Large asteroid zipping past Earth, dragging its own moon

(CNN) -- An asteroid is whizzing past Earth on Friday -- and it's traveling with its own moon in tow.

1998 QE2, as NASA has named it, will not come anywhere near enough to collide with our world.

The closest it will come is about 3.6 million miles away -- that's over 15 times the distance to our moon. It will reach that point just before 5 p.m. ET.

But it's giving astronomers the "best look at this asteroid ever," NASA said.

Scientists have been rubbing their hands for a decade and a half for this opportunity since they discovered the asteroid on August 19, 1998, the year for which it is named. The letter "Q" stands for the month of August.

A milestone asteroid

1998 QE2 represents a milestone in NASA's Near Earth Object Project, which scopes out the heavens for potential danger from celestial projectiles whizzing past.

"It's one of the initial successes of our effort to find the big asteroids that could hit the Earth and cause global catastrophe," said Paul Chodas, a scientist with the project. "It's certainly one to keep an eye on."

NASA has been tracking it with radar devices since Thursday, not to clock its speed but to get good pictures of it. A day before, scientists got a shot of its moon. The images look less like photos and more like ultrasound images.

The discovery of its moon surprised the astronomers, said NASA radar scientist Marina Brozovic, who helped take the images at Deep Space Network antenna at Goldstone, California. "It turns out that 1998 QE2 is a binary asteroid," she said. "This is something we did not expect."

More than 15% of asteroids travel in groups of two or three objects revolving around one another, according to NASA.

Destructive potential

1998 QE2's moon, which is 2,000 feet wide, is large enough for NASA to term it a "potential city killer."

The asteroid it revolves around is 1.7 miles wide. "This is one of the big ones," Chodas said.

To put the potential for damage by an asteroid into perspective, the one that paleontologists believe triggered the extinction of dinosaurs on Earth 65 million years ago was six miles in diameter.

The meteor that exploded over Russia in February, injuring more than 1,000 people and causing millions of dollars in damage, was a "very small asteroid," according to the space agency.

Any asteroid as large as a half-mile across would cause a global catastrophe, if it struck the blue planet, Chodas said.

The most dangerous asteroids contain a lot of stone or iron, according to NASA. 1998 QE2 contains a good bit of carbon and well as amino acids, the building blocks of protein.

The NEOP has identified 95% of asteroids of this most dangerous order, Chodas said. Luckily, there is no known possibility of one slamming into the planet.

But NASA has not yet done much work on the meteors one class lower, known as the "potential city killers." They start at a size of 150 yards in diameter. NASA astronomers have identified only 10% of the 10,000 they believe pass close to Earth.

NASA this year told a congressional panel in Washington, which was considering future defense systems to prevent a potential asteroid strike, that there is only a chance of one in 20,000 that a truly dangerous one could hit Earth in a year's time.

Having a look

Astronomers will continue making images of 1998 QE2 through June 9 with two radar antennas -- the one in California and a second one in Puerto Rico.

Amateur astronomers with telescopes as small as 10 inches long may just barely be able to eyeball it in the southern skies. But the devices should be computer controlled because locating it otherwise will be difficult, NASA advises. The coordinates to locate the asteroid are on the Jet Propulsion Laboratory website.

NASA takes threats from asteroids seriously, and will keep calculating the orbits of the large ones they identify long to check their flight paths for any potential danger to Earth.

1998 QE2 will curve back out toward the solar system's outer asteroid belt, which is just short of Jupiter.

It gets its next shot at hitting Earth in 200 years, and will likely miss again.