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KNOXVILLE, Tennessee – A strange blue asteroid that behaves like a comet and seems to be responsible for the annual demonstration of the Geminid meteor over the Earth, giving astronomers the opportunity to study the object with a level of detail unprecedented. They discovered that the asteroid was even stranger than they had imagined.
The Asteroid 3200 Phaethon is a special space rock with a rare blue color and an extremely eccentric orbit in which the object passes superclose to the sun and then exceeds the orbit of March. An orbit takes about 1.4 Earth years. This type of orbit is more typical of comets than asteroids.
But although Phaethon acts like a comet, he does not look like one. When comets approach the sun, they form a cloud called "coma" and a long tail of dust and gas. Phaethon, however, still looks like a tiny spot floating in space. [The 7 Strangest Asteroids in the Solar System]
On December 16, 2017, the asteroid Phaethon approached the closest to the Earth since 1974, passing 10.3 million kilometers from our planet. While backyard astronomers pointed their telescopes at the space rock to glimpse the historical overview, astronomers from observatories around the world took the opportunity to learn more about the nature of this object and its provenance.
Teddy Kareta, a graduate student at the University of Arizona who led an international survey of Phaethon during the flyby, presented his team's findings at the 50th Annual Meeting of the Planetary Science Division of the Society. astronomical society. Kareta and his colleagues observed Phaethon's close-up approach using NASA's infrared telescope on Mauna Kea in Hawaii and the Tillinghast telescope on Hopkins Mountain in Arizona.
One of their discoveries could upset the current theory of the origin of Phaethon. Astronomers have long suspected that Phaethon is a much larger fragment of the blue asteroid, Pallas. "However, the albedo of Pallas [or reflectivity]is about twice what we found for the Phaethon albedo, "said Kareta. With an albedo of about 8%, Phaethon is slightly brighter than charcoal and only about half as brilliant as Pallas, said Kareta.
The researchers also found that the Phaethon surface is also blue, meaning that the object was "uniformly burned" or "cooked" by the heat of the sun. The blue color of Phaethon indicates that the rock has undergone intense heating, said Kareta. During his travels around the sun, Phaethon heats up to temperatures of up to 800 degrees Celsius (1500 degrees Fahrenheit), which is "so hot that the metals on the surface are degrading," he said.
The Geminid meteor shower, which arrives every year in December, is the only meteorite shower that seems to come from anything but a comet. Comets are icy bodies containing a mixture of ice, rock, dust and frozen gas. When a comet gets closer to the sun, some of this material vaporizes and small pieces of the comet come off, leaving behind a trail of comet crumbs in the space. When the Earth crosses such a trail of debris, we have meteor showers.
Asteroids like Phaethon are rocky objects that do not behave the same way as comets do when they get closer to the sun, and astronomers do not know how Phaethon could have created the Geminids. Before the discovery of Phaethon in 1983, astronomers had no idea where the Geminids came from. After observing that the orbit of Phaethon corresponded to the trail of debris that causes the annual meteor shower, astronomers have, however, determined that Phaethon should be its source.
Kareta explained that the way Phaethon created this trail of debris remains a mystery. Although it is possible that materials swept on the surface of the asteroid contribute to debris, "the amount of dust that is removed is far from sufficient to support the Geminids", did he declare. One possibility is that Phaethon collided with another object in space and the Geminids are the debris of this "catastrophic break," he said. "So, in this case, you basically see dust, which looks like a splash of blood, to be horrible, from this really violent event."
Another possibility is that Phaethon is a sleeping comet, or a comet that has turned into an asteroid over time. "If it was cometary at some point in the past, maybe the meteor would spill out normally and leave behind the comet crumbs … but since then it has been cooked and extinguished and it looks like a rock Said Kareta. .
Phaethon may look more like an asteroid than a comet, but it presents the qualities of both types of objects. It does not have the coma and tail characteristics of comets, but it releases "a tiny dust when it gets closer to the sun, in a process that looks like a dry riverbed cracking under the heat from the afternoon. "Officials from the University of Arizona said in a statement." 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 results of this new research will be useful to scientists at the Japan Aerospace Exploration Agency (JAXA), which is currently planning a mission to Phaethon. The mission is called DESTINY + (abbreviation for Demonstration and Experimentation of Space Technology for an Interplanetary Journey, Phaethon Fyby and Dust Science), and its launch is currently scheduled for 2022.
DESTINY + will go through Phaethon and other objects close to Earth to study how dust is ejected from these objects. This should help explain the little tail of Phaethon's dust. DESTINY + could help scientists determine if Phaethon is an asteroid, a comet or something else. "It's probably somewhere in the middle," said Kareta.
Email Hanneke Weitering at [email protected] or follow @hannekescience. Follow us on Twitter @Spacedotcom and on Facebook. Space.com.
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