This NASA Hubble Space Telescope reveals a never-before-seen set of six comet-like tails radiating from a body in the asteroid belt, named P/2013 P5. The asteroid was discovered as an unusually fuzzy-looking object with the Panoramic Survey Telescope and Rapid Response System survey telescope in Hawaii. 
A diagram shows the orbit of an asteroid named 2013 TV135 (in blue), which made headlines in September 2013 when it passed closely by Earth. The probability of it striking Earth currently stands at 1 in 63,000, and even those odds are fading fast as scientists find out more about the asteroid. It will most likely swing past our planet again in 2032, according to NASA. 
Asteroid 1998 QE2 about 3.75 million miles from Earth. The white dot is the moon, or satellite, orbiting the asteroid. 
Asteroid 2012 DA14 made a record-close pass -- 17,100 miles -- by Earth on February 15. Most asteroids are made of rocks, but some are metal. They orbit mostly between Jupiter and Mars in the main asteroid belt. Scientists estimate there are tens of thousands of asteroids and when they get close to our planet, they are called near-Earth objects. 
Another asteroid, Apophis, got a lot of attention from space scientists and the media when initial calculations indicated a small chance it could hit Earth in 2029 or 2036. NASA scientists have since ruled out an impact, but on April 13, 2029, Apophis, which is about the size of 3½ football fields, will make a close visit -- flying about 19,400 miles (31,300 kilometers) above Earth's surface. The images above were taken by the European Space Agency's Herschel Space Observatory in January 2013. 
If you really want to know about asteroids, you need to see one up close. NASA did just that. A spacecraft called NEAR-Shoemaker, named in honor of planetary scientist Gene Shoemaker, was the first probe to touch down on an asteroid, landing on the asteroid Eros on February 12, 2001. This image was taken on February 14, 2000, just after the probe began orbiting Eros. 
The first asteroid to be identified, 1 Ceres, was discovered January 1, 1801, by Giuseppe Piazzi in Palermo, Sicily. But is Ceres just another asteroid? Observations by NASA's Hubble Space Telescope show that Ceres has a lot in common with planets like Earth. It's almost round and it may have a lot of pure water ice beneath its surface. Ceres is about 606 by 565 miles (975 by 909 kilometers) in size and scientists say it may be more accurate to call it a mini-planet. NASA's Dawn spacecraft is on its way to Ceres to investigate. The spacecraft is 35 million miles (57 million kilometers) from Ceres and 179 million miles (288 million kilometers) from Earth. The photo on the left was taken by Keck Observatory, Mauna Kea, Hawaii. The image on the right was taken by the Hubble Space Telescope. 
One big space rock got upgraded recently. This image of Vesta was taken by the Dawn spacecraft, which is on its way to Ceres. In 2012, scientists said data from the spacecraft show Vesta is more like a planet than an asteroid and so Vesta is now considered a protoplanet. 
The three-mile long (4.8-kilometer) asteroid Toutatis flew about 4.3 million miles (6.9 million kilometers) from Earth on December 12, 2012. NASA scientists used radar images to make a short movie. 
Asteroids have hit Earth many times. It's hard to get an exact count because erosion has wiped away much of the evidence. The mile-wide Meteor Crater in Arizona, seen above, was created by a small asteroid that hit about 50,000 years ago, NASA says. Other famous impact craters on Earth include Manicouagan in Quebec, Canada; Sudbury in Ontario, Canada; Ries Crater in Germany, and Chicxulub on the Yucatan coast in Mexico. 
NASA scientists say the impact of an asteroid or comet several hundred million years ago created the Aorounga crater in the Sahara Desert of northern Chad. The crater has a diameter of about 10.5 miles (17 kilometers). This image was taken by the Space Shuttle Endeavour in 1994. 
In 1908 in Tunguska, Siberia, scientists theorize an asteroid flattened about 750 square miles (1,200 square kilometers) of forest in and around the Podkamennaya Tunguska River in what is now Krasnoyarsk Krai, Russia. 
What else is up there? Is anyone watching? NASA's Near-Earth Object Program is trying to track down all asteroids and comets that could threaten Earth. NASA says 9,672 near-Earth objects have been discovered as of February 5, 2013. Of these, 1,374 have been classified as Potentially Hazardous Asteroids, or objects that could one day threaten Earth. 
One of the top asteroid-tracking scientists is Don Yeomans at the Jet Propulsion Laboratory, which is managed by the California Institute of Technology. Yeomans says every day, "Earth is pummeled by more than 100 tons of material that spewed off asteroids and comets." Fortunately, most of the asteroid trash is tiny and it burns up when it hits the atmosphere, creating meteors, or shooting stars. Yeomans says it's very rare for big chunks of space litter to hit Earth's surface. Those chunks are called meteorites. 
