and comets, which probably brought water and the raw materials for life to Earth, said Watson.

Astronomers have found organic chemicals in space before (SN: 5/1/04, p. 280), but "this confirms ... that organic matter can be brought into a planetary system while it's in formation" says Werner.

The Spitzer telescope also photographed a far-flung nebula littered with more than 300 newborn stars. No one "in their wildest dreams" expected to find a region such as this, said Edward Churchwell of the University of Wisconsin-Madison. A closer look at two of the stars revealed potentially planet-forming disks around them, he said.

The current findings paint a surprising portrait of the cosmos. "Solar systems like our own are not rare in our galaxy" said Boss. "They're probably quite common."