KNOXVILLE, Tenn.– A strange, blue asteroid that imitates a comet and seems accountable for the yearly Geminid meteor shower made a close flyby of Earth in 2015, providing astronomers a chance to study the item in extraordinary information. They discovered that the asteroid is even weirder than they had actually thought of.

Asteroid 3200 Phaethon is an unique area rock with an uncommon blue color and an exceptionally eccentric orbit that has the item pass superclose to the sun and after that out past the orbit of Mars. One orbit takes about 1.4 Earth years. This sort of orbit is more normal for comets than asteroids

However while Phaethon imitates a comet, it does not appear like one. When comets get near to the sun, they form a cloud referred to as a “coma” and a long tail of dust and gas. Phaethon, nevertheless, constantly appears like a small speck drifting through area. [The 7 Strangest Asteroids in the Solar System]

On Dec. 16, 2017, the asteroid Phaethon made its closest method to Earth considering that 1974, passing within 6.4 million miles (103 million kilometers) of our world. While yard astronomers pointed their telescopes towards the area rock to see the historical flyby, astronomers in observatories all over the world seized the day to read more about what the item is and where it originated from.

Teddy Kareta, a college student at the University of Arizona who led a worldwide effort to examine Phaethon throughout the flyby, provided his group’s findings here at the 50 th yearly conference of the American Astronomical Society’s Department for Planetary Sciences today (Oct. 23). Kareta and his associates observed Phaethon’s close method utilizing NASA’s Infrared Telescope Center on Mauna Kea in Hawaii and the Tillinghast telescope on Mount Hopkins in Arizona.

Among their findings might reverse the present dominating theory about the origin of Phaethon. Astronomers have actually long presumed that Phaethon is a piece of the much bigger blue asteroid Pallas. “Nevertheless, Pallas’ albedo [or reflectivity] has to do with two times what we discovered for Phaethon’s albedo,” Kareta stated. With an albedo of about 8 percent, Phaethon is a little brighter than charcoal and just about half as intense as Pallas, Kareta stated.

The scientists likewise discovered that the surface area of Phaethon is similarly blue all around, which implies that the item has actually been “equally burnt” or “prepared” by the sun’s heat. Phaethon’s blue color suggests that the rock has actually gone through extreme heating, Kareta stated. Throughout Phaethon’s journeys around the sun, it gets warmed to temperature levels of as much as 1,500 degrees Fahrenheit (800 degrees Celsius), which is “so hot that metals on the surface area rely on goo,” he stated.

The Geminid meteor shower, which gets here every year in December, is the only meteor shower that appears to have actually stemmed from anything besides a comet. Comets are icy bodies including a mix of ice, rock, dust and frozen gas. When a comet gets near to the sun, a few of this product gets vaporized and little pieces of the comet break out, leaving a path of comet crumbs in area. When Earth travels through such a path of particles, we get meteor showers.

Asteroids like Phaethon are rocky things that do not act the very same method as comets do when they get near to the sun, and astronomers aren’t sure how Phaethon might have produced the Geminids. Prior to Phaethon was found, in 1983, astronomers had no concept where the Geminids originated from. Having actually observed that Phaethon’s orbit matched the path of particles that triggers the yearly meteor shower, however, astronomers figured out that Phaethon should be the source.

This diagram shows the highly eccentric orbit of 3200 Phaethon.

This diagram reveals the extremely eccentric orbit of 3200 Phaethon.

Credit: NASA JPL

Precisely how Phaethon produced that path of particles stays a secret, Kareta stated. While it is possible that product swept the asteroid’s surface area might add to the particles, “the quantity of dust that gets swept is no place near sufficient to sustain the Geminids,” he stated. One possibility is that Phaethon hit another item in area and the Geminids are the particles from that “devastating separation,” he stated. “So, because case, you’re basically seeing dust, which is sort of like blood splatter, to be gruesome, from this truly violent occasion.”

Another possibility is that Phaethon is an inactive comet, or a comet that became an asteroid in time. “If it was cometary eventually in the past, perhaps it made the meteor shower the regular method and left those comet crumbs … however ever since, it’s been prepared through and switched off and it simply appears like a rock,” Kareta stated.

Phaethon might look more like an asteroid than a comet, however it shows qualities of both kinds of things. It does not have the coma and tail that are particular of comets, however it does launch “a small dust tail when it gets closest to the sun in a procedure that is believed to resemble a dry riverbed breaking in the afternoon heat,” University of Arizona authorities stated in a declaration. “This sort of activity has actually just been seen on 2 things in the whole planetary system– Phaeton and another, comparable item that appears to blur the line typically believed to set comets and asteroids apart.”

Findings from this brand-new research study will can be found in convenient for researchers with the Japan Aerospace Expedition Company (JAXA), which is presently preparing an objective to Phaethon. The objective is called FATE+ (an abbreviation for Presentation and Experiment of Area Innovation for Interplanetary Trip, Phaethon Fyby and Dust Science), and it is presently set up to introduce in 2022.

FATE+ will zip Phaethon and other near-Earth challenge study how dust is ejected from these things. This ought to assist to discuss Phaethon’s small dust tail. FATE+ might assist researchers determine whether Phaethon is an asteroid, a comet or something else. “It’s most likely someplace in the middle,” Kareta stated.

Email Hanneke Weitering at hweitering@space.com or follow her @hannekescience Follow us on Twitter @Spacedotcom and on Facebook Initial post on Space.com