Rare Blue Asteroid Behaves Sometimes Like a Comet | Space

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Blue asteroids are rare and blue comets are almost unknown. An international team of astronomers has investigated 3200 Phaethon, a bizarre blue asteroid that sometimes behaves like a comet and finds it even more enigmatic than previously thought.

On December 16, 2017, the asteroid approached the closest to Earth since 1974, rising to less than 10.3 million km. The team has analyzed flyover data from several telescopes around the world to learn more about this mysterious object that has intrigued astronomers since its discovery in 1983. The researchers presented the results of their study of 23 October 2018 during the annual meeting of the Planetary Science Division of the American Astronomical Society in Knoxville, Tennessee.

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 1500 degrees Fahrenheit (800 degrees C), 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 shower occurs when the Earth crosses the trail of dust left in the orbit of a comet. When they occur and 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.

The study was conducted by Teddy Kareta, PhD student at the Lunar and Global Laboratory at the University of Arizona. Karate said in a statement:

At the time, the hypothesis was that Phaethon was probably a dead comet and consumed, but comets are usually red in color and not blue. So, even though the very eccentric orbit of Phaeton must shout "comet dead," it's hard to tell if 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 gained new information about Phaethon after analyzing data from NASA's infrared telescope facilities in Hawaii and the Tillinghast telescope in Arizona. They think that Phaethon could be linked to or separated from 2 Pallas, a large blue asteroid further down the solar system. Karate said:

Interestingly, we found that Phaethon was even darker than what had been observed before, about half as reflective as Pallas. This makes it more difficult to say how Phaethon and Pallas are related.

The team also observed that the blue color of Phaethon is the same over its entire surface, which indicates, she says, that it has been cooked uniformly by the sun in recent years.

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In summary: new ideas on 3200 Phaethon, an asteroid that often acts as a comet.

Via the University of Arizona