Blue asteroids are rare, and blue comets are almost unknown. An international team led by Teddy Kareta, a graduate student at the University of Arizona's Lunar and Planetary Laboratory, (3200) studied Phaethon, a bizarre asteroid that sometimes behaves like a comet and finds it even more enigmatic than previously thought.
The research team's findings will be presented during a press conference on October 23 at the 50th Annual Meeting of the Planetary Sciences Division of the American Astronomical Society at Knoxville, Tennessee.
Using telescopes in Hawaii and Arizona, the team studied sunlight reflected by Phaethon, who 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. Much of the asteroid is dull gray to red, depending on the nature of the material on its surface
Phaethon differs for two reasons: it seems to be one of the "blueest" similarly colored asteroids or comets in the solar system; and its orbit brings it so close to the sun that its surface heats up to about 800 degrees Celsius, hot enough to melt aluminum.
Astronomers were fascinated by Phaethon for other reasons as well. It has the properties of both an asteroid and a comet because of its appearance and behavior.
Phaethon always appears like a dot in the sky, like thousands of other asteroids, rather than a blurry spot with a tail, like a comet. But Phaethon is the source of the annual Geminid meteor shower, which is easy to see in early to mid-December.
Meteor showers occur when the earth flies through the dust trail on a comet's orbit. When they occur and where they seem to come from depends on how the orbit of the comet is aligned with respect to the earth. It is believed that Phaethon is the "parent" of the Geminid meteor shower because its orbit is very similar to the orbit of Geminid meteors.
Until Phaeton was discovered in 1983, scientists combined all known meteor showers with active comet asteroids
"At the time, the assumption was that Phaethon was probably a dead, burnt-out comet," Kareta said, "but comets are typically red So, although Phaeton's highly eccentric orbit should scream "dead comet," it's hard to say if Phaethon is more like an asteroid or more like a dead comet. "
Phaethon also releases a tiny dust tail when he comes closest to the sun in a supposed process similar to cracking a dry riverbed in the afternoon heat. This type of activity has been observed only on two objects throughout the solar system – Phaeton and another similar object that appears to blur the line traditionally believed to separate comets and asteroids.
The team received several new findings about Phaethon after analyzing data from 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 could be related to or removed from (2) Pallas, a large blue asteroid further out in the solar system.
"Interestingly, we found that Phaethon was even darker than previously observed, about half as reflective as Pallas," Kareta said, "which makes it harder to say how Phaethon and Pallas are related."
Das Team also observed that the blue color of Phaethon is the same on all parts of the surface, suggesting that it has been cooked evenly by the sun lately
The team is now conducting observations of 2005 UD, another small blue one Asteroid that astronomers think is akin to Phaethon to see if they have the same rare properties, this and other work will help unravel the mystery of what Phaethon really is.
A new puzzle has been discovered with respect to the active asteroid Phaethon