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Blue asteroids are rare and blue comets are almost unknown. An international team led by Teddy Kareta, PhD student at the Lunar and Planetary Laboratory of the University of Arizona, studied (3200) Phaethon, a bizarre asteroid that sometimes behaves like a comet and has it found even more enigmatic than previously thought.
Kareta presented the results at a press conference on October 23 at the 50th Annual meeting of the Planetary Science Division of the American Astronomical Society in Knoxville, Tennessee.
Using telescopes installed in Hawaii and Arizona, the team studied solar radiation reflected by Phaethon, known for its blue color. Blue asteroids, which reflect more light in the blue part of the spectrum, are only a fraction of all known asteroids. The majority of asteroids range from dull gray to red, depending on the type of material on their surface.
Phaethon stands out for two reasons: it seems to be one of the "blueest" asteroids or comets of the same color in the solar system; and its orbit approaches so close to the sun that its surface heats up to about 800 degrees Celsius (1500 degrees Fahrenheit), hot enough to melt aluminum.
Phaethon intrigued astronomers for other reasons as well. It possesses the qualities of an asteroid and a comet because of its appearance and behavior.
Phaethon always appears as a point in the sky, like thousands of other asteroids, and not as a blurred drop with a tail, like a comet. But Phaethon is the source of the annual Geminid meteor shower, easily visible from early to mid-December.
Meteor rain occurs when the Earth crosses the trail of dust left in the orbit of a comet. When they occur and from where they seem to come from, it depends on the orientation of the orbit of the comet relative to the Earth. Phaethon is thought to be the "parent body" of geminid meteor shower because its orbit is very similar to that of geminid meteors.
Until the discovery of Phaeton in 1983, scientists associated all known meteor showers with active comets and not with asteroids.
"At the time, the assumption was that Phaethon was probably a comet dead and consumed," said Kareta, "but comets are usually red in color and not blue. Extremely eccentric orbit of Phaeton should shout "comet dead", it is hard to say whether Phaethon looks more like an asteroid or more than a dead comet. "
Phaethon also releases a small trail of dust when it gets closer to the sun, in a process that looks like a dried-up riverbed cracking under the heat of the afternoon. This type of activity has been observed only on two objects from the entire solar system – Phaeton and another, a similar object that seems to blur the line traditionally thought to differentiate comets and asteroids .
The team obtained several new information about Phaethon after analyzing data obtained from NASA's infrared telescope center on Mauna Kea in Hawaii and the Tillinghast telescope, operated by the Smithsonian astrophysics observatory on Mount Hopkins in Arizona. They think that Phaethon could be related to (2) Pallas, a large blue asteroid further down the solar system.
"Interestingly, we found that Phaeton was even darker than we had previously observed, about half as much as Pallas," Kareta said. "It makes it more difficult to say how Phaethon and Pallas are related."
The team also observed that the blue color of Phaethon is identical throughout its surface, indicating that it has been uniformly cooked by the Sun in recent years.
The team is currently observing 2005 UD, another small blue asteroid that is linked to the Phaethon, to see if they share the same rare properties. This work and further work will help solve the mystery of what Phaethon really looks like.
Source of the story:
Material provided by University of Arizona. Original written by Teddy Kareta. Note: Content can be changed for style and length.
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