Astronomy

Sedna, the tenth planet in the Solar System?

Sedna, the tenth planet in the Solar System?


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Researchers sponsored by NASA have discovered the most distant object in orbit of the Sun. It is a mysterious planet-like body in the confines of the Solar System, which is three times farther from Earth than Pluto.

The Sun appears so small from that distance that it could be completely covered with the head of a pin. The object, called Sedna by the Inuit goddess of the oceans, is 13 billion kilometers (8 billion miles) away, at the ends of the solar system.

This is, most likely, the first observation of the hypothetical "Oort cloud", a super remote site where small icy bodies are found that provides comets that cross the Earth. Other notable features of Sedna are its size and its reddish color. After Mars, it is the second reddest object in the solar system. Sedna is estimated to be approximately three quarters the size of Pluto.

Sedna is definitely the largest object found in the solar system since the discovery of Pluto in 1930. Brown, along with Drs. Chad Trujillo of the Gemini Observatory, Hawaii, and David Rabinowitz of Yale University in New Haven, found the planet-type object, or planetoid, on November 14, 2003. The researchers used the Samuel Oschin 48-inch Telescope at the Observatory from Caltech in Palomar near San Diego.

A few days later, telescopes in Chile, Spain, Arizona and Hawaii observed the object. NASA's new Spitzer Space Telescope also searched for it. Sedna is extremely remote from the Sun, in the coldest region of our solar system, where temperatures never reach 240 degrees Celsius below zero. The planetoid is even colder because it only briefly approaches the sun during its solar orbit of 10, 500 years. In its greater distance Sedna is 130 billion kilometers (84 billion miles) from the Sun, 900 times the distance from Earth to the Sun.

The scientists used the fact that even the Spitzer telescope was unable to detect the heat of such an extremely distant and cold object, to determine that it must be less than 1,700 kilometers in diameter, which is less than Pluto.

Combining the available data, Sedna's size was calculated midway between Pluto and Quaoar, a small planetoid discovered by the same team in 2002. Sedna's elliptical orbit is not similar to anything previously seen by astronomers. It resembles predicted orbits for objects found in the hypothetical Oort cloud, a distant reserve of comets.

But Sedna is 10 times closer than the predicted distance for the Oort cloud. Astronomers believe that this "internal Oort cloud" could have formed billions of years ago when a colored star passed through the Sun, dragging in some of the comet-like bodies. The star would have been close enough to be brighter than the full moon and would have been visible during the day in the sky for 20,000 years. Worse, it would have displaced comets beyond in the Oort cloud, leading to an intense rain of comets that could have made some or all of the life forms that existed on Earth disappear at that time. There is indirect evidence that Sedna has a moon. The researchers hope to verify this possibility with the NASA Hubble Space Telescope.

Sedna will approach Earth in the coming years, but even at its maximum approach, in about 72 years, it will be far away, much more than Pluto. Then you will begin your return trip of 10,500 years to the confines of the solar system. The last time Sedna was seen so close to the Sun, the Earth was just coming out of the last ice age. The next time I return, the world may be a completely different place.

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