Asteroid or Comet? Weird Blue Space Rock 'Phaethon' Gets to Close-Up

Asteroid or Comet? Weird Blue Space Rock 'Phaethon' Gets to Close-Up

Asteroid or Comet? Weird Blue Space Rock 'Phaethon' Gets to Close-Up







		KNOXVILLE, Tenn. - A strange and blue asteroid that acts like a comet and seems to be responsible for the annual publication. Geminid meteor shower He made an upcoming trip to Earth last year, giving astronomers the opportunity to study the object in unprecedented detail. They discovered that the asteroid is even more rare than they had imagined.

		Asteroid 3200 Phaethon is a special space rock with a rare blue color and an extremely eccentric orbit that makes the object pass superclose to the sun and then pass the orbit of Mars. An orbit takes about 1.4 Earth years. This type of orbit is more typical for comets what asteroids.

		But while Phaeton acts like a comet, it does not look like it. When comets approach the sun, they form a cloud known as "coma" and a long tail of dust and gas. Phaethon, however, always looks like a little speck floating in space.

The[[The 7 strangest asteroids in the solar system]     

		On December 16, 2017, the asteroid Phaeton made his closer approach to Earth since 1974, passing to 6.4 million miles (10.3 million kilometers) of our planet. While backyard astronomers pointed their telescopes at the space rock to glimpse the historic flyby, astronomers from observatories around the world took the opportunity to learn more about what the object is and where it comes from. 

		Teddy Kareta, a graduate student at the University of Arizona who led an international effort to investigate Phaethon during the overflight, presented his team's findings here at the 50th annual meeting of the Division of Planetary Sciences of the American Astronomical Society (23 October). Kareta and his colleagues observed the approach of Phaethon using the installation of the NASA Infrared Telescope at Mauna Kea in Hawaii and the Tillinghast telescope at Mount Hopkins in Arizona.

		One of his findings may override the current theory that prevails over Phaeton's origin. Astronomers have long suspected that Phaethon is a fragment of the much larger blue asteroid Pallas. "However, the albedo of Pallas [or reflectivity] "It's about double what we found for the Phaethon albedo," Kareta said. With an albedo of about 8 percent, Phaethon is slightly brighter than coal and only half as bright as Pallas, Kareta said.

		The researchers also found that Phaeton's surface is equally blue throughout, which means that the object has been "uniformly burned" or "cooked" by the sun's heat. The blue color of Phaeton indicates that the rock has undergone an intense heating, said Kareta. During Phaethon's travels around the sun, it is heated to temperatures of up to 1,500 degrees Fahrenheit (800 degrees Celsius), which is "so hot that the surface metals become sticky," he said.



		Creating the Geminid meteor shower

		the Geminid meteor shower, which arrives every year in December, is the only meteor shower that seems to have originated in something other than a comet. Comets are frozen bodies that contain a mixture of ice, rock, dust and frozen gas. When a comet approaches the sun, part of this material vaporizes and small pieces of the comet come off, leaving a trail of comet crumbs in space. When the Earth passes through a trail of debris, we have meteor showers.

		Asteroids like Phaethon are rocky objects that do not behave in the same way as comets when they approach the Sun, and astronomers are not sure how Phaethon could have created the Geminids. Before Phaeton was discovered in 1983, astronomers had no idea where the Geminids came from. However, having observed that Phaeton's orbit coincided with the debris trail caused by the annual meteor shower, astronomers determined that the source must be Phaethon.





						


This diagram shows the highly eccentric orbit of 3200 Phaeton.

            						    Credit: NASA JPL 


		Exactly how Phaethon created that trail of debris remains a mystery, Kareta said. While it is possible that material swept from the surface of the asteroid contributes to the debris, "the amount of dust that is removed is not close enough to hold the Geminids," he said. One possibility is that Phaethon collided with another object in space and the Geminids are the rubble of that "catastrophic rupture," he said. "Then, in that case, you're essentially seeing dust, which is like splashing blood, to be frightening, of this really violent event."

		Another possibility is that Phaethon is an inactive comet, or a comet that became an asteroid over time. "If it was cometary at some time in the past, maybe he made the meteor shower in the normal way and left behind those crumbs of the comet ... but since then, it was cooked and turned off and it only looks like a rock, "Kareta said.

		Phaethon may look more like an asteroid than a comet, but it shows qualities of both types of objects. It does not have the coma and tail that are characteristic of comets, but it releases "a small tail of dust when it approaches the sun in a process that is believed to be similar to a cracking of a dry river bed in the heat of the late". "Officials at the University of Arizona said in a statement," This type of activity has only been seen in two objects throughout the solar system: Phaeton and another similar object that seems to blur the line traditionally thought to separate comets and asteroids. "     



		A mission to Phaethon: DESTINY +

		The results of this new research will be useful for scientists at the Japan Aerospace Exploration Agency (JAXA), which is currently planning a mission to Phaethon. The mission is called DESTINY + (an abbreviation of Demonstration and Experiment of Space Technology for Interplanetary Travel, Phaethon Fyby and Dust Science), and is currently scheduled for launch in 2022.

		DESTINY + will fly through Phaeton and other near-Earth objects to study how dust is ejected from these objects. This should help explain Phaeton's small tail of dust. DESTINY + could help scientists discover if Phaethon is an asteroid, a comet or something else. "It's probably somewhere in the middle," Kareta said.



	Send an email to Hanneke Weitering at hweitering@space.com or follow it @hannekescience. Follow us on Twitter @Spacedotcom and in Facebook. Original article about Space.com.

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