A painting of an exoplanet (right of center) that, like HIP 13044b, orbits an older sunlike star. A new planet was discovered orbiting a bloated red star.
Since the mid-1990s astronomers have been adding to the list of known exoplanets. Almost 500 exoplanets found so far all formed in our home galaxy, the Milky Way.
(exoplanets: planets that exist outside our solar system.)
The newfound planet "likely formed when the star was not yet a part of the Milky Way. It's traveled with the star all this time," said study leader Johny Setiawan, an astronomer at the Max-Planck Institute for Astronomy in Germany.
Astronomers think stars and their planets are made from the same initial building blocks, so if a star has few metals, the disk of material that surrounded the star when it was young—and from which its planets are born—was also metal-poor.
Even though gas giants are made of mostly hydrogen and helium, astronomers think the planets still require an initial core of heavy elements to attract lighter gases and grow.
Alan Boss, a planet-formation theorist at the Carnegie Institution for Science in Washington, D.C., said HIP 13044b is "big news," because it's such an anomaly in terms of its origins.
"This object ... is unlikely to have formed by the conventional mechanism of first building a massive core of rock and ice and then pulling on enough gas to form a true gas giant planet," said Boss, who was not part of the study team.
Study leader Setiawan agrees: "Now we have this finding, and it suggests maybe there are other mechanisms of planet formation around metal-poor stars that we don't know about."
reference: http://news.nationalgeographic.com/news/2010/11/101118-science-space-new-planet-discovered-outside-galaxy/
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