Asteroids and comets are popular fodder for Earth-ending science fiction movies. Two of the biggest blockbusters came out in 1998: "Deep Impact" and "Armageddon." (Walt Disney Studios) Others include "Meteorites!" (1998), "Doomsday Rock" (1997), "Asteroid" (1997), "Meteor" (1979), and "A Fire in the Sky" (1978). Can you name others?
- Gravity of Jupiter has influenced movement of asteroids
- There are more than 500,000 known rocks in main asteroid belt
- Study in journal Nature throws a new light on this belt
(CNN) -- If you want to find an asteroid, the region between Mars and Jupiter is a great place to look. That area where asteroids hang out is called the main asteroid belt
A study in the journal Nature throws a new light on this strip of our solar system, where most of the asteroids in our solar system reside. Whereas scientists once believed that these asteroids formed more or less in place, new modeling suggests they have been scattered all over.
Scientists believe "the asteroid belt is a melting pot of bodies that formed all over the solar system," said Francesca DeMeo, lead study author and an astronomer at the Harvard Smithsonian Center for Astrophysics.
Back in the 1980s, when only about 10,000 asteroids were known, it seemed that asteroids that appeared to have formed in a cold environment were farther away from the sun, while those that formed in a hot environment were closer to the sun.
Defending earth from asteroids 
Could we really capture an asteroid? But DeMeo and co-author Benoit Carry of the Paris Observatory studied hundreds of thousands of asteroids and they found that this trend did not hold. Instead they spotted many "rogue" asteroids: Rocks formed in hot environments that were in regions where cold-environment-formed asteroids were expected, and so on.
The main asteroid belt is much more diverse than originally thought, the study shows. Dante Lauretta, lead scientist on the asteroid sample return mission OSIRIS-REx and professor at the University of Arizona, said in an e-mail that the study "represents a new paradigm in our understanding of the compositional diversity of the asteroid belt." Lauretta was not involved in the Nature study.
Although astronomers cannot directly measure temperatures of asteroids, they can infer a rock's origin through geology. For instance, an asteroid with a lot of carbon probably formed far from the sun, in colder temperatures.
The theory is that the planets of our solar system have moved over time. Jupiter, the largest planet in our solar system and the one with the most gravitational pull, had a big part to play. As Jupiter moved toward the sun, it scattered asteroids, "like a snow globe," DeMeo said.
Over time, she said, there was "a big mess of asteroids everywhere." The only place for them to remain was the asteroid belt.
Why asteroids don't surprise us anymore
Near-Earth asteroids, space rocks that approach our planet's orbit, originated between Mars and Jupiter, she said. By understanding the diversity of the main asteroid belt, we can understand better the asteroids that come close to Earth, DeMeo said.
Such a large amount of mixing in the asteroids is not surprising, Lauretta said.
"This study shows that, indeed, a dynamical process has stirred the asteroid pot, so to speak," he said.
Computer simulations called dynamical models simulate the behavior of thousands of asteroids over time -- even over millions of years. In this way, scientists can see how the solar system might have evolved, how the giant planets may have migrated, and how the migration could have affected the distribution of various types of asteroids.
Dynamical models over the last decade have suggested the main asteroid belt has been sculpted by giant planet resonance, a position where an asteroid feels a regular gravitational pull from Jupiter or Saturn, Lauretta said.
Astronomers have figured out that this happens in connection with a mathematical relationship between the asteroid's orbital period and the planet's orbital period. When the orbital period -- how long it takes go to around the sun -- of the asteroid is an integer multiple of the planet's orbital period, you see this effect -- and there tend not to be any large asteroids in these locations.
For example, there is a location where an asteroid would go around the sun twice for every time that Jupiter circles once. The asteroid feels regular tugging from the planet, and its orbit become unstable. That explains the emptiness of that part of the asteroid belt.
There are several sky surveys that look out for asteroids on a regular basis as part of NASA's Near Earth Object Program. The program found that a very small asteroid entered the Earth's atmosphere over the mid-Atlantic Ocean at the beginning of January and probably broke up.
Today we know of about 500,000 asteroids in the main belt, but astronomers believe there are at least 1 million asteroids there that are larger than 1 kilometer in diameter, and even more that are small. The next one we spot will also come from this shaken solar system.
Follow Elizabeth Landau on Twitter at @lizlandau
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