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A Star Is Born? No, But Maybe a Planet
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03/01/2013 10:41 AM
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Astronomers have spotted what they believe is a planet in the dramatic and violent process of being born in another solar system, an event that may shed light on how planets come into being.
Astronomers say they may have spotted a possible planet in the dramatic and violent process of being born, an event that may shed light on how large, gaseous planets come into being. Gautam Naik reports on Lunch Break. Photo: AFP/European Southern Observatory.
An international team of researchers said the so-called protoplanet has a mass that appears to be at least the size of Jupiter, and perhaps two to three times its size. It is located about 335 light years from Earth, within the Milky Way. That isn't too far in cosmic terms; the Milky Way itself is about 100,000 light years across.
"If we are correct, this is the first time we are seeing a planet forming inside its natal environment," said Sascha Quanz, an astronomer at the Swiss university ETH Zurich and leader of the team. The findings are reported in Astrophysical Journal Letters, a scientific publication.
There are two leading theories of planet formation. Under one, small dust grains circling around a parent star collide, get larger and larger, and under the force of gravity develop into a much larger object. Over hundreds of thousands of years, this object accumulates enough material to become a planet. That is how the planets of our solar system most likely formed.
Another theory suggests that material surrounding a young star can undergo gravitational collapse under its own mass. This causes debris to clump together in that region, creating a planet in just a few thousand years. It isn't clear how the latest suspected protoplanet is being formed.
Spotting the earliest birth pangs of a planet is notoriously hard. In 2011, astronomers said they had discovered a protoplanet, though some signs indicated it was an older entity. In January, another team of researchers reported evidence of vast streams of gas flowing across a gap in a disk of material around a young star. Giant planets, they surmised, would guzzle gas in a similar way as they grow.
If it holds up, the latest finding would be one of the first direct observations of the very early stages of a planet's birth. Dr. Quanz and colleagues based their discovery on observations by a high-resolution infrared camera linked to a telescope located in Chile's Atacama Desert.
The telescope was pointed at a young star, HD 100546, about 2.5-times the size of our sun. Astronomers were interested in the star because the disk of materials around it showed certain asymmetries. "It's a good indication that something might be hiding or forming in the disk," said Dr. Quanz.
The infrared imagery revealed a little bright blob in the disk, suggesting an entity emitting radiation. When the picture of the blob was laid over an image of the asymmetry, they coincided perfectly. The conclusion: The blob was an object embedded in the material around the star, suggesting a nascent planet.
The protoplanet would take tens of thousands of years to grow up. But scientists still hope to study the entity and glean insights into how it was created and how it might evolve. "We can try to find out the chemical and physical properties of the disk that causes a planet to form there," said Dr. Quanz.
[link to online.wsj.com]