Rare blue asteroid-comet reveals itself during fly-by

Blue asteroids are rare, and blue comets are almost unheard of. An international team led by Teddy Kareta, a graduate student at the University of Arizona's Lunar and Planetary Laboratory, investigated (3200) Phaethon, a bizarre asteroid that sometimes behaves like a comet, and found it even more enigmatic than previously thought.

The research team's results will be presented during a press conference on Oct. 23 at the 50th annual meeting of the American Astronomical Society's Division for Planetary Sciences in Knoxville, Tennessee.

Using telescopes in Hawaii and Arizona, the team studied sunlight reflected off Phaethon, which is known to be blue in color. Blue asteroids, which reflect more light in the blue part of the spectrum, make up only a fraction of all known asteroids. A majority of asteroids are dull gray to red, depending on the type of material on their surface.

Phaethon sets itself apart for two reasons: it appears to be one of the "bluest" of similarly colored asteroids or comets in the solar system; and its orbit takes it so close to the Sun that its surface heats up to about 800 degrees Celsius (1,500 degrees Fahrenheit), hot enough to melt aluminum.

Astronomers have been intrigued by Phaethon for other reasons, too. It has the qualities of both an asteroid and a comet based on its appearance and behavior.

Phaethon always appears as a dot in the sky, like thousands of other asteroids, and a fuzzy blob with a tail, like a comet. But Phaethon is the source of the annual Geminid meteor shower, easily seen in early to mid-December.

Meteor showers occur when Earth passes through the trail of dust left behind on a comet's orbit. When they occur and where they appear to be of the origin of the comet's orbit is with respect to the Earth. Phaethon is thought to be the "parent body" of the Geminid meteor shower because its orbit is very similar to the orbit of the Geminid meteors.

Until Phaeton was discovered in 1983, all meteor showers to active comets and not asteroids.

"At the time, the assumption was that Phaethon probably was a dead, burnt-out comet," said Kareta, "but comets are typically red in color, and so blue, so it should be. , 'it's hard to say whether Phaethon is more like an asteroid or more like a dead comet. "

Phaethon also releases a tiny dust when it gets closer to the Sun. This article is only available in French – Phaeton and one other, as well as on the other side of the world.

NASA 's Infrared Telescope Facility on Mauna Kea in Hawaii and the Tillinghast telescope, operated by the Smithsonian Astrophysical Observatory on Mount Hopkins in Arizona. They think Phaethon might be related to (2) Pallas, a large blue asteroid farther out in the solar system.

"Interestingly, we found that Pallas," Kareta said. "This makes it more difficult to say how Phaethon and Pallas are related."

The team also observes that Phaethon 's blue color is the same on all parts of its surface, which indicates that it has been cooked by the Sun in the recent past.

The team is now conducting observations of 2005 UD, another small blue asteroid astronomers are related to Phaethon, to see if they share the same rare properties. Phaethon is really like.

Related Links

Lunar and Planetary Laboratory

Asteroid and Mission Comet News, Science and Technology

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Greenbelt MD (SPX) Oct 22, 2018

